No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Catchment Liming to Restore Degraded, Acidified Heathlands and Moorland Pools
Abstract
Current restoration measures of degraded, acidified heathland ecosystems have not always been successful in the Netherlands. Positive effects of a restored hydrology are often counteracted by acidification of the soil and the local groundwater system. Liming of the heathlands in the catchment of moorland pools might contribute to the restoration of both habitats. Experimental catchment liming was carried out in two degraded Dutch heathlands, with doses varying between 2 and 6 tons/ha. Catchment liming resulted in increased pH and base cation concentrations in the highest elevated limed parts, as well as in the lower situated, nonlimed heath areas and moorland pools. Generally, catchment liming created suitable conditions for the return of heathland target species, and the positive effects lasted for at least 6 years. The response of the heathland vegetation to the liming has, however, been slow because only a small number of endangered plant species increased in abundance. In contrast, four Red List soft-water macrophytes strongly increased in abundance in the moorland pool. Our results show that, even with the slow return of Red List plant species, catchment liming can be a successful management tool for the restoration of the acidified heathland landscape.
... Restoration projects that reduce soil pH with additions of elemental sulfur, ferric compounds, and organic matter have reduced the spread of weedy plants and increased establishment of native plants (Farrel et al. 2011, Novak et al. 2009. Adding lime also has increased soil pH in degraded landscapes, resulting in increased calcium and manganese availability, facilitated the establishment of both endangered and indicator plant species, and reduced recruitment of invasive plants (Dorland et al. 2005, Kirkham et al. 2008, Longhurst et al. 1999. ...
... Altering soil pH in combination with soil disturbance could increase potential for restoration by providing conditions that favor some native plants Longhurst et al. 1999;. Adding elemental sulfur can increase soil fertility and native plant cover ) and liming can reduce soil toxicity in acidic soils and increase native forbs (Dorland et al. 2005;Elliot et al. 2013;Longhurst et al. 1999). An observed change in soil pH from applying sulfur may take months (Owen and Marrs 2001;Tibbet and Diaz 2005), whereas soil pH responds to liming immediately . ...
... Initial soil chemistry may have influenced the efficacy of our soil treatments. In previous studies, soils treated with lime or sulfur were acidic before treatment (Dorland et al. 2005;Elliot et al. 2011;, whereas untreated soils in our study were alkaline. Carbonate compounds commonly buffer out acidic or basic components in alkaline soils . ...
Plant invasions are a threat to biodiversity, as changes in plant community characteristics resulting from invasion can affect other organisms, such as arthropods. The effects of invasions may interact with other disturbances and alter the efficacy of restoration strategies. We sought to understand the effects of Old World bluestem grasses (OWBs, Bothriochloa, Dichanthium spp.), which have become dominant in prairie ecosystems and reduce the quality of habitat for wildlife. In an attempt to reduce OWBs, we applied treatments to modify soil conditions to a state which favors native plants and arthropods. We conducted our research in 2011, which coincided with extreme drought and provided us with the opportunity to test the efficacy of soil modification under varying conditions. First, we explored the effects of plant invasion and drought on native plant and arthropod communities by comparing characteristics of plots dominated by native plants to plots dominated by OWBs. As drought subsided, we observed a shift from an arthropod community driven by detritivores to one driven by herbivores associated with plant invasion. Arthropod communities were dominated by invasive species. Second, we explored the efficacy of soil modification and seeding treatments to reduce OWBs in the presence and absence of drought based on a field experiment and a more controlled microcosm experiment. Although changes in soil chemistry from soil treatments were short-lived, we observed reduced dominance of OWBs in areas treated with soil disturbance and seeding in both experiments and we observed no differences between experiments when we alleviated the effects of drought. Finally, we examined the concomitant effects of our soil modification and seeding treatments on arthropod communities in the field experiment. We observed fewer arthropods in treated plots than undisturbed OWB monocultures, but soil and seeding treatments increased arthropod diversity and reduced dominance of invasive arthropods relative to undisturbed OWB monocultures. Based on our findings, simple soil disturbance in combination with seeding of native plants may increase diversity of native plants and arthropods where invasive plants are dominant in the short term, but monitoring over longer time frames may reveal additional benefits from soil modification.
... Depending on the sulphate supply to the system, sulphide can accumulate in the organic layer and promote internal eutrophication . Since the end of the 20th century, many projects have been carried out to restore acidified and/or eutrophied softwater lakes, most of them in the Netherlands (Bellemakers 2000, Rhazi et al. 2005, Dorland et al. 2005, Van Wichelen et al. 2007). These measures basically restored the environmental requirements of the well-studied Littorellion alliance. ...
... It has become the most important acidifying substance in shallow softwater lakes in recent decades. High ammonium/nitrate ratios are detrimental to several plant species of nutrient-poor ecosystems (de Graaf et al. 1994, van den Berg et al. 2005, Stevens et al. 2011. Eleocharis multicaulis seems to be such a sensitive species, requiring at least as much nitrate as ammonium. ...
... Ionic ratios may have a high potential as proximal predictors to plant performance and abundance, as has been demonstrated by other authors (e.g. Roelofs et al. 1985, de Graaf et al. 1997, Güsewell et al. 2003, Güsewell 2005, van den Berg et al. 2005, Stevens et al. 2011. However, they are not often applied in plant habitat studies. ...
In the thesis, several questions are raised that are related to the niche concept and population ecology. They are within a framework of the amphibious softwater plant community Eleocharition multicaulis Vanden Berghen 1969. The research questions in the thesis can be broadly summarized as 1) which environmental factors define the realized niche of the species, and what is the realized niche of these species, 2) how important are environmental gradients compared to biotic interactions in determining community structure, 3) to what extent do the realized niches of the species support theoretical models of coexistence, and 4) is relative population performance related to species strategy?
... Adding chalk after removal of the sediment can only raise the pH over a short period of time , after which rapid reacidification will take place. Therefore, direct liming of pools is now discouraged, and catchment liming is seen as more promising , DORLAND et al. 2005. After sod cutting in heathlands doses varying between 2 and 6 tons of Dolokal were applied per hectare on the highest parts of the terrain. ...
... This resulted in an increase of pH in these highest parts as well as in the lower, non-limed heath and in the pools. The increase lasted during the whole study period (6 years) (DORLAND et al. 2005). ...
The western distribution border of Rana arvalis runs through the Netherlands, where one of the westernmost populations of the species occurs. The moor frog has been found in all provinces and occupies a wide variety of habitats, with concentrations on inland sand and peat. In the Netherlands Red List of 1996 the species was listed as vulnerable. In the new Red List it is listed as least concern, because recent inventories brought many new locations to light. Nevertheless, there is a decrease of 28.7 % be-tween 1950 and 2006. Especially the cultivation of heathland and raised bogs as well as the lowering of ground water levels and intensification of agricultural practices account for the decrease of R. arvalis. Conservation measures for different habitat types are presented. The construction of new ponds is hardly an effective protective measure for Rana arvalis in the Netherlands.
... Hence, there is a considerable colonisation debt for the habitat and community restoration in such systems (Cristofoli and Mahy 2010). Liming of acidified wet heathlands in combination with reintroducing G. pneumonanthe can lower the soil pH and improves the germination possibilities of Marsh Gentians (Dorland et al. 2005b;Cools et al. 2020). This technique was successfully applied in one of the former sites of P. alcon (Vallei van de Ziepbeek, Zutendaal) and could be considered for a reintroduction project of P. alcon in the near future (see further). ...
In the NW-European region of Flanders (northern Belgium), wet heathlands harbour several threatened species among which the emblematic Alcon Blue butterfly Phengaris alcon is rapidly declining. Since 1990, the number of occupied grid cells in Flanders has decreased from 61 to only six in 2023, a decline of 90%. Due to the loss of many populations, the mean distance between populations tripled from 9 km in the period 1950–1990 to 27 km now. Site-wide egg counts in one of the strongholds of the Alcon Blue in Flanders revealed a strong increase after some initial intensive care conservation measures in the 2000s, but since 2013 a steep decline of 99% has been observed. The standardised egg counts in the remaining six Flemish populations (i.e., monitoring within the framework of the Natura2000 reporting) showed a yearly decrease of 18% since 2016. Despite increased conservation attention and targeted management since the end of the 1990s, the current situation of P. alcon in Belgium is more precarious than ever. Causes of this rapid decline are manifold and they are likely to be amplified by extreme weather conditions caused by climate change. More efficient intensive care measures and more intense cooperation across national borders are now quickly required to regionally preserve this habitat specialist with a unique eco-evolutionary profile.
Implications for insect conservation By analysing the causes of the decline of the threatened Alcon Blue butterfly in Flanders, we suggest management and policy measures in an attempt to conserve this and other threatened heathland species in a highly anthropogenic region.
... 3130 versus 3160) en de mate waarin bufferstoffen via natuurlijke weg worden aangevoerd. Indien toch nodig geacht, is het herstellen van de waterhuishouding, of het onrechtstreeks verhogen van de buffertoestand door middel van grondwater of bekalken in het waterleverend gebied (Dorland et al. 2005;Brouwer & Lucassen 2013), te verkiezen boven het rechtstreeks bekalken van het wateroppervlak of de natte oever'. Het bekalken van het inzijggebied valt echter onder het item 'herstel grondwaterkwaliteit'. De dosering moet in alle gevallen goed ingeschat worden en opvolging is nodig. ...
... Numerous studies have focused on the response of soil solution and surface water to liming (e.g. Geary and Driscoll, 1996;Driscoll et al., 1996;Traaen et al., 1997;Frank and Stuanes, 2003;Hindar et al., 2003;Dorland et al., 2005). However, the impact of liming on groundwater quality is rarely addressed. ...
From a biogeochemical perspective, catchments can be regarded as reactors that transform the input of various substances via precipitation, deposition, or human activities as they pass through soils and aquifers towards receiving streams. Understanding and modeling the variability of solute concentration in catchment waters require the identification of prevailing processes, determining their respective contributions to the observed transformation of substances, their interplay with hydrological processes, and the determination of anthropogenic impacts. However, numerous biogeochemical processes often interact in a highly non-linear way and vary on temporal and spatial scales, resulting in temporally and spatially varying water chemistry in catchments. This is particularly true for riparian wetlands. Processes in this catchment area often superimpose the influence of the hill slope (and largest) area of the catchment on surface water quality. Accordingly, the first part of this thesis (Study 1 and 2), focuses on the temporal and spatial variability of biogeochemical processes at the catchment scale. Therefore, the first aim was to identify the prevailing biogeochemical processes which affect the quality of catchment waters in two forested granitic catchments. Based on these results, (i) the long-term behavior of these processes was determined (Study 1) and (ii) hot spots of these processes at the catchment scale along different flow paths were identified (Study 2). The second part (Study 3) focuses on the interplay between hydrological and biogeochemical processes in a riparian wetland, with the aim of systematically tracing back the temporal patterns of stream water chemistry to different biogeochemical processes and antecedent hydrological boundary conditions in the wetland. The third part (Study 4 and 5) focuses on weathering processes with the goal (i) of identifying the mineralogical sources of the groundwater’s buffer capacity against acid atmospheric deposition in a forested granitic catchment and (ii) determining the mineralogical sources of the high cation loads in surface water, induced by intensive agricultural activities in two agricultural granitic catchments. To reach these aims, multivariate statistical methods of dimensionality reduction (linear Principal Component Analysis, non-linear Isometric Feature Mapping), a low-pass filtering of time-series, a Cluster analysis, and major and trace element ratios and strontium isotopes were used. A small number of biogeochemical process bundles explained 94% and 89% of the variance of the data set in Study 1 and 2, respectively. In Study 1, redox and topsoil processes, road salt and sulfate contamination were identified as predominating processes influencing water chemistry in the respective catchments. Low-pass filtered time series of component scores revealed a different long-term behavior at different sampling sites in both catchments, which could be traced back to the fraction of wetland area in the respective subcatchments as well as by the varying thickness of the regolith. Study 2 revealed that the upper 1 m topsoil layer could be considered as a biogeochemical hot spot for redox processes, acid-induced podsolization, and weathering processes along different flow paths. Up to 97% of the biogeochemical transformation of the chemical composition of soil solution, groundwater and stream water in the Lehstenbach catchment was restricted to this soil layer representing less than 2% of the catchment’s regolith. Wetland stream water, mobilized in the topsoil layer being considered a biogeochemical hot spot, showed a highly dynamic temporal pattern of component scores. Study 3 revealed four different types of wetland stream water chemical status, depending on the interplay between discharge dynamics, biological activity, and the water table position in the wetland. The sequence of different stream water types roughly followed a seasonal pattern, albeit being heavily modified by the respective hydrological boundary conditions for different years. Extended periods of low groundwater level in the second half of the growing season drastically changed the chemical boundary conditions, becoming evident in a drastic reoxidation of reduced species like sulfides and corresponding effects. Weathering processes are one of the predominating biogeochemical process bundles influencing water chemistry in forested catchments. Study 4 showed that the mineralogical sources of the groundwater’s buffer capacity against acid atmospheric deposition were dominated by the release of base cations from apatite dissolution, preferential cation release from feldspars and biotite, and feldspars weathering. In Study 5, determining the mineralogical sources of the high cation loads in surface water induced by intensive agricultural activities revealed a dominant manure contribution in the topsoil, and enhanced mineral dissolution (plagioclase and biotite) by fertilizer application in subsoils, becoming the unique source of base cations in the saprolite. Stream water chemistry differed from that of soil water, suggesting that stream water chemistry was dominated by elements issued from enhanced mineral and rock weathering. Soil acidification induced by agriculture allows the mobilization of cations stored in soil layers, enhances the rock weathering and accelerates plagioclase dissolution, which can highly influence stream water quality. Numerous biogeochemical, hydrological, and anthropogenic processes were found to interact with each other, mostly with non-linear patterns, influencing catchment water chemistry. The integral approach used in this thesis would be a useful prerequisite to develop accurate and parsimonious models commonly used for water management purposes by distinguishing between short- term and long-term shifts, reducing the number of processes to the predominating ones ultimately to be included in the model, focusing on hot spots and including spatial patterns where necessary and appropriate.
... Indien het niet mogelijk is om de hydrologie afdoende te herstellen, kan voor 'catchment liming' gekozen worden. Hierbij wordt niet het verzuurde deel van het terrein zelf bekalkt, maar het inzijggebied ervan, zodat de aanvoer van basen via lokale kwel kan plaatsvinden, in plaats van door directe kalkgift (Dorland et al., 2005a). Op plaatsen waar hydrologisch herstel niet van toepassing of geen optie is, kan direct bekalkt worden. ...
... 3130 versus 3160) en de mate waarin bufferstoffen via natuurlijke weg worden aangevoerd. Indien toch nodig geacht, is het herstellen van de waterhuishouding, of het onrechtstreeks verhogen van de buffertoestand door middel van grondwater of bekalken in het waterleverend gebied (Dorland et al. 2005;Brouwer & Lucassen 2013), te verkiezen boven het rechtstreeks bekalken van het wateroppervlak of de natte oever'. Het bekalken van het inzijggebied valt echter onder het item 'herstel grondwaterkwaliteit'. De dosering moet in alle gevallen goed ingeschat worden en opvolging is nodig. ...
Restoration strategies to mitigate effects of atmospheric nitrogen deposition on Natura2000 habitat in Flanders.
In this report we describe 25 restoration measures that can (temporarily) mitigate negative effects by nitrogen deposition on 84 Natura2000 habitat and subhabitat types in Flanders (northern Belgium). For each restoration measure, the positive effects or negative unintended consequences are briefly listed. We discern for this purpose
eutrophication, acidification and other effects, the latter in particular on fauna.
Restoration measures were prioritized and related to each other, which resulted in restoration strategies for each
habitat or subhabitat type. These restoration strategies are based on expert judgement and give an indication of the relevance of measures at the scale of Flanders as a whole. Local managers can use it as a support, but in many cases adjustment to local conditions will be necessary.
This report also discerns habitat or subhabitat for which restoration measures are unable to stop degradation by persistent nitrogen deposition (type A), from habitat for which restoration measures can be more successful (type B). The nutrient status of type A habitat and subhabitat is mostly determined by the quality of precipitation, and
they are therefore very sensitive for simultaneous acidification and eutrophication. By contrast, type B habitat and subhabitat is buffered by (moderately) mineral rich soil or groundwater, implicating that measures to counteract eutrophication do not cause further acidification.
In dit rapport worden 25 herstelmaatregelen beschreven, die de negatieve effecten kunnen mitigeren van te hoge depositie van stikstof, op 84 Europese habitat(sub)typen uit Vlaanderen die gevoelig zijn voor deze milieudruk. Het rapport heeft tot doel een beknopte onderbouwing te leveren van de werking van de maatregelen en de neveneffecten die ze kunnen hebben, zodat ze kunnen gebruikt worden om in het kader van de programmatisch
Aanpak Stikstof (PAS) negatieve effecten van stikstofdepositie te mitigeren.
Op basis van een expertenoordeel werd aan de herstelmaatregelen in tabelvorm een globale prioritering op het niveau van Vlaanderen toegekend, die in een begeleidende tekst werd onderbouwd. Het pakket van herstelmaatregelen en hun onderlinge prioritering, vormen samen een herstelstrategie voor elk van de habitat(sub)typen die stikstofgevoelig zijn.
Met deze globale herstelstrategieën als houvast kan de beheerder een herstelstrategie op maat uitwerken, die is aangepast aan de lokale kenmerken van de Europese habitats. Dit betekent dat de prioriteit van de maatregelen lokaal tegen het licht wordt gehouden en zo nodig kan aangepast worden, om zo goed mogelijk tegemoet te komen aan de lokale problematiek.
Het rapport bevat ook een beoordeling van de effectiviteit van het herstelbeheer (A of B), die variabel is en afhankelijk van systeemkenmerken van het habitat(sub)type waarvoor het van toepassing is
... For example, the restored meso-xeric grassland case study shows that dispersion strengthening by hay transfer increases CSII value. Environmental conditions may be too far from the growth optimum of target species, in which case management should involve trying to 90 restore suitable conditions (Bakker and Berendse, 1999;Dorland et al., 2005). Target species may also be in competition with non-target species (D'Antonio et al., 2003), which will be expressed with high values of HAI. ...
Ecosystem restoration has been identified as one approach to slow down the loss of biodiversity and to protect all the biodiversity-based goods and services from which humankind benefits. Restoration feeds from knowledge coming from both community ecology and restoration ecology. The objectives of the thesis are to provide insights on both the dynamics of a mediterranean steppe after changes in land-use and the implementation of techniques which could be applied to restore this ecosystem after severe anthropogenic disturbances. The thesis takes as a study object the La Crau Mediterranean steppe, and especially former cultivated fields to study the recovery after cultivation and the Cossure large scale rehabilitation project to experiment rehabilitation and restoration techniques. Concerning dynamics after severe exogenous anthropogenic disturbances, we confirmed the low resilience of the steppe plant community both at mid- (30-40 years) and long-term (150 years) while the resilience of soil parameters and mycorrhizal infestation rate are effective on the long-term. Moreover we confirmed the role played by the three filters in the plant community recovery and found that for the La Crau steppe, this is firstly driven by the abiotic filter, then by the dispersion filter and finally by the biotic filter. Given this low resilience, we tested several restoration techniques applied at large-scale within the Cossure rehabilitation project: nurse species seeding, topsoil removal, hay transfer and soil transfer. In order to assess the efficiency of restoration techniques we developed indices to measure the community structure integrity, disentangling lower and higher abundances compared to the reference. The best results were obtained with soil transfer, followed by topsoil removal, then nurse species seeding and finally hay transfer. The research conducted for this thesis shows that current knowledge in ecological restoration makes it possible to restore at least partially some La Crau ecosystem components, but ought to lead us to understand the importance of in situ conservation of natural habitats as a better alternative to restore them after they were destroyed
... Koolstofgradiënten in een ven kunnen ook worden versterkt door bijvoorbeeld de windwerking op de open delen en de geëxponeerde oevers te vergroten, maar er tegelijkertijd voor te zorgen dat luwe delen ook luw blijven. De wind veroorzaakt waterstroming aan het oppervlak en een onder- (Dorland et al., 2005). De sterk verminderde zuurdepositie draagt wel bij aan een nieuw probleem, in combinatie met klimaatopwarming. ...
... The acidification of freshwater ecosystems is a continuing concern. Lime is commonly used in both catchments and surface waters as a means to increase buffering capacity and alleviate the effects of acid rain and acid mine drainage (Covert 1990, Dorland et al. 2005, Petty and Thorne 2005; wollastonite (a silicatious mineral) can also be used (Likens et al. 2004). As is the case for chemical additions for phosphorus control, the effect of altering the buffering capacity of the ecosystem on all resident or potential organisms must be considered. ...
The ecological restoration of aquatic systems is becoming a common goal in ecological management. Although ecological restoration shows great promise, a high failure rate still persists. Many projects do not assess or address the altered environmental processes that cause ecosystem degradation, due in part to a lack of collaboration between practitioners and scientists. This thesis examines the need to focus on processes in ecological restoration design, as well as communication and collaboration between multiple fields. The environmental processes that shape ecosystems are discussed, and their role in a case study is explored. Finally, the role of the landscape architect in ecological restoration planning is discussed and a process-based restoration protocol is proposed.
... For example, the restored meso-xeric grassland case study shows that dispersion strengthening by hay transfer increases CSII value. Environmental conditions may be too far from the growth optimum of target species, in which case management should involve trying to restore suitable conditions (Bakker and Berendse, 1999;Dorland et al., 2005). Target species may also be in competition with nontarget species (D'Antonio et al., 2003), which will be expressed with high values of HAI. ...
... In wet acidified soils, hydrological measures are often taken to counteract acidification (e.g. Roelofs et al., 1996;Jansen et al., 2004;Dorland et al., 2005b;Klimkovska et al., 2007), whereas in dry soils liming is an appropriate measure (De Graaf et al., 1998a,b). Increasing base cation and (bi-) carbonate concentrations not only counteracts soil acidification, it also reduces ammonium toxicity by (1) lowering soil ammonium concentrations by increasing nitrification rates at higher pH (Dorland et al., 2004) and (2) by the fact that ammonium is less or non-toxic at higher soil pH (Lucassen et al., 2003;Van den Berg et al., 2005). ...
The northwest European heathland landscape with its characteristic communities of nutrient-poor and acidic soils has a high nature value, because of its locally high biodiversity and the distinct site conditions. In order to conserve and restore the heathlands, numerous rehabilitation projects have been performed, although with varying success. This is partly due to the fact that the key biogeochemical processes distinguishing the various vegetation types within the heathlands are not known in detail.Therefore, we performed a statistical survey on the main communities and their soil characteristics. In addition, we analyzed the data for key factors determining biodiversity in the heathland landscape.Data from previous studies and surveys was used to compile a dataset of 267 vegetation relevés (classified as EUNIS habitat types) with extensive soil measurements (22 parameters). A canonical discriminant analysis revealed that soil acidity explained most of the differences between the habitat types, while soil moisture content and soil fertility were less important. Acidity-related factors as Al3+, Al/Ca-ratio and pH were also strongly correlated to plant diversity in the majority of the habitat types, respectively, the species-rich Nardus grasslands, the Rhynchosporion communities and the species-rich Molinia meadows. In the dry heaths and over the total heathland landscape, plant diversity was negatively correlated with soil NH4+-concentrations. Only in wet heath, nutrient availability, in this case P, was the primary factor in explaining plant diversity.This study presents ranges for all major soil parameters for the studied well-developed heathland habitat types, thereby providing clear guidelines for conservation and restoration.
... Numerous studies have focused on the response of soil solution and surface water to liming (e.g. Geary and Driscoll, 1996; Driscoll et al., 1996; Traaen et al., 1997; Alewell et al., 2000; Frank and Stuanes, 2003; Hindar et al., 2003; Dorland et al., 2005). However, the impact of liming on groundwater quality is rarely addressed. ...
The role of different minerals in base cation release and thus the increase of buffering capacity of groundwater against acid deposition is controversially discussed in the literature. The ⁸⁷Sr/⁸⁶Sr ratios and base cation concentration were investigated in whole rock leachates, mineral separates, precipitation, soil solution, groundwater and stream water samples in the Lehstenbach catchment (Germany) to identify the weathering sequence of the granite bedrock. Three different approaches were followed in parallel. It was assumed that the contribution of different minerals to base cation supply of the groundwater with increasing weathering intensity would be observed by investigating (1) unweathered rock leachates, deep groundwater and shallow groundwater, (2) groundwater samples from new groundwater wells, reflecting the initial weathering of the drilled bedrock, and groundwater from wells that were drilled in 1988, (3) stream water during baseflow, dominated by deep groundwater, and stream water during high flow, being predominantly shallow groundwater. Whereas the first approach yielded consistent patterns, there was some evidence that groundwater from the new wells initially reflected contamination by the filter gravel rather than cation release in an initial stage of weathering. Time series samples of stream water and groundwater solute concentrations and isotope ratios turned out to reflect varying fractions of soil water and precipitation water at baseflow and high flow conditions rather than varying contributions of different minerals that prevail at different stages of granite weathering.
... Het zou vooral worden toegepast na plaggen, wanneer de buffercapaciteit van de bodem als gevolg van verwijdering van de strooisel-en humuslagen is gedaald. Wanneer vrijwel alle organische stof is verwijderd is de kans op versnelde mineralisatie als gevolg van het toedienen van kalk (als carbonaat of als calciumoxide) beperkt ( Dorland et al. 2005). ...
De laatste tijd doen zich bij de ontwikkeling en het beheer van natuurgraslanden verschillende knelpunten voor. Literatuur en gesprekken met beheerders van natuurgraslanden hebben inzicht gegeven in het huidige beheer, de optredende knelpunten en de mogelijke aangrijpingspunten voor vernieuwing. Beschreven wordt welke vernieuwingsmogelijkheden er zijn en welke onderdelen in een pilot zouden kunnen worden opgenomen
Peatlands are wetlands whose soils consist almost entirely of organic matter derived from the remains of dead and decaying plant material. Peat forms from a variety of vegetation, including the moss Sphagnum, herbaceous vegetation, and woody vegetation. Succession is autogenic and driven by accumulating peat that, over time, alters hydrology, soil and water chemistry, and plant communities. Because of its high organic carbon content and water-holding capacity, peat has been harvested for fuel and for horticultural use. Historically, peat was harvested by hand cutting relatively small areas. Today, vacuum mining is used to harvest peat over much larger areas. Restoration of Sphagnum-dominated bog peatlands consists of restoring hydrology by blocking ditches, creating pools and depressions, and mulching with straw to enable colonization by Sphagnum. Sphagnum is a foundation species that grows very slowly and is difficult to reestablish. It is reintroduced by collecting diaspores from a donor site and spreading them atop the restoration site. Nurse plants such as brown mosses (Polytrichum) and cotton grass (Eriophorum) and P fertilization accelerate Sphagnum colonization, but restoring a fully functioning, peat-accumulating wetland is slow.
Renaturierung ist durch abiotische und biotische Faktoren limitiert. Zu den abiotischen Faktoren zählen der Wasserhaushalt, die Nährstoffverhältnisse sowie die Versauerung. Die Wiederherstellung eines adäquaten Wasserhaushalts erweist sich besonders bei Mooren als schwierig und ist oft nur eingeschränkt möglich. Ein zentrales Problem der Renaturierung ist die gezielte Absenkung des Nährstoffniveaus der Projektflächen, um die Existenz von artenreichen Zielgemeinschaften zu ermöglichen. Von einer Versauerung durch atmosphärische Deposition betroffen sind vor allem schwach gepufferte Systeme wie Weichwasserseen, Sandheiden, bodensaure Magerrasen und Niedermoore. Ausdauernde Samenbanken im Boden vermögen in feuchten oder stark störungsgeprägten Lebensräumen und nach Brache einen wesentlichen Beitrag zur Renaturierung zu leisten. Unter den biotischen Faktoren hat die Ausbreitungslimitierung von Zielarten als Folge von Habitatfragmentierung sowie fehlenden Ausbreitungsvektoren an Bedeutung gewonnen. In ähnlicher Weise kann eine dichte Vegetation und das Ausbleiben von Störungen die Etablierung von Zielarten einschränken. Strategien und Techniken zur Übertragung von Zielarten gehören daher zum Standardrepertoire der ökologischen Renaturierung.
1. A field experiment was established near Holme Moss in the Dark Peak SSSI in the summer of 2006 by researchers at Manchester Metropolitan University (MMU) in collaboration with ‘Moors for the Future’ to increase scientific knowledge underpinning current landscape restoration on bare and eroded peat soils in the Southern Pennines. The experiment aimed to investigate how 3 different rates of lime (0, 500, 1000 kg ha-1 y-1) and fertiliser (0, 183, 365 kg ha-1 y-1) application (in 9 factorial combinations) affected: (a) the growth of nurse grasses, (b) the rates of soil CO2 emissions associated with respiration; (c) associated changes in soil acidity and nutrients.
2. Lime and fertiliser increased establishment of the grass mix in comparison with seeded plots without these treatments. Lime was most beneficial and promoted growth in the absence of added nutrients. In contrast, fertiliser addition was only of benefit when lime was also added. The optimum growth was found when both fertiliser and lime were added together at the maximum rates in the experiment. This rate is the same as applied at the landscape level in current restoration management.
3. The pH of the soil in control plots varied over the year, increasing from approximately pH 3.4 in July 2006 to approximately pH 4.1 in March 2007. Fertiliser had no significant effect on soil pH, but increasing lime tended to raise pH by about 0.4 pH units at most. However, in some months there was no significant lime effect on soil pH.
4. The rates of soil CO2 efflux (hereafter termed soil respiration) were measured monthly before and after soil treatments and grass seed were applied. Soil respiration in the untreated, unseeded bare peat was low and showed no seasonal change. Rates on these bare peats were significantly lower than measured at 3 other healthy peatlands in the UK (by the same operator) and also lower than measured on soils below vegetation just metres away from the bare soil.
5. No significant changes in soil CO2 release due to the treatments were recorded until 3 months after application in October 2006, when increasing lime treatment caused a significant step-wise increase in the rate of release of CO2. There was no clear influence of fertiliser addition. Rates recorded in the highest treatment were significantly greater than average values measured on other peatlands sites around the country at similar soil temperature. It is not known for how long the CO2 burst in October was maintained but there were no significant differences between any treatments in the following last two months of 2006.
6. In a follow-up experiment in January 2007, soils from bare and adjacent vegetated areas away from the plots were taken to a greenhouse and supplied with lime and fertiliser. Assays ten days later found the soil respiration rate was stimulated much more in the vegetated than in the bare soils. This result suggested that the respiratory response to lime and fertiliser addition of the bare soils was limited by factors associated with the absence of vegetation.
7. Related studies over winter 2006-7 at Holme Moss found that bare soils contained very small culturable populations of both bacteria and fungi in comparison with the adjacent vegetated soils. At the same time the bare soils contained very much higher concentrations of ammonium. It is likely that the ammonium accumulates in these soils as a result of the absence of plant and microbial uptake, and because the bacterial populations and the rates of nitrification are too low to convert it to nitrate.
8. Soils collected for pH assay in March 2007 were assayed for concentrations of water-extractable nutrients. Contrasts have been in investigated so far in the ammonium and nitrate concentrations in response to lime only addition. The nitrate was not influenced by lime treatment but the level of ammonium was significantly reduced in the highest (1000 kg per hectare) treatment plots. The fall in ammonium due to liming is again likely to be a consequence of increased microbial biomass, plant uptake and the conversion of ammonium to nitrate in the process of nitrification.
9. In conclusion, the following interpretation of the results is proposed regarding soil carbon and nutrient cycling. The very small culturable microbe populations explain the low rates of both respiratory CO2 release and of nitrogen cycling in the untreated bare peat soils. On vegetated soils, the process of photosynthesis supplies carbon to the rooting zone, increasing root and microbial biomass, with a concomitant increase in soil respiration. This effect is further enhanced by liming, which raises the pH and stimulates root and microbial growth. Improved biomass uptake of ammonium together with the higher nitrification rates associated with pH levels of 4 and above then acts to reduce the accumulation of ammonium in these soils. The first stages of this process can now be seen on the treated plots, with a developing pattern of increased soil respiration and reduced ammonium on the limed treatments. .
10. Future research should aim to understand:
• Which specific nutrients are required to stimulate plant growth, both for nurse grass and the succeeding heather vegetation?
• If soil respiration is stimulated by lime addition over the longer time scale?
• If the respired carbon come from the peat or from newly assimilated products of photosynthesis?
• Does any increase in microbial and plant activity also raise the release of DOC?
• What the consequences of lime addition are for mobilizing stored nitrogen in the peat?
• Are the high ammonium concentrations found on the bare peats at Holme Moss typical of the
other sites in the region and do these levels (in combination with acidity and imbalance of other
nutrients) inhibit natural and facilitated revegetation and microbial rehabilitation?
• The stages by which the bare peats of the Southern Pennines may evolve from being an essentially life-less, inhospitable substrate into a healthy soil, and how this can be enhanced by
In den dicht besiedelten und agrarisch besonders intensiv genutzten Regionen Mittel- und Westeuropas ist seit Ende des Zweiten Weltkrieges ein fortschreitender Verlust an naturnahen Ökosystemen mit hoher biologischer Vielfalt zu verzeichnen. Spätestens seit den 1970er-Jahren ist daher die Neuschaffung und Wiederherstellung gefährdeter Lebensräume und Biozönosen zunehmend in den Mittelpunkt von Naturschutzmaßnahmen gerückt (Bakker 1989, Muller et al. 1998, Bakker und Berendse 1999). Aufgrund fehlender wissenschaftlicher Grundlagen und praktischer Erfahrungen wurden Renaturierungsmaßnahmen anfangs fast durchweg nach dem trial and error-Prinzip durchgeführt. Im Vordergrund standen dabei zunächst die Wiederherstellung adäquater abiotischer Standortbedingungen sowie die Reorganisation traditioneller Nutzungsmanagements. Bei Ersterem ging es neben der Wiedervernässung entwässerter Feuchtgebiete (Pfadenhauer und Grootjans 1999) vor allem darum, Eutrophierungseffekte zu beseitigen und die Produktivität des Standortes auf das Niveau der Zielgemeinschaft zurückzuführen (Gough und Marrs 1990, Oomes et al. 1996, Snow et al. 1997, Tallowin et al. 1998). Im Bereich nutzungsgeprägter Halbkulturfomationen wie Feuchtwiesen, Magerrasen und Heiden gingen diese Maßnahmen häufig einher mit einer Reduktion der Nutzungsintensität oder bei Brachen mit einer Wiederaufnahme der Nutzung. Die Wiedereinführung eines entsprechenden Managements konnte vor allem durch Ausgleichszahlungen und vertragliche Vereinbarungen mit Landwirten über Agrarumweltprogramme erzielt werden.
Het verspreidingsgebied van natte heiden is in omvang min of meer gelijk gebleven sinds de laatste ontginningen. De kwaliteit blijft echter een dalende trend vertonen door de inwerking van stikstofdepositie en verdroging. Tegelijkertijd zijn er veelbelovende resultaten geboekt door nieuwe vormen van herstelbeheer. OBN heeft daarvoor de kennisbasis ontwikkeld. In dit artikel worden de daaruit voortvloeiende inzichten uiteen gezet en worden uitdagingen voor de toekomst geschetst.
Peatlands are wetlands whose soils consist almost entirely of organic matter derived from the remains of dead and decaying plant material. Peat forms from a variety of vegetation, including the moss, Sphagnum, herbaceous vegetation, and woody vegetation. Succession is autogenic and driven by accumulating peat that, over time, alters the hydrology, soil, and water chemistry, and plant communities. Because of its high organic carbon content and high water holding capacity, peat has been harvested for fuel and for horticultural use. Historically, peat was harvested by hand cutting relatively small areas. Today, vacuum mining is used to harvest peat over much larger areas. Restoration of Sphagnum-dominated bog peatlands consists of restoring hydrology by blocking ditches, creating pools and depressions, and mulching with straw to enable colonization by Sphagnum. Sphagnum is a keystone species that grows very slowly and is difficult to reestablish. It is reintroduced by collecting diaspores from a donor site and spreading them atop the restoration site. Nurse plants such as brown mosses (Polytrichum) and cotton grass (Eriophorum) and P fertilization accelerate Sphagnum colonization but restoring a fully functioning, peat-accumulating wetland is slow because of its slow growth in the harsh, often cold and dry, environment. In Western Europe, fen peatlands, dominated by species-rich graminoids, are degraded by drainage, acidification, and eutrophication. Restoration of these wetlands involves reintroducing base-rich groundwater or liming, sod cutting to remove excess nutrients especially P, and periodic disturbance such as mowing or prescribed fire to increase species richness.
The Netherlands is a densely populated and industrialized country with corresponding environmental challenges and loss of natural habitat. The strong pressure on our natural capital also resulted in a relatively early awareness of the necessity and possibilities of ecological restoration. Over the past decades various restoration efforts have been undertaken to counteract the effects of landscape degradation. Important lessons have been learned regarding the effective management of knowledge that is needed for successful (forest) landscape restoration. A key element of success in all situations is that restoration arrangements include practitioners, representatives of the research community and governmental policy makers. In this chapter we sketch out the developments in the Netherlands and the relationship with the learning network of the Global Partnership on Forest Landscape Restoration.
Erica tetralix is the key species on NW European wet heathlands, where it is often found to be the dominating plant species. Consequently, it is of considerable concern that the species has decreased significantly in cover from 28% to 18% over a six-year period. In order to understand the underlying causes, a structural equation modeling (SEM) approach was applied on ecological data from 1130 wet heathland plots. Both atmospheric N deposition and soil acidification were included in the SEM. The most important causal effect revealed by the SEM was a significant negative effect of N deposition on the cover of E. tetralix, whereas soil acidity tended to have a negative effect of relatively less importance. There was no significant effect of N deposition on soil pH, which indicates that there are no major indirect effects of N deposition on the cover of E. tetralix mediated by soil acidification.
. The success inrestoring seven low-production vegetation types on former agricultural soil after top-soil removal was investigated. The colonization and establishment of target species in permanent plots was recorded during the first nine years after restoration measures were taken. For each permanent plot abiotic site conditions were used to determine which of the vegetation types could persist there. A comparison of the actual vegetation in the permanent plots with reference releves of the selected vegetation type revealed a gradually increasing similarity during consecutive years for five vegetation types. This was due to the occurrence of an increasing number of target species and the number of permanent plots they occurred in. However, nine years after top-soil removal a large number of the target species were still lacking from the vegetation in the permanent plots, although most were present in the local species pool. Seed dispersal therefore seems to be a major limiting factor for restoration of these low-production vegetation types on formerly agricultural soils.
Functionele biodiversiteit Ammonium Herstelmaatregelen Heidelandschap Een deel van het Stimuleringsprogramma Biodiversiteit besteedde aandacht aan de biodiversiteit in bestaande reservaten. Eén subprogramma ging in op de functionele rol van biodiversiteit en interacties tussen boven grondse en ondergrondse diversiteit in matig voedselrijke graslanden. Een ander subprogramma onderzocht sturende factoren en processen bij de achteruitgang en het herstel van plantendiversiteit in het droge en natte heidelandschap. Dit artikel geeft de belangrijkste onderzoeksresultaten weer en de toepasbaarheid daarvan bij beheer en herstel van natuurreservaten. Een belangrijk deel van de biodiversiteit van Nederland wordt aangetroffen in natuurreservaten, nu veelal gelegen binnen de Ecologische Hoofdstructuur (EHS). Echter, ook in deze natuurreservaten staat de biodiversiteit al decennia onder druk; in de periode voor 1950 vooral door habitat-vernietiging en versnippering, later door aantastingen als verzuring, vermesting en verdroging in combinatie met steeds toenemende biologische isolatie. Veel natuur in bestaande natuurreservaten is ontstaan onder invloed van oud landgebruik door de mens en om in deze halfnatuur-lijke systemen de kenmerkende biodiversiteit te handha-ven (of te vergroten) is bijna altijd enige vorm van regulier beheer noodzakelijk. Maar ook herstelbeheer kan essenti-eel zijn voor het definitief voortbestaan van kenmerkende planten-en diersoorten. De variatie in natuurreservaten van Nederland is groot: van open water en moerassen (va-riërend van zout tot zoet) tot zeer droge terrestrische mi-lieus op verschillende bodemtypen met grote verschillen in nutriëntenniveaus (onder andere Jansen & Schaminée, 2003). Twee typen zijn door het Stimuleringsprogramma Biodiversiteit nader onderzocht: matig voedselrijke gras-landen en het droge en natte heidelandschap.
There is a growing evidence base demonstrating that atmospheric nitrogen deposition presents a threat to biodiversity and ecosystem function in acid grasslands in Western Europe. Here, we report the findings of a workshop held for European policy makers to assess the perceived importance of reactive nitrogen deposition for grassland conservation, identify areas for policy development in Europe and assess the potential for managing and mitigating the impacts of nitrogen deposition. The importance of nitrogen as a pollutant is already recognized in European legislation, but there is little emphasis in policy on the evaluation of changes in biodiversity due to nitrogen. We assess the potential value of using typical species, as defined in the European Union Habitats Directive, for determining the impact of nitrogen deposition on acid grasslands. Although some species could potentially be used as indicators of nitrogen deposition, many of the typical species do not respond strongly to nitrogen deposition and are unlikely to be useful for identifying impact on an individual site. We also discuss potential mitigation measures and novel ways in which emissions from agriculture could be reduced.
While it is well established that ecosystems display strong responses to elevated nitrogen deposition, the importance of the ratio between the dominant forms of deposited nitrogen (NH(x) and NO(y)) in determining ecosystem response is poorly understood. As large changes in the ratio of oxidised and reduced nitrogen inputs are occurring, this oversight requires attention. One reason for this knowledge gap is that plants experience a different NH(x):NO(y) ratio in soil to that seen in atmospheric deposits because atmospheric inputs are modified by soil transformations, mediated by soil pH. Consequently species of neutral and alkaline habitats are less likely to encounter high NH(4)(+) concentrations than species from acid soils. We suggest that the response of vascular plant species to changing ratios of NH(x):NO(y) deposits will be driven primarily by a combination of soil pH and nitrification rates. Testing this hypothesis requires a combination of experimental and survey work in a range of systems.
Soils of wet heathlands have lost their buffering capacity as a result of acidification, eutrophication, and desiccation. Many characteristic plant species have disappeared from these ecosystems because of the unfavourable soil conditions. Restoration projects should aim at counteracting the negative effects of acidification in particular. Blocking of drainage ditches to increase groundwater influence and lime application to improve soil pH and buffering capacity have been applied in many restoration projects in the Netherlands, but with varying success. In this mesocosm experiment, the restoration of the soil buffering capacity of degraded wet heath soil was studied. Groundwater with low or high calcium and bicarbonate concentrations and low or high flow velocities was applied to soil columns filled with wet heath soil. Measurements of the nutrient concentrations in soil pore water and soil extractions revealed that restoration of the soil buffering capacity was optimal at both high calcium concentrations and high through-flow velocity. It was concluded that high concentrations of calcium are more effective than high flow velocity in the reloading of the buffer capacity. Furthermore, the restoration was limited to the soil layers that were in direct contact with the groundwater, which stresses the need for higher groundwater levels in degraded wet heathlands.
To assess changes as a result of reduced acidifying deposition, water chemistry data from 68 Dutch moorland pools were collected during the periods 1983-1984 and 2000-2006. Partial recovery was observed: nitrate- and ammonium-N, sulphur and aluminium concentrations decreased, while pH and alkalinity increased. Calcium and magnesium concentrations decreased. These trends were supported by long term monitoring data (1978-2006) of four pools. Increased pH correlated with increases in orthophosphate and turbidity, the latter due to stronger coloration by organic acids. Increased ortho-phosphate and turbidity are probably the result of stronger decomposition of organic sediments due to decreased acidification and may hamper full recovery of moorland pool communities. In addition to meeting emission targets for NO(x), NH(x) and SO(x), restoration measures are still required to facilitate and accelerate recovery of acidified moorland pools.
Dit rapport geeft een overzicht van de huidige toestand van de vennen en enkele zwak gebufferde wielen in Noord-Brabant. Daarvoor is een steekproef van 126 locaties onderzocht. Er zijn zoveel mogelijk gegevens verzameld over beheer, chemie, fytoplankton (o.a. sieralgen), macrofyten, fytobenthos (kiezelwieren), macrofauna en vissen, vooral uit de perioden 1990-1994 en 2000-2004. De effecten van genomen beheersmaatregelen worden geëvalueerd en er wordt een plan van aanpak voor komende venherstelprojecten en de monitoring van de ecologische toestand gepresenteerd. In het afgelopen decennium is de verzuringstoestand van de vennen, voornamelijk door vermindering van de atmosferische depositie van zwavel- en stikstofverbindingen sterk verbeterd
Arnica montana and Cirsium dissectum, typical of species-rich heathlands and acidic grasslands, have declined rapidly in The Netherlands in recent years. Field surveys suggest that the decline is caused by soil acidification as a result of enhanced atmospheric N and S deposition. Therefore, the survival, growth and development of these species were studied in a water culture experiment, using nutrient solutions which differed both in mineral nitrogen form and in ammonium concentration. For comparison, the performance of a third, acid tolerant species, Calluna vulgaris, was studied. The results showed that both Arnica and Cirsium performed better using nitrate than when using ammonium as a sole nitrogen source, whereas ammonium toxicity became apparent when ammonium concentrations were raised above 100 µM. Ammonium toxicity was expressed by an increase in mortality of Arnica plants with increasing ammonium concentrations and by a reduction of biomass in Arnica and Cirsium. Furthermore, cation concentrations in both roots and shoots decreased when ammonium was supplied as a nitrogen source. In contrast, Calluna showed optimal development when using ammonium as a sole nitrogen source. In this species, only root biomass was negatively affected by high ammonium concentrations. The ecological implications of these preferences are discussed in relation to soil acidification.
1. The catchments of three acidified streams in mid Wales were limed in 1987/88. Here we assess their chemical and biological response in comparison with unmanipulated reference streams over a period of 5 years post-liming.
2. Stream chemistry was measured weekly/fortnightly between 1985 and 1992, while macroinvertebrates were sampled annually. Colonization by acid-sensitive taxa was assessed and trends in community structure were monitored by TWINSPAN. Real biological responses were compared with those predicted by an empirical model constructed using chemical data.
3. There were marked changes in stream chemistry following liming: calcium concentrations and pH values increased, while aluminium concentrations decreased to levels similar to those in naturally circumneutral streams. These conditions have persisted since liming.
4. Empirical models predicted that stream invertebrates would respond to the altered stream chemistry, with the establishment of communities typical of circumneutral conditions.
5. Following liming, the taxon richness and abundance of acid-sensitive taxa was significantly higher in limed compared with reference streams. Colonization by, and persistence of acid-sensitive taxa was patchy, however, and richness was still substantially lower than in naturally circumneutral streams. Moreover, contrary to the model predictions, there were no wholesale changes in the structure of macroinvertebrate communities.
6. We conclude that liming has created and maintained chemical conditions suitable for macroinvertebrate communities typical of circumneutral streams, but these chemical changes have not been matched by sustained responses among the biota. The views expressed in this article are those of the authors and do not necessarily reflect those of the NRA.
The effects of increased atmospheric nitrogen inputs, from both NO y and NH x, on diversity in various semi‐natural and natural ecosystems are reviewed. The severity of these impacts depends on abiotic conditions (e.g. buffering capacity, soil nutrient status and soil factors that influence the nitrification potential and nitrogen immobilization rate) in the particular system. The sensitivity of fresh water ecosystems, wetlands and bogs, species‐rich grasslands, heathlands and field layer of forests, all of which have conservational value, are discussed in detail.
The most important effects of nitrogen deposition are: (i) accumulation of nitrogenous compounds resulting in enhanced availability of nitrate or ammonium; (ii) soil‐mediated effects of acidification; and (iii) increased susceptibility to secondary stress factors.
Long‐term nitrogen enrichment has gradually increased the availability of nitrogen in several vegetation types, leading to competitive exclusion of characteristic species by more nitrophilic plants, especially under oligo‐ to mesotrophic soil conditions.
Soil acidification (with losses of buffering capacity and increased concentrations of toxic metals) is especially important after nitrification of ammonium in weakly buffered environments: acid‐resistant plant species then become dominant at the expense of the often rare plants typical of intermediate pH. The related change in the balance between ammonium and nitrate may also affect the performance of several species.
The susceptibility of plant species to secondary stress factors (pathogens; frost and drought) may be affected by air‐borne nitrogen but data are only available for a few communities (e.g. dry heathlands).
Most global biodiversity is contained within natural and semi‐natural vegetation. It is thus crucial to control emissions of nitrogenous compounds to the atmosphere, in order to reduce or prevent effects on diversity in these systems. Most research has focused on acidification in forestry stands and lakes and on the effects on trees. We highlight serious gaps in knowledge of other ecosystems.
The effects of sod cutting, a common restoration measure to remove excess nutrients from grass-dominated heathlands, on nitrification were studied in dry and wet Dutch heathlands and in incubation experiments. In the field, soil ammonium and nitrate concentrations were measured after treatment by sod cutting, with or without additional liming. Potential net nitrification was measured by incubating soil samples of all treatments with extra ammonium in a climate chamber at pH 6. Potential net nitrification of heaths dominated by Molinia caerulea was significantly higher than that of dwarf-shrub dominated heaths. Sod cutting of the former areas significantly decreased potential net nitrification, whereas in the latter areas no differences were found. Liming of sod-cut soils greatly increased potential net nitrification and the accumulation of ammonium in the soil up to toxic concentrations could be prevented. Our results show that the combination of sod cutting and liming would create suitable soil conditions for the germination and establishment of endangered plant species of dry and wet heathlands. The success of restoration projects of these areas can thus be increased.
A 38 ha near-barren experimental catchment area near an abandoned Cu and Ni smelter in Sudbury, Canada was treated with 410 tons of coarse dolomitic limestone in 1994. An additional 54 tons of pelletized fine dolomite were added to 15 wetlands within the experimental catchment in 1995. The treatments significantly increased the pH and base cation concentrations in the outlet stream. Cu and Ni concentrations initially rose after the wetland treatment, but then declined to levels below those of the reference site. Bioassay tests revealed that the toxicity of the drainage water was greatly reduced by the liming, but some localized inputs of highly toxic groundwater still posed a problem for aquatic biota. The pH of surface water in the wetlands has been maintained at >6.0 for over 4 years. The wetland liming appeared to be highly effective at neutralizing drainage water, however there may be some adverse effects on wetland plant communities as a consequence.
Soft water lakes possess a highly characteristic vegetation adapted to limitation of carbon. Based upon hydrology, vegetation and geographic distribution, boreal and Atlantic lake types can be distinguished. Reducing the input of nutrients or liming, or both, the stream or its catchment is generally sufficient to restore typical soft water vegetation of boreal soft water lakes. The vegetation of Atlantic soft water lakes is subject to many anthropogenic degradation processes. Therefore, spontaneous recovery in the near future is not expected and restoration is urgently required. Removal of nutrient-rich, anoxic, organic sediments is a prerequisite for restoration of these lakes. In acidified or acid-sensitive lakes, additional measures against acidification are required. Controlled supply of calcareous, nutrient-poor water is much better than direct liming. The effects of these restoration measures strongly depend on the detrimental effects of processes such as atmospheric deposition, drainage, catchment acidification, eutrophication and reduced colonisation rates.
Increased atmospheric nitrogen deposition and changes in the management of heathlands have caused a significant change in the species composition of the NW-European heathlands. This change from ericaceous towards gramineous dominance is analysed in detail in Heathlands: Patterns and Processes in a Changing Environment. Special emphasis is put on the effects of increased atmospheric nutrient input on nutrient cycling, competition between plant species and plant--herbivore interactions. The possibilities for the long-term conservation of heathlands are discussed by considering regeneration from seed and the usefulness of mathematical management models.
The book provides a synthesis of pure and applied plant ecology. It is vital reading for plant ecologists, biological conservationists, heathland managers and government decision makers.
We shall, in this last chapter, treat the floristic-sociological or Braun-Blanquet approach to classification and interpretation of communities.
Throughout western Europe heathlands dominated by ericaceous subshrubs occur on poor soils. Mostly, these heaths have developed and have been maintained by human activities. Traditional management has perpetuated ecosystems of a low nutrient status in which plant succession is arrested. Traditional management has involved a complex interaction between grazing, arable cultivation and the use of turf and plant material from the heaths. This basic system occurs throughout the European heathlands but with local variants. This paper reviews and compares the various systems of heathland use and management with the aim of developing new methods to maintain these cultural landscapes.
On the basis of a field experiment in Norway spruce with acid irrigation and compensatory liming of the soil surface (Höglwald, S-Bavaria), liming effects are described as lime dissolution rate, transformation of carbonate buffer to exchange buffer, time required for deacidification of soil and drainage water, mobilization of Cu and Pb, changes in soil organisms, humus decomposition, and nitrogen turnover. It was shown that lime dissolution followed an exponentially decreasing curve. 4 t ha-1 dolomitic lime were dissolved within 6 years. Additional acid irrigation of 4 kmol H+ ha-1 yr-1 as sulphuric acid speeded up the lime dissolution to about 4 years. After dissolution of lime about 70% of Ca and about 30% of Mg, both originating from lime dissolution, are retained in the surface humus layer, loading the exchange buffer capacity there. Liming acted as a protection against acid irrigation but the extension of soil deacidification downwards proceeded slowly due to the high base neutralizing capacity of protonated functional groups of the organic matter. The main depth effect is caused by Mg translocation. A significant increase of organic Cu complexes occurred due to mobilization of water soluble humus decomposition products. The effect of liming on litter decomposing organisms is demonstrated with microorganisms, collembolae and earthworms regarding the abundance and the structure of dominance. It was shown that liming may induce unusually large changes in biocenoses of forest soils. The decay of surface humus accounted for 7.2 t ha-1 or 23% of the store within 7 years. Within the same time span, liming caused a loss of about 170 kg N ha-1 or 14% of the store of the surface humus layer. The nitrate concentration in the drainage water thus increased by about 50 to 60 mg NO3 - L-1. Site-specific conditions are discussed, which produce such negative liming effects as increased nitrate concentration of seepage, humus decay and heavy metal mobilization. Redistribution of tree roots, induction of boron deficiency and root rot are also considered. It is indicated that liming may aggravate the increasing problem of nitrate contamination of forest ground water resources which is associated with deposition of atmogenous nitrogen compounds. Some recommendations are given regarding forest practice.
After acidification of shallow softwater lakes as a consequence of atmospheric sulphur and nitrogen deposition, the concentrations of nitrogen and carbon dioxide in the water layer are raised and the cation reserves in the sediment are depleted. Liming can counteract acidification, but can also lead to further nutrient mobilisation. Controlled supply of calcareous groundwater is an alternative method to restore the pH and alkalinity of the water layer. Sediment removal and subsequent restoration of pH leads to a reversal of the nutrient status towards pre-acidification levels. However, rapid re-acidification may occur as a consequence of supplying water from the catchment which is acid and rich in nitrogen. After three years of repeated groundwater supply, the base saturation of the sediment was higher than that of adjacent reference lakes where the sediment had been removed simultaneously. This base saturation is possibly a key factor in the prevention of re-acidification. During a five-year period after the start of groundwater supply, CO2 and nitrogen concentrations in the water layer decreased and were not higher compared to adjacent reference lakes. Characteristic softwater macrophytes returned, but not in the reference lakes.
Germination experiments were conducted in a heathland after turf cutting and in a climate chamber to investigate the effects of turf cutting depth, aluminium toxicity and aluminium detoxification by humic acids and base cations on the germination and establishment of Arnica montana. Turfs were cut at three different depths, creating a gradient from organic to mineral soils. Germination and establishment of A. montana were negatively correlated with turf cutting depth. The removal of organic matter resulted in a major decrease in organic fraction of the soil and its nutrients. It also resulted in a considerable decrease in moisture content and humic acids. Additional liming after turf cutting increased germination and establishment in all plots and at all depths.
Germination experiments under controlled conditions in a climate chamber revealed a significantly higher germination at low aluminium/calcium (Al:Ca) ratios. High Al:Ca ratios resulted in poor germination, suggesting Al toxicity. Addition of humic acids increased germination, even at high Al:Ca ratios, suggesting immobilization of Al by humic acids.
It is concluded that turf cutting can have a marked effect on the success of heathland restoration. It results in the intended removal of the eutrophic layer but also in the unintentional removal of much of the buffering mechanisms and/or Al immobilizing compounds. Additional buffering and/or less deep turf cutting may be necessary to allow germination and establishment of rare herbaceous species such as A. montana.
Lowland heaths are high-profile ecosystems for conservation action in Britain, but many areas have been invaded by successional species. Management to restore heathland on successional sites provides an opportunity to remove nutrients from part of the system and helps maintain the low soil nutrient levels typical of heathland. Estimates were made of the nutrients removed during management on successional sites dominated by Betula spp., Pinus sylvestris, Pteridium aquilinum, Rhododendron ponticum and Ulex europaeus in Dorset. When both the above ground biomass and litter are removed between 12–45 kg P ha−1, 561–2661 kg N ha−1 and 157–776 Ca ha−1 are removed, depending on the successional species. Results are also provided for Mg, K and Na. For Ca, Mg and N the nutrients removed are equivalent to between 41 and 197 years of atmospheric inputs, for P it may be as much as several thousand. Equations are provided to enable predictions of nutrient offtake on other sites to be made. The importance of nutrient removal in relation to heathland re-establishment, successional change, the effects of atmospheric nitrogen deposition and habitat management requirements are discussed.
Isoetes-Lobelia clear water lakes in an ultraoligotrophic area of south-western Norway were studied. Most lakes in the area are acidified, with a vegetation dominated by small isoetids such as Lobelia dortmanna L., Littorella uniflora (L.) Aschers. and Isoetes lacustris L. After liming, however, dense stands of Juncus bulbosus L. often have developed, filling up the water layer completely at relatively shallow sites and resulting in suppression of the original vegetation.In this study a comparison is made between plant growth and physical and chemical properties of water and sediment pore water in six limed and five non limed ‘reference’ lakes. It appears that liming leads to a strong increase in CO2 production and mobilisation of nitrogen, phosphorus and iron in the sediment. Probably as a result of the high mobilisation of iron and the increased iron cycle no increased levels of phosphate in the water layer occur.As a result the waters are still very clear after liming. The rooted macrophyte Juncus bulbosus can benefit from this situation, as it is able to take up nutrients from the sediment pore water by its roots. It is discussed that the success of Juncus bulbosus is not only caused by the increased carbon dioxide, phosphate and nitrogen levels in the sediment pore water (internal eutrophication), but also by the fact that the sediment becomes anoxic, leading to a decrease in nitrate concentrations and a very strong increase in ammonium levels. It is known from experimental studies that Juncus bulbosus can only reach a very high biomass at high carbon dioxide levels in combination with high ammonium concentrations.
As a result of air pollution, considerable deposition of ammonium sulphate occurs on vegetation and soil in the vicinity of chicken farms and fields dressed with animal slurry. A clear relation exists between this ammonium sulphate deposition and the distance to certain agricultural activities. Field investigations and ecophysiological experiments both show that the needles ofPinus nigra var.maritima (Ait.) Melville take up ammonium and excrete potassium, magnesium and calcium. This often results in potassium and/or magnesium deficiencies and may lead to premature shedding of needles. The high levels of nitrogen in the needles are strongly correlated to fungal diseases.
Whether the observed cation leaching will result in disturbed nutrient budgets depends mainly on soil conditions. Leaching of K, Mg and Ca from the soil, caused by ammonium sulphate, may further inhibit nutrient uptake.
Field investigations show a clear correlation between increased ratios of NH4 to K, Mg and Ca in the soil solution and the damage to pine forests.
The effects of liming on soft-water aquatic macrophytes are reviewed, based on data from the many limed lakes and rivers in Sweden and Norway. Liming usually leads to a re-establishment of acidification-sensitive species such as Fontinalis spp., Myriophyllum alterniflorum and Potamogeton spp. Most sensitive species have a critical level at pH ca. 5.5, and are believed to depend on availability of HCO3− in the water. Some more or less acidophilic bryophytes, Nardia compressa and Sphagnum auriculatum coll. have declined, and usually die when directly exposed to lime deposits. Submerged Sphagnum mats have, however, in some cases increased temporarily after liming, probably due to an increased production of CO2. The graminoid Juncus bulbosus (=J. supinus) showed a temporary massive expansion and nuisance growth in (over)limed lakes in SW Norway in the beginning of the 1990s. This extreme growth is explained by a combination of: (i) lime deposits on the sediments leading to mobilisation of CO2 and NH4; and (ii) re-acidification of the water layer, promoting high levels of CO2. In some lakes that have been limed for more than 10 years, M. alterniflorum has expanded considerably, reaching densities probably much higher than in the pre-acidification conditions. This situation is believed to be due to increased alkalinity and possibly due to eutrophication of the sediment.
Limestone neutralization of the acidic water of Dog-way Fork in West Virginia resulted in significant improvements in both water quality and fish populations. Pretreatment water chemistry showed the stream to be highly acidified by acid precipitation, with pH under 5.0 and high aluminum concentrations. During treatment, the goals for the target area of pH 6.5 and acid-neutralizing capacity of 50 μmeq/L were met for 75.8% and 67% of the time, respectively. A pH 6.0 or above was maintained over 93% of the time. Monomeric aluminum concentrations were reduced significantly, and calcium to hydrogen ionic ratios were over 10 in the target area. Prior to treatment, no resident fish population was found in Dogway Fork. During five years of treatment, conditions were favorable for fish reproduction and survival. Eight fish species inhabited the stream, six were reproducing there, and a fishable brook trout population was established.
Laurel Branch (Tennessee, U.S.A.), an acid-sensitive stream in the southern Appalachian Mountains, was limed as a part of the Acid Precipitation Mitigation Program funded by the U.S. Fish and Wildlife Service. Objectives were (1) to evaluate the effectiveness of stream liming by means of a hydropowered doser design, and (2) to monitor stream response(s) to increased pH and alkalinity. Precipitation in the region was documented to be acidic, with a mean pH of 4.54 in 1987. Preliming evaluations conducted from 1986 through 1988 depicted Laurel Branch as soft (hardness less than 5 mg/L CaCO3, pH 6.2–6.6), dilute (ionic strength less than 400 μeq/L), and lightly buffered (alkalinity less than 100 μeq/L). Because of the apparent relationship between flow and water chemistry, Laurel Branch was considered susceptible to episodic acidification caused by storms. In June 1989, a hydro–powered limestone doser was installed to treat the lower 3 km of the stream. Approximately 8.2 tonnes of crushed limestone were added during an 18–month treatment phase that concluded in December 1990. Technical and design problems with the doser reduced efficiency and limited the scale of liming through much of the first 6 months of operation. Design modifications and equipment upgrades in late 1989 corrected most of the problems and improved doser performance in 1990. No substantial chemical or biological changes were detected within the treated reach of Laurel Branch as a result of liming. Time–series statistical analyses showed small but significant changes in total alkalinity (10 μeq/L average increase) and dissolved calcium at all limed sites. pH (as hydrogen ion) increased 0.16 and 0.13 units at two limed sites that were 1 km and 2 km below the doser, respectively. At the lowermost limed site 3 km below the doser, a significant decrease in pH was detected which was probably flow-related. Mean length of age–0 (juvenile) and age-1 rainbow trout increased marginally during liming, suggesting improved fish growth, but increases were not significant. Densities of an acid-sensitive macrobenthic taxon (Baetis spp.) increased during liming, whereas densities of an acid-tolerant taxon (Leuctra spp.) remained unchanged. In general, observed biological changes were considered minimal; they were judged unrelated to liming but rather of seasonal and/or spatial origin. The regional drought of 1987 and 1988 was considered a confounding factor. With most of the baseline data collected during these years, vastly differing hydrology in 1989 and 1990 (“wet” years regionally) became problematic and may have distorted some responses and masked others. It is also possible that biological responses may have been delayed because of the small magnitude of chemical changes, particularly pH and alkalinity. A calcium mass budget estimated that up to 62% of the calcium added was accounted for in chemistry data from limed sites, with increases most visible in the spring and summer of 1990. Results indicated that, although the Laurel Branch watershed does receive acidic precipitation, current biological communities show high levels of integrity and little apparent degradation related to acidification. If watershed buffering capabilities are depleted from continued acidic deposition, however, stream biota may be at risk in the future.
Thrush Lake, Minnesota, was treated with limestone in 1988 to evaluate the efficacy of protective base addition against the loss of sport fisheries in a sensitive, mildly acidic lake. Prior to treatment, the lake was stressed (pH 6.46, ANC 64 μeq/L) but not severely degraded by acidic deposition and had a macrophyte community typical of lakes in northeastern Minnesota with low acid-neutralizing capacity (ANC). This paper describes the changes observed in aquatic plant communities during the 5 years after treatment, as pH and ANC slowly returned to pretreatment levels. Sphagnum platyphyllum, intolerant of non-acid conditions, was completely eliminated from the lake. The charo-phyte, Nitella, that originally shared dominance in the deep littoral zone with S. platyphyllum, decreased in importance during the first 2 years after treatment. Two vascular plants, Potamogeton pusillus and Najas flexilis, were first found in the lake the year after treatment and were abundant for 2 years after liming, probably in response to a combination of more neutral pH and reduced cover of Nitella. As the ANC and pH slowly returned to pretreatment conditions, Nitella again increased in coverage and depth range, with a concomitant decrease in P. pusillus and N. flexilis. The moss, S. platyphyllum, had not reinvaded the lake by 1993, 2 years after its dramatic decline.
Whetstone Brook is a trout stream located in north-central Massachusetts that is degraded by acid precipitation. The stream was treated with 56 tonnes of powdered limestone by a prototype, water-powered doser as part of the U.S. Fish and Wildlife Service's Acid Precipitation Mitigation Program. The goal of liming Whetstone Brook was to raise the pH to 6.5 and acid neutralizing capacity (ANC) to at least 50 μeq/1 in a 3.2-km reach. This goal was achieved despite the fact that during the 31 months of treatment stream flow was 37% higher than during the pretreatment period. During the treatment period, pH averaged 6.54 and ANC averaged 69.75. During the pretreatment period average pH was 5.97 and average ANC was 20.26. In the control section of Whetstone Brook, both pH and ANC were lower during the treatment period than during the pretreatment period. During treatment, monomeric aluminum, a form toxic to fish, declined in the treated section and increased in the control section. Total calcium, sediment calcium, and pore-water calcium increased in the treated section during treatment but declined in the control section. The other base anions and cations, nutrients, and physical parameters were not significantly affected by liming.
Restoration of formerly species‐rich wet heaths and matgrass swards has not always been successful. The constraints on this restoration process are not yet fully understood and need further investigation, particularly the accumulation of ammonium in the soil after sod cutting, i.e. the removal of the vegetation and topsoil layer. This accumulation is known from sod cutting experiments in dry heaths, but had not previously been studied in wet heaths and matgrass ecosystems.
In 2000, sods were cut from two degraded Dutch wet heaths. Soil chemistry and germination in the sod‐cut plots were measured at irregular intervals between April 2000 and August 2001. To test the influence of ammonium on germination and survival, a glasshouse dose–response experiment was conducted with two endangered wet heath plant species.
In both wet heaths, an accumulation of KCl‐extractable ammonium up to 600 µmol kg ⁻¹ dry soil was found in the upper 10 cm of the soil within the first year after sod cutting. These high ammonium concentrations lasted for about 10 months. Germination was very low in the sod‐cut plots in 2000 and 2001, and few target species were found, although they were present in the vicinity.
The dose–response experiment indicated a significant, negative correlation of both germination and survival with increasing ammonium addition for both plant species. Mean soil ammonium concentrations of the control, 100 and 250 µ m ammonium treatments were significantly lower than those of the 500 and 1000 µ m ammonium treatments (47, 45, 70, 144 and 252 µmol kg ⁻¹ dry soil, respectively).
Maximum concentrations of KCl‐extractable ammonium in the field corresponded to water‐extractable concentrations that were higher than those found to be limiting germination and growth in the glasshouse experiments. The low germination in the field is likely to have been adversely affected by high concentrations of ammonium as a result of sod cutting.
Synthesis and applications . High ammonium concentrations occur in wet heaths following sod cutting. Low rates of germination of restoration target plant species occur under such conditions. To increase the success of wet heath restoration, the accumulation of ammonium after sod cutting should be prevented by additional measures, such as liming. Because sod cutting is also applied as a restoration measure in the restoration of other ecosystems, such as fens, the effects on increased soil ammonium concentrations need further attention.
Habitat fragmentation as a result of intensification of agricultural practices decreases the population size and increases the site productivity of remnant populations of many plant species native to nutrient‐poor, species‐rich grasslands. Little is known about how this affects the colonization capacity of populations, which is highly important for regional species survival. We studied the effects on four wind‐dispersed forbs that represent two major dispersal strategies in grasslands: Cirsium dissectum and Hypochaeris radicata , which have plumed seeds and are adapted to long‐distance dispersal by wind, and Centaurea jacea and Succisa pratensis , which have plumeless seeds and are adapted to only short‐distance dispersal by wind.
Colonization capacity decreased with decreasing population size. This was due to lower seed germination ability in all species, and a lower seed production and a narrower range of seed dispersal distances in the species with plumed seeds. Inbreeding depression is the most likely cause of this. We found no evidence for a stronger selection for reduced dispersal in smaller populations.
Increasing site productivity changed the colonization capacity of all species. The capacity for colonization of nearby sites increased, due to higher seed production and seed germination ability, but the capacity for colonization of distant sites decreased, due to a lower long‐distance dispersal ability.
Seed dispersal ability and germination ability were negatively correlated in the species with plumeless seeds, but not in the species with plumed seeds. The dispersal ability of individual plumed seeds remained constant under changes in population size and site productivity. This indicates a strong selection pressure for long‐distance dispersal ability in these species.
When habitat fragmentation results in a simultaneous decrease in population size and increase in site productivity, both the local survival probability and the colonization capacity of remnant populations of wind‐dispersed grassland forbs are likely to be severely reduced. This increases regional extinction risks of the species.
The Experimental Watershed Liming Study (EWLS) evaluated the application of CaCO3, to a forested watershed to mitigate the acidification of surface water. During October 1989, 6.9 Mg CaCC3/ha was applied by helicopter to two subcatchments of about 50% (102.5 ha) of the Woods Lake watershed area. The EWLS team investigated the response to treatment of soils (chemistry and microbial processes), vegetation, wetland, stream and lake waters, and phytoplankton and fish, and applied the Integrated Lake Watershed Acidification (ILWAS) model in predicting a watershed treatment duration of up to 50 years. Observations showed a gradual change in pH, acid neutralizing capacity (ANC) and Ca2+ in the water column; direct lake additions of CaCO3 (three different times) were characterized by abrupt changes following base addition and subsequent rapid reacidification. Moreover, the watershed treatment eliminated the snowmelt acidification of the near-shore region of the lake observed during direct lake treatments. Positive ANC water in the tributary and near-shore area improved conditions for fish reproduction and for a viable fish population. Budgets for 12-month periods before and after the watershed treatment showed that the lake shifted from a source of ANC to a sink due to retention of elevated inputs of Ca2+ from the watershed CaCO3 application.
The Swedish liming programme was initiated in 1977 to counteract the effects of anthropogenic acidification on aquatic ecosystems until the acid deposition has been reduced. Ecosystem development in limed waters has been followed since 1989 in a programme for integrated studies of the effects of liming acidified waters (ISELAW). The main objectives are to assess a) the long-term ecological effects of liming, b) to what extent ecosystems recover to a pre-acidification state, and c) to elucidate possible detrimental effects of lime treatment. The programme comprises monitoring of water chemistry, phyto- and zooplankton, vegetation, benthic invertebrates and fish in 13 limed and 5 non-limed lakes, and 12 limed and 10 non-limed streams. Paleolimnological studies are performed to reveal pre-acidification lake history. The results show that lime treatment detoxifies the water, although chemical and biological development varies among and within sites. In general the long-term changes are small compared to the initial changes associated with first treatment. Water chemical changes over time are reflected as reduced sulfur concentrations and increased nitrogen concentrations. Treated ecosystems seem not to recover fully to the situation before acidification, and due to re-colonization failure, several species are lacking in the limed waters.
In June 1983 a whole-catchment liming experiment was conducted at Tjønnstrond, southernmost Norway, to test the utility of terrestrial liming as a technique to restore fish populations in remote lakes with short water-retention times. Tjønnstrond consists of 2 small ponds of 3.0 and 1.5 ha in area which drain a 25-ha catchment. The area is located at about 650–700 meters above sea-level in sparse and unproductive forests of spruce, pine and birch with abundant peatlands. A dose of 3 ton/ha of powdered limestone were spread by helicopter to the terrestrial area. No limestone was added to the ponds themselves. The ponds were subsequently stocked with brown and brook trout.
Liming caused large and immediate changes in surface water chemistry; pH increased from 4.5 to 7.0, Ca increased from 40 to 200μeq/L, ANC increased from −30 to +70μeq/L, and reactive-Al decreased from about 10 to 3μmol/L. During the subsequent 11 years the chemical composition of runoff has decreased gradually back towards the acidic pre-treatment situation. The major trends in concentrations of runoff Ca, ANC, pH, Al and NO3 in runoff are all well simulated by the acidification model MAGIC. Neither the measured data nor the MAGIC simulations indicate significant changes in any other major ion as a result of liming.
The soils at Tjønnstrond in 1992 contained significantly higher amounts of exchangeable Ca relative to those at the untreated reference catchment Storgama. In 1992 about 75% of the added Ca remains in the soil as exchangeable Ca, 15% has been lost in runoff, and 10% is unaccounted for.
The whole-catchment liming experiment at Tjønnstrond clearly demonstrates that this liming technique produces a long-term stable and favourable water quality for fish. Brown trout in both ponds in 1994 have good condition factors, which indicate that the fish are not stressed by marginal water quality due to re-acidification. The water quality is still adequate after 11 years and >20 water renewals. Concentrations of H+ and inorganic Al have gradually increased and approach levels toxic to trout, but the toxicity of these are offset by the continued elevated Ca concentrations. Reduced sulphate deposition during the last 4 years (1990–94) has also helped to slow and even reverse the rate of reacidification. The experiment at Tjønnstrond demonstrates that for this type of upland, remote terrain typical of large areas of southern Norway, terrestrial liming offers a suitable mitigation technique for treating acidified surface waters with short retention times.
Operational liming of surface waters is part of Sweden and Norway's strategy to counteract freshwater acidification caused by air pollutants. Smaller scale liming efforts are performed as research or experimental programs in other countries. Yearly, approx. 300,000 tons of fine-grained limestone (CaCO3) is spread in lakes and streams and on wetlands to raise the pH in surface water at a cost of approximately 40–50 million $US. The chemical target is set by the biological goals and objectives. A total of over 11,000 lakes and streams are treated on a continuing basis. Dose calculations consider pH, inorganic monomeric Al, dissolved organic matter and the necessary buffering. Lake liming, limedosers at streams and terrestrial liming are used. A mix of different liming techniques is often preferred to get an optimal result. The vast majority of changes are desirable and expected Undesirable effects may appear and damaged wetlands are probably the most serious ones. Cost-benefit analysis show that liming may be profitable for the society. Recovery of the systems can take up to 10–20 years. Liming will in the long run restore the ecosystems but will not make them identical to what may be the original ones. In some cases, complementary measures, e.g. facilitation of recolonization, are necessary to enhance recovery. Reduced emissions of acidifying pollutants according to signed protocols will decrease the need for liming, but still liming is needed for several decades in large regions to preserve biodiversity.
Acidification of surface waters and forest soils is severe in large parts of southern Sweden. The shallow groundwaters are also affected. Large scale liming of surface waters and streams is in operation, often combined with wetland liming to limit the effects of acid episodes, e.g. at snow melt. Acid episodes are perhaps the most severe problem in limed surface waters and in many as yet well buffered waters, because of temperature-layered acid inflow, often superficial. As a result of some investigations, a large scale forest liming programme covering 6.500–10.000 km2 was recently suggested. The main objectives of this forest liming programme are to retard cation depletion and to prevent nutrient imbalance and forest decline in acidified areas. This paper deals with the effects of forest soil liming on streams and surface waters. The response of water chemistry is very dependent on hydrological and soil properties. Although pH itself may be little affected by liming, the acidity (or negative ANC) decreases, inorganic Al-species decrease and the Al/BC-ratio increases in the runoff water. Especially interesting is that this is also true during acid episodes. This means that toxicity for acid sensitive biota decreases. These results indicate that large scale liming may have beneficial effects on surface water chemistry. Furthermore, as surface waters are expected to respond to smaller decreases in acid deposition than do forests soils, forest soil liming may allow less frequent liming of lakes. Consequently, forest soil liming in combination with the anticipated emission reductions may have very beneficial results on surface waters in certain areas of Sweden.
The wet heathland communities of the Ericetum tetralicis and the Cirsio-Molinietum have declined in the Netherlands due to acidification, eutrophication and lowering of the water table. To investigate the prospects of restoration of both communities, the effects of sod cutting and hydrological measures on vegetation and soil chemistry were studied in two nature reserves where these plant communities occurred decades ago. The combination of sod cutting and hydrological measures has restored several rare, groundwater dependent heathland communities. Sod cutting has restored the Ericetum tetralicis, but not the Cirsio-Molinietum. This might be due to the absence of viable seeds of characteristic species of the Cirsio-Molinietum and/or the absence of optimal site conditions, especially high phosphorus concentrations in the top soil. The high phosphorus concentrations might be a consequence of high mineralization rates and/or prolonged inundation with iron-poor water and the decreased flux of iron-rich groundwater into the topsoil. Restoration of the Cirsio-Molinietum only seems possible when sod cutting is carried out together with hydrological measures that counter prolonged inundation and reinforce the discharge of base and iron-rich groundwater.
Critical loads of sulphur and nitrogen are exceeded in South Sweden, and nutritional imbalances are expected to appear with time in forests. During 1984 paired catchments were established in a northwestern-southeastern gradient in South Sweden. The aim was to study long-term liming effects on throughfall, soil water, groundwater and runoff. Dolomitic limestone and wood ash were tested at one locality, Hagfors (59 N).Three adjacent catchments were used; one reference area, one treated with dolomitic lime (0.5 kg/m2) in 1985, and one with wood fly ash (0.22 kg/m2) in 1988. The lime and the fly ash was granulated and applied by a helicopter in the end of May. Measurements concerning chemistry of the precipitation, throughfall, soil water and runoff has been conducted since spring 1984.The results showed that top-soil spreading of liming agents, besides the desired effects on soil chemistry, after some years also affected the quality of the recipient water. In the dolomitic lime treated catchment the positive effects were most obvious, with raised pH-, Ca-, and Mg-values and lowered Al-, Fe- and Mn-values. A positive trend regarding lower nitrogen (NO3
–) leaching could also be calculated. Wood ash in the used amount affected only slowly, but after six years the runoff water indicated increased pH-values as well as increased Ca- and K-values and Ca/Al-ratios. Dolomitic lime in the amounts of 0.5 kg/m2 was concluded to be sufficient to achieve positive effects in catchments of the present type. Wood ash in the amount of 0.22 kg/m2 although enough for recycling purposes, was not sufficient enough in increasing pH in runoff to prevent acid leaching from the forest soils.
Long-term monitoring, 1973 to 1987, of reactions to liming and reacidification of a forest lake ecosystem near the Swedish west coast is reported in this study. Treatment of Lake Lysevatten with a slag product of limestone in 1974 resulted in neutralization and a positive alkalinity. Prolonged dissolution proceeded for about 7 yr whereby 86% dissolved. During 1984–86 Lake Lysevatten approached maximum reacidification with high Al concentrations and an affected biota. Asellus aquaticus L. decreased and dominance within chironomid groups approached preliming conditions. However, the most obvious biological change was the development of the filamentous algal genus Mougeotia and increased growth of Sphagnum. Populations of both plants increased notably when pH declined to about 5. Our study suggests that extensive reacidification (pH < 6.0)="" of="" limed="" lakes="" should="" be="" avoided="" by="" successive="" treatments="" to="" prevent="" development="" of="" destabilized="" lake="">
On the basis of a field experiment in Norway spruce with acid irrigation and compensatory liming of the soil surface (Hglwald, S-Bavaria), liming effects are described as lime dissolution rate, transformation of carbonate buffer to exchange buffer, time required for deacidification of soil and drainage water, mobilization of Cu and Pb, changes in soil organisms, humus decomposition, and nitrogen turnover. It was shown that lime dissolution followed an exponentially decreasing curve. 4 t ha-1 dolomitic lime were dissolved within 6 years. Additional acid irrigation of 4 kmol H+ ha-1 yr-1 as sulphuric acid speeded up the lime dissolution to about 4 years. After dissolution of lime about 70% of Ca and about 30% of Mg, both originating from lime dissolution, are retained in the surface humus layer, loading the exchange buffer capacity there. Liming acted as a protection against acid irrigation but the extension of soil deacidification downwards proceeded slowly due to the high base neutralizing capacity of protonated functional groups of the organic matter. The main depth effect is caused by Mg translocation. A significant increase of organic Cu complexes occurred due to mobilization of water soluble humus decomposition products. The effect of liming on litter decomposing organisms is demonstrated with microorganisms, collembolae and earthworms regarding the abundance and the structure of dominance. It was shown that liming may induce unusually large changes in biocenoses of forest soils. The decay of surface humus accounted for 7.2 t ha-1 or 23% of the store within 7 years. Within the same time span, liming caused a loss of about 170 kg N ha-1 or 14% of the store of the surface humus layer. The nitrate concentration in the drainage water thus increased by about 50 to 60 mg NO3
- L-1. Site-specific conditions are discussed, which produce such negative liming effects as increased nitrate concentration of seepage, humus decay and heavy metal mobilization. Redistribution of tree roots, induction of boron deficiency and root rot are also considered. It is indicated that liming may aggravate the increasing problem of nitrate contamination of forest ground water resources which is associated with deposition of atmogenous nitrogen compounds. Some recommendations are given regarding forest practice.
Rapid expansion of Juncus bulbosus L. and the concomitant suppression of isoetid plant species has often been observed in acidifying soft water lakes in Western Europe. Experimental studies have shown that this mass development of J.bulbosus was caused by changes in the carbon and nitrogen budgets in these ecosystems. Acidification leads to temporarily strongly increased carbon dioxide (CO2) levels in the slightly calcareous sediment and to accumulation of ammonium as a result of a reduced nitrification rate in acidifying waters. Many acidifying Scandinavian soft water lakes, however, have a well developed macrophyte vegetation. It is suggested that this is related with the non-calcareous sediments of these lakes. After liming, however, mass development of J. bulbosus and/or Sphagnum spec. has been observed in Swedish and S.W. Norwegian lakes. From field experiments it has become clear that part of the lime is deposited on the sediments leading to an increase of mineralisation rates, CO2 production, sediment pore water levels of phosphate and ammonium and to a decrease of the nitrate concentrations in the sediment. These changes have been earlier observed in acidifying West European waters. Rooted species like J.bulbosus can only benefit from the higher nutrient levels in the sediment when the CO2 level of the water layer is relatively high as this species is adapted to leaf carbon uptake. It is demonstrated that gradual reacidification by the acid water from the catchments and the increased flux of carbonic acid from the limed sediments to the overlying water leads to increased CO2 levels in the water layer of the limed lakes already a few months after liming.
High atmospheric deposition of ammonium affects the physical and chemical status of the soil, increasing nitrogen availability, soil acidity and the mobilization of toxic metal ions. To investigate whether and how the decline of several herbaceous plant species in Dutch heathlands is associated with these processes, the chemical composition of the soil on which these species grow has been compared with the soil on which heathland species such asCalluna vulgaris (L.) Hull,Erica tetralix L. andMolinea caerulea (L.) Moench dominate.The discrimination between both soil types was primarily based on differences in pH (H2O), pH (NaCl) and the aluminium/calcium ratio in the waterextracts. Within the group of endangered herbaceous heathland species these soil parameters also varied. This led to a division into 4 groups of species:u
Dominating species growing on acid soils
Herbaceous species growing together with dominating species on acid soils
Herbaceous species growing together with dominating species on moderately acid soils
Herbaceous species growing together with dominating species on weakly acid soils.
This study indicated that, unlike the decline of heather species, the decline of herbaceous species is not likely to be due to increased competition from grass species as a result of eutrophication. Soil acidification and the changed mineral balance in the soil are most likely to be responsible for the decline of all three groups of herbaceous plant species. ei]R F Huettl
An acidified, 0.8 km2 coniferous-forested catchment was limed with 3 t ha−1 of coarse-grained dolomite powder in September 1994. The liming resulted in an immediate change in runoff water chemistry relative to the stream of an adjacent reference catchment. pH, calcium, magnesium and acid neutralising capacity (ANC) increased and inorganic Al decreased after liming. Potential favourable water quality for sensitive organisms remained relatively constant over the post-liming period (7 years), and model simulations indicate that adequate water quality may last for an additional 40–50 years. NO3 concentrations showed no significant change due to liming. A significant increasing trend in TOC was attributed to liming. Concentrations of Cd, Co, Fe, Mn, Ni and Zn were lower in the limed stream than in the reference stream during a period of 3 years after liming, whereas concentrations of As, Cu, and Pb were not significantly different. Steep slopes, thin soils, high amounts of precipitation and thus dominance of surface and subsurface flow in this catchment may explain the rapid response in runoff. During the first 6 years after liming there have been no significant effects on tree growth and vitality (crown density and crown colour). This experiment shows that liming of forested catchments may be a viable method to obtain long-term improvement in water quality and potential positive effects for acid-sensitive aquatic organisms.
The growth of J. bulbosus was investigated in a cultivation experiment with a two-way factorial design for liming and reacidification. The growth of J. bulbosus on limed sediment in a reacidified water layer clearly differed from the growth in the other treatments. Dry weight was approximately five times higher after a growth period of five months which was the result of more rapid shoot growth and a higher production of rosette-bearing segments. Enhanced growth of J. bulbosus corresponded with increased concentrations of ammonium in the sediment pore water and increased carbon dioxide concentrations in the water layer. It is concluded that J. bulbosus benefits from higher nutrient concentrations in limed sediment when the carbon dioxide concentration in the water layer is relatively high. This occurs after reacidification of the water layer when the bicarbonate–carbon dioxide equilibrium is shifted towards carbon dioxide. As regular liming leads to accumulation of calcium carbonate in the sediment, it is to be expected that enhanced growth of J. bulbosus will continue in reacidifying limed lakes in the future.
Softwater lakes possess a highly characteristic vegetation adapted to limited carbon availability. Based on hydrology, vegetation and geographic distribution, a boreal and an atlantic lake type can be distinguished. In general, boreal softwater lakes occur in remote areas where eutrophication is a local phenomenon and acidifying input is low. A number of these lakes are, however, very susceptible to eutrophication and acidification. Reducing the input of nutrients and/or liming the stream or catchment is generally sufficient to restore typical softwater vegetation. The vegetation of atlantic softwater lakes are subject to many anthropogenic degradation processes. Removal of nutrient-rich, anoxic, organic sediments is a prerequisite for restoration of these lakes. In acidified or acid-sensitive lakes, subsequent controlled inlet of calcareous, nutrient-poor water is more adequate than direct liming. The effects of these restoration measures strongly depend on interaction with processes, such as atmospheric deposition, drainage, catchment acidification, eutrophication and reduced colonisation rates.
The catchment is the smallest natural unit of the landscape that combines linked terrestrial and aquatic ecosystems. The fluxes of water and elements through the catchment link the various components of the system; biotic and abiotic, terrestrial and aquatic, plants and soils, atmosphere and vegetation, soils and waters. A large amount of empirical evidence now demonstrates that the impacts of natural and anthropogenic changes on the various components of catchment ecosystems are tightly connected.
With the recent appearances of a new and well-documented classification of the Dutch plant communities (Schaminee et al. 1995a,b; 1996) and a database on the seed longevity of plant species of North West Europe (Thompson et el. 1997a) it was possible to investigate patterns of seed longevity in Dutch plant communities, considering the frequencies of plant species in various communities. This study revealed that arable weed communities have long-lived seeds compared to the transient seed bank of deciduous woodland; species-rich grassland communities tend to have a short-lived soil seed bank, intermediate between the latter two communities. Moreover, the present study showed that significant differences in community longevity exist between weed communities as well as between grassland communities. The approach based on soil seed bank spectra of plant communities gives support to existing phytosociological theories on different strategies of plant communities sensu Stortelder (1992) and Schaminee and Stortelder (1996). The information on seed longevity of communities is essential to the practice of nature conservation and nature development because it reveals the possible vulnerability of plant communities to extinction, including their soil seed banks, the necessity of their conservation and their possibilities for regeneration.
Modeling and monitoring of acidification patterns in a limed forest catchment in the Ore Mountains, SE Germany are presented. A lumped-parameter model, MAGIC, satisfactorily reproduced the main parameters of stream water chemistry. Despite repeated whole-catchment liming, between 1993 and 1999 stream water pH increased from 4.3 to only 4.6, while calcium concentrations declined slightly. Stream water sulfate concentration declined from 687 to 396 microeq l(-1), and the pronounced effect of deposition decline during the 1990s was probably more important than liming.
Whole-catchment liming at Tjønnstrond, Norway: an 11-year record Restora-tion of heathlands in the Netherlands: the effects of turf-cut depth, aluminium and dissolved organic carbon on the germination of Arnica montana L
- Wright
- L J L Berg
- Ph
- J G M Vergeer
- Roelofs
Wright. 1997. Whole-catchment liming at Tjønnstrond, Norway: an 11-year record. Water, Air and Soil Pollution 94:163–180. van den Berg, L. J. L., Ph. Vergeer, and J. G. M. Roelofs. 2003. Restora-tion of heathlands in the Netherlands: the effects of turf-cut depth, aluminium and dissolved organic carbon on the germination of Arnica montana L. Applied Vegetation Science 6:117–124. van der Meijden, R. 2002. Heukel’s Flora van Nederland. Wolters-Noordhoff bv, Groningen, The Netherlands
The lowland heathland management handbook. English Nature
- C H Gimingham
Gimingham, C. H. 1992. The lowland heathland management handbook.
English Nature, Peterborough, United Kingdom.
Tho ¨rnelo ¨f Freshwater liming
- L Henrikson
- A Hindar
Henrikson, L., A. Hindar, and E. Tho ¨rnelo ¨f. 1995. Freshwater liming. Water, Air and Soil Pollution 85:131–142
The Braun-Blanquet Approach. Pages 287–378 in The Hague, The Netherlands
- V Westhoff
- E Van
Westhoff, V., and E. van der Maarel. 1978. The Braun-Blanquet
Approach. Pages 287–378 in R. H. Whittaker, editor. Classification
of plant communities. Dr. W. Junk bv Publishers, The Hague, The
Netherlands.