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... Although tree-fall gaps are a very common process in different forests, very few dendrochronological studies have studied the fall of individuals or small group of trees in the Patagonian Andes (Veblen et al. 1996(Veblen et al. , 2004. The first study in Patagonia using tree ages based on ring counting was conducted by Veblen (1989). Age structures and species composition in gaps originated from the fall of individuals were determined for mixed stands of A. chilensis, N. dombeyi and N. antartica. ...
... Although Theodor Hartig laid the foundations of dendroecology in the midnineteenth century, it was not until the mid-1970s that it gained attention and became accepted as a subdiscipline in the field of dendrochronology (Hough and Forbes 1943;Lorimer 1980;Schweingruber 1988;Fritts and Swetnam 1989;Speer 2010). In the Patagonian Andes, the first dendroecological studies began in the late 1980s but they were based only on the simple determination of tree ages through the counting of rings (Veblen andLorenz 1987, 1988;Veblen 1989). It was not until the mid-1990s that more elaborate dendroecological methods began to be applied for the study of the forest dynamics in the Patagonian Andes (Veblen et al. 1995). ...
... Although Theodor Hartig laid the foundations of dendroecology in the midnineteenth century, it was not until the mid-1970s that it gained attention and became accepted as a subdiscipline in the field of dendrochronology (Hough and Forbes 1943;Lorimer 1980;Schweingruber 1988;Fritts and Swetnam 1989;Speer 2010). In the Patagonian Andes, the first dendroecological studies began in the late 1980s but they were based only on the simple determination of tree ages through the counting of rings (Veblen andLorenz 1987, 1988;Veblen 1989). It was not until the mid-1990s that more elaborate dendroecological methods began to be applied for the study of the forest dynamics in the Patagonian Andes (Veblen et al. 1995). ...
The study of forest dynamics over large temporal and spatial scales has widely benefited from dendrochronological techniques. Patagonia is home to several long-lived tree species (Austrocedrus chilensis, Araucaria araucana, Fitzroya cupressoides, Nothofagus dombeyi and N. pumilio) with well-defined tree rings suitable for reconstructing tree establishment, mortality, spatio-temporal growth patterns and disturbance regimes with annual resolution. The first dendrochronological studies in the region date back to the 1950s and had a strong emphasis on hydroclimatology. It was not until the last few decades that studies using dendroecological techniques began to emerge. In this chapter, we review the experience gained by the tree-ring lab at IANIGLA (CONICET, Mendoza, Argentina) and colleagues from other institutions over the past 30 years applying dendroecological techniques to understand the role of climate and disturbances (insect outbreaks, snow avalanches, windblows, fires and decline) on forest dynamics. For each case, we summarized the process, and the dendrocronological methods used. In this way, it was possible to detect those gaps of knowledge that still can be explored using dendroecological methods in the Patagonian forests of Argentina.
... Physical and biotic disturbances are major influences on the structure and composition of most temperate forests around the world (Pickett andWhite 1985, Glenn-Lewin et al. 1992). Many tropical and temperate studies indica-te that small-scale disturbances that generate canopy gaps (< 2,000 m 2 ) are key to the population dynamics of trees and to the resulting forest structure and composition (Runkle 1982, Veblen 1985a, 1989, Brokaw 1987, Stewart et al. 1991. Moreover, several studies have related forest composition and regeneration patterns to specific gap characteristic such as size and frequency as well as type of tree-fall and gap-maker species (Runkle 1982, Veblen 1985a, Brokaw 1987, Stewart et al. 1991. ...
... Typically, Nothofagus species have limited opportunities to recruit even in large canopy gaps (i.e., > 1,000 m 2 ) due to the release of advance regeneration of the shade-tolerant trees and the vigorous proliferation of the Chusquea spp. bamboos (Veblen et al. 1981(Veblen et al. , 1985a(Veblen et al. , 1989. Establishment of Nothofagus species in gaps occurs occasionally on elevated surfaces such as treefall mounds and large logs where competition with other species is reduced (Veblen et al. 1981(Veblen et al. , 1985a(Veblen et al. , 1989. ...
... bamboos (Veblen et al. 1981(Veblen et al. , 1985a(Veblen et al. , 1989. Establishment of Nothofagus species in gaps occurs occasionally on elevated surfaces such as treefall mounds and large logs where competition with other species is reduced (Veblen et al. 1981(Veblen et al. , 1985a(Veblen et al. , 1989. In this regard, forest structure and composition may influence the recruitment opportunities of Nothofagus and other late successional species (Veblen 1989, Veblen et al. 1996. ...
Canopy gaps have been recognized as an important process in the regeneration dynamics of Andean old-growth forests (ca. 40 degrees S). The objectives of the study were to determine main tree-fall gap attributes and to assess tree recruitment and growth patterns in tree-fall gaps of two mid-elevation Andean old-growth forests. We measured the canopy and expanded area of each gap, and for the gap-maker species we measured its diameter at breast height (dbh), felling direction and type of treefall. In each gap, tree seedlings, saplings and bamboo culms were counted in subplots. Increment cores of potential successors were obtained to examine growth patterns. There was a larger area in canopy gaps in NF than in STF (25.8 vs. 11.9 %). Expanded gaps were on average larger in NF than in STF (547 vs. 440 m(2)). Most gaps were originated by wind-snap and upturned root-plates of all the major tree species (Laureliopsis philippiana, Saxegothaea conspicua and Dasyphyllum diacanthoides, and Nothofagus dombeyi in NF). The understory species Chusquea culeou was an important competitor in gaps, especially in STF where the bamboo was more effective inhibiting the recruitment of tree seedlings. The successful recruitment of shade-tolerant tree species beneath endogenous tree-fall gaps indicates that these species follow a gap-phase regeneration mode through which -after several growth releases-they can reach the main canopy. These studies could offer valuable insights for the urgently required restoration and management of Andean old-growth forests.
... Our study motivation is to deepen our understanding of the regeneration biology of Nothofagus dombeyi which has been addressed earlier under different aspects, e.g., the establishment success of seedlings (Veblen et al., 1981(Veblen et al., , 1996, the influence of disturbance on regeneration (Veblen, 1989;Veblen et al., 1996;Larraín, 1997), and the effects of light regimes on regeneration patterns (Encina et al., 2019). There is a knowledge gap on how grazing affects the regeneration of N. dombeyi. ...
... In our multivariate analysis, no significant relationship between the canopy cover as a measure for light availability and the regeneration of N. dombeyi has been found. In contrast, several studies have reported that the regeneration and growth of this tree species increases with light availability (Veblen, 1989;Donoso et al., 2013;Caselli et al., 2021b). Furthermore, Caselli et al. (2021a), state that the "lack of canopy cover can be beneficial for the growth […] if moisture is not limiting". ...
Natural forests and stands subjected to little to moderate human impact are continuously declining worldwide and with these, their biodiversity and ecosystem services. Many Nothofagus forests in the south of the South American continent are in a pristine state or only moderately impacted by humans. Forest grazing by livestock, in the past and still today often practiced in a non-sustainable way is, however, increasingly under discussion to meet current environmental and socio-economic challenges. Accordingly, we investigate the regeneration of Nothofagus dombeyi, a keystone species of the Patagonian Andes, in secondary forests in Argentinian northern Patagonia, particularly addressing the role of disturbance through grazing by livestock at various intensities. We test the hypothesis that the regeneration of this tree species is favored by grazing impact and, thus, disturbance of the herb layer and soil surface. In support of our hypothesis, Nothofagus dombeyi regeneration was significantly higher in terms of individuals and height classes in moderately grazed forests. Multivariate analysis shows significant positive effects of moderate grazing pressure, herb layer cover, and the occurrence of bare soil on the regeneration of Nothofagus dombeyi. Our results show that an integration of livestock grazing and forest regeneration is possible and that agroforestry systems can be an adequate management option for stakeholders in the region. A grazing management can also be part of a forest fire prevention strategy. However, the regeneration success and grazing pressure should be continuously monitored.
... Seedlings of Nolhofagus Species often survive and grow slowly for very long lime periods in lhe shaded underslory (Rebertus and Veblen, 1993), crealing a seedling bank (Cuevas and AIroyo, 1999) wilh a polenlial advanlage in reestablishing canopy dislurbances after lhe openlng of gaps due lo windslorms, ice damage, limber harvesling or beaver engineering (Veblen, 1989;Rebertus and Veblen, 1993;Guliérrez 1994;Rebertus el al., 1997;Heinemann el al.. 2000;Martinez Paslur el al.. 2000;2006;Anderson el al., 2006). However, while il is generaUy accepled lhal lhese foresls regenerale in a gap dynamic from an eslablished seedling bank, lhe eco-physiological faclars lhal delermine lhe seedllng bank ilself are much less known. ...
... the rale al net photosynthesis diminishes about 60-65% in severe water-Iogged conditions (Sun el al., 1995). Regeneralion 01 N. pwnilio is produce mainly lhrough gap dynamies (Veblen, 1989) due lo Ihe light availability under lhe overslory. Another limiting factor in lhis response is the waler stress, which could switch the processes from a light-to a water-limited system (Heinemann el al.. 2000;Heinemann and KilZberger. ...
Las propuestas silvícolas de los bosques de Nothofagus pumilio se basan en la apertura del dosel para estimular el crecimiento de la regeneración, cambiando la disponibilidad de agua y luz. Las plántulas sobreviven como si fueran especies tolerantes y crecen lentamente por largo tiempo (más de 20 años) bajo altas coberturas. Sin embargo, cuando el dosel se abre debido a la cosecha o volteos por viento, la regeneración reacciona como una especie intolerante, colonizando rápidamente los sectores abiertos. El objetivo del estudio fue efectuar una comparación, analizando las características fisiológicas y morfológicas de plántulas de N. pumilio creciendo en un gradiente de luz bajo condiciones controladas de riego y temperatura.
... El coihue presenta dificultades para regenerar bajo dosel cerrado aparentemente debido a su baja tolerancia a la sombra (Müller-Using and Schlegel 1980;Dezzotti 1996;Amoroso and Larson 2010), por lo que se espera que cuanto mayor sea IAF del dosel menor sea el crecimiento de su regeneración. En cambio, el ciprés es algo más tolerante a la sombra que coihue, lo que le permite persistir mucho más tiempo bajo dosel (Veblen and Lorenz 1987;Veblen 1989;Kitzberger et al. 2000), lo que implica que sería menos sensible a aumentos del IAF del dosel. Si bien existen antecedentes importantes de estudios del efecto de diferentes condiciones de crecimiento sobre los renovales de coihue (Müller-Using and Schlegel 1980;Veblen et al. 1995;Dezzotti 1996;Weinberger and Ramirez 2001;Dezzotti et al. 2004;Soto et al. 2009;Donoso et al. 2013;Pafundi et al. 2016;Caselli et al. 2019Caselli et al. , 2021b y de ciprés (Dezzotti 1996;Gobbi and Schlichter 1998;Arturi et al. 2001;Letourneau et al. 2004;Defossé 2013, 2019;Pafundi et al. 2014Pafundi et al. , 2016Caselli et al. 2019Caselli et al. , 2021b, hasta la actualidad no se ha estudiado la relación entre el crecimiento de la regeneración natural y el espacio de crecimiento ocupado por el dosel. ...
... Estos resultados coinciden con lo hallado en la misma zona de estudio por Palenzuela y colaboradores (2018), quienes mostraron que existen mayores tasas de crecimiento de coihue cuando existe una reducción de la cobertura del dosel, mientras que la reacción en crecimiento del ciprés ante cambios en el dosel es más discreta. Dado que el IAF del rodal y la luz que llega a la regeneración tienen una relación asintótica inversa (Waring 1983;O'Hara et al. 2007;Comeau et al. 2009), las diferencias en el comportamiento de las especies bajo estudio son las esperables según su afinidad por la luz, siendo el ciprés la más tolerante a la sombra (Veblen and Lorenz 1987;Veblen 1989;Kitzberger et al. 2000). Esto implica que para que los renovales de ciprés puedan mostrar mayor crecimiento podrían necesitar reducciones fuertes de la cobertura del dosel (Arturi et al. 2001), o bien cambios en la competencia más cercana (del sotobosque). ...
La ocupación del espacio de crecimiento del dosel tiene influencia sobre el desarrollo de la regeneración natural. El índice de área foliar (IAF) del dosel es una variable que se puede utilizar en estudios ecológicos y en la toma de decisiones silviculturales para representar el espacio de crecimiento ocupado en un rodal. Es especialmente útil en bosques mixtos, ya que permite captar mejor la complejidad de la
estructura forestal que otras variables de densidad. El ciprés de la cordillera (Austrocedrus chilensis) y el coihue (Nothofagus dombeyi) son especies de importancia forestal de los bosques andino-patagónicos, que pueden crecer en formaciones mixtas con potencial productivo. Determinar cuáles son las estructuras forestales necesarias para promover la regeneración implica conocer cómo el espacio de crecimiento que ocupa el dosel afecta el crecimiento de la regeneración avanzada. El objetivo de este estudio fue evaluar la relación entre el IAF del dosel y su distribución entre especies y estratos de altura con el incremento en altura de la regeneración
avanzada de ciprés y coihue. El incremento en altura de los renovales muestra una tendencia opuesta al IAF del dosel, aunque esta relación es significativa sólo para coihue, para el cual por debajo de un IAF cercano a 4 favorece el crecimiento de los renovales. A su vez, el incremento en altura de los renovales, en especial del coihue, se ve influenciado negativamente por una participación mayor de coihue en el IAF del dosel. A partir de los resultados se infiere que para promover el crecimiento de la regeneración de ambas especies es necesario mantener, mediante raleos, el IAF por debajo de 4 en los sectores que se requiera promover la regeneración de coihue, y por encima de 4 para la de ciprés de la cordillera.
... Seedlings of Nolhofagus Species often survive and grow slowly for very long lime periods in lhe shaded underslory (Rebertus and Veblen, 1993), crealing a seedling bank (Cuevas and AIroyo, 1999) wilh a polenlial advanlage in reestablishing canopy dislurbances after lhe openlng of gaps due lo windslorms, ice damage, limber harvesling or beaver engineering (Veblen, 1989;Rebertus and Veblen, 1993;Guliérrez 1994;Rebertus el al., 1997;Heinemann el al.. 2000;Martinez Paslur el al.. 2000;2006;Anderson el al., 2006). However, while il is generaUy accepled lhal lhese foresls regenerale in a gap dynamic from an eslablished seedling bank, lhe eco-physiological faclars lhal delermine lhe seedllng bank ilself are much less known. ...
... the rale al net photosynthesis diminishes about 60-65% in severe water-Iogged conditions (Sun el al., 1995). Regeneralion 01 N. pwnilio is produce mainly lhrough gap dynamies (Veblen, 1989) due lo Ihe light availability under lhe overslory. Another limiting factor in lhis response is the waler stress, which could switch the processes from a light-to a water-limited system (Heinemann el al.. 2000;Heinemann and KilZberger. ...
The silvicultural proposals tor Nothofagus pumilio foresls are mainly based on canopy open lo stimulate regeneration growth by moditying water and light availability al understory leve!. Seedlings and saplings aften survive as tolerant species and grow slowly for a long time (up to 20 years) under shaded overstory. However, when canopy is open by harvesling or wind-Ihrows, young Irees aeting as intolerant speeies and can quiekly colonize the opened areas. The objeetive was to make a eomparative and lunetional approaeh analyzing morphologieal and physiologieal eharaeteristies 01 N. pumilio seedlings. growing in a pre-defined lighl gradienl under controlled conditions of ¡rrigalion and temperature. Seedlings of 2-3 years were collected in a closed canopy natural stand during September. Then, they were transferred to pats under a greenhouse, where three light levels were assayed (4%-26%-64% of the total natural incident light). Irrigation was made manually, maintaining a soil humidily 01 40-60% so;1 eapaeity. while lemperalure was eonlrolled through loroed ventilation (Iess than 24'C). Thirty six planls in 6 elusters per eaeh Irealment where measured during January (heighl, number, size and shape 01 leaves. braneh number and inserlion angle), while 6 plants (one per elusler) was seleeted lor physiologieal parameters measurement (dark respiration rate.lighl compensation poi nI, photochem;cal effieieney, lighl saturation point and chlorophyll content). Photo-respiration was measured using an infra red gas analyzer 01 CO, model 5151 01 Qubit 5yslem Ine. wilh a leal ehamber 01 9 em'. Twenly-lhree variables related wilh three lunelionallevels (leal. shool and erown, whole planl) were analyzed. Al leaf level, mast of physiological variables were higher in luminous treatment. while biometric variables were higher in mlddle lighl trealmenl. This lasl lreatmenl has more ehlorophyll a-b (0.033 and 0.011 mg/em'), while luminous trealment has more earolenoids (0.010 mg/em'). However. dark lreatment presenled Ihe lower speeifie leal mass (0.0007 g/em').At shoot and erown level, no differenees were found in branch number and insertion angle, bul plants growing in middle Iight trsalment were tallertllan the olhers (17 cm compared lo 12 cm). At whole planl level. best values were lound in middle lighl treatmenl. However, the higher leal area ralio was measured in dark trealmenl (389 em'lg). Nothofagus pumilio seedlings have morphological and physiological characteristics related to loleranl species, but eould quiekly ehange lo Ihose adapled lo inloleranl species when the Iighl availabilily ¡ncreases. It is necessary to make comparative and functional models to develap better silvicultural Irealmenls whieh maximize the seedling polenlial during Ihe installalion and ear1y growth phase.
... Lower numbers of yew saplings in less shaded conditions (over 7% of full sun) may be due to competition with herbaceous plants and fastgrowing seedlings of other tree species (Veblen, 1989;Takahashi, 1997;Mason et al., 2004), because densities of the plants that compete with yew seedlings increase with increased light intensity. At the same time, environmental conditions in open habitats may impede germination (Suszka, 1985) and lower the soil moisture content, which hampers both the germination and growth of the youngest seedlings (Becker et al., 1988;Battaglia et al., 1999). ...
... Similar conclusions were drawn by Austrian researchers who on the basis of population viability risk management (PVRM) determined the optimum methods of management of yew reserves in the Austrian Alps (Dhar et al., 2006;. This strategy consists in: (1) fencing of yew populations and game management; (2) thinning of canopy density (3) sanitary thinning; (4) careful logging; (5) promotion of natural regeneration, supplemented by planting; (6) informing the society about the need to protect yew populations. ...
Short title: Influence of biotic and abiotic factors on natural regeneration of European yew This study examines the factors affecting the lack of success in regeneration of natural populations of European yew. Among the numerous local factors that can be important in the existing populations, the lack of reproductive success is most probably due primarily to shading, combined with low temperatures in winter, impact of herbivores, and limitations associated with dioecy. In many cases it seems necessary to apply active protection measures supporting this species within its natural range of distribution. The major recommended actions include fencing of yew populations and thinning of the canopy.
... The importance of canopy gaps' features for the regeneration of a forest, species coexistence and general structuring of a forest has been a topic of ecological and forestry research for decades (e.g. Grubb, 1977;Pickett & White, 1985;Veblen, 1989Veblen, , 1992. In the absence of largescale disturbances, the fall of a big tree creates a canopy gap that represents a spatial and temporal opportunity for new propagules, or already established advance regeneration, to establish and preempt resources, and therefore thrive. ...
Worldwide, the implementation of forest management guidelines has tried to mimic natural forest dynamics. The Oliver forest stand dynamics model has been successful in bridging natural forest dynamics associated with the disturbances of various spatial scales and silviculture also related to various spatial scales of management. However, the application of this model (and others) is restricted to tall forests.
We claim here that the general research and commercial interest bias towards tall tree species has permeated silviculture and forest management, and that both the stand dynamics of short‐stature tree species and their treatment have remained largely unexplored and unknown.
Using one short‐stature tree species, Nothofagus antarctica , as a model system, we show that this species indeed follows a stand dynamic different from other tall Nothofagus ‐dominated forests in southern South America. This species forms short, mature, even‐aged stands without large canopy gaps that promote tree regeneration. With this in mind, we propose a conceptual ecology‐based silvicultural guideline focusing on the creation of strip cuts or gaps along with topsoil scarification to ensure regeneration and forest reorganization after disturbances.
Policy implications . The acknowledgement that short‐stature tree species follow a stand dynamic different from tall tree species necessarily implies that they must be managed differently. This recognition, along with the implementation of ecology‐based silvicultural recommendations, represents strong arguments to make modifications to forest legislation that, together, must be aimed at conservation and sustainable forest management.
... e) Cabe destacar la importancia de factores externos tales como el pastoreo y las quemas (observados en algunos fragmentos), cuyo accionar puede modificar y hasta condicionar la vegetación futura del bosque (Chalukian Madrid, 1991). f) Por último, las estructuras diamétricas alteradas, la menor cantidad de árboles padres o semilleros, las peores categorías de calidad existentes, las menores densidades de árboles adultos, el ciclaje de nutrientes y -en general-el hábitat alterado, pueden afectar la cantidad y calidad de regeneraciones futuras (Veblen, 1989;Wunderle, 1997;Viana et al, 1997;Takyu, 1998;Wickman et al, 1999). ...
... Es importante tener en consideración que los patrones de regeneración, que incluyen todos aquellos eventos que deben ocurrir para que una especie logre regenerarse en un contexto determinado, no son inherentes a las especies individuales sino que pueden variar geográficamente, en función de la composición de la comunidad en la que participan y de los factores abióticos del sitio en particular en el que se encuentran (Veblen, 1989;Díaz y Armesto, 2007). Por lo mismo, la regeneración es capaz de verse afectada tanto por cambios en los factores abióticos del lugar, como también por cambios en las comunidades biológicas, cuando desaparecen/aparecen especies dentro del paisaje. ...
Este texto tiene como objetivo recopilar reflexiones en torno a las implicancias que conlleva la incorporación de los Derechos de la Naturaleza dentro del ordenamiento jurídico de Chile. Estas reflexiones surgieron de los ciclos de lectura y discusión generados en el Centro de Estudios FIMA, el cual es un espacio de discusión e investigación de diversos temas de derecho ambiental entre estudiantes y profesionales de diversas disciplinas de las ciencias sociales y ciencias ambientales
... Foto: Gustavo Aprile. disturbios naturales y/o antrópicos que favorecen la dominancia de especies arbóreas heliófilas (Veblen, 1989). Por encima de los 700 metros de altitud, el bosque se empobrece y los árboles son más bajos y delgados. ...
Se estima la abundancia de huemul (Hippocamelus bisulcus) en el sector este de la Reserva Provincial Lago del Desierto, Santa Cruz, Argentina.
The abundance of andean deer (Hippocamelus bisulcus) that inhabits the east
area of the Lago del Desierto Provincial Reserve (Santa Cruz, Argentina) was estimated.
... These may include reductions in numbers of pollinators, seed dispersers, alterations in plant-herbivore relationships and the possibility that timber exploitation may ultimately produce conditions in which it is difficult for many forest species to regenerate (Peters, 1996). Numerous studies have related forest composition to the size and frequency of disturbances (Veblen, 1989;Whitmore, 1989). In general, plant communities respond to disturbances differently, and their responses vary with the type of disturbance, be it logging (Yoshida et al., 2005) anthropogenic pressure, fires (Loeb, 2001), or natural tree falls. ...
Studies on the knowledge and use of natural resources by local populations may contribute to finding economic alternatives for these populations, especially in terms of the use of plants for treating health problems. In this research, the ethnobotany and ecology of the medicinal plants of the Bia Biosphere ecosystem was studied, in order to identify the plant species used for reproductive healthcare and provide baseline information for future pharmacological and photochemical studies. Furthermore, this research aimed at promoting the conservation of medicinal plants as well as the traditional knowledge associated with them, so that long-term biodiversity values would not be lost.
... There may even be an increase in the number of species in some disturbed ecosystems but, as noted above, this may occur with a concomitant reduction in the abundance of individuals or local extinction of the rarer species. Numerous studies have related forest composition to the size and frequency of disturbances (Veblen, 1989;Whitmore, 1989). In general, plant communities respond to disturbances differently, and their responses vary with the type of disturbance, be it logging (Yoshida et al.,20'05) anthropogenic pressure, fires (Loeb,200 I), or natural tree falls. ...
Ethnobotanical and ecological studies were carried out to take inventory of the species used by the inhabitants surrounding the Subri River Forest Reserve for reproductive health care and to assess the ecological status of woody plant species of this reserve. The study was carried out between November 2005 and December 2006. Medical ethnobotanical knowledge was gathered from 80 inhabitants in 25, communities using questionnaires. Reproductive health conditions were categorized into 19 major conditions, some of which included abortion, breast cancer, miscarriage and sexual impotence; and 7 corporeal or body systems. A total of 185 medicinal plants species, distributed in 60 families and 155 genera were cited. The most cited species was Gouania longipetala (4.23%). Of these 185 species, 72.97% were woody, while 27.03% were herbaceous. The most frequently employed plant part was barks (32.49 %), followed by roots (29.95%) and leaves (21.32%). Phytosociological studies on woody species with girth of at least 10 cm were undertaken in 50 circular plots of 0.l ha, making a total of 5ha study area. A total of 128 species belonging to 104 genera and 45 families were encountered. The importance value indices of these species were generally low (0.28 to 20.09). Their distribution into Raunkiaer's frequency classes showed that 92.19% of the species were rare and none was common. There were high species diversity indices of Simpson (0.96) and Shannon-Weaver (4.00). Species evenness was also high (0.82). Only 57 (44.53%) of the woody species were cited for reproductive health conditions. The Relative Importance (RI), calculated from an ethnobotanical perspective, showed that approximately 28% of the 57 plant species were
versatile. Alchomca cordifolia was the most versatile species for the reproductive health conditions. However, there was no significant (p>O.05) association between the RI and the phytosociological parameter values of the 57 woody medicinal species. Provisions of sustainable harvesting methods, adequate knowledge about forest management and cultivation among others, will ensure the conservation and sustainable use of these medicinal plants.
... These resources can act as a limiting factor that could be https://doi.org/10.17221/138/2020-JFS responsible for the expansion of diversity in a forest ecosystem as explained by Veblen (1989). The present study area has open canopies due to illegal cutting of mature trees which is the threat to regeneration by losing seedlings, saplings and reproductive trees. ...
This article encompasses the impacts of disturbance, regeneration potential of conifers and the dynamics of tree species seedlings along the spatial scale in Murree forest. The seedling status preferably of conifers along with associated broadleaved dominant tree species is determined by a quantitative evaluation of diversity functions. An empirical approach is applied to predicting the future of seedlings under stress as well as the current hypothetical appearance of seedlings in the forest. The need of analysing diversity of this forest is due to highly disturbed conditions there, and this paper is designed to know the recent trends of species diversity in the area. Species diversity and species abundance at a seedling level are estimated by using standard formulas of diversity measurements. Thirty stands are used for the evaluation of seedling abundance in highly disturbed conditions with the examination of diversity in the area. Seedling density is too low in the forest whereas diversity is also in poor condition. Seedlings from four conifers with three broadleaved species in different stands indicated the low density of future trees. The mean density·ha<sup>–1</sup> of pine seedlings is consecutively low in Pinus wallichiana (16 ± 2), Pinus roxburghii (11 ± 3), Cedrus deodara (9 ± 3), Abies pindrow (8 ± 3). The correlation coefficient is as low as 0.76, 0.66 and 0.61 in Pinus roxburghii, Cedrus deodara and Abies pindrow, respectively, while Pinus wallichiana showed a significant correlation, i.e. P > 0.5. Hence, this study claims that the survival of the forest is threatened as seedling density and diversity are too low. This forest needs serious attention towards preventing and conserving pines and other associated species seedlings for the existence of this forest in future.
... Decomposing tree trunks (termed coarse woody debris, CWD) may harbor less fungal pathogens and more wood decomposers compared to the forest floor soil (O'Hanlon-Manners and Kotanen, 2004). In addition, dead wood has higher capacity to retain moisture (DeLong et al., 1997) that may significantly affect germination and regeneration of tree seedlings (Veblen, 1989) as well as fungal communities associated with the roots of those trees that proliferate on CWD. Ericoid dwarf shrubs represent another factor that may affect the composition of fungal communities on tree roots (Kohout et al., 2011). ...
Belowground litter derived from tree roots has been shown as a principal source of soil organic matter in coniferous forests. Fate of tree root necromass depends on fungal communities developing on the decaying roots. Local environmental conditions which affect composition of tree root mycobiome may also influence fungal communities developing on decaying tree roots. Here, we assessed fungal communities associated with decaying roots of Picea abies decomposing in three microhabitats: soil with no vegetation, soil with ericoid shrubs cover, and P. abies deadwood, for a 2-year period. Forest microhabitat showed stronger effect on structuring fungal communities associated with decaying roots compared to living roots. Some ericoid mycorrhizal fungi showed higher relative abundance on decaying roots in soils under ericoid shrub cover, while saprotrophic fungi had higher relative abundance in roots decomposing inside deadwood. Regardless of the studied microhabitat, we observed decline of ectomycorrhizal fungi and increase of endophytic fungi during root decomposition. Interestingly, we found substantially more fungal taxa with unknown ecology in late stages of root decomposition, indicating that highly decomposed roots may represent so far overlooked niche for soil fungi. Our study shows the importance of microhabitats on the fate of the decomposing spruce roots.
... Although we hypothesize a framework of causality where bamboo affects forest structure, it is still not possible to determine whether bamboo creates or thrives under these structural conditions. For instance, it is possible that bamboo does not cause increases in tree mortality and growth rates, but rather that bamboo a posteriori colonizes areas with low tree densities and high mortality rates, such as treefall gaps and landslides (both of which are common in Andean forests) (Veblen 1989b, Tabarelli and Mantovani 2000, Clark et al., 2015a. It is also unclear whether the bamboo biomass compensates for the decrease in tree biomass associated with high bamboo densities (Arango and Camargo, 2010). ...
Forest structure and composition play an essential role in determining the carbon storage capacity of tropical forests. Andean forests, with great potential for carbon accumulation, include large expanses of high-density woody bamboo communities. Woody bamboos can potentially alter forest structure, composition and dynamics and thus can affect carbon storage capacity; however, they are commonly excluded from forest monitoring and modelling. With the aim of documenting patterns of bamboo abundance and disentangling its association with forest structure, we carried out a bamboo census in seven 1-ha long-term forest monitoring plots situated across a large elevation gradient (1000–3600 m a.s.l.) in the Peruvian Andes. We determined that bamboo is a dominant plant group in the study area. In every plot, bamboos were the most common genera in terms of number of stems, and in two of the plots bamboo species were among those with the greatest basal area. We used a combination of Generalized linear mixed models (GLMM) and structural equation modelling (SEM) to hypothesize a causal framework and determine the direction and size of the effects of bamboo abundance (basal area) on number of individual trees, total tree basal area, mean tree basal area, mean tree growth rate and tree mortality rate. We found an overall negative association between bamboo abundance and total tree basal area driven mainly by reduced tree density (directly and indirectly mediated by an increase in tree mortality). However, the decrease in tree density and the increase in tree mortality are also associated with a small increase in tree diameter (mean tree basal area). Overall, the negative association between bamboo abundance and tree basal area suggests a lower biomass accumulation and thus a lower carbon storage capacity of trees in Andean forests where bamboo is dominant. Our results, which show the importance of bamboo in determining forest function, highlight the need for including bamboo in monitoring efforts and modeling studies.
... On these subalpine forests, however, gaps are mainly created by windrelated disturbances, such as stem breakage, treefall, and uprooting of canopy trees due to wind storms (i.e., typhoon) (Komiyama et al., 1981;Kanzaki and Yoda, 1986;Yamamoto, 1992). Disturbance regimes differ in frequency, average gap size, and subsequently environmental changes among the major types of disturbance agents, such as fire, wind storms and insect outbreaks (Oliver et al., 1985;Veblen, 1989;Turner et al., 1997). As for snow avalanches, Johnson (1987) reported that re-establishment of dominant tree species differed largely even within a given avalanche slope due to difference in average event frequency. ...
We examined the effects of snow avalanche on stand structure and the subsequent regeneration of subalpine Abies mariesii Mast forest in northern Japan, and discussed whether gap formation after avalanche disturbance leads to immediate seedling establishment or not. Tree size and age, tree-ring chronology, and seedling density were compared between, on, and around a relatively large avalanche path, which was created in the mid-1980s within Hachimantai National Park. On the avalanche path, only smaller and younger trees (height <5 m, 50–100 yr old) escaped the mechanical damage of avalanche by leaning into the remaining snowpack, and old canopy trees were mostly killed by stem breakage. Tree size structure of the avalanche path, including both living and dead individuals, was relatively similar to that of nearby undisturbed forest, indicating that a mature stand (>ca. 200 yr old) had been previously developed on the avalanche slope without large-scale disturbances in the past. Most of the surviving, younger trees showed abrupt growth release during the few years (1987–1989) after the avalanche event. However, densities of both post-avalanche (<15 yr old) and pre-avalanche (≥15 yr old) seedlings were much lower on the avalanche path than in the nearby forest, especially at microsites covered with dense dwarf bamboo (Sasa kurilensis) shrub. The pre-avalanche seedlings on the avalanche path sharply increased annual height growth rates after the mid-1980s avalanche, but such positive growth response did not continue longer than 6 to 7 yr. These findings suggested that gap formation following the infrequent, large-scale avalanche disturbance did not necessarily lead to immediate seedling recruitment and/or further growth release of pre-avalanche seedlings. The constraint of seedling establishment was primarily explained by the lack of potential seed supply, and shading effect of the dwarf bamboo bush. Consequently, post-avalanche regeneration of the subalpine fir forest was likely to depend on the smaller individuals (2–5 m in height) that were able to avoid both the mechanical damage of avalanche and mortality from shading by the dwarf bamboo.
... Una manera de decidir entre las alternativas de manejo es optar por aquellas que imitan la dinámica natural de la especie (Donoso y Lara, 2007). En el caso de lenga, se ha reportado la ocurrencia de dinámica de claros (Veblen, 1989a;Veblen, 1989b;Rebertus y Veblen, 1993;Veblen et al., 1996;Bava, 1999). Los claros se producen por la caída de árboles sobremaduros, lo que afecta la estabilidad de individuos vecinos, por lo que generalmente la caída se ve acompañada por el desmoronamiento de dos o tres vecinos. ...
... Light is also a major limiting factor for natural regeneration potential of species in the higher altitudinal region. Study on the effect of light has been conducted by Veblen (1989). They suggest that the successful regeneration of light loving species is directly related to increasing level of light. ...
Increasing anthropogenic pressure and dependence on plant products have has let to widespread exploitation of natural forest in Uttarakhand Himalaya. The study area is located between 29 0 24' and 29 0 26' N latitude and 78 0 53' and 78 0 59' E longitude between 280 and 370 m elevation in Uttarakhand Himalaya. A total of 17 tree species were present in different forest, out of which 8 species existed in disturbed site and 11species in least disturbed site. Total tree density ranged from 250.3-340 trees/100 m 2 and total basal area from 18.1-76.15 m 2 /ha across the disturbance, which was higher for least disturbed forest and lower for highly disturbed forest. Vegetational parameters showed that protected forest areas are important for maintaining the species richness, regeneration and the ecosystem as a whole.
... Aunque la dependencia de las especies del género Nothofagus respecto a la ocurrencia de disturbios de gran escala ha sido establecida con bastante claridad, principalmente en el caso de los bosques lluviosos del distrito Valdiviano, este fenómeno también ha sido observado en el bosque lluvioso patagónico, entre los 43º20' y los 47º30' latitud sur (Innes, 1992;Szeicz, 1998). En mayores latitudes y altitudes, o en sitios secos, con escasa o nula representación de especies tolerantes a la sombra, la tendencia sucesional al reemplazo de árboles del género Nothofagus por otras especies es obviamente menor o no existe (Veblen, 1989). ...
... This study addresses vegetation recovery after removal of nonnative conifers (primarily Pinus ponderosa and Pseudotsuga menziesii) in Nahuel Huapi National Park in north-west Patagonia, Argentina. Sites that have been targeted for removal occur mainly in temperate evergreen mixed Nothofagus/Austrocedrus forests that occur in the central region of the park along a sharp west to east gradient from Nothofagus-dominated rain forest to xeric Austrocedrus woodlands and bunchgrass steppe (Veblen 1989a). We surveyed understorey vegetation in clearcut sites where passive restoration has been the primary postremoval management strategy. ...
Nonnative conifers are widespread in the southern hemisphere, where their use as plantation species has led to adverse ecosystem impacts sometimes intensified by invasion. Mechanical removal is a common strategy used to reduce or eliminate the negative impacts of nonnative conifers, and encourage native regeneration. However, a variety of factors may preclude active ecological restoration following removal. As a result, passive restoration – unassisted natural vegetation regeneration – is common following conifer removal. We asked, ‘what is the response of understorey cover to removal of nonnative conifer stands followed by passive restoration?' We sampled understorey cover in three site types: two‐ to ten‐year‐old clearcuts, native forest and current plantations. We then grouped understorey species by origin (native/nonnative) and growth form, and compared proportion and per cent cover of these groups as well as of bare ground and litter between the three site types. For clearcuts, we also analysed the effect of time since clearcut on the studied variables. We found that clearcuts had a significantly higher average proportion of nonnative understorey vegetation cover than native forest sites, where nonnative vegetation was nearly absent. The understorey of clearcut sites also averaged more overall vegetation cover and more nonnative vegetation cover (in particular nonnative shrubs and herbaceous species) than either plantation or native forest sites. Notably, 99% of nonnative shrub cover in clearcuts was the invasive nonnative species Scotch broom (Cytisus scoparius). After ten years of passive recovery since clearcutting, the proportion of understorey vegetation cover that is native has not increased and remains far below the proportion observed in native forest sites. Reduced natural regeneration capacity of the native ecosystem, presence of invasive species in the surrounding landscape and land‐use legacies from plantation forestry may inhibit native vegetation recovery and benefit opportunistic invasives, limiting the effectiveness of passive restoration in this context. Abstract in Spanish is available with online material. Las coníferas exóticas están ampliamente distribuidas en el hemisferio sur, donde su uso como especies forestales ha dado lugar a impactos adversos en los ecosistemas, algunas veces potenciados por su invasión. La eliminación mecánica es una estrategia comúnmente utilizada para reducir o eliminar los impactos negativos de las coníferas exóticas y promover la regeneración de especies nativas. Sin embargo, diversos factores pueden impedir la restauración ecológica activa luego de la eliminación. Como resultado, la restauración pasiva, es decir la regeneración de la vegetación natural sin intervención humana, es común después de la eliminación de coníferas exóticas. En este trabajo nos preguntamos: ¿cuál es la respuesta de la cobertura de sotobosque a la eliminación de los rodales de coníferas exóticas seguida de restauración pasiva? Muestreamos la cobertura de sotobosque en tres tipos de sitios: talas rasas de dos a diez años de edad, bosque nativo y plantaciones actuales. Agrupamos las especies del sotobosque por origen (nativas / exóticas) y forma de crecimiento, y comparamos la proporción y el porcentaje de cobertura de estos grupos, así como de suelo desnudo y hojarasca, entre los tres tipos de sitios. En el caso de las talas rasas, también analizamos el efecto del tiempo desde la tala en las variables estudiadas. Encontramos que las talas rasas tenían una proporción significativamente más alta de cobertura vegetal exótica que los sitios de bosque nativo, donde la vegetación exótica estaba casi ausente. El sotobosque de los sitios talados también presentó una mayor cobertura de vegetación total y de vegetación exótica (en particular, arbustos exóticos y especies herbáceas exóticas) en comparación con los sitios de plantación y bosque nativo. Notablemente, el 99% de la cobertura de arbustos exóticos en las talas rasas estuvo dado por la especie exótica invasora retama (Cytisus scoparius). Luego de diez años de recuperación pasiva desde la tala, la proporción de cobertura de vegetación nativa en el sotobosque no ha aumentado y se mantiene muy por debajo de la proporción observada en los sitios de bosque nativo. La reducida capacidad de regeneración natural del ecosistema nativo, la presencia de especies invasoras en el paisaje circundante, y los legados del uso de la tierra debido a las plantaciones, podrían inhibir la recuperación de la vegetación nativa y beneficiar a los invasores oportunistas, limitando la efectividad de la restauración pasiva en este contexto.
... Finally, the third significant change on the human occupation curve concerns the re-occupation of the region after the hiatus around 7800 cal yr BP, contemporaneous with the Hudson eruption, which probably occurred at 7960-7430 cal yr BP (Stern, 2008). This eruption is considered the largest of all 12 eruptions recorded for this volcano (Veblen, 1989;Naranjo and Stern, 1998;Fontijn et al., 2014). For example, although it had a significantly lower impact, the 1991 Hudson eruption caused the sealing of shallow-water ponds, lake turbidity, and high ash-load levels in water bodies for several months (Inbar et al., 1995). ...
This contribution discusses possible relationships between human populations and Holocene environmental deterioration phenomena (cold/arid pulses and volcanic eruptions) in the Fuegian Archipelago (South America), based on summed probability distributions of archaeological dates, paleoenvironmental information, geospatial data, and archaeological evidence. During the first millennia after peopling, only the Hudson (ca. 7700 cal yr BP) and the first Monte Burney (ca. 8600 cal yr BP) eruptions might have played a role in human dispersion. Particularly, a more intense human occupation around the Beagle Channel and long-distance interactions are proposed as risk-buffer strategies related to the Hudson eruption. A cooling phase and a demographic growth at ca. 5500 cal yr BP might have favored more dispersed spatial occupations and a subsistence diversification in the Beagle Channel. In the northern steppes, the second Monte Burney eruption (ca. 4300 cal yr BP) and an arid episode (ca. 2600 cal yr BP) are proposed as the main triggers for changes in land-use patterns, long-network interactions, and subsistence strategies. Even though occupation changes in the Fuegian Archipelago coexist with environmental deterioration episodes after 1500 cal yr BP, demographic processes and the European colonization most likely explain this trend. Similarities between the steppe/ecotone and forest occupation curves suggest common behavioral patterns across the Holocene.
... Previous results suggested that both N. dombeyi and A. chilensis behave similarly as a consequence of canopy openings, with equal possibilities of reaching the canopy when growing above a shrub layer (Suarez and Sasal 2012); however, the response to canopy opening may vary according to understory conditions. In austral forests, the shrub layer potentially plays a major role in the differential recruitment and establishment of these species (Veblen 1989b;Suarez and Kitzberger 2008). Previous monitoring, supported by manipulative experiments, showed a lower recruitment and survival of N. dombeyi than A. chilensis in the shadier understory environment after drought mortality (Suarez and Kitzberger 2008). ...
The spectrum of structural response in drought-induced mortality (degree of partial crown mortality) could play a key role in pervasive changes in plant composition, as individual openings could reset self-replacement dynamics or trigger shifts in vegetation. Here we capture the community pattern 17 years after a drought episode over a range of canopy responses in Nothofagus dombeyi forests. We applied a widespread demographic approach to address evidence of species shifts vs. self-replacement and to relate partial dieback to understory structure and composition. Assuming that the outcome of growth release of the understory components can be observed 17 years after canopy loss, this study reveals evidence of self-replacement in N. dombeyi forests heavily affected by drought. Alternatively, when the co-dominant species A. chilensis is widely present in the understory and large gaps are opened, a compositional shift may be possible, with a potential change in forest functionality. Individual partial openings do not favor more shrubby communities or a shift toward a new community. Thus, partial crown dieback contributes to self-replacement mechanisms by hampering strong growth release in understory shrubs, as evident in plots with high mortality, and by facilitating the growth of dominant tree species.
... The interpretation that disturbance favours Nothofagus persistence is also supported by life history traits expected for long-lived pioneer species, including rapid tree growth rates under open conditions, longevity of at least several centuries, and effective seed dispersal into canopy openings (Veblen et al. 1996b;Lusk & del Pozo 2002;Pollmann 2004). In species-rich lowland forests intense competition from abundant shade-tolerant species precludes regeneration of Nothofagus beneath tree-fall gaps (Veblen et al. 1979;Veblen 1985), but at higher elevations or drier sites with fewer tree species the same size gap may result in successful regeneration of Nothofagus (Veblen 1989a(Veblen , 1989bPollmann & Veblen 2004). ...
Ecological disturbances triggered by earthquakes and volcanic eruptions are of fundamental importance in structuring the temperate forests of southwestern South America and New Zealand. We review studies of the ecological effects of these tectonic phenomena and how they have been central to progress in the modern development of forest ecology in both regions. Studies of tectonic influences on the dynamics of southern temperate rainforests of Chile and New Zealand published in the 1970s and early 1980s contributed prominently to the shift away from the equilibrium paradigms dominant globally in the 1960s and towards modern non-equilibrium frameworks of forest dynamics. Empirical studies of tectonic ecology in these temperate forests in combination with critical evaluations of earlier successional theory have significantly advanced understanding of the roles of coarse-scale disturbance in the dynamics of forests in southwestern South America and New Zealand. Recognition that cohort forest structures triggered by exogenous disturbances such as wind storms and tectonic events are the norm rather than all-aged structures has been of fundamental importance to understanding the dynamics of these forests. The non-equilibrium patch dynamics framework for interpreting forest structure and dynamics bolstered by tectonic ecology studies in southern South America and New Zealand was of key importance in refining older views of these forests as being out of equilibrium with contemporary climate, revising understanding of the effects of introduced browsing animals on forest structure, and guiding the development of appropriate forest management practices. ARTICLE HISTORY
... As the precipitation declines toward east, only 80 km far, drought conditions in summer have a stronger effect on the vegetation and can extend for several weeks ( Veblen 1998, Villalba et al. 2003, Suarez and Kitzberger 2010). In Argentina, the species dynamics is determined by small-scale gap-phase regeneration following tree fall across the climatic gradient, and comprises both monospecific stands and mixed forests with the evergreen conifer Austrocedrus chilensis (Veblen 1989). The absence of strong competition of shade-tolerant species favors N. dombeyi regeneration even in small gaps, and also in the presence of A. chilensis, a more shadetolerant species (Suarez and Kitzberger 2008). ...
Drought-induced episodes of tree mortality can determine forest dynamics and structure, particularly in forests dominated by single species. Short- and mid-term climate projections indicate that strong changes in annual precipitation may strike more often in northern Patagonia. Data for recruitment, growth, and survival of Nothofagus dombeyi tree individuals were collected at several sites across the Nahuel Huapi National Park in Argentina. We combined mathematically all these different demographic stages into an Integral Projection Model to simulate 100-yr projections of simulated stand structure under different frequencies of extreme drought episodes. We projected total basal area and the number of individuals for three different initial stand types (i.e., young, medium, and old) and for varying drought frequencies (i.e., from 1 to 5 drought events every 100 years). Recruitment into the dbh ≥ 10 cm size class under normal conditions (i.e., without drought) was higher than under episodic drought conditions. In addition, survival under normal conditions was higher than under drought conditions, especially for small trees. Differences in growth were also important, with trees growing more vigorously under normal than under drought conditions. Our simulations predicted that N. dombeyi populations would experience a reduction in tree density in the mid-term if, as predicted by the IPCC projections, the frequency of future drought events increased. The simulations also showed that in those cases, young stands should suffer the most. Drought-mediated changes may induce a decline in the development of N. dombeyi forests in the mid- and long term by a drastic reduction in tree density.
... Rotten downed-wood microsites (hereafter referred to simply as wood microsites) facilitate seedling growth by lessening the destructive influence of snow movement, known as snow glide, reducing species competition, increasing mycorrhizal populations, and having fewer pathogens than the adjacent soil (Zhong and van der Kamp 1999;Baier et al 2007). Wood microsites are key substrates in subalpine forests (Veblen 1989;Gratzer et al 1999;Zielonka and Niklossen 2001;Brang et al 2003;Narukawa et al 2003;Motta et al 2006;Baier et al 2007). A reconnaissance study of wood microsites in the Pacific Northwest found that mature trees, typically Abies lasiocarpa, which commonly fell directly into alpine meadows from the forest line via blow-down and wind snap, decayed and created warmer and moister conditions that produced greater seedling density and seedling survival than the adjacent soil substrates (6.85 seedlings per meter squared on wood versus 3.64 seedlings per meter squared on soil, P ¼ 0.026; Johnson and Yeakley 2013). ...
Although climate warming is generally expected to facilitate upward advance of forests, conifer seedling regeneration and survival may be hindered by low substrate moisture, high radiation, and both low and high snow accumulation. To better understand substrate-related factors promoting regeneration in the alpine treeline ecotone, this study compared 2 substrates supporting conifer seedlings: rotten downed wood and adjacent soil. Study locations, each with 3 levels of incoming radiation, were randomly selected at forest line–alpine meadow borders in Pacific Northwest wilderness areas extending along an east–west precipitation gradient. Associations among substrate type, seedling density, radiation, site moisture, site temperature, plant water potential, and plant stomatal conductance were assessed. Wood microsites, flush with the ground and supporting Abies spp conifer seedlings, extended up to 20 m into alpine meadows from the forest line. Although wood microsites thawed later in the spring and froze earlier in the fall, they had warmer summer temperatures, greater volumetric water content, and more growing degree hours, and seedlings growing on wood had higher water potentials than seedlings growing on adjacent soil. At drier eastern sites, there was a positive relationship between seedling density and volumetric water content. Further, there was a positive relationship between seedling stomatal conductance and volumetric water content. Our study indicates that in the Pacific Northwest. and likely elsewhere, seedlings benefit from wood microsites, which provide greater water content. Given predictions of increased summer drought in some locations globally, wood microsites at forest line–alpine meadows and forest line–grasslands borders may become increasingly important for successful conifer regeneration.
... The interpretation that disturbance favours Nothofagus persistence is also supported by life history traits expected for long-lived pioneer species, including rapid tree growth rates under open conditions, longevity of at least several centuries, and effective seed dispersal into canopy openings (Veblen et al. 1996b;Lusk & del Pozo 2002;Pollmann 2004). In species-rich lowland forests intense competition from abundant shade-tolerant species precludes regeneration of Nothofagus beneath tree-fall gaps (Veblen et al. 1979;Veblen 1985), but at higher elevations or drier sites with fewer tree species the same size gap may result in successful regeneration of Nothofagus (Veblen 1989a(Veblen , 1989bPollmann & Veblen 2004). ...
Ecological disturbances triggered by earthquakes and volcanic eruptions are of fundamental importance in structuring the temperate forests of southwestern South America and New Zealand. We review studies of the ecological effects of these tectonic phenomena and how they have been central to progress in the modern development of forest ecology in both regions. Studies of tectonic influences on the dynamics of southern temperate rainforests of Chile and New Zealand published in the 1970s and early 1980s contributed prominently to the shift away from the equilibrium paradigms dominant globally in the 1960s and towards modern non-equilibrium frameworks of forest dynamics. Empirical studies of tectonic ecology in these temperate forests in combination with critical evaluations of earlier successional theory have significantly advanced understanding of the roles of coarse-scale disturbance in the dynamics of forests in southwestern South America and New Zealand. Recognition that cohort forest structures triggered by exogenous disturbances such as wind storms and tectonic events are the norm rather than all-aged structures has been of fundamental importance to understanding the dynamics of these forests. The non-equilibrium patch dynamics framework for interpreting forest structure and dynamics bolstered by tectonic ecology studies in southern South America and New Zealand was of key importance in refining older views of these forests as being out of equilibrium with contemporary climate, revising understanding of the effects of introduced browsing animals on forest structure, and guiding the development of appropriate forest management practices.
... Mixed-severity fires scars typically have higher beta-diversity and result in more complex landscapes with variation in vegetation patches driven by fire severity and fire history (Taylor and Skinner, 1998). In addition, disturbance patterns and stand regrowth vary geographically as does the proportion of different severity classes within a scar (Spies and Franklin, 1989;Veblen, 1989;Veblen et al., 1992). As such, higher resolution information across latitudinal and ecosystem gradients is valuable for management decisions on fire mitigation and control (Taylor and Skinner, 1998). ...
Taking advantage of the improved radiometric resolution of Landsat-8 OLI which, unlike previous Landsat sensors, does not saturate over snow, the progress of fire recovery progress at the landscape scale (< 100 m) is examined. High quality Landsat-8 albedo retrievals can now capture the true reflective and layered character of snow cover over a full range of land surface conditions and vegetation densities. This new capability particularly improves the assessment of post-fire vegetation dynamics across low- to high-burn severity gradients in Arctic and boreal regions in the early spring, when the albedos during recovery show the greatest variation. We use 30 m resolution Landsat-8 surface reflectances with concurrent coarser resolution (500 m) MODIS high quality full inversion surface Bidirectional Reflectance Distribution Functions (BRDF) products to produce higher resolution values of surface albedo. The high resolution full expression shortwave blue sky albedo product performs well with an overall RMSE of 0.0267 between tower and satellite measures under both snow-free and snow-covered conditions. While the importance of post-fire albedo recovery can be discerned from the MODIS albedo product at regional and global scales, our study addresses the particular importance of early spring post-fire albedo recovery at the landscape scale by considering the significant spatial heterogeneity of burn severity, and the impact of snow on the early spring albedo of various vegetation recovery types. We found that variations in early spring albedo within a single MODIS gridded pixel can be larger than 0.6. Since the frequency and severity of wildfires in Arctic and boreal systems is expected to increase in the coming decades, the dynamics of albedo in response to these rapid surface changes will increasingly impact the energy balance and contribute to other climate processes and physical feedback mechanisms. Surface radiation products derived from Landsat-8 data will thus play an important role in characterizing the carbon cycle and ecosystem processes of high latitude systems.
... Los patrones de regeneración de N. dombeyi ilustran claramente cómo el modo de regeneración de una especie puede variar geográficamente en función de las especies dominantes asociadas, la composición específica del sotobosque, y los factores abióticos de un sitio en particular (Veblen, 1989b (Veblen et al., 1981, Rusch, 1987, Schlegel et al., 1979, Rebertus y Veblen, 1993b. Al norte de su distribución (es decir, al norte de 43 de latitud S), la caña Chusquea inhibe frecuentemente la regeneración de N. pumilio, aún cuando no llega a impedirla totalmente. ...
... landscape equilibrium, Turner et al. 1993 qualitative equilibrium, quantitative equilibrium, White and Jentzch 2001 statistical equilibrium, stationary/dynamic equilibrium, White Runkle 1981Denslow 1980Nakashizuka 1987Canham 1988Spies and Franklin 1989Veblen 1989 Lertzman and Krebs 1991Lusk and Smith 1998Gutiérrez et al. 2004Parish and Antos 2004, 2006Gutiérrez et al. 2008 ...
Variability in the composition, structure, and dynamics of ecosystems has been widely recognized in recent studies. It is thought that forest ecosystems barely reach the steady-state and equilibrium status. This non-equilibrium status of forest ecosystems is regulated by natural disturbances. Consequently, forest dynamics have been clarified in many regions by focusing on natural disturbance regimes. Furthermore, in current terrestrial ecosystem management, natural disturbances in ecosystems and landscapes have been acknowledged as part of the dynamics of ecological processes, one that helps to maintain ecological integrity and conserve biological diversity at various levels. However, the variability and complexity of forest ecosystems remain unknown. Natural disturbances, particularly larger ones, are unpredictable and their impacts on ecosystems are highly uncertain. For ecosystem management and restoration, clarification of the ecosystem responses to environmental variability is critical, and we should further investigate the complexity, unpredictability, and non-equilibrium nature of ecological processes. Therefore, data on the dynamic nature of ecosystems and ecological processes from the specific plot to the landscape level, as regulated by various natural disturbances, is needed to assess the non-equilibrium paradigm of forest ecosystems.
... W badanych drzewostanach przewa− żały luki o małej i średniej powierzchni. W badaniach prowadzonych w Chile [Veblen 1985], północnej Patagonii [Veblen 1989], Nowej Zelandii [Stewart, Rose, Veblen 1991], a także w drze− wostanach klonowo−bukowych w Stanach Zjednoczonych [Runkle 1990] stwierdzono przewagę luk o małej powierzchni. ...
... In many cases , both pioneer and non-pioneer species grow in gaps (POUlson and Platt 1989, Spies and Franklin 1989, Veblen 1989, Whitmore 1989). In stage 3 of site type A, beech and pine trees grow together competing with each other. ...
The study was conducted in second growth stands in the central Rhodope mountains and (specially) in the region of Xanthi. In order to determine the dynamics and the development patterns of Pinus sylvestris-Fagus sylvatica stands, 39 plots were established, trees were cut, increment cores were taken, and stem analysis was conducted in 4 couples of dominant (competitive) pine and beech trees. The main results of this research indicate that a) The population structures, the regeneration and development patterns are strongly influenced by human and natural disturbances and species 'life history characteristics'. b) The difference in site quality between site types results in differences in the duration of beech invasion (under pine) and in species basal area distribution. c) In good site qualities when individual dominant beech and Scots pine (competitive) trees with a small age difference grew together, the beech trees, in some cases, have almost the same height growth as the pines and the pine trees showed a delayed (for the species) culmination in current annual volume increment which is not followed by a abrupt fall. d) The process of secondary succession is influenced by disturbances regime, environment, propagule availability and species biology.
Actualmente se plantea manejar los bosques de lenga de Tierra del Fuego con cortas de selección en grupos. Sin embargo, este tipo de manejo, que basa su éxito en la recuperación del volumen maderable a partir de los árboles remanentes, podría fracasar si el rodal sufre excesivos daños posteriores a la corta. Por ello se analizó el porcentaje de pérdidas (por caídas o mortalidad) posteriores al aprovechamiento en 60 parcelas de distintas estructuras y calidades de sitio, donde se estimaron los parámetros del bosque al momento de la corta y la intensidad de la misma, en términos de volumen maderable y porcentaje del área basal (AB) original extraída.
p>This thesis evaluates the potential of fine (<5 m) spatial resolution remotely sensed data and alternative classification methods to characterise windthrown gaps. The study site was Cwm Berwyn Forest, in central Wales, a planted forest of predominantly Sitka spruce ( Picea sitchensis (Bong.) Carr.) containing windthrown gaps ranging in size from 50 to 3000 m<sup>2</sup>. The remotely sensed data used were acquired by an 11 waveband airborne thematic mapper (ATM) sensor with a spatial resolution of � 4m. This spatial resolution is finer than the windthrown gaps on the site and comparable to that of future satellite sensors. A thematic map depicting land cover was produced using a conventional maximum-likelihood classification of the ATM data and provided an accurate representation of the land cover (> 90% of the pixels allocated correctly). This hard classification was also softened to output typicality and posterior class membership probabilities.
The results indicated that the hard classification provided an accurate means of identifying windthrown gaps (>95% of known gaps identified) and was capable of identifying a greater number of gaps, than manual interpretation of temporally coincident aerial photographs. Estimates of windthrown gap area, perimeter and shape were derived from the hard and softened classifications. The results indicated the potential to derive more accurate spatial representations of windthrown gaps than a conventional hard classification, by softening the output to derive typicality class membership probabilities. However, the major contribution of the research within this thesis to previous work on windthrown gap formation and progression, is the potential to use rate of change of typicality and posterior class membership probabilities to derive information on various windthrown gap properties, such as exposed soil and living windthrown tree canopies.</p
Silvopastoral use (combined livestock and forestry) is widely distributed in South America's native forests. Without medium to long-term planning, this activity may affect the population dynamics of the dominant canopy tree species, resulting in forest degradation. The early stages of tree life cycles are usually the most vulnerable, so the successful establishment and development of seedlings and saplings is a key indicator of the potential for continuity of the tree layer over time. This study evaluated the effect of silvopastoral use intensity (SUI) upon the density and development of dominant tree species - Austrocedrus chilensis and Nothofagus dombeyi - along a gradient generated by spatially and temporally heterogeneous livestock activity and forest harvesting in mixed forests of northwestern Patagonia, Argentina. We monitored the survival and growth of 740 seedlings and saplings over two years (2018–2020) in three medium-sized estates with SUI gradients and upland migration of livestock during the summer season. We also evaluated changes in biophysical variables that influence the tree regeneration process: light input, soil moisture, and understory vegetation structure. We found that higher SUI modifies the biophysical environment, increasing light input and horizontal understory cover. The response of saplings and seedlings to SUI was not homogenous; N. dombeyi showed significant changes in its regeneration dynamics, denoted by a decrease in the density of seedlings and an increase in the density and height growth of the saplings along the SUI gradient. Meanwhile, A. chilensis only showed tendencies to deformation by browsing (height: diameter ratio). Thus, in medium-size estates with low stocking rates and which are free of herbivory during summers; fast-growing species (e.g. N. dombeyi) could be favored by the slight canopy openings, compensating for the negative impact of browsing. However, it is necessary to monitor and potentially individually protect A. chilensis saplings until browsing height is exceeded.
The thesis seeks to illuminate the character of later prehistoric woodlands on the Thames floodplain and their use by contemporary communities. This is achieved by the application of a two-pronged research agenda which examines both non-cultural and cultural waterlogged wood assemblages from east London. The non-cultural data is obtained from the mapping, recording and species identification of 1679 tree trunks, stumps and root systems preserved on the Thames foreshore at Erith in Kent. This research facilitates the characterisation of four temporally distinct woodlands dating from the Later Neolithic through to the Early Iron Age period. Application of ecological and forest stand dynamics models provides a detailed reconstruction of the prehistoric landscape including the species composition, density, canopy height and maturity of the floodplain woodlands. As such, the three-dimensional woodland reconstructions provide the tangible character of the wooded landscape within which prehistoric activity is contextualised. Bronze Age trackway assemblages from Beckton Nursery in Newham and the Thames foreshore at Erith are simultaneously examined. Morphological and tree-ring analysis illuminates the nature of prehistoric wood use on the Thames floodplain, including evidence for tree species selection, woodland management and various woodworking techniques. This information is then placed within the reconstructed wooded landscape to facilitate comparison of the two datasets. It is suggested that the targeting of specific timber resources on the floodplain and the introduction of woodland management regimes linked to animal husbandry characterised woodland use. Furthermore, the contextualisation of the trackway features within the reconstructed landscape enables wider suggestions pertaining to contemporary cultural perceptions of the wooded landscape and alternative interpretations of later prehistoric activity on the floodplain.
Increasing anthropogenic pressure and dependence on plant products has led to widespread exploitation of natural forest in Uttarakhand Himalaya. The study area was selected on the Southern Boundry of Corbett National Park. The objective of the present study was to understand the regeneration status of important tree species in three different types of forests categorized as Highly Disturbed, Moderately disturbed and Least Disturbed sites. Total tree density was higher for least disturbed forest and lower for highly disturbed forest. The regeneration was poor in highly disturbed site compared to least disturbed site. Mallotus philippinensis was germinating and growing as a dominant under canopy tree species across all the sites except least disturbed sites. Sal (Shorea robusta) regeneration was found to be a serious problem. Mallotus philippinensis, Aegle marmelos and Lagerstroemia parviflora showed their dominance across all the sites proving broad ecological amplitude and high tolerance against grazing pressure. At highly disturbed site, species like Mallotus philippinensis, Diospyros tomentosa and Lagerstromeia parviflora were regenerating fairly well with seedlings and saplings but the number of saplings were either less than or equal to adults. Vegetational parameters showed that protected areas ( least disturbed areas ) are important for maintaining regeneration and ecosystem.
Masting, or mast seeding, is the synchronous seed production in certain years by a population of plants (Kelly 1994). The reproductive activity of plants in forests often fluctuates considerably between years, and flowering and fruit production are synchronised over long distances (Koenig and Knops 1998, 2000, Koenig et al. 1999). Mast seeding has clear disadvantages such as higher density-dependent mortality of seedlings and lost opportunities for reproduction (Waller 1979). In addition, field observations suggest that seed production fluctuates more than the level that can be explained by climate-mediated variation in resource availability (Büsgen and Münch 1929). Two major questions arise from ecological studies on masting: Why is masting evolutionarily favoured regardless of apparent disadvantages? How do plants allocate resources to realise variable flowering efforts in a way synchronised over different individuals? A family of resource budget models that have recently been studied provides answers to both questions: on the physiological mechanism by which plants may successfully generate such intermittent and synchronous reproduction (Isagi et al. 1997, Satake and Iwasa 2000, 2002a, b) and on the conditions for which masting is adaptive (Rees et al. 2002, Tachiki and Iwasa 2008). Resource budget models assume that plants accumulate resources every year and set flowers and fruits at a rate limited by pollen availability when the stored resources exceed a reproductive threshold level. The model predicts that individual plants flower intermittently when their resources are depleted after heavy flowering and fruiting, and that synchrony emerges in self-organised fashion by coupling through the need to receive outcross pollen from other plants (Satake and Iwasa 2000).
In contrast with the fundamental ecological expectation that similarity induces competition and loss of species, temporal dynamics allows similar species to co-occur. In fact, the coexistence of similar species contributes significantly to species diversity and could affect ecosystem response to climate change. However, because temporal processes take place over time, they have often been a challenge to document or even to identify. Temporal Dynamics and Ecological Process brings together studies that have met this challenge and present two specific aspects of temporal processes: reproductive scheduling and the stable coexistence of similar species. By using plants to extract general principles, these studies uncover deep ties between temporal niche dynamics and the above central ecological issues, thereby providing a better understanding of what drives temporal processes in nature. Written by leading scientists in the field, this title will be a valuable source of reference to research ecologists and those interested in temporal ecology.
Over 50 years ago, Hutchinson (1941) noted that variation in environmental conditions could alter the outcome of competition. One implication of his observation was that environmental fluctuations could promote coexistence, allowing many species to persist in a habitat where all but one would be excluded under constant conditions. By the end of the 1980s, Chesson and colleagues had clearly described the theoretical requirements for coexistence via the storage effect (Chesson and Warner 1981, Warner and Chesson 1985, Chesson and Huntly 1989). Yet despite the long history of these ideas, relatively few direct empirical tests of the storage effect exist. Studies from a variety of natural ecosystems provide partial evidence for the storage effect (Pake and Venable 1995, 1996, Kelly and Bowler 2002, Descamps-Julien and Gonzalez 2005, Facelli et al. 2005, Kelly et al. 2008), but tests of all the required conditions or quantification of the strength of the effect are much rarer (Cáceres 1997, Adler et al. 2006, 2009, Angert et al. 2009). The lack of rigorous case studies limits our ability to generalise about the role of the temporal storage effect in maintaining diversity. We know that multiple coexistence mechanisms will operate in different communities, but currently we cannot say where the storage effect makes an especially important contribution. This information will be essential for understanding the consequences of expected increases in climate variability (Karl and Trenberth 2003, Jain et al. 2005, Salinger 2005, Allan and Soden 2008), which could impact species diversity in systems where the storage effect is important (Adler and Drake 2008). Understanding the influence of the storage effect on coexistence across a variety of ecosystems is therefore a prerequisite for anticipating future changes in species diversity.
Plant communities are structured in time as well as space. Their component species may differ in the timing of establishment, growth and reproduction both within and between years, creating temporal differences in relative abundances. Under appropriate conditions, temporal differences among co-occurring species can allow their coexistence (Grubb 1977, Chesson and Huntly 1997, Higgins et al. 2000, Kelly and Bowler 2002, 2005, Chesson et al. 2004, Schwinning et al. 2004, Adler et al. 2006). Whether or not temporal differences are responsible for the coexistence of any given pair or set of species, temporal niches are a fundamental part of community structure. Understanding this aspect of community structure is becoming even more important as we are called upon to interpret and to predict responses of communities to climate change (Dukes and Mooney 1999, Walther et al. 2002, Fischlin et al. 2007). In this study we examine temporal variation in population dynamics in a set of eight co-occurring herbaceous perennials. In addition to examining temporal variation in population sizes (densities), we use simple population dynamic models to provide estimates of temporal variation in equilibrium population density. Because actual densities lagged equilibrium population densities, the latter were more useful for comparing the temporal niches of different species and for relating temporal variation in precipitation to population dynamics. The degree of lag itself can be interpreted as a measure of the intensity of density-dependent population regulation, and variation in the degree of lag as another aspect of a species’ temporal niche.
Although all the trees that compose a mature forest originate as seedlings on the forest floor, the composition of a seedling or sapling community of ten differs from that of the adult trees. While this discrepancy may signal a shift or fluctuation in the forest (see Chapter 6), it can be attributed to demographic behaviors of each species (e.g., Harcombe 1987; Aiba and Kohyama 1997). To understand the maintenance mechanisms of a forest community, or to predict the forest dynamics, we must consider the seedling and sapling stages, since they, as well as the seed stage, are the stages subject to drastic demographic changes (see Chapter 1). Following on the previous chapters of this volume on seed production (Chapter 9), dispersal (Chapter 10), and dormancy and germination (Chapter 11), I describe the young tree community in Ogawa Forest Reserve (OFR) in this chapter, especially as it relates to forest disturbances.
The German textbooks of Bick (1989) and Klôtzli (1989) present surveys on modern ecosystem researcH, While The First English Translation Of Ellenberg’S (1988) Vegetation Ecology of Central Europe opens a wide range of central European literature Englishspeaking ecologists. Although the book edited by Rambler et al. (1989) acknowledges current interdisciplinary efforts in ecosystem ecology, biogeochemistry, and geomicrobiology, it calls for an even higher level of synthesis. Its goal is the establishment of a new and totally integrated science of life and environment. The purpose of Odum’s (1989) new book is to serve as a guide to ecological principles. A particularly useful teaching sourcebook to current problems in environmental research is edited by Friday and Laskey (1989), while the main goal of the book edited by Grubb and Whittaker (1989) was to anticipate new developments in ecology, considering in particular the most fruitful current approaches and technologies. When planning research involving aboveground vegetation measurements, ecologists would do well to consult the book of Bonham (1989). An introduction to the use of mathematical models by ecologists is given by Jeffries (1989). Wetland Modelling, edited by Mitsch et al. (1988), will be of interest not only to ecological modelers and wedand researchers, but more generally to those concerned with the development of ecological theory.
The study was conducted in the Jata reserve (total area is 1117 ha), which is the furthest natural silver fir (Abies alba Mill.) location in north-eastern Europe. The aim of the investigation was to: (i) determine influence of stand structure and species composition on regeneration, (ii) reveal the role of canopy gaps in the forest development, (iii) recognize how the gap size determines the establishment, growth and development of tree species in the mixed stands. The investigation was carried out in chosen mixed stands with the share of fir (<= 50%). All gaps defined as openings in the canopy >= 20 m(2) in area that intersected the transect were localized. Natural regeneration was measured in gaps. Gaps initiated the processes of regeneration in mixed stands. It was found that gaps increased biodiversity in mixed stands - the regeneration of shrubs was possible only in gaps. Gap size did not influence the quantity of tree species regeneration. On the quantity of fir, spruce, hornbeam, sycamore and aspen influence the number of tree species in gap surrounding. Better conditions for regeneration of tree species were under the fresh mixed broadleaved site type (LMsw). The dominant tree species regenerated in gaps were hornbeam and sycamore.
The subalpine southern Andean timberline is characterized by deciduous Nothofagus pumilio forests, which change with increasing altitude to Nothofagus krummholz, built of deciduous N. pumilio and N. antarctica. The current study examines the structure and species composition in timberline ecotones of the southern Andes to assess whether the deciduous timberline in the Andes results as convergent structure of, for example, Betula-timberlines of the Northern Hemisphere. Through a Braun-Blanquet phytosociological approach, we show how the characteristic structure and combination of timberline vegetation in the southern Andes vary in latitudes from 33°S to 55°S and altitudes between 2000 m and 600 m. Timberline composition was distinct at sites and included a variety of assemblages ranging from northern Azaro-Nothofagetalia communities to assemblages of the Adenocaulo-Nothofagetalia and Violo-Nothofagetalia in the South. Krummholz generally occurred in a ten to some hundred meter wide ecotone. Four distinctive N. pumilio growth forms were identified; (1) 'elfin woods' where trees become more and more stunted as they approach the woodland limit readily observed in previous studies; (2) 'cornice-like' growth form characterized by branches close to the ground; (3) restricted to the leeward side, a single-stemmed habit occurred that was characterized by stems aligned downhill before curving up into vertical alignment; and (4) on the wind-exposed side, growth forms were characterized by single-stemmed habit and long branches running uphill. These growth form changes were apparently controlled by changes in abiotic factors and climate rather than genetically determined. In conclusion, the recognition of the deciduous foliage and deformed habit of timberline trees in the southern Andes is explained by extreme climate. Comparison of same latitudes revealed that maximum altitudes of southern Andean timberline were generally higher than those of evergreen Nothofagus limits in New Zealand but lower than timberlines of Holarctic mountain ranges. These results serve to emphasize that understanding structure and physiognomy of the southern Andean timberline and its apparent stability may require attention to ecophysiological adaptations and responses of timberline Nothofagus to high-mountain environment.
The survival of a cohort of Abies religiosa seedlings was investigated during eight years in an intact forest (NAF) and forest patches affected by: shallow fires (SUPAF), intermediate canopy fires (ICAF), and full canopy fires (FCAF). The objective of this paper was to provide a better understanding on the natural regeneration processes of A. religiosa. In each patch eight 1m 2 plots were established and all rooted seedlings within each plot from the 1998 cohort were tagged. Seedling mortality and type of associated damage were recorded throughout censuses from 1998 to 2006. Fallen branches and desiccation of seedlings were the two most important factors associated with their death. Survival probabilities were the lowest in SUPAF and none in NAF. The highest survival probabilities were under ICAF condition, and it suggests that this type of fire is an important component of the A. religiosa regeneration niche.
We evaluated the influence of long-auricled indocalamus (Indocalamus longiauritus Hand.-Mazz.) monodominant thickets in understory layers of tree regenerations during the reestablishment process of natural forests. A manipulative field experiment was performed in pure Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations in Huitong, Hunan Province, located in the subtropical part of China. Ten 1hm2 permanent plots with long-auricled indocalamus in understory (I) were selected as treatment and another ten 1 hm2 permanent plots (C) were used as control plots in which there is no any bamboo. In 1996, all canopy Chinese fir individuals were removed to improve understory light condition and to promote the establishment of monodominant thickets in these plots. After 10 years, dense bamboo layers with about 95% cover were successfully established. In 2007, we measured the abundance, diversity and biomass of tree seedling, sapling and adult tree by height class in all treatment and control plots. The formation of long-auricled indocalamus monodominant thickets significantly impeded the tree survival and growth. The abundance and diversity of saplings in the 18 -390 cm height classes were lower in the treatment plots. Although the dense bamboo layers did not significantly reduce the abundance and diversity of tree seedlings of less than 18 cm height and canopy trees, the biomass of seedlings, saplings and canopy trees decreased by 47.45%, 39. 87% and 59. 64% for the aboveground portion and by 55.70%, 46.08% and 63.62% for the belowground portion, respectively. Non-metric multidimensional scaling (NMS) ordination showed different patterns in species compositions between treatment and control plots, which further indicated that tree regeneration in these two types of plots was not in the same succession phase. Our results support the hypothesis that the formation of dense bamboo thickets would slow the tree regeneration process. Our study suggests that the formation of monodominant understory layers during reestablishment of natural forest should be avoided.
The relations between Photosynthetic photon flux density (PPFD) and both the number of silver fir (Abies alba) seedlings per unit area and their height growth were investigated. The study was carried out in the Sudety Mts (SW Poland, 50°28'N, 16°19'E), in a forest stand dominated by spruce (Picea abies), growing on site of mixed broad-leaved mountain forest. This site type is very commonly colonized by silver fir in this part of Europe. The number of fir seedlings per unit area decreased with growing PPFD values, whereas seedling height increased. Our results suggest that greater access of sunlight, at least within the recorded PPFD range (0-40% of full irradiation) improves the growth conditions of fir seedlings but at the same time the spread of grasses (mainly Deschampsia flexuosa) inhibits the rooting and development of new seedlings. Thus regenerative felling should be conducted in forest stands in these places where fir seedlings are numerous.
The aim of this study was to simulate the gap areas formed after logging in a management gardening system, using geoprocessing techniques. In a 5.6 ha of a seasonal semi deciduous forest located in Linha Canudos, Santa Maria, Rio Grande do Sul state, 924 trees were georeferenced using a GPS receiver. In these trees was determined the sustainable cutting rate beyond balanced distribution frequencies by diameter class selecting 82 cutting trees through this analysis. At the selected cutting trees, the releasing areas of canopy gaps and the impacting areas were estimated from falling cutting trees using GIS and reduced impact logging techniques as known as directed tree felling. Altogether, 98 trees (32 m3) will benefit from releasing of canopy and 63 trees (12.07 m3) will be impacted by the falling of the explored trees. Therefore, it is concluded that the geoprocessing techniques applied to native forest management is an important feature when you want to intervene in the forest, aiming to reduce the forest cutting impact.
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