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Seed and vegetation dynamics in an alpine herb field: effects of disturbance type
Abstract
Examined a late seral herb field characterized by pocket gopher disturbance and an early seral gravel borrow that had been severely disturbed 35 yr ago on the Beartooth Plateau, Montana. The seed rain (filled seeds) on the borrow area ranged from 7730-14 009 seeds/m2 and was higher than that found on other alpine sites: that on the Geum turf ranged from 3375-6179 seeds/m2 and was similar to that for other alpine sites. Seed bank density ranged from 1980-6003 seeds/m2 on the borrow area and from 3202-4647 seeds/m2 on the Geum turf area. The Geum turf area had higher vegetation cover than the borrow area (87 vs. 25%) and higher numbers of species in the aboveground vegetation, seed rain, and seed bank. Medium-lived species, primarily grasses, with high production of small and compact seeds had colonized the borrow area. Some 35 yr after disturbance the medium-lived species still dominated the aboveground vegetation, seed rain, and seed bank. On the Geum turf area long-lived forbs that produced low numbers of relatively large seeds dominated the aboveground vegetation and persisted on the area primarily in the vegetative state. The same medium-lived species that dominated the borrow area had the highest abundance in the seed rain on the Geum turf area and appeared to persist by colonizing small-scale disturbances caused by gopher burrowing. Short-lived species with small, long-lived seeds existed on the site primarily through a highly persistent seed bank. -from Author
... In nitrogen-limited systems such as Niwot Ridge (Bowman et al., 1993;Bowman and Fisk, 20(1), low available soil nitrogen overall and lower concentrations in some disturbed areas may slow seedling establishment and colonization of disturbed sites. Chambers et al. (1990) and Chambers (1993) found that seedlings of alpine plants in low nitrogen environments grew more slowly than those in high nitrogen situations. Seedlings with shorter and/or smaller roots would be more susceptible to drought and to heaving by needle ice (Heidmann, 1976). ...
... Lack of seeds does not likely limit recovery in these communities. Moderate-sized seed banks exist in several Rocky Mountain alpine communi tics (Archibold, 1984;Chambers, 1993;Humphries. 1993). so seed banks probably exist under communities studied here. ...
... A 0.5-ha, 35-yr-old borrow pit had ca. 25% cover (Chambers, 1993), much more than expected on disturbances of similar size and age in the Front Range. Grasses, especially Deschampsia caespitosa and Trisetum spicatum, dominated many disturbed sites with a variety of soils and climates (Chambers et al., 1984). ...
Small plots (0.25 to 1.0 m²) denuded 13 and 31 yr previously were studied to investigate vegetation recovery at the alpine site of the Long-Term Ecological Research network. Recovery was slow, probably due to poor seedling survival. Covers of vascular plants and lichens were much lower on denuded plots than on controls except in late-melting snowbanks where natural disturbance by pocket gophers may have selected for disturbance-adapted species. Moister communities generally regained cover faster than drier communities. Vegetative expansion from plot edges provided most cover, although some colonizers originated from seed. Kobresia myosuroides, previously unknown to reproduce sexually in the Southern Rocky Mountains, occasionally colonized by seed. Essentially all vascular species acted as both colonizers and components of mature vegetation, and the vast majority of species are present in similar relative frequencies in control and disturbed plots. Previously studied alpine sites show either a similar lack of differentiation of early- and late-successional species or higher relative abundance of grasses in disturbed sites. In contrast to vegetation recovery in most temperate ecosystems, in these small plots on Niwot Ridge sequential replacement of species after disturbance does not occur.
... It was previously generalized that sexual reproduction is relatively unimportant in tundra environments compared to vegetative reproduction (Billings and Mooney, 1968;Bliss 1971;Savile, 1972;Grime, 1979;Bell and Bliss, 1980;Archibold, 1984). Although this opinion holds true relative to temperate environments, sexual reproduction within the tundra biome itself is important (McGraw, 1980;Chambers, 1995;Murray, 1987;Diemer and Prock, 1993;Murray, 1995), particularly in disturbed habitats (McGraw and Vavreck, 1989;Freedman etal, 1982;Chambers etal, 1990;Chambers, 1993;Chambers, 1995). Disturbed habitats tend to provide conditions that are relatively favourable for germination and seedling establishment of early successional species, presumably due to increased light levels, higher soil temperatures (McGraw and Vavreck, 1989;Chambers, 1995) and reduced competition (McGraw and Vavreck, 1989). ...
... Information regarding the seed bank and seed rain of a site provides an approximate record of the past and present above-ground vegetation community. Early successional or ruderal species are usually abundant in the soil seed bank, whereas late successional dominants are usually under-represented (Harper, 1977;Thompson and Grime, 1979;Freedman et al, 1982;Chambers, 1993;Chambers, 1995). Relatively few seed rain studies have been conducted in the context of succession. ...
... The result that the germinable seed bank was dominated by ruderal species (Luzula confusa and Papaver radicatum) is consistent with other studies (e.g. Johnson, 1975;Freedman et al. 1982;Chambers, 1993;Chambers, 1995;Levesque and Svoboda, 1995). The ruderal strategy is associated with a short life span, a fast growth rate and the production of large numbers of germinable seed (Grime, 1977). ...
... For a plant individual to successfully establish at a given site, all stages of the regeneration pathway must be accomplished; seed set, seed dispersal, germination and seedling establishment and survival (Welling et al. 2002). Seed set in the alpine is assumed to be infrequent due to abiotic constraints (Chambers 1993), and results from seed addition experiments suggest that seed limitation is a main factor restricting plant species richness (Lindgren et al. 2007, Mayer et al. 2011, Myers et al. 2009). Seeds are often small and lack specialized adaptions for dispersal, or they are adapted to wind dispersal. ...
... Hence, their distribution is mainly influenced by wind and soil surface characteristics (Chambers et al. 1994). The cold soils promote seed longevity, but with few species in the ecosystem, the seed bank composition is mostly similar to the standing vegetation (Chambers 1993). It has also been suggested that availability of suitable microsites is the key factor governing recruitment patterns (Cichini et al. 2011, and there is evidence suggesting that the transition from seed pool to the phase of seedling emergence is more critical than the transition from seedling emergence to survived seedling (Chambers 1993, Clark et al. 2007. ...
... The cold soils promote seed longevity, but with few species in the ecosystem, the seed bank composition is mostly similar to the standing vegetation (Chambers 1993). It has also been suggested that availability of suitable microsites is the key factor governing recruitment patterns (Cichini et al. 2011, and there is evidence suggesting that the transition from seed pool to the phase of seedling emergence is more critical than the transition from seedling emergence to survived seedling (Chambers 1993, Clark et al. 2007. The complex interactions between recruitment filters may pose bottlenecks to successful establishment beyond that of each discrete factor (Garcia-Camacho et al. 2010). ...
... Clonal growth is considered the major factor in maintaining the vegetation structure in subarctic and arctic habitats. Observations on low floristic similarity between the standing vegetation and the product of sexual reproduction, the seed bank (e.g., Chambers, 1993;Kiirikki, 1993;Jensen, 1998;Holmes and Cowling, 1997;Morgan, 1998;Arroyo et al., 1999), support this finding. Although the presence of seed bank is important for recovery after disturbances, the roles of soil seed bank and the field seedlings in vegetation structure are still relatively unknown (Freedman et al., 1982;Leck and Simpson, 1995). ...
... Morphological characteristics of seed, such as seed size and appendages, can influence the success of sexual regeneration and hence the floristic similarity between seed bank, field seedlings, and standing vegetation. Small seeds accumulate in the seed bank more effectively than large seeds (Thompson et al., 1998), and hence standing vegetation dominated by species with small seeds may show floristic similarity between the seed bank (Chambers, 1993). On the other hand, the germination of small seeds and the survival of seedlings from small seeds are more vulnerable to competition, shade, nutrient deficiency and aridity compared with large seeds or seedlings (Eriksson and Jakobsson, 2000). ...
... .5.0 mg similarity coefficient (Jongman et al., 1987;Welling and Laine, 2000b) and Spearman's correlation analysis (Chambers, 1993;Larson, 1998, 2000;Welling and Laine, 2000b) were used. The equation for the qualitative Jaccard's similarity ...
This study investigated the relationship of seed bank and field seedlings on the structure of standing vegetation. We also studied the roles in sexual regeneration of seed size, diaspore morphology, and the ability to regenerate vegetatively. Seed banks, field seedlings, and standing vegetation were sampled in 8 subarctic plant communities in Kilpisjärvi, Finland, in, 1995–1998. The seed bank densities varied from 99 to, 1109 viable seeds m2−1 and decreased toward higher altitudes. The seed bank densities were significantly larger than the field seedling densities in the closed vegetation of the lower slopes, whereas the differences were smaller in the open, late-melting snowbeds on higher slopes. The species that occurred only in the seed bank had small seeds or appendaged diaspores. The field seedling densities were high in plant communities dominated by species with ineffective vegetative reproduction or by species with diaspores and with pappus. The floristic similarity was low between the seed bank, field seedlings, and standing vegetation. The nonmetric multidimensional scaling revealed that the species diversity was lower in the seed banks than in standing vegetation and field seedlings. The results indicate that all transitions equally constrain the sexual regeneration of vegetation. Clonality, very small and very large seed sizes, appendaged diaspores, and possibly narrow first leaves in seedlings are traits that limit the transition of plants from standing vegetation to the phase of field seedlings via seed bank. Persistent seed bank has a minor role compared to clonal growth in the regulation of vegetation structure.
... In alpine habitats, disturbances can be caused by geomorphological processes such as landslides, road building, or mining activities, as well as be a result of cryogenic soil movement (Johnson and Billings, 1962), small mammal burrowing and tunneling (Thorn, 1982), and recreational activities. In some cases, removal of superficial soil horizons also removes seed banks (Brown et al., 1978), while in the other cases, soils are well developed and highly organic, and usually contain large seed pools (Chambers, 1993). ...
... Initial establishment after disturbance is often dominated by short-lived species that produce great amounts of seeds capable of forming highly persistent seed banks or disperse long distances (Grubb, 1977;Grime, 1979;Pickett and McDonnell, 1989). For example, on severely disturbed alpine herb-fields in which surface soil and buried seed pools have been removed, initial colonization is carried out by grasses with high dispersal capacity (Chambers et al., 1984;Chambers, 1993). In contrast, in undisturbed sites, longlived species establish and develop more slowly, and typically produce low numbers of relatively large, short-lived seeds, dominating the aboveground vegetation (Chambers, 1993). ...
... For example, on severely disturbed alpine herb-fields in which surface soil and buried seed pools have been removed, initial colonization is carried out by grasses with high dispersal capacity (Chambers et al., 1984;Chambers, 1993). In contrast, in undisturbed sites, longlived species establish and develop more slowly, and typically produce low numbers of relatively large, short-lived seeds, dominating the aboveground vegetation (Chambers, 1993). Thus, seed availability is an important factor driving differences in seedling emergence between disturbed and undisturbed areas. ...
Disturbance is likely to affect Multiple life stages and may be most critical in seedling germination and establishment through indirectly affecting soil properties. Following disturbance, plants establish from seeds that either exist on the site or that disperse onto the site. Here, A,c examined the effects of a I-year-old severe human disturbance (approx. 1 ha) on alpine vegetation recovery in the Andes of central Chile (33 degrees S. 60 degrees W) at 2800 in a.s.l. during two growing seasons (2006-2007). Particularly, we assessed the effects of soil properties and seed rain on post-disturbance seedling emergence using two sets of denuded slopes of different exposure (South and northwest, respectively) and two appropriate control areas. The disturbed area oil the south-facing slope was drier than its respective control. while the opposite was observed on the disturbed area on the northwest-facing slope, The differences in soil water content between both slopes coincided with the results of seedling recruiting. The south-facing slope, with a more humid undisturbed area, showed a greater number of emerging seedlings than the disturbed slope. Conversely, on the northwest-facing slope, the Main recruiting of seedlings was observed on the disturbed area, while the undisturbed area showed practically no emergence of new individuals. In addition, our results indicate that seedling recruitment Occurred from a persistent seed bank constituted mostly by species with long-lived and deeply viable seeds, though in this particular Study. we could not corroborate it empirically. Although long-term Studies are desirable to make more definitive Conclusions, our results provide the First step to understanding the capacity for vegetation recovery after I Severe human disturbance in the Andes of central Chile, where seed banks and soil moisture seem to play a pivotal role.
... The harsh environmental conditions of high-elevation ecosystems favour seed persistence in the soil (Cavieres and Arroyo, 2001;Walck et al., 2011), and large soil seed banks have been recorded before (e.g. Chambers, 1993;Sizov et al., 2004;Ma et al., 2010;Venn and Morgan, 2010;Hoyle et al., 2014). Despite this, little is known about the effects of climate change on soil seed banks . ...
... The herbfield had a soil seed bank almost ten times larger than that previously reported for the same area (382 ± 35 seeds m −2 by Hoyle et al., 2013) and 2.5 times larger than that reported for other alpine areas in Australia (1330 ± 294 seeds m −2 by Venn and Morgan, 2010). However, similar densities have been reported for other alpine herbfields in the Northern Hemisphere (Chambers, 1993;Sizov et al., 2004), an alpine meadow on the Tibetan plateau (Ma et al., 2010) and other arctic plant communities (Molau and Larsson, 2000;Alsos et al., 2003;Cooper et al., 2004). The treeline soil seed bank density was higher than what has been reported for a subarctic treeline (Molau and Larsson, 2000) and an anthropogenically disturbed treeline in the Himalayas (Phartyal et al., 2023), but relatively smaller than what has been reported for a subalpine treeline in East Asia (Erfanzadeh et al., 2013). ...
Background and Aims
Seed persistence in soil depends on environmental factors that affect seed dormancy and germination, such as temperature and water availability. In high-elevation ecosystems, rapid changes in these environmental factors due to climate change can impact future plant recruitment. To date, our knowledge on how soil seed banks from high-altitude environments will respond to climate change and extreme climate-related events is limited. Here, using the seedling emergence method, we investigated the effects of reduced snow cover, fire and drought on the density and diversity of germinants from soil seed banks of two high-altitude plant communities: a tall alpine herbfield and a treeline ecotone.
Methods
In Autumn 2020, we collected soil samples and characterized the standing vegetation of both communities at Kosciuszko National Park, Australia. Then, we employed a factorial experiment and subjected the soil samples to a series of manipulative treatments using greenhouse studies.
Key results
The treeline had a larger and more diverse soil seed bank than the herbfield. A reduction in snow had a negative effect on the number of germinants in the herbfield and increased the dissimilarity with the standing vegetation, while the treeline responses were mainly neutral. Fire did not significantly affect the number of germinants but decreased the evenness values in both communities. The drought treatment reduced the number and richness of germinants and increased the dissimilarity with the standing vegetation in both communities. Plant functional forms explained some of the detected effects but seed functional traits did not.
Conclusions
Our study suggests that simulated climate change will affect plant recruitment from soil seed banks in a variety of ways. Changes in snow cover, incidences of fire and drought may be key drivers of germination from the soil seed bank and therefore the future composition of alpine plant communities.
... Several decades later, 180 Freedman et al. (1982) and McGraw and Shaver (1982) also found high total seedling densities in the arctic region: at Ellesmere Island, High Arctic Canada, 13-5916 seedlings / m 2 , and in Alaska, 35-3376 seedlings / m 2 . Furthermore, the total densities of seed banks are often several hundreds or even thousands of seedlings / m 2 (Freedman et al. 1982, Fox 1983, Roach 1983, Chambers 1993, Semenova and Onipchenko 1993, Welling and Laine 2000. Seedling survivorship can be surprisingly high, more than 50% after two growing seasons (Chambers 1995). ...
... The consequences of seed sizesmall or large -are apparent in regeneration. Small seeds dominate the seed rain (Chambers 1993, Welling and Laine b, in prep.) and the seed bank (Chambers 1993, Thompson et al. 1998). On the other hand, a large seed is an advantage in colonization, especially that of closed vegetation (Kiviniemi 1999) Appendaged diaspores have an ability to disperse longer distances than non-appendaged diaspores, but appendages may limit burial in the soil (Rabinowich 1981). ...
Article in English - Icelandic summary
SAMANTEKT
Meginmarkmið þessara rannsókna er að afla þekkingar til þess að geta
hagnýtt beinar sáningar barrtrjáfræs í nýskógrækt á Íslandi.
Helstu niðurstöður þessa verkefnis eru þær að í kjölfar beinna sáninga
barrtrjáfræs spírar fræið ágætlega og sáðplöntur komast á legg. Ekki er
sjáanlegur marktækur munur á því milli Suður- og Austurlands. Af þeim
trjátegundum sem notaðar voru gaf sáning stafafuru jafn bestan árangur.
Á Héraði skilaði þó sáning rússalerkis viðunandi árangri, en vegna þess
hve fræverð er hátt um þessar mundir er aðferðin tæpast raunhæfur
kostur í lerkiskógrækt. Á sama hátt gaf notkun plastkeilu jafnbestan
árangur við sáningar, bæði hvað varðar spírun, lifun og vöxt plantnanna.
Þess ber þó að geta að á Héraði voru áhrif keilunnar mun minni en í
Mosfelli, sérstaklega á lifun og vöxt plantna. Skýrist það væntanlega af
hagstæðu veðurfari svæðisins. Í Mosfelli virðist skjólið af keilunni ráða
úrslitum fyrir lífslíkur plantna. Keilan kemur einnig í veg fyrir afrán á fræi, en það getur verið mikið vandamál við beinsáningar hér, bæði í Mosfelli og Höfða.
Athygli vekur hversu vöxtur á sáðplöntunum er lítill fyrstu sumrin. Þær
virðast lenda í vaxtarstöðnun (stagnation) sem væntanlega skýrist af næringarskorti
og hugsanlega skorti á sambýlisörverum, s.s. svepprót. Tilraunir
sem hófust haustið 1997 með áburðargjöf benda til þess að hún
auki vöxt plantna og sé nauðsynleg við beinar sáningar hérlendis.
Afföll plantna orsakast af svipuðum þáttum og þekkt eru úr gróðursetningarstarfinu,
þ.e.a.s. frostlyftingu, frostskemmdum, þurrki og
ranabjöllunagi. Skipulag beinna sáninga þarf að taka tillit til allra þessara
þátta ef vel á að takast til.
Ávinningur beinna sáninga virðist vera mestur þegar notuð er stafafura.
Orsakast það af nokkrum þáttum. Fræ hennar er tiltölulega ódýrt og
fyrirsjáanlega verður töluvert framboð af því hér innanlands. Hún er
ræktuð í tiltölulega þurru mólendi, en þar er helst hægt að mæla með
sáningum og einnig ættu rótarvansköpun og stofnsveigjur að vera minna
vandamál eftir beina sáningu en eftir gróðursetningu.
Þessar tilraunir renna stoðum undir það, að beinar sáningar á barrtrjáfræi
í útjörð geti gefið áþekkan árangur og vænta má af hefðbundnum
gróðursetningum. Mikill munur er þó á milli einstakra sáningaraðferða og
ljóst að ekki dugir að sá fræinu einu og sér. Hjálparaðgerðir eru því
nauðsynlegar ef fullnægjandi árangur á að nást.
... Still, many short-lived and nonclonal alpine plants allocate a high proportion of annual production for sexual reproduction (Maessen et al. 1983 ), and indirect evidence for the importance of sexual reproduction in alpine plants is obtained from genetical analyses of individuals within a population (Jonsson et al. 1996 ). Studies from North American subalpine grasslands showed high seed production and recruitment under favorable conditions, but large variations among years (Gartner et al. 1983; Chambers 1989 Chambers , 1993 Chambers et al. 1990). This variability implies that safe sites depended strongly on the time for recruitment, and the importance of habitat heterogeneity was found to increase during cool and short growing seasons (Chambers 1995). ...
... If germination requires both open soil and a sufficient soil moisture level, as suggested in this study, and to a large extent depends upon the time of recruitment in a variable environment (Chambers 1995), the number of seeds should be high to compensate for rare safe sites. Seed availability is limited by both a varying local seed production (Chambers 1989Chambers , 1993) and low dispersal frequencies at a larger spatial scale (Kiviniemi and Eriksson 1999). Local seed production is probably most important, and Peart (1989) found that species with the highest seed production were the most frequent recruiters in disturbed grassland patches. ...
Recruitment is critical for the maintenance of plant populations and community diversity, but sexual regeneration is considered to be infrequent in climatically harsh habitats such as subalpine grasslands. This study examines the importance of regeneration through seed for 16 sparse herb species, and we asked whether their populations are limited by safe sites or the availability of seeds. Seedling recruitment and winter survival were recorded after sowing in an experimental split-plot design in (i) pasture grazed by livestock, and (ii) exclosed grassland cultivated for annual mowing. In addition we examined the effect of disturbance and local seedbank recruitment. All species were able to recruit and survive the first winter in at least some of the experimental plots, although none were initially present. Recruitment mainly occurred in disturbed plots, and disturbed pasture plots had a significantly higher recruitment than disturbed exclosures for all species except Silene dioica. We further examined whether specific plant traits were related to variation in recruitment. Lower recruitment in the disturbed exclosure was associated with higher specific leaf area, leaf dry weight, and seed number. In contrast, seeds sown in disturbed pasture recruited more independently of species traits. The exception was a negative correlation between recruitment and leaf dry weight, and an unexpected negative correlation with seed weight. We suggest that recruitment differences among habitats mainly reflect lower humidity in the exclosure. Consequently, small stature plants with small specific leaf area should have the highest recruiting probability when exposed to drought. The almost exclusive recruitment on disturbed plots indicates a strong competitive effect on the target species in vegetated plots, and suggests that safe sites for regeneration through seed are rare in subalpine grasslands.
... Gopher modifications of the ecosystem therefore also may be manifest in the characteristics of colonizing and/or recovering vegetation. Many studies show that gopher disturbances increase species diversity at least for the short term (e.g., Tilman, 1983; Inouye et al., 1987; Chambers, 1993). Gopher disturbance can also alter plant species composition and growth form, usually with preferred dietary species decreasing in disturbed areas (Ellison and Aldous, 1952; Laycock and Richardson, 1975; Foster and Stubbendieck, 1980). ...
... We chose instead to focus on whether alpine forbs are modified by pocket gopher mounding activities. Chambers et al. (1990) and Chambers (1993) have examined the potential of Acomastylis rossii seedling establishment on disturbed substrate, but to our knowledge there are no published studies of any alpine forb's ability to survive following burial of aboveground structures. Excluding a hypothesized keystone species from an ecosystem for an extended duration is the classic approach to determining its role (e.g., Brown and Heske, 1990). ...
We evaluated the importance of the northern pocket gopher (Thomomys talpoides) in controlling plant species composition and richness in two alpine tundra plant communities. We hypothesized that forb diversity and relative abundance is modified by gopher mounding activities in moist meadows of Niwot Ridge, Colorado, U.S.A., where both the pocket gopher and forbs are most concentrated. We tested this hypothesis with simulated gopher mounds. Forbs recovered faster following burial than graminoids or cushion plants, demonstrating a resilience that we propose confers a competitive advantage over other growth forms and favors forb dominance in moist meadows. Gopher effects on species richness varied according to spatial scale of measurement and community type. For one decade we monitored the responses of a sedge-dominated community to gopher activity in 1.5 m(2) plots that included both gopher mounds and intermound spaces and found that species richness was significantly positively correlated with recent disturbance. Species richness on the simulated gopher mounds (0.2 m(2)) immediately declined significantly after burial but recovered within a year. When evaluated in conjunction with studies of gopher diet preferences and effects on ecosystem biogeochemistry, our findings suggest that the northern pocket gopher is instrumental in constructing a locally diverse alpine plant community.
... Bossuyt et al. 2002;Olano et al. 2002). Furthermore, in the present study, a layer-wise comparison revealed a significant spatial variation in soil seed bank composition as in various other studies on soil seed bank reserve in alpine or high-subalpine grasslands (Archibold 1981;Roach 1983;Morin & Payette 1988;McGraw & Vavrek 1989;Chambers 1993;Ingersoll & Wilson 1993;Semenova & Onipchenko 1994). ...
Many alpine plants disperse dormant seeds at maturity towards the end of the growing season, characterised by cooler temperatures preventing immediate seed germination. The seeds then accumulate in the soil and germinate in the next growing season, or remain buried until favourable conditions occur. Since soil seed bank potential depends on species-specific (intrinsic) and site-specific(extrinsic) characteristics, it is worth to ask: can anthropogenically disturbed Himalayan alpine meadows form a soil seed bank? Two hundred and sixty soil cores were sampled down to 10 cm depth in two layers from alpine meadows parallel to the Tungnath treeline in Uttarakhand State of India. Sampling was carried out in autumn (after seed dispersal) and spring (before seed germination) and incubated under ex situ (net house) and in situ (on-site field) conditions for seedling emergence. Overall, 2,141 seeds/m2 of 13 species were recorded from in situ incubated samples. Seed density and species number substantially decreased with increasing soil depth. The upper layer(0-5 cm) had a mean density of 3,586 seeds/m2, while the lower layer (5-10 cm) had 697 seeds/m2, respectively. The study revealed that anthropogenically disturbed Himalayan alpine meadows have low soil seed bank potential compared to alpine meadows of other mountain systems. High disturbance pressure like grazing and high human footfalls probably damaged the reproductive phase of plant life and led to low seed production, hence the low seed inputs in the soil. Some methodological issues in studying soil seed banks of alpine plants were also discussed.
... Bossuyt et al. 2002;Olano et al. 2002). Furthermore, in the present study, a layer-wise comparison revealed a significant spatial variation in soil seed bank composition as in various other studies on soil seed bank reserve in alpine or high-subalpine grasslands (Archibold 1981;Roach 1983;Morin & Payette 1988;McGraw & Vavrek 1989;Chambers 1993;Ingersoll & Wilson 1993;Semenova & Onipchenko 1994). ...
... The soil seed bank provides propagules for vegetation restoration after disturbance, which is the core of vegetation renewal (Chameres, 1993;Plue et al., 2013). Therefore, the soil seed bank could function as a key indicator in assessing the impact of grazing exclusion along an altitudinal gradient in an alpine ecosystem (Ortega et al., 1997;Osem et al., 2006). ...
Grazing exclusion by fencing is the principal option to restore degraded grassland, but its effects on recovery and succession of vegetation are not clear, especially in high mountain areas. In this study, we filled this gap by assessing the effect of seven‐year grazing exclusion on vegetation and soil seed bank along an altitudinal gradient in northern Tibet, China. Species richness, Shannon‐Wiener index and Simpson's diversity index of vegetation and soil seed bank, seed density, and the Sørensen index all displayed a mid‐domain (hump‐shaped) pattern with increasing altitude, except for the Shannon‐Wiener and Pielou indices of soil seed bank in fenced grasslands. These results demonstrated that the impact of grazing exclusion on the patterns of vegetation and soil seed bank change with altitude but are not synchronous. Grazing exclusion increased vegetation coverage but decreased soil seed bank density, and species diversity of vegetation and soil seed bank. The Sørensen index (0.03~0.2) and non‐metric multidimensional scaling (NMDS) analysis indicated that the species composition differed between vegetation and soil seed bank, but no difference was found between fenced and grazed grasslands. The low similarity suggests that the soil seed bank contributes little to vegetation recovery in alpine grassland. Seven‐year grazing exclusion had no effect on either vegetation succession or species composition of soil seed bank in alpine grassland. Overall, our findings suggest reconsidering the use of long‐term grazing exclusion to restore degraded grassland at high altitudes (above 4400 m above sea level) on the Tibetan plateau. This article is protected by copyright. All rights reserved.
... No attempt to connect the governing chain with changes in real environmental factors that determine seed germination and plant growth/development has come to our notice. Meanwhile, the factors themselves certainly exist and have been noted by biologists of A. albana and other alpine species (Rabotnov, 1950(Rabotnov, , 1978Grime, 1979Grime, , 2001Serebryakova, 1985;Zhukova, 1986Zhukova, , 1995Chambers, 1993;Bowers et al., 1995;Bender et al., 2000;Körner, 2003;Onipchenko, 2004Onipchenko, , 2013Adzhiev and Onipchenko, 2011;Keller and Vittoz, 2014). Presenting the course of changes in those factors over the years in the form of a Markov chain that would govern the changes of PPMs in the random sequence (5) is the task whose solution would make the direct method for estimating λ S truly the most reliable. ...
... Compared with the other two marshes, Cg was characterized by a high seed density (especially in the upper sediment layer), greater similarity between the seed bank and vegetation, and low species diversity in the established vegetation and seed bank. This is associated with the presence of a greater number of annual species in the Cg vegetation (Chambers, 1993) and suggests that they form a persistent seed bank. The presence of annual plants in saline (Ungar & Woodell, 1996b;Bossuyt & Honnay, 2008) and freshwater wetlands (Middleton, 2003) is favored by their ability to tolerate natural and anthropogenic disturbance and to produce a large amount of long-lived seeds (van der Valk & Davis, 1978;Matus et al., 2005;Brock, 2011). ...
Banco de semillas y vegetacion establecida en los ultimos remanentes de los humedales de la Meseta Central Mexicana: las cienagas de Lerma. Seed banks play a central role in vegetation dynamics of many wetlands. Therefore, knowledge of seed reservoirs in the soils of aquatic communities should provide useful tools for conservation and restoration efforts. This study was conducted in the Lerma marshes, one of the last remnants of the vast wetlands that were once in the Mexican Central Plateau. The main objective was to determine the composition and abundance of seed bank and its relationship with established vegetation of the three Lerma marshes. In each marsh, we systematically selected 18 to 40 sampling sites. In each site, the composition of vascular plant vegetation was evaluated in two 10m lines perpendicular to the shore. Every 0.5m, we determined the coverage of species by measuring the intercepted length for each plant or group of plants. At each sampling site where we had evaluated the established vegetation, we collected a sample of the top 10cm of sediment; the soil cores were divided into an upper layer (0-5cm) and a lower layer (5-10cm). These samples were used to evaluate the seed bank by the seedling emergence method. All samples were placed in a greenhouse at 20-25oC and remained flooded for 15 weeks. Forty-nine species were recorded in the vegetation. Chiconahuapan had the richest and most diverse flora and the greatest number of perennial species. A life-forms analysis showed that perennial herbs, especially rooted-emergent hydrophytes, dominated in the three wetlands. Sixty-one species were identified in the total seed bank; Chimaliapan had the most diverse total seed bank, whereas the mean seedling density was higher in Chignahuapan. Only two species of the total seed bank of each marsh had a density greater than 10% of the total, and more than half were uncommon. The upper layer of sediment (0-5cm) contained two times more seeds/m 2 and species per sample than the lower layer (5-10cm), and there was a significant decrease of seed density with depth. The detrended correspondence analysis produced a clear separation between the composition of the seed banks and established vegetation. In general, in each marsh there was less species diversity in the established vegetation than in the seed bank. Dominance by a few spe- cies in the seed bank, the presence of opportunistic species, and the low representation of established species in the seed bank suggest wetland degradation and a low probability of regenerating the natural communities from the seed bank. To ensure the permanence of these marshes, their biodiversity, and therefore the environmental services they provide, up to date planning is a must, and efforts to control and monitor hydrology, water qual- ity, and the influence of human activities are suggested. Rev. Biol. Trop. 62 (2): 455-472. Epub 2014 June 01.
... Both openness and temperature regime in the tundra habitat have been suggested to promote the fruit maturation and seed quality of E. hermaphroditum (Graae et al. 2008;Bienau et al. 2014). Seed bank density in our study is roughly comparable to studies conducted in other subarctic and alpine areas (Diemer and Prock 1993;Vieno et al. 1993;Alsos et al. 2003;Welling et al. 2004, but see Chambers 1993). High seed bank density in the mountain birch forest is explained by the high number of seeds of B. pubescens ssp. ...
Successful sexual reproduction may be more important for regeneration of clonal species in high-latitude and -altitude areas than has been previously suggested. We investigated the potential of Vaccinium myrtillus, V. vitis-idaea and Empetrum nigrum ssp. hermaphroditum (E. hermaphroditum) for sexual reproduction at three sites in the forest–tundra ecotone in Finnish Lapland. We studied whether the potential differs between plant communities, whether disturbance enhances germination, and whether seedling emergence is limited by seed availability. We established a field experiment with disturbance and sowing treatments, and monitored seed and seedling numbers and survival rates for two years. The number of mature seeds of V. myrtillus was higher in plants from the tundra heath than in those from the coniferous and mountain birch forests. The number of mature seeds and seedlings emerging from the seed bank of E. hermaphroditum tended also to be higher in the tundra heath. Disturbance marginally increased the seedling emergence of V. myrtillus and E. hermaphroditum, whereas sowing generally increased the seedling numbers. The seedling number of V. myrtillus was lower in the tundra heath and that of E. hermaphroditum was lower in the coniferous forest than at the other sites. Seedling survival was equal for all plant species at all sites. We conclude that the capacity for sexual reproduction varies among plant communities, and seed availability is a stronger constraint than microsite availability for the studied species. Once the crucial early phase of seedling establishment is overcome, seedling survival enables successful recruitment of V. myrtillus, V. vitis-idaea and E. hermaphroditum in the subarctic area.
... Billings and Mooney, 1968;Bliss, 1971), but more recent studies have found high seedbank densities (e.g. Chambers, 1993;Vandvik et al., 2015;Zabinski et al., 2000), and diversity of genotypes (e.g. Gabrielsen, 1998;Steltzer et al., 2008) consistent with a history of repeated sexual reproduction in alpine environments. ...
How plants allocate biomass to different parts strongly affects vegetation dynamics and ecosystem processes and services such as productivity and carbon storage. We tested the hypothesis that plant size explains the majority of variation in the size of plant parts (as predicted by Allometric Partitioning Theory, APT) and that additional variation is explained by optimal responses for a given individual reproductive state and environment (as predicted by Optimal Partitioning Theory, OPT) for alpine-lowland species pairs from three genera of grassland plants (Veronica, Viola and Carex) sampled along orthogonal gradients in temperature and precipitation. We found general patterns of allometric scaling (allometric exponents) of roots, stems, leaves and flowers, more or less as predicted by APT, and these patterns remained fairly constant across temperature and precipitation gradients. In contrast, basic allocation (allometric coefficients) was clearly related to climate, such as less allocation to leaves but more to roots, stems and flowers with increasing temperatures, in accordance with OPT. Furthermore, our results show that basic allocation is related to habitat affinity (alpine, lowland) and individual life-history states (reproductive or not) and that there is greater variability in small plants, which suggests that biomass partitioning theory should consider both the life-history and ecology of small plants to accurately predict climate-related grassland plant allocation and its implications.
... It has been widely accepted that small gaps, which can act as safe sites for recruitment, are a universal mechanism for maintaining diversity (see Huston 1979, Pickett 1980, Pickett and White 1985, Chesson 1986, Chambers 1995. Different results have been found in various communities, however, demonstrating that small-scale disturbances increase (Chambers 1993, Boeken et al. 1998 or decrease (Wilson and Tilman 1991, Collins et al. 1995 species richness. Huston (1979Huston ( , 1994 provided a more general approach, claiming that diversity reflects the dynamic equilibrium between competitive displacement and disturbance. ...
... Similarly, the importance of the soil seed bank in seedling recruitment is well known (Willems 1995;Welling et al. 2004;Cheplick 2006;Venn and Morgan 2010;Salazar et al. 2011). Finally, for a given level of seed availability, seedling recruitment is a function of the abiotic and biotic conditions at a site that affect germination and emergence rates, and seedling growth and survival (Chambers et al. 1990;Chambers 1993Chambers , 1995. ...
Background: Seedling recruitment is widely recognised to be important in the maintenance of diversity and coexistence of species. It is not clear how local abiotic factors mediated by litter and biotic interactions influence plant species recruitment in alpine grasslands.Aims: To determine how litter and standing vegetation affected seedling recruitment in plant communities in Tibetan alpine grasslands.Methods: Seedling recruitment was quantified in response to experimental treatments: (1) removal of standing vegetation and litter; (2) removal of standing vegetation with litter intact; (3) intact standing vegetation and removal of litter and (4) control: intact standing vegetation and litter.Results: Litter removal increased seedling numbers, while standing vegetation removal had no effect. An interaction between litter and standing vegetation removal marginally increased seedling number. Species richness of seedlings was not related to either litter removal or standing vegetation removal. Species composition of seedling differed significantly between removal of both litter and standing vegetation and control.Conclusions: Litter and its interaction with standing vegetation has an important role in affecting plant species recruitment in this alpine plant community. In contrast, biotic interactions, such as competition or facilitation from standing vegetation, appear to have only minor effects on recruitment.
... These findings show that species influenced by historical effects of snowmelt schedule may (Sibbaldia) or may not (Trifolium) respond to shortterm changes in growing-season length. A. scopulorum, and P. alpina) that are also common in more exposed sites (Heide 1992, Chambers 1993, Walker et al. 1993). Effects of the timing of leaf and fruit development on plant production are most pronounced in habitats characterized by a short growing season and growing seasons in which resource availability declines progressively (Kirner 1991, Roberts 1991, Rice et al. 1992). ...
We assessed the role of growing-season length in regulating absolute and relative cover of six coexisting dominant plant species in an alpine snowbed habitat. To help explain disparity in species-specific responses to growing-season length, we examined the developmental phenology and distribution of each species in relation to natural snow depth variation. Season length varies from approximate to 50 d on early-melting edges of the snowbed to 35 d in the late-melting center, 100 m away. By experimentally altering snowpack, we uncoupled the relationship between spatial location and snowmelt schedule in three consecutive years, imposing the same early dates of snow release in a ''long growing-season'' treatment and the same late dates of snow release in a ''short growing-season'' treatment near the edge and center of the snowbed. Over the course of the experiment, growing-season length had significant effects on absolute and relative cover of the species studied (P < 0.025 and P < 0.005, respectively), and these effects were similar near both the edge and center of the snowbed. Yet, only for the snowbed specialist, Sibbaldia procumbens, were changes in absolute and relative cover under early and late snowmelt schedules predictable from the species' distribution along the historical snow depth gradient. S. procumbens increased in cover under a long growing-season and was more common in historically early-melting portions of the snowbed. Other species (e.g., Ranunculus adoneus, Artemisia scopulorum) were equally common in historically early- and late-melting locations within the snowbed, but showed discordant responses to experimentally imposed changes in snowmelt schedule. That the cover of many species under long- vs, short growing seasons was not predictable from their current distributional affinities in relation to snowmelt pattern likely reflects the disparity between the rates of processes exerting long-term control on species' abundances (colonization, soil development) and more immediate effects of growing-season length on plant growth. Consistent with this view, differences in developmental phenology better predicted species-specific responses to snowmelt schedule than distributional affinities. Species having leaf expansion schedules that are poorly synchronized with snowmelt typically had similar cover under early vs. late schedules of snow release (Geum rossii, Trifolium parryi, and Poa alpina). In contrast, species in which leaf expansion schedules are synchronized with snowmelt responded positively to early snow release (Ranunculus adoneus and Sibbaldia procumbens). We hypothesize that maintaining metabolic ''readiness'' under snowcover provides a mechanism for monopolizing nutrient flushes and competitor-free intervals at snowmelt, and exploiting occasional long intervals for growth in years of little snow accumulation, but incurs a respiratory cost that is manifest as reduced growth and vegetative cover when snowmelt is delayed. Our results suggest that interspecific differences in growth phenology of coexisting species will promote shifts in snowbed plant communities with climate change within generations.
... Seedling recruitment of D. virgatus CPI 78382 was much higher under grazing and was significantly related to rainfall events (Borrows and Porter 1993). These results were similar to those obtained by other authors working with other species (Harper 1977 c;Ward and Jennings 1990;Kinucan and Smeins 1992;Chambers 1993;Tremont 1994). ...
... The amount of produced seeds recorded at Lusia in 2003 (20,100 seeds solely from the main grasses) was much higher than those found in most of the seed rains of grasslands located in the alpine belt. For example, the annual seed rain amounted to about 1300 seeds m 22 in a New Zealand tussock grassland above the timberline (Spence 1990), to 930 seeds in a Caricion curvulae vegetation in the Alps (Urbanska et al. 1998), and to 5233 and 10,725 seeds, respectively, in a late seral Geum turf area and in an early seral herbaceous vegetation of the alpine belt in Montana (Chambers 1993). Instead, the seed quantities obtained at Lusia were more similar to nutrient-poor low altitude grasslands. ...
Studying the seed production of semi-natural grasslands helps to understand their regeneration processes and to evaluate the possibility of collecting seed useful for ecological restoration. In a subalpine Festuca nigrescens–Agrostis capillaris meadow, the development of the main grasses' seed production and the standing seed yield at meadow maturity were studied. The inflorescence size was in the lower part of the variation range reported in previous studies. The seed viability was average to high and durable. The biological floret site utilization was mostly above 50%. With 458 fertile stems m− 2, the seeds produced (all seeds produced up to the time of the meadow maturity) by the main grasses were 21,000 m− 2, of which 77% were of A. capillaris and 81% were viable. On a 3-year average, the standing seed yield (seeds present on the plants, i.e. produced minus shed seeds) at meadow maturity was 6953 seeds m− 2. Amount and composition of the produced seeds were affected mainly by the variability among years of the fertile stems density of the perennial grasses and the annual hemiparasite Rhinanthus freynii. The percentage of produced seeds which formed the standing seed yield was affected mainly by the collecting date.
... So, the degree of disturbance could affect the floristic composition and density of soil seed bank. Disturbance also influences the proportion of annual versus perennial species in vegetation (Ma et al., 2010) which, therefore, may affect the degree of similarity between vegetation and seed bank (Chambers, 1993; Touzard et al., 2002). Wadi microhabitats are subjected to different degrees of disturbance due to flooding, being highest in channel, moderate in bank, and least in terrace. ...
Due to extreme variability in patterns of rainfall, plant seed banks are an important component of desert habitats. Here I report on effects of standing vegetation and three different microhabitats (channel, bank and terrace) on the soil seed bank of a desert wadi ecosystem in the Eastern Desert of Egypt. A total of 450 soil samples at 45 stands were collected to represent the different wadi microhabitats. The germinable seed bank was estimated by controlled counts of seedling emergence. The floristic composition, functional properties and diversity of the soil seed bank, as well as its similarity with the standing vegetation varied among wadi microhabitats. Such variation could be attributed to differences in disturbance intensity among microhabitats (terrace < bank < channel) and variation of soil factors along the microtopographic gradient. Channel showed the highest species richness and size of soil seed bank, followed by bank and then terrace. Moreover the Shannon index of diversity of the seed bank and its similarity with standing vegetation were significantly greater in both channel and bank microhabitats than in terrace. At the level of plant functional groups, number of seeds of annuals was higher in both channel and bank than in terrace. Shrubs were more abundant in seed banks of channel compared to terrace. The size and species richness of seed bank were increased with the total plant cover, annual/perennial ratio and species richness of the standing vegetation.
... Por otra parte, considerando que los in-dividuos que habitan estas zonas presentan una alta longevidad, se postuló que la mantención de grandes cantidades de reserva de semillas en el suelo no sería estrictamente adaptativo (Thompson 1978, Archibold 1984 ). La gran mayoría de los trabajos que han documentado la presencia de bancos de semillas en el suelo de zonas de alta montaña se han realizado en el Hemisferio Norte (e.g., Archibold 1984, Miller & Cummins 1987, Morin & Payette 1988, Ebersole 1989, Chambers et al. 1990, Spence 1990, Ingersoll & Wilson 1993, Chambers 1993, Diemer & Prock 1993, Onipchenko et al. 1998) siendo muy escasos aquellos para las altas montañas de Sudamérica (Guariguata & Azócar 1988, Cavieres & Arroyo 1999). ...
... New Zealand (Spence 1990), and in the North American Rocky Mountains (Chambers 1993), but data are scarce for grassland and cushion vegetation near the upper distributional limits of vascular plants in the European Alps. ...
Background: Propagule production and dispersal largely determine the distribution and potential migration ability of alpine plant species. Variation in reproductive success caused by year-to-year variation in climate may critically influence these processes. Aims: To obtain estimates for the propagule rain in high-alpine plant communities and detect potential dispersal events from lower elevations. Methods: The magnitude and composition of the propagule rain was studied in different plant communities along an elevation gradient from the upper alpine to subnival zone. Propagules were trapped at eight elevations from 2760 to 3070 m a.s.l. for three years from July to September 2003–2005. Vascular plant species and their cover were recorded in an area with a radius of 10 m surrounding the traps. Results: A five- to 10-fold higher propagule rain was observed in 2003, a year with an exceptionally hot summer, compared to 2004 and 2005. Propagule and species numbers varied highly among years and community types. Few propagules of non-local origin were recorded in any year. Conclusions: Extremely hot summers are likely to greatly magnify the propagule rain size of species in alpine habitats. Such ‘mast years’ may contribute to enhanced and accelerated vegetation changes in alpine habitats in the absence of limiting factors.
... Seedling emergence and the establishment of R. nobile in disturbed plots were higher than in undisturbed plots, indicating that the recruitment of the species was negatively affected by the surrounding closed vegetation and hence it was microsite-limited (Turnbull et al. 2000). This is consistent with the results of many previous studies conducted in alpine and arctic areas (Chambers 1993;Suzuki and Kudo 2005;Gough 2006;Olofsson and Shams 2007;Frei et al. 2012). ...
Background: Species persistence, particularly in monocarpic species, depends on the successful recruitment of individuals. An understanding of the factors that limit the recruitment of rare monocarpic plant species is therefore vital for their conservation. Aims: To identify the factors limiting the recruitment of Rheum nobile, a rare and highly specialised monocarpic giant herb endemic to the high eastern Himalayas. Methods: Seed sowing (seeds added or not added) and seedling transplanting experiments were conducted in disturbed (vegetation removed) and undisturbed plots in the vicinity of established populations of R. nobile to explore the mechanisms of recruitment limitation. Four levels of photosynthetically active radiation (0, 15, 30 and 50 μmol m−2 s−1) and two sowing positions (beneath and above grass litter or moss layer) were manipulated in the laboratory to determine how ground cover limited seedling emergence. Results: Seed addition increased seedling recruitment. Disturbance significantly increased seedling emergence and establishment. Seed germination significantly decreased with the reduction of light availability, but 31.7% of all seeds germinated in complete darkness. Seedling emergence was close to zero when seeds were sown on top of a layer of grass litter or moss, but rose to 34.5% when the seeds were sown beneath such layers. Conclusions: Our results indicate that the recruitment of R. nobile is limited by a combination of seed and microsite availability. Therefore, in order to conserve this species, we suggest adding seeds to suitable sites and implementing soil disturbances in existing populations to create suitable microsites.
... Compared with the other two marshes, Cg was characterized by a high seed density (especially in the upper sediment layer), greater similarity between the seed bank and vegetation, and low species diversity in the established vegetation and seed bank. This is associated with the presence of a greater number of annual species in the Cg vegetation (Chambers, 1993) and suggests that they form a persistent seed bank. The presence of annual plants in saline (Ungar & Woodell, 1996b;Bossuyt & Honnay, 2008) and freshwater wetlands (Middleton, 2003) is favored by their ability to tolerate natural and anthropogenic disturbance and to produce a large amount of long-lived seeds (van der Valk & Davis, 1978;Matus et al., 2005;Brock, 2011). ...
Seed banks play a central role in vegetation dynamics of many wetlands. Therefore, knowledge of seed reservoirs in the soils of aquatic communities should provide useful tools for conservation and restoration efforts. This study was conducted in the Lerma marshes, one of the last remnants of the vast wetlands that were once in the Mexican Central Plateau. The main objective was to determine the composition and abundance of seed bank and its relationship with established vegetation of the three Lerma marshes. In each marsh, we systematically selected 18 to 40 sampling sites. In each site, the composition of vascular plant vegetation was evaluated in two 10m lines perpendicular to the shore. Every 0.5m, we determined the coverage of species by measuring the intercepted length for each plant or group of plants. At each sampling site where we had evaluated the established vegetation, we collected a sample of the top 10cm of sediment; the soil cores were divided into an upper layer (0-5cm) and a lower layer (5-10cm). These samples were used to evaluate the seed bank by the seedling emergence method. All samples were placed in a greenhouse at 20-25 degrees C and remained flooded for 15 weeks. Forty-nine species were recorded in the vegetation. Chiconahuapan had the richest and most diverse flora and the greatest number of perennial species. A life-forms analysis showed that perennial herbs, especially rooted-emergent hydrophytes, dominated in the three wetlands. Sixty-one species were identified in the total seed bank; Chimaliapan had the most diverse total seed bank, whereas the mean seedling density was higher in Chignahuapan. Only two species of the total seed bank of each marsh had a density greater than 10% of the total, and more than half were uncommon. The upper layer of sediment (0-5cm) contained two times more seeds/m2 and species per sample than the lower layer (5-10cm), and there was a significant decrease of seed density with depth. The detrended correspondence analysis produced a clear separation between the composition of the seed banks and established vegetation. In general, in each marsh there was less species diversity in the established vegetation than in the seed bank. Dominance by a few species in the seed bank, the presence of opportunistic species, and the low representation of established species in the seed bank suggest wetland degradation and a low probability of regenerating the natural communities from the seed bank. To ensure the permanence of these marshes, their biodiversity, and therefore the environmental services they provide, up to date planning is a must, and efforts to control and monitor hydrology, water quality, and the influence of human activities are suggested.
... Curiously, no seeds of shrubby species commonly represented above-ground in disturbed habitats, such as Mulinum spinosum, were found in the seed bank. This observation is in accordance with reports of a low representation of long-lived dicots in the seed bank of disturbed areas (Chambers, 1993). Seed bank functional types do not change in terms of relative proportions of IGSB and NIGSB under dierent vegetation states, although dierences in the absolute and the relative size of each SBFT may be found among states as previously reported by Bertiller (1996). ...
We addressed the following questions: (a) May different seed bank functional types (SBFT), defined on the basis of singularities of their persistence in soil, be identified in the Festuca pallescens grasslands? (b) Do different above-ground vegetation states modify the expression of SBFT singularities? (c) Is the potential for vegetation recovery from the soil seed bank associated with the characteristics of their SBFT? To address these questions we examined the sizes of immediately and non-immediately-germinable seed banks (IGSB and NIGSB, respectively) in four different vegetation states of the steppe of F. pallescens resulting from the combined effects of topography and grazing. The results show that four lifeforms (perennial grasses, perennial graminoid non-grasses, annual dicots and annual grasses) display three characteristic SBFT. These are: (1) a transient type constituted by perennial grasses (SBFT1), (2) an intermediate type represented by annuals (SBFT2), and (3) a persistent type characteristic of one perennial graminoid non-grass (SBFT3). Other lifeforms (perennial dicots and biennials) could not be assigned to any of these types or characterized into a definite one. Seed bank functional types do not change among vegetation states in terms of the relative proportions of IGSB and NIGSB, although differences in the absolute and the relative size of each SBFT could be found. Species with persistent or mixed persistent/non-persistent seed bank types (SBFT2, SBFT3, etc.) colonize habitats disturbed by grazing with more success than those with non-persistent seed banks (SBFT1). Species with persistent seed banks are over-represented in the soil seed bank in relation to their contribution to above-ground cover. Management strategies for conservation in these grasslands could conveniently be targeted to increase the seed rain of perennial grasses as well as to the creation of suitable micro-environmental conditions to enhance their establishment.
... Compared with the other two marshes, Cg was characterized by a high seed density (especially in the upper sediment layer), greater similarity between the seed bank and vegetation, and low species diversity in the established vegetation and seed bank. This is associated with the presence of a greater number of annual species in the Cg vegetation (Chambers, 1993) and suggests that they form a persistent seed bank. The presence of annual plants in saline (Ungar & Woodell, 1996b;Bossuyt & Honnay, 2008) and freshwater wetlands (Middleton, 2003) is favored by their ability to tolerate natural and anthropogenic disturbance and to produce a large amount of long-lived seeds (van der Valk & Davis, 1978;Matus et al., 2005;Brock, 2011). ...
... Consequently, seedling recruitment patterns in arctic-alpine habitats should be reflected by the rodent population cycles, with an especially high recruitment in the year following a peak (Ericson et al. 1992). Recurrent disturbances resulting in opportunities to reproduce by seeds every third to fifth year, followed by years with a much lower disturbance level, could be important to maintain species richness in arctic-alpine habitats by providing frequent opportunities for recruitment (Warner & Chesson 1985;Chesson 1986) and by preventing competitive exclusion (Chesson 1986;Chambers 1993). The rodent population cycles have been fading out in many places in Scandinavia and in the rest of Europe over the past two decades (Ims et al. 2008;Kausrud et al. 2008;Cornulier et al. 2013), and the absence of the regular disturbance regime could be hypothesized to influence plant recruitment patterns in these sites. ...
QuestionsHow do rodents with cyclic population dynamics affect seedling recruitment in alpine habitats? Does disturbance from rodents have larger implications on seedling recruitment in some plant communities than in others?LocationSnowbeds and sheltered heaths in the low-alpine zone in areas of Børgefjell and Dovrefjell, Norway.Methods
We recorded seedling emergence, rodent activity and cover of mosses, lichens, litter and bare ground in 270 plots in snowbeds and sheltered heaths in a rodent population peak year and in the following low-density year.ResultsSeedling recruitment was positively correlated with disturbances from lemmings and voles in both years. More seedlings emerged in the low-density year than in the year of the population peak. Snowbeds had higher seedling recruitment than the sheltered heaths, but both habitats were equally affected by disturbances from rodents.Conclusions
Rodent activity created gaps and increased seedling emergence in these alpine plant communities, particularly in the year after the rodent peak, both in snowbeds and sheltered heath habitats. Our study therefore suggests that regeneration patterns in alpine vegetation are tightly linked to the population cycles of lemmings and voles, which peak in density at 3- to 5-yr intervals.
... Soil between tussocks , even only 10 cm away, may completely lack deposited seeds (median = 0;Table 1). The size of the soil seed bank of P. annua is within the limits reported for the Arctic (3,400 seeds m -2 in undisturbed sites; McGraw and Vavrek 1989) and alpine (6,000 seeds m -2 in a disturbed site; Chambers 1993) tundra. The seed bank of sub-Antarctic regions has received less attention and seems to be smaller—about 1,000 seeds m -2 (Arroyo et al.1999). ...
Poa annua L. (annual bluegrass) is the only non−native flowering plant species that
has successfully established a breeding population in the maritime Antarctic and has
been shown to maintain a soil seed bank. The characteristic of the spatial structure of
the Antarctic population of this species is the formation of distinct dense clumps -
tussocks. In the temperate zone the species is only loosely tufted. We focused on the
characteristics of seed deposition associated with the tussocks and some aspects of
the spatial heterogeneity of the soil seed bank of P. annua in the Antarctic. We wanted
to assess the microspatial structure of the soil seed bank of annual bluegrass at
Arctowski Station. Therefore we compared the number of seeds deposited underneath
and in the vicinity of P. annua clumps.
Our results indicate that P. annua in the Antarctic maintains a soil seed bank
comparable to species typical for the polar tundra. The microspatial structure of P.
annua soil seed bank in the Antarctic is highly associated with the presence of
tussocks. Seeds are deposited underneath the tussock rather than in the vicinity of the
clump. Our results also indicate that seeds are able to survive the Antarctic winter and
readily germinate under optimal conditions.
... In fact, seedling establishment in alpine species was the same as, or even higher than, that in perennial species of other habitats (Forbis, 2003). The importance of recruitment by seeds varies with the successional stage, the frequency of disturbances, the soil surface characteristics, the drought stress, and the seed morphology (Chambers, 1993(Chambers, , 1995Niederfriniger Schlag and Erschbamer, 2000), and various types of habitats or plant growth forms favour different regenerative abilities and reproduction strategies Laine, 2000a, 2000b;Welling et al., 2005). Critical moments in the early life stages of alpine species may be species-specific or habitat-specific. ...
Differences in seedling recruitment of Gentiana pannonica were
investigated between the primary (relict) and the secondary
(semi-natural) forest-free habitats of the Bohemian Forest (870-1200 m
a.s.l.) and of the Alps (1045-1935 m a.s.l.) to understand the factors
promoting the seedling recruitment of G. pannonica and their importance
for species distribution, population structure, and conservation. In the
communities with adult plants of G. pannonica, we recorded environmental
variables (the slope, the altitude, and the covers of bare ground,
litter, and rocks), estimated parameters of the vegetation (the covers
of herbs, bryophytes, and dwarf shrubs), and counted the seedlings of G.
pannonica. In a field experiment, we investigated seedling survival
under different soil moisture regimes. We also observed seasonal
dynamics of seedling recruitment in permanent plots over the course of
three years. In the primary habitats of both regions, G. pannonica grew
in a relatively wide range of communities, and its seedlings occurred in
each area. In the secondary habitats of the Bohemian Forest, a very low
frequency of the seedlings was recorded. The number of seedlings
increased with the covers of the moss layer and of bare soil and
decreased with the cover of the herb layer, especially of graminoids.
The seedling mortality was significantly lower in the plots with higher
soil moistures, and the emergence of new-born seedlings was concentrated
in the spring season, when the soil received a high water supply due to
melting of snow. For the successful generative reproduction of G.
pannonica, our findings highlight the critical importance of the
microsites with low levels of competition and of sufficient soil
moisture G. pannonica. It seems that because of the long-term lack of
grazing disturbances, the structures of the secondary habitats of G.
pannonica in the Bohemian Forest have become unfavourable for seedling
establishment and generative reproduction of this threatened species.
... In the present study the seedbank was probably of limited importance as the top 10 cm of soil (which usually contains most of the seedbank) had been removed. Studies in other alpine grasslands have shown seedbank contributions that range from negligible (Spence, 1990b;Urbanska and Fattorini, 1998) to high (Diemer and Prock, 1993;Chambers, 1993;Semenova and Onipchenko, 1996). The seed rain in alpine environments is known to be very variable in space and time (Spence, 1990a;Molau and Larsson, 2000). ...
We describe the colonisation of artificially created gaps in an alpine grassland dominated by Chionochloa pallens. Twelve years after their creation, the 50 cm × 50 cm gaps supported a distinctive vegetation composed of a mixture of perennial forbs, grasses and mosses. Three species (Bryum sp., Epilobium alsinoides and Plantago novae-zelandiae) were recorded only in the gaps. Plantago novae-zelandiae and Polytrichum juniperinum had their highest frequency in the centres of the gaps, while Celmisia gracilenta and Geranium microphyllum were most frequent at the edges. The distinctive species composition of the gap plots indicates that they are still in an early stage of succession, assuming an eventual reversion to the surrounding 'climax' grassland.
... On the other hand, the temporary very humid conditions in rocky outcrops and sandy bogs contribute to a random distribution of groups of seed (Houle & Philips 1988, Chambers 1993, Yu et al. 2003, because there is a great proportion of species with passive dispersal syndromes, mainly by water (Bigwood & Inouye 1988), which normally accumulates in specific microsites. This characteristic reduces the quality of sampling. ...
O potencial nato de uma área regenerar após um distúrbio é um fator crucial para sua conservação e manejo. A chuva e o banco de sementes são agentes importantes dessa regeneração. Bancos de sementes são particularmente importantes em comunidades onde a proporção de espécies com reprodução estritamente por sementes é alta. Nesses casos, o banco de sementes é a principal via de regeneração. Afloramentos rochosos são ambientes onde a maior parte das espécies dependem de sementes para reproduzir e manter populações viáveis. Assim, testamos a hipótese de que os afloramentos rochosos da Serra do Cipó teriam solos com bancos de sementes mais ricos e densos do que as outras fisionomias vegetacionais adjacentes. Comparamos então a abundância, riqueza e composição de espécies dos bancos de sementes dos solos dos afloramentos rochosos com os dos brejos arenosos e turfosos, capões de mata, matas de galeria e cerrados. Avaliamos a regeneração natural através da emergência de plântulas. O solo foi coletado entre 0 e 5 cm e entre 5 e 10 cm de profundidade. Os afloramentos rochosos apresentaram os bancos menos densos e mais pobres em espécies, sendo a emergência de plântulas maior nas camadas mais superficiais do solo. Entretanto, a proporção de espécies endêmicas e ameaçadas foi maior, demonstrando que esses solos são importantes para a conservação da biodiversidade dos campos rupestres da Serra do Cipó.
... Many studies have therefore been directed to several complementary aspects of the problem. Knowledge of the ecology of alpine species (Urbanska, 1986) and of the natural dynamism in disturbed environments (Chambers et al., 1984;Chambers, 1989Chambers, , 1993Chambers et al., 1990Chambers et al., , 1991Chambers 1995aChambers , 1995bFattorini, 1998a, 1998b;Urbanska et al., 1998) is assumed as a base to identify the most appropriate plant materials and seeding techniques to obtain a continuous cover and increase floristic richness (Bozzo et al., 2000;Dinger, 1997Dinger, , 2001Urbanska and Chambers, 2002;Krautzer et al., 2004). Moreover, recent criteria of restoration ecology have been directed to the transplantation of single plants (Urbanska et al., 1988;Urbanska, 1994;Fattorini, 2001) or turf transplants of wild alpine species so as to create a wholly autochthonous community (Conlin and Ebersole, 2001;Urbanska, 1994Urbanska, , 1997Ebersole et al., 2002). ...
Construction of ski runs has a very heavy impact on alpine ecosystems since it results in total destruction of the existing vegetation and profound alteration of the soil. Restoration work must thus set out to develop a protective plant cover immediately and promote re-establishment of a functional plant-soil system in the long term. The aims of the present study, conducted at the Monterosa ski resort (Val d'Ayas, Aosta, Italy) were to evaluate (1) how disturbance related to ski run construction at high altitude (2200-2600 m a.s.l.) has affected vegetation and soil properties compared to undisturbed sites, and (2) how vegetation and soil properties change in machine-graded ski runs with increasing time after hydroseeding. Herbaceous cover and specific composition, root density, physico-chemical soil properties, and aggregate stability were evaluated to determine the vegetation and soil dynamics of four runs constructed above timberline and hydroseeded 4, 6, 10, and 12 years ago, respectively, and of the adjacent undisturbed alpine pasture as control. The seeded species had quickly formed a cover that was still high even after 10 years. However, cover values were always extremely low for wild species, and this could be related to their strategies and to altered soil properties (higher pH, organic matter impoverishment, and loss of both fine particles and aggregates). The study indicated that more has to be done to conserve or restore physico-chemical soil properties as a decisive factor in establishing a self-sustaining native plant community.
... The species that recolonised disturbed areas were present in the seed bank and this could have been the reason for the high similarity between seed bank and disturbed areas found there (more than 50 % in some disturbances quadrats). These latter findings agree with results of Chambers (1993) in alpine meadows and of Lavorel et al. (1993) in Mediterranean oldfields who showed that the similarity between the disturbed areas and the seed bank could be very high (about 70 %). ...
The study deals with the influence of land use and abandonment on species composition of vegetation and seed bank in grasslands and oldfields. We wanted to explore:
(1)How the seed bank changes when agricultural practices cease? In convergence with proposals in the literature, we addressed in particular the following two questions that have been proposed by Symonides (1986), Pickett & McDonnell (1989) and Roberts & Vankat (1991) for seed bank characteristics under secondary succession: (i) Does species richness and species diversity in the soil seed bank decrease during succession? (ii) Does the density of buried seed decline during succession?
(2)What is the role played by seed bank in the recolonisation of plots disturbed by experimental disturbances?
We studied species composition of vegetation and seed bank in an experiment with grassland and oldfield plots in old embanked marshlands (called “Marais Poitevin”). In these wetlands, artificial disturbances (mowing) and natural disturbances (cattle, roebucks, coypus, voles) are very frequent. In order to mimic disturbances, experimental disturbances were generated in spring after the end of the winter flooding and emerged seedlings counted three months later. Data about the seed bank, the undisturbed vegetation and seedlings emerging in disturbed quadrats were sampled. Detrended Correspondence Analysis (DCA) of the undisturbed quadrats, disturbed quadrats and seed bank samples showed significant differences of species composition. Similarity between seed bank and undisturbed aboveground vegetation was low and not very different between grassland and oldfield. Very few seedlings emerged in the undisturbed vegetation both in grassland and oldfield, which potentially indicates the importance of gaps for seed bank expression. In Marais Poitevin, the seed bank contributed very little to the seedling flora, and vegetative regrowth clearly predominated recolonisation after disturbances. In the seed bank, few species lost after succession from grassland to oldfield vegetation were still present as seeds in the soil, but in most cases species lost were not recorded in the seed bank. The results have shown that species richness and species diversity in the seed bank decrease during succession. On the other hand, the density of buried seeds did not decrease significantly from grassland to oldfield.
... Following Thompson & Grime (1979) who studied the seasonal variation of seed banks from ten different habitats, other authors have addressed this topic (Houle & Phillips, 1988;Henderson et al., 1988;Graham & Hutchings, 1988;Coffin & Lauenroth, 1989;Russi et al., 1992;Bertiller, 1992;Lavorel et al., 1993;Chambers, 1993). ...
The qualitative and quantitative composition of a seed bank in a semi-arid grassland ofStipa speciosaTrinius et Rupecht in north-western Patagonia (Argentina) was studied. The total number of seeds was compared in late summer, winter and spring, both inside and outside a fenced area. Each time the same three species contributed most seed to the bank:Erophila vernaL., with a persistent bank of type III,Rumex acetosellaL., with a persistent bank of type IV, andVulpia australis(Nees) Blom, with a transient bank of type I. The native and dominant species,Stipa speciosa, was among the rarest species in the bank. The highest total number of seeds was found in March (early autumn). A greater number of seeds was found inside than outside the fenced area in the two first sampling months, March and August, whereas no significant difference could be observed in December.Nomenclature:follows Correa M.N. (1969–1988).
... This effect was significant only in the large and small plots (Fig. 3) when the vegetation cover was significantly weaker in the disturbed plots (20% and 60% of total cover, respectively) than in their corresponding control plots (approximately 40% and 90% of total cover, respectively). Generally, disturbances lead to partial or complete destruction of plants and limit biomass (Chambers 1993;Grime 2001;Sahib et al. 2009). In our study, vegetation cover was very low when the disturbance was applied (in summer), because the vegetation in this pool is composed mainly of winter and spring annuals (70%). ...
Mediterranean temporary pools are frequently visited habitats where domestic livestock and wild herbivores generate numerous physical soil disturbances. Using two sizes of experimental plots (large, 1.20 m × 1.20 m; small, 0.3 m × 0.3 m), the effects of soil disturbances on vegetation dynamics and the vertical distribution of seeds were studied in one Moroccan temporary pool. Results show a very rapid regeneration of temporary wetland vegetation in disturbed plots. The speed of regeneration depends on the size of disturbance and hydrology. There was an almost complete return of vegetation to the reference state in the small disturbed plots by the end of the 1st year. This fast restoration was mainly due to seed banks, which play a key role in the resilience of pools to the different sizes of disturbances frequently generated by herbivores, but also to lateral colonization by perennials.
... Soils between turf blocks had more organic matter and extractable N on Mount Belford than on Humboldt Peak because the Belford soils came from the surface and those on Humboldt originated from under talus (Bay and Ebersole, in review). Surface soils from other Rocky Mountain alpine communities contain moderate numbers of seeds (Archibold 1984;Chambers 1993;Humphries 1993). The inferred Belford seed bank and the more favorable soils and moisture regime account for the much greater density of seedlings on Mount Belford. ...
Heavy and rapidly increasing recreation on Colorado's high peaks requires restoration of closed social trails. We tested several restoration techniques on three peaks at elevations of 3660 to 3900 m. Species in turf blocks cut from newly constructed trails survived extremely well 3 yr after transplanting to closed trails. Most species did not decrease in cover although the sums of covers of all vascular species decreased 12 to 31%. The high species richness did not decline after transplanting. Grasses increased moderately in transplants, while sedges and forbs decreased moderately. On one peak, turf blocks provided safe sites for naturally colonizing seedlings. Surface soils backfilled around turf blocks presumably contained a seed bank, and natural seedlings ranged from 10 seedlings/30 cm2 plot adjacent to turf blocks to 3 seedlings/30 cm2 plot 15 cm away from blocks. Seedlings were rare at the same distances from turf blocks on another peak, presumably because surrounding soils originated under talus and contained no seeds. Plugs (10-cm diameter and 15-cm deep) from undisturbed vegetation showed excellent survival of all species in a wet area after 1 yr. Seeding of two common graminoids, Carex scopulorum and Deschampsia caespitosa, under erosion matting produced 400 monocot seedlings/m2 after 2 yr, 5 to 6 times more than seeded areas without matting and 20 to 28 times more than untreated plots. Density of unseeded dicots also increased to 190 seedlings/m2,
... a An increase of relative abundance of competitive grasses of the C-S-R and C types in the C-S-R model of primary strategies (C competitive, S stress-tolerant, R ruderal) proposed by Grime et al. (1988) by increasing stocking rate, b an increase of relative abundance of forbs with a stocking rate decrease, c an increase of relative abundance of stress-tolerant grasses of the S and S-C types of the same model with a stocking rate decrease, and d an increase of relative abundance of legumes when stocking rate increases (modified from Dumont et al. 2009) establishment (Watt and Gibson 1988) or re-growth from vegetative parts (Amiaud and Touzard 2004; Milberg 1993). The literature on the role of gap dynamics in herbaceous communities in relation to grazing seasonality is extensive (Bullock et al. 1995; Chambers 1993; Edwards and Crawley 1999; Rapp and Rabinowitz 1985). Gap creation during winter seems to be more important for the establishment of dicotyledonous species than reduced competition from dominant grasses through intensive summer grazing (Bullock et al. 1994; Watt et al. 1996). ...
Research has delivered convincing findings on the effect of biodiversity on ecosystem functioning and humankind. Indeed, ecosystems
provide provisioning, regulating, supporting, and cultural services. The global value of annual ecosystem services of grasslands
and rangelands is about US$ 232 ha−1 year−1. Nevertheless, the precise evaluation of biodiversity benefits remains challenging. This issue is due to valuation methods,
subjective assumptions, and complexity of drivers of plant community dynamics. Here, we review the primary factors that influence
plant diversity of permanent grasslands, and we describe underlying processes. These factors must indeed be identified to
focus policies meant to preserve and restore plant diversity and to advise farmers about efficient decision rules. We show
that plant dynamics of permanent grasslands cannot be explained simply by agricultural management rules, e.g., grazing, fertilization,
and mowing, implemented at the field scale. The configuration of the surrounding landscape, e.g., landscape heterogeneity,
habitat fragmentation, and connectivity, acts as a species filter that defines the regional species pool and controls seed
flow. The regional species pool often contains higher species richness in a heterogeneous landscape, because of a higher diversity
of suitable habitats. This regional pool could be a major species sources for permanent grasslands according to the seed flow.
We discuss the need to consider all of these factors to understand plant species composition of permanent grasslands and the
necessity to study plant communities using both taxonomic and functional approaches. In order to report this integrative approach,
we propose a conceptual model based on three ecological challenges—dispersal, establishment, and persistence—that are considered
to act as filters on plant diversity, and a graphical representation of the complexity of such studies due to the interaction
effects between plant dispersal abilities, forage productivity, disturbances induced by farming practices, and landscape heterogeneity
on plant diversity. Last, we discuss the ability of farmers to manage each factor and the necessity of such study in the improvement
of the current agro-environment schemes efficiency for farmland biodiversity restoration or preservation.
... It has been widely accepted that small gaps, which can act as safe sites for recruitment, are a universal mechanism for maintaining diversity (see Huston 1979, Pickett 1980, Pickett and White 1985, Chesson 1986, Chambers 1995). Different results have been found in various communities, however , demonstrating that small-scale disturbances increase (Chambers 1993, Boeken et al. 1998) or decrease (Wilson and Tilman 1991, Collins et al. 1995) species richness. Huston (1979 Huston ( , 1994) provided a more general approach, claiming that diversity reflects the dynamic equilibrium between competitive displacement and disturbance. ...
To evaluate the relative roles of seed availability and competitive,interactions in creating within-community patterns of species richness in unproductive grassland, we conducted a sowing experiment in a dry calcareous (alvar) grassland, where both the number of arriving seeds and the number,of arriving species were,approximately,doubled,compared to the natural seed rain. Also, in half of the plots, 36% of the vegetation and bryophyte cover was removed,to simulate,disturbance. Sowing significantly increased,species richness and,the number,of seedlings,in plots. Disturbance,increased,the number,of seedlings,but had no significant effect on species richness. In the first year, the highest number of seedlings was,found in disturbed and sown,plots. The dynamics,of seedling numbers,differed among species. Of the 15 sown species, seedlings of nine species were found in some plots. The number of seedlings of two species were not dependent on treatments, those of three species depended only on sowing, and for four species there was a significant positive interaction between,sowing,and disturbance. The establishment,of sown,species was,not dependent,on initial species richness or number,of adult ramets,in experimental,plots. It was,concluded that, though the behavior of individual species may differ, the local deficiency of seeds may,be an important,force generating,small-scale community,patterns of calcareous,grass- lands. Key words:,alvar grassland; calcareous grassland; community,pattern; disturbance; dynamic equilibrium; gap; perennial grassland; seed limitation; seedlings; species richness.
Unsanctioned travel routes through alpine ecosystems can influence water drainage patterns, cause sedimentation of streams, and erode soils. These disturbed areas can take decades to revegetate. In 2012 a volunteer‐driven project restored a 854 m section of unsanctioned road along the Continental Divide in Colorado, USA. The restored area was seeded with three native grass species and then treated by installing erosion matting or adding supplemental rock cover. Four years later, results suggest that the seeding, along with the use of erosion matting or supplemental rock can enhance revegetation. Matting appeared to accumulate litter, and this effect might have contributed to enhanced moisture retention. Treated areas contained 40% of the vegetation cover found on adjacent controls, which averaged 69% vascular plant absolute cover. Recovery on both treatments was markedly higher than published estimates of passive revegetation of disturbed areas measured elsewhere suggesting seeding with added cover or protection led to substantial vegetative cover after four years. Two of the three seeded grass species, Trisetum spicatum and Poa alpina, dominated the restored plots, composing 81.7% of relative vegetation cover on matting sites and 73.4% of relative cover on rock supplemented areas. Presumably due to its preference for moister sites, Deschampsia cespitosa, had low establishment rates. Volunteer species, i.e., species that appeared on their own, contributed 6.3% to the absolute vegetation cover of matting and rock sites, and species such as Minuartia biflora, Minuartia obtusiloba, Poa glauca and Festuca brachyphylla, should be considered for use in future restorations. This article is protected by copyright. All rights reserved.
Coastal freshwater wetlands are amongst the world’s most modified but poorly researched ecosystems and some of the most vulnerable to climate change. Here, we examine vegetation resilience in coastal wetlands of subtropical Australia to altered salinity and flooding regimes likely to occur with climate change. We conducted field surveys and glasshouse experiments to examine plant diversity and regeneration responses of understorey and canopy species across four habitats. Vegetation composition, but not richness, varied between seaward and inland habitats while soil seed bank diversity was greatest in more inland sites. Experimental salinity and flooding treatments strongly influenced emergence from seed banks with most species germinating under fresh, waterlogged conditions and very few in saline treatments. Composition of emerging seedling assemblages was similar across habitats and treatments but differed considerably from the extant vegetation, indicating a relatively minor role of soil seed banks in sustaining current vegetation structure in this wetland. An exception to this was Sporobolus virginicus (marine couch) which was common in both the vegetation and seed banks suggesting a high capacity for this species to re-establish following disturbances. Seedlings of dominant canopy species also reacted strongly to increased salinity treatments with decreased survivorship recorded. Overall, our findings suggest a high probability of constrained vegetation regeneration in this wetland in response to key projected climate change disturbances with implications for vegetation diversity at a landscape scale including declines in the extent and diversity of more landward vegetation communities and expansion of salt-tolerant marshes dominated by Sporobolus virginicus.
Seed banks on cliffs of the Niagara Escarpment, southern Ontario, Canada, were examined and compared to different, but immediately adjacent, communities on plateaus and talus slopes to evaluate the role of the seed bank in controlling the mature vegetation of cliff-face communities. Soil samples were collected five times at two sites over three years. Data were analyzed three ways: multiple discriminant analysis on community composition, univariate ANOVAs of seed density data, and analysis of seed characteristics. The emergence of constraints on final plant community structure was clearest for the discriminant analysis: year of collection separated the seed bank centroids the most, but a secondary effect we observed was the clear separation of the three community types and their association with species found in their specific mature communities. ANOVAs and the analyses of seed characteristics did not show statistically significant community-related sorting. Although the cliff-face community structure was discriminated at the seed bank stage, it was not directly correlated with the above-ground vegetation; therefore subsequent processes such as seed germination and seedling survivorship must also be responsible for final community composition.
Seed bank is a central topic for plant community restoration. We determined the potential and regeneration capacity of soil seed banks of woody plant patches in conservation of the vegetation in an alpine habitat, since vegetation has completely disappeared in some sites by intensive grazing in the habitat. The study was done in mountainous area of Alborz in Iran. A total of 20 individual shrubby patches were selected and two quadrats were established in and out of each patch. Soil samples were then collected from each quadrat in spring, 2011. Above-ground vegetation was estimated in each quadrat in the growing season. The soil seed bank was determined by Seedling Emergence method in the greenhouse. The results showed that the soil seed bank density inside the shrub patches was much higher than outside the patches. This differentiation was more pronounced for forbs. However, seed density of the between-patches was strongly correlated to seed density of the within-patches, indicating the so-called patch effect. Similarity between the soil seed bank and aboveground vegetation was lower inside the patches than outside. This study revealed that the limited woody patches that have remained in the study area could play an important role in conservation of herbaceous and palatable species by their positive effects on the aboveground vegetation and the soil seed bank.
Riparian forests have been adversely affected by human land use and are threatened across North America. Seed banks play an important role in the maintenance and regeneration of forests, yet effects of land use and fragmentation on forest seed banks remain poorly understood. In 1998 and 1999, we assessed impacts of human disturbance on the diversity and species composition of seed banks in upland portions of riparian forests along an urban-rural gradient in southern Manitoba. Twenty-five forest fragments were categorized according to the following land-use: urban, suburban, high-intensity rural, low-intensity rural, and relatively undisturbed reference classes. Seeds of weedy and exotic species were positively associated with fragmentation, high levels of disturbance, and dry alkaline soils. Seed bank species diversity was lower in urban sites than in rural sites, and the similarity of urban to reference sites was significantly lower than that of rural to reference sites. In contrast, the proportion of exotic to native species richness was highest in seed banks of urban sites. Exotic species Hackelia virginiana and Poa pratense were associated with urban and suburban sites, respectively. Six exotic species were unique to urban sites; these included Hesparis matronalis and Plantago major. In contrast, many of the frequently encountered native species were absent from urban sites; these included Anemone canadensis and Rubus idaeus. These changes in seed bank may affect the ability of riparian forests to recover from adverse impacts associated with urban development and agriculture.
The seed bank is the collection of viable seeds present on or within the soil at any given time. Soil seed bank is an important indicator in response to changes in land utilization and climate, and also forms the basis for desert vegetation restoration and development. Nitraria vegetation is typical of desert vegetation and with nebkhas is widely distributed along the periphery of oasis in the arid regions of Northwest China, playing an important role in desertification control around oases. In recent decades, Nitraria vegetation in the oasis-desert ecotone has been seriously degraded due to the rapid decrease of the groundwater table caused by agricultural over development. However, there is little information regarding the change in characteristics of the soil seed bank of Nitraria nebkhas in arid desert areas. Using the method of substituting space for time, the species composition, distribution pattern and quantitative variation of soil seed banks of N. Tangutorum nebkhas in initial, stable, degraded and severely degraded stages were studied in the lower reaches of the Shiyang River. Results showed that the soil seed bank of N. Tangutorum nebkha in the lower reaches of the Shiyang River was composed of 18 species, belonging to 9 families. Herb species accounted for 55%-80% and were the main body of soil seed banks. The soil seed density of the stable stage was 660.7 seeds/m2, and was the highest, being 5.6, 14.5 and 6.2 times greater than those measured in the initial stage, degraded stage and severely degraded stage, respectively. The soil seed density of the degraded stage was 45.7 seeds/m2, and was the lowest, only accounting for 38.9%, 6.9% and 42.5% of those measured in the initial stage, stable stage and severely degraded stage, respectively. The soil seed density of the N. Tangutorum population at the different succession stages was also significantly different, showing a decreasing trend after the initial increase. The soil seed density of N. Tangutorum population at the stable stage reached 9.33 seeds/m2. The soil seed density in different positions of N. Tangutorumnebkhas was significantly different and was mainly distributed in the central parts of the windward and leeward slopes of N. Tangutorum nebkhas, with seed densities of 329 seeds/m2 and 309 seeds/m2, respectively. The mean soil seed density of the nebkhas was 1.9 times that in the depressions within the nebkhas. Similarity coefficients of soil seed banks between the different succession stages were less than 0.6, which were recognized as having a moderate similarity level except for the stable stage which showed a low similarity coefficient. There were more common species which accounted for over 65% of vegetation above ground and the soil seed bank. Similarity coefficients between vegetation above ground and the soil seed bank were more than 0.5, which showed a moderate to extreme similarity level, and demonstrated a decreasing trend after the initial increase. The findings have proven the importance of soil seed banks and Nitraria nebkhas in Nitraria vegetation and also suggest that human disturbance has impacted potential underground vegetation and its restoration capacity. Therefore, man-made soil seed banks or vegetation construction should be adopted to contain Nitraria nebkhas activation and restore degraded Nitraria vegetation in arid desert areas.
Restoration of degraded high-altitude ecosystems takes place in conditions where both vegetation, soil and relief have been intensely disturbed. Consequently, restoration often fails to recreate a structure and functioning close to the original ecosystem. Even though, in mountain, it is known that vegetation is organised with relief forms, the underpinned mechanisms are misunderstood.
To better manage establishment and dynamics of the vegetation, we propose a model that links constraints determined by the relief to adaptative characteristics of plant functioning. Plant functional traits identification and measurements at their different life stages help us to determine those characteristics. Elsewhere, we suppose that relief induce variations in climatic and soil factors, biotic interactions (competition, predation), as well as constraints related to geomorphological processes (erosion/sedimentation). Studies are conducted in subalpine zone (la Plagne, Northern French Alps), and mountain level (le Saignon, Southern French Alps).
The first part, shows variation in biological traits involved in resource use, response to grazing and regeneration, with mesotopographical gradient. This one closely determines temperature cycles, soil resource level, grazing pressure, and snow pack duration.
Studies of the second part analyse biological traits in relation with geomorphological processes. Slope determines dispersal of seeds at the soil surface. The extent of seed movements is strongly related to seed shape, and to the presence of two types of seed traps: (a) soil mounds close to the plant and generated by a barrier effect on sediment, (b) hoof prints of large herbivores.
Studies in the part three, show that these traps also facilitate plant recruitment. Seed bank analysis reveals that abundance of seed in the traps is different in function of seed shape. Elsewhere, an experimentation points up that the germination and the seedling performance are affected by soil chemistry, and depend moreover of the plant functional type.
In the fourth part, modelling approach and experimentation explore relationships between functional traits and competitive performance. Results show that plant distribution in the community is linked with soil resource availability and plant traits involved in resource use.
To conclude, we propose the application of an eco-geomorphological model in the context of high altitude ecosystems. This model enlarges the view of traits/environment and species/habitat relationships. This provides a special way to analyse and apply restoration in high-altitude ecosystems.
Four years after a trench was dug through alpine habitat on Mount Washington, New Hampshire, we surveyed vascular plants, bryophytes, and lichens in the disturbed area, analyzing species richness and abundance compared with values in adjacent, undisturbed areas. Plants had begun recolonizing the disturbed area, but species richness and abundance remained far lower than in the undisturbed community. Among vascular plants, graminoids colonized most quickly, and woody species were largely absent. Species with the highest frequency and greatest abundance in the disturbed area also were common and abundant in the undisturbed community. Bryophytes appeared to be colonizing no more quickly than vascular plants. Treeline and elevation exerted separate effects on community structure and recovery. Treeline influenced species richness, abundance, and the rate of recovery of vascular plants, but there was no evidence of an additional effect of elevation either above or below treeline. Treeline also influenced species richness of bryophytes and lichens. In addition, elevation appeared to have a separate effect on their rate of recovery in alpine habitat: species richness of bryophytes and lichens declined with elevation in the disturbed community but not in the undisturbed community. This suggests that elevation has a transient effect on colonization and/or survival, but only above treeline. In general, recovery has occurred more quickly below treeline. This survey establishes baseline information that will be useful in assessing the rate of recovery after future surveys.
Soil diaspore reserves are considered to support self-healing processes after vegetation disturbances. Therefore, the stratified reserves of viable diaspores in superimposed soil layers of four sites above the timberline in the Austrian Alps were assessed. At each site, a semi-natural (“undisturbed”) extensive alpine pasture and the disturbed vegetation on hiking trails were investigated. Eighty soil cores in total (corresponding to 400 slices, each representing a 1-cm layer between 0 and 5cm depth) were taken in autumn and subjected to germination tests after vernalization. The total diaspore numbers in disturbed and undisturbed plots did not differ significantly, but all undisturbed soils contained higher species numbers than disturbed ones. Seed shape and size clearly influenced the vertical distribution. Intact soils showed a significant decrease in big/long diaspores with increasing soil depth. Disturbances influenced the aboveground species composition and therefore the distribution of seeds of different size. In case of disturbances, the restriction of most big seeds to superficial layers means a threat for small populations of rare and protected species such as Viola lutea subsp. sudetica with relatively big seeds near the soil surface. When the disturbances stop, the diaspore communities might initiate a first, but with respect of landscape protection and preservation of species diversity insufficient step of vegetation restoration.
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