Woody Species In Forest Research Articles

Effect of Small-Scale Variations in Environmental Factors on the Distribution of Woody Species in Tropical Deciduous Forests of Vindhyan Highlands, India

The aim of this study is to investigate the changes in the composition of mature, naturally established and unmanaged TDF in response to small-scale variations in environmental factors. All woody species with a minimum circumference of 10 cm at 1.37 m height were surveyed in forty-five 20×50 m plots distributed over 5 sites in the TDF of Vindhyan highlands, India. Cluster analysis identified two distinct groups of plots. Group 1 plots had higher soil moisture content (SMC), clay, organic C, total N, total P, and light attenuation than group 2 plots. A total of 48 native species belonging to 25 families were encountered in the sampled area. High eigenvalues for the first two Canonical Correspondence Analysis (CCA) axes indicated the occurrence of species in distinct groups, and significant correlations of the axes with environmental variables indicated the effect of these variables on species grouping. In conclusion, patchiness in the soil resources needs to be considered in restoration efforts. The results of this study are expected to facilitate the decision regarding choice of species in afforestation programmes for restoring the TDF.

The Effects of Removal of Juniperus virginiana L. Trees and Litter from a Central Oklahoma Grassland

We studied species composition after Juniperus virginiana tree and litter removal in a central Oklahoma grassland. Tree removal had the most significant effect on stems per quadrat and vegetation cover. Litter removal effects were not as strong. However, stems per quadrat and vegetation cover in litter removal treatments were higher than in litter intact treatments. Species richness increased for all treatments in the first year post-treatment, after which species richness declined at every sampling period and in every treatment for the duration of the study. Absolute cover of typical prairie species increased in the cut with no litter treatment hereas cover of woody forest species increased in the no cut with no litter treatment. We suggest that even without prescribed fire, redcedar tree removal may result in a return of prairie vegetation. However, additional efforts besides tree removal may be required to restore some invaded grasslands.

Diversity and regeneration status of woody species in Tara Gedam and Abebaye forests, northwestern Ethiopia

A study was conducted in Tara Gedam and Abebaye forests l, northwestern Ethiopia to investigate the diversity, regeneration status, socio-economic importance and the factors causing destruction of the forests. A total of 30 plots, measuring 20 m ×20 m, were established along line transects laid across the forests. Participatory Rural Appraisal (PRA) method was employed to generate the socio-economic data. Primary data were collected by field observation, semi-structured interview with key informants and discussion with relevant stakeholders. A total of 143 woody species belonging to 114 genera and 57 families were recorded, and of all the species 44 (30.8%) were trees, 57 (39.9%) trees/shrubs, 33 (23.1%) shrubs and 9 (6.3%) lianas. The diversity and evenness of woody species in Tara Gedam forest are 2.98 and 0.65, respectively, and in Abebaye forest they are 1.31 and 0.31, respectively. The total density and basal area of woody species in Tara Gedam forest are 3001 individuals·ha−1 and 115.36 m2·ha−1, respectively, and in Abebaye forest the values are 2850 individuals·ha−1 and 49.45 m2·ha−1, respectively. The results on the importance value index (IVI) and DBH class distributions suggest that the species with low IVI value and poor regeneration status need to be prioritized for conservation. In the socio-economic survey, the responses from the key informants indicated that the forests are the major sources of fuelwood (90%), construction material (80%), timber (75%) and farm implements (55%). The forests are also sources of medicines, animal fodder, bee forage and edible fruits. Tara Gedam monastery, assisted by the local people who have strong religious belief and high respect to the monastery, has played a great role in the maintenance of the sacred forest since a long time. At present, the conservation efforts are made jointly by the monastery and institutions concerned with conservation. The major factors that cause destruction of the forests are livestock grazing, tree cutting for various purposes and farmland expansion. The implications of the results are discussed, and the recommendations are suggested for conservation, management and sustainable utilization of the forest ecosystems.

Understory Invasion by Acacia longifolia Alters the Water Balance and Carbon Gain of a Mediterranean Pine Forest

In water-limited ecosystems, where potential evapotranspiration exceeds precipitation, it is often assumed that plant invasions will not increase total ecosystem water use, because all available water is evaporated or transpired regardless of vegetation type. However, invasion by exotic species, with high water use rates, may potentially alter ecosystem water balance by reducing water available to native species, which may in turn impact carbon assimilation and productivity of co-occurring species. Here, we document the impact of invasion by an understory exotic woody species (Acacia longifolia) in a semi-arid Mediterranean dune pine forest. To quantify the effects of this understory leguminous tree on the water use and carbon fixation rates of Pinus pinaster we compare an invaded and a non-invaded stand. A. longifolia significantly altered forest structure by increasing plant density and leaf area index in the mid-stratum of the invaded forest. A. longifolia contributed significantly to transpiration in the invaded forest (up to 42%) resulting in a slight increase in stand transpiration in the invaded relative to non-invaded forest. More importantly, both water use and carbon assimilation rates of P. pinaster were significantly reduced in the invaded relative to non-invaded stand. Therefore, this study shows that exotic plant invasions can have significant impacts on hydrological and carbon cycling even in water-limited semi-arid ecosystems through a repartitioning of water resources between the native and the invasive species.

Fleshy fruit characteristics in a temperate deciduous forest of Japan: how unique are they?

This study investigated the fleshy fruit characteristics of 28 woody species in a Japanese temperate forest where large sedentary seed-dispersing mammals are present. We tested whether the findings in previous studies in temperate forests of Europe and North America are universal or not. Results have suggested that fruits of all species were eaten both by birds and mammals except for four species with larger fruits, which were eaten only by mammals. A gradient was found from a syndrome characterized by small, oily, and large-seeded fruits to a syndrome characterized by large, succulent, non-oily, and small-seeded fruits. The sizes and colors of the fruits were not conspicuously different from previous findings in Europe and North America. On the other hand, nitrogen and lipids in the fleshy part did not show seasonally increasing trends, or even seasonally decreasing trends in terms of dry weight. This result, suggesting the absence of community-level adaptation of fruit traits to migratory bird dispersers, contrasted with findings in Europe and North America. Large sedentary arboreal or tree-climbing mammals may have a greater effect on the evolution of fruit-disperser relations than opportunistic migratory birds.

Seed Dispersal Spectrum of Woody Species in South Ecuadorian Dry Forests: Environmental Correlates and the Effect of Considering Species Abundance

ABSTRACTThis study examines the seed dispersal spectrum of the tropical dry forests of Southern Ecuador, in an effort to contribute to the knowledge of the complex dynamics of tropical dry forests. Seed dispersal spectrum was described for a total number of 160 species. Relationships of dispersal syndromes with plant growth form and climatic seasonality were explored. For a subset of 97 species, we determined whether dispersal spectrum changes when species abundance, in addition to species number, is taken into account. The same subset was used to relate dispersal syndromes with the environmental conditions. Zoochorous species dominated in the studied community. When considering the individual abundance of each species, however, anemochory was the prevalent dispersal syndrome. We found a significant difference in the frequency of dispersal syndromes among plant growth forms, with epizoochory only occurring in shrub species. The dispersal spectrum was dependent on climatic seasonality. The largest proportion of anemochorous species fructified during the dry season, while zoochorous diaspores dominated during the rainy season. A fourth‐corner analysis indicated that the seed dispersal spectrum of Southern Ecuador dry forests is controlled by environmental conditions such as annual precipitation, annual temperature range or topography. Our results suggest that spatio‐temporal changes in the environmental conditions may affect important ecological processes for dispersal. Thus, the predominance of one syndrome or another may depend on the spatial variation of environmental conditions.Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp.

Nurse rocks influence forest expansion over native grassland in southern Brazil

Questions: Do small rocky outcrops favor forest plant colonization and establishment in grasslands? If so, what are the potential mechanisms involved in this process? Location: Araucaria forest and Campos grassland mosaic in southern Brazilian highlands (29°29′S, 50°12′W). Methods: We collected data on the density of forest woody species in plots located on rocky outcrops and in open fields subject to different management regimes. We evaluated the influence of outcrops on the density of forest plants ≤60-cm tall, and the effects of other environmental variables and of site on plant density; we also used information on diaspore traits of the species to discuss the way in which plants disperse to the outcrops. Results: Rocky outcrops harbored a significantly higher density of forest plants than open fields, irrespective of site effect, and rock height was the best predictor for plant density on outcrops. Diaspores of all recorded species possess characteristics associated with dispersal by birds or mammals or by both. Conclusions: Small rocky outcrops markedly influence forest expansion by acting as perches for vertebrate dispersers and as nurse objects and safe sites for plants. Forest expansion starting in small outcrops possibly occurs as follows: perching of dispersers and increase of seed rain on rocks, promotion of better conditions of establishment for forest plants by nurse rocks, protection of plants sensitive to grazing and fire, and nucleation of forest vegetation.

Síndromes de dispersão de espécies arbóreas de florestas ombrófilas submontanas do estado do Rio de Janeiro

O objetivo deste trabalho foi verificar as diferenças nas proporções das síndromes de dispersão de propágulos de espécies arbóreas entre florestas ombrófilas submontanas secundárias e preservadas no Estado do Rio de Janeiro. Foram utilizadas listas de espécies de sete florestas secundárias e cinco preservadas. Partiu-se da hipótese de que as florestas secundárias apresentariam menor riqueza e densidade de espécies arbóreas com síndrome de dispersão biótica (zoocoria). As médias das proporções de árvores com síndrome de dispersão biótica entre florestas secundárias e preservadas foram comparadas pelo teste U. Apesar de preponderarem em ambas, florestas secundárias e preservadas diferiram significativamente em riqueza e densidade de espécies com dispersão biótica (P < 0,01). Essas proporções foram menores nas florestas secundárias, corroborando essa hipótese. As florestas secundárias também apresentaram menor densidade de espécies zoocóricas pertencentes a famílias dispersadas por grandes vertebrados frugívoros (Lauraceae, Myrtaceae e Sapotaceae). Futuras práticas de manejo e conservação nessas florestas secundárias devem incorporar as interações plantas-dispersores, devido aos riscos nos processos de regeneração sem a presença da fauna dispersora adequada.

Characteristics of woody plant regeneration in karren-habitats successional plant communities in Yunnan Shilin karst area of China

Aims Degraded karst ecosystems appear around the world and include the European Dinaric Karst and the South China Karst. The relationship between karst habitats and biodiversity and response to disturbance are essential for karst vegetation succession. Our objective was to study woody plant regeneration in different successional stages in karren-habitats of Yunnan Shilin (Stone forest) Geopark,China. Methods Based on relationships among karrens,soils and plants,we divided karren-habitats into five types:solution corridors; solution wells or shafts; kluft karren; deep solution pits; and solution rock debris. We sampled seedlings and sprouts of woody species in zonal forest,secondary forest,shrubland,shrub tussock and rocky-desertified grassland that encompass succession in karst plant communities. The Shannon-Wiener,Pielou,Simpson and Margalef diversity indices were calculated. Important findings The length and width of each karren-habitat was different and the percentage of karren-habitat changed within the five communities and with disturbance intensity. The fruiting species and number of seedlings decreased with karst vegetation degradation,and the number of sprouts reached a maximum in shrubland and decreased respectively toward the zonal vegetation and rocky-desertified grassland. The Shannon-Wiener and Pielou indices for sprouts in the karren-habitat background communities decreased with plant community degradation,and the Simpson index increased. The Shannon-Wiener and Pielou indices for seedlings were highest in shrubland. The seedlings and sprouts in the five kinds of karren-habitats had different values of biodiversity depending on the succession stage. It is inferred that plants of different successional stages have different regeneration strategies. Sprouting plays an important role in the early stages,and seeding is more important toward the zonal plant community. This is partly because some karren-habitats have remains such as stumps and roots of some species that can repeatedly sprout with continuous disturbance. After the disturbance stops,these sprouts can mature and set seed and seedling regeneration can play a major role towards the middle and late stages of succession. The different karren-habitats play different roles in biodiversity conservation and natural restoration of karst plant communities during succession.

Forest loss and fragmentation effects on woody plant species richness in Great Britain

Studies on the effect of forest loss and fragmentation on plant species richness at different spatial scales have yielded contradictory results that have been attributed to different ways to measure fragmentation. The main goal of this study was to investigate the independent and combined effects of forest loss and habitat fragmentation on woody species richness. Woody species were grouped according to their habitat requirements (forest specialists, forest generalists, non-forest and total woody species). We used regression models to investigate the effect of fragmentation and human occupation on woody species richness. The underlying factors were investigated by partitioning of the variation, i.e. decomposing the variation in species richness between the pure effects of forest loss, fragmentation and human occupation. The relationship between species richness and forest loss resulted extremely non-linear. The models for forest specialist, generalist and total woody species richness accounted for 35%, 31% and 33% of the total variance respectively. Model for non-forest species richness only accounted for 7% of the total variance. The largest fraction of variability in species richness was accounted by fragmentation variables for all groups (except for non-forest species). Results emphasize the larger independent effect of fragmentation over forest loss, suggesting that species variation is mainly conditioned by the spatial configuration of the habitat.

Weed community dynamics in two pastures grown after clearing Brazilian Amazonian rainforest

Mitja D & Miranda IS (2010). Weed community dynamics in two pastures grown after clearing Brazilian Amazonian rainforest. Weed Research50, 163–173.SummaryTo explain the dynamics of the weed vegetation in the Amazonian pastures after clearing of the rainforest, the diversity and floristic composition of 15 Brachiaria brizantha pastures and seven Panicum maximum pastures of various ages were studied. These pastures reflect the original forest, from which they retain a high species richness (from 20 to 73 species on average per 50 m2), a high proportion of forest woody species (from 26% to 65%) and rare species (>50%). The four ecological groups of plants, namely forest woody species, pioneer/secondary woody species, forest herbaceous species and secondary herbaceous species, are present in all pastures immediately after the clearing and burning of the forest and have to compete with the two sown forage species, B. brizantha and P. maximum. Because of its erect habit, P. maximum is rapidly invaded by secondary herbaceous weeds, whereas B. brizantha with its spreading habit slows down their proliferation, which therefore takes about 10 years to complete. The study showed the importance of factors such as the initial vegetation, manual‐clearing practices, duration of cropping and species grown in influencing the floristic composition of the pastures and on the diversity of weeds. These results show the response of weeds faced with human disturbance. The results also demonstrate that farmers can manage pastures in a spirit of conservation of diversity or for weed control.

The effect of different cutting cycle on component woody species in beech-oak coppice forests

The effect of different cutting cycle on component woody species in beech-oak coppice forests

Selective cutting of woody species in a Mexican tropical dry forest: Incompatibility between use and conservation

A major challenge of forest management is to maintain the biodiversity and integrity of the forests while at the same time satisfying human needs through productive activities. While selective extraction of natural resources has less severe consequences on biodiversity and ecosystem function than complete removal of vegetation, such consequences need to be evaluated in detail. “Varas” or stems cut from small trees of tropical dry forests (TDF) in the Pacific Coast of Mexico have been used as plant support stakes in horticultural fields (mainly tomato crops) since the middle of the last century. In this study, we evaluated the effects of selective cutting of plant support stakes on the diversity of woody vegetation of a TDF in northwestern Mexico. Stakes were cut by local harvesters before our assessment of cutting effects. In each of three cutting treatments (T 0 = uncut, T 1 = one cut event, and T 2 = two cut events), we established three sampling plots each consisting of ten 50 m × 2 m parallel transects. All woody plants (stems ≥1.0 cm diameter at 1.3 m height, DBH) were identified and measured on each transect. Species richness ( S) decreased as the number of cuts increased (T 0 = 65 species, T 1 = 50 species, and T 2 = 38 species). The Simpson ( C) and the Shannon ( H′) diversity indices, as well as the rarefaction curves and non-parametric estimates of diversity (Chao1 and ACE) confirmed this tendency of change. Comparison of dominance–diversity curves showed that the woody plant community loses equitability with every additional stake cutting event. The total number of stake providing species did not vary notably across treatments (T 0 = 8 species, T 1 = 9 species, and T 2 = 7 species), but four species reduced their dominance considerably in T 2, while Croton septemnervius, the most used species, increased its abundance and relative basal area with each additional stake harvest, reaching a representation of more than 59% of total number of stems in T 2. The reduction in species diversity, changes in patterns of dominance, and the proliferation of species associated to disturbed sites suggest that current practices of selective cutting require adjustments to make this forest management application more consistent with local conservation of woody plant species diversity and community structure.

Effects of deer and mice on seedling survival in a temperate mixed forest of Japan

To detect the magnitude of indirect positive effects of deer and mice on seedling survival of some woody species in a Japanese temperate forest, we analyzed the data from an earlier field experiment using a hierarchical Bayesian approach. The forest studied was inhabited by sika deer ( Cervus nippon) and mice ( Apodemus spp.), and the floor was covered with dwarf bamboo, Sasa nipponica, which negatively affected tree seedlings and was in turn negatively affected by deer and mice. The field experiment was designed as the combination of exclusion or removal of these factors: deer, mice and dwarf bamboo. A hierarchical Bayesian model was constructed and the parameters were estimated by the Markov chain Monte Carlo method. The model successfully showed the indirect positive effects of deer and mice, which improved the survival rate of five cohorts of the seedlings of three tree species by ameliorating the direct negative effect of dwarf bamboo. The cohorts studied were formed by the seedlings of Abies homolepis that emerged in 1997 and 2002, those of Fraxinus lanuginosa f. serrata that emerged in 1998 and 2002, and those of Fagus crenata that emerged in 1999. The positive indirect effect was especially large in F. crenata, which is known to be severely affected by dwarf bamboo. The total effect of deer was shown to be positive for all cohorts except the A. homolepis cohort that emerged in 1997, at which time the dwarf bamboo had not yet fully recovered from the browsing pressure of deer. The total effect of mice was shown to be positive for all of the cohorts. We conclude that these positive effects were due to the large negative effect of dwarf bamboo on the seedlings.

Impacts of contrasting land-use history on composition, soils, and development of mixed-oak, coastal plain forests on Shelter Island, New York

The Mashomack Preserve on Shelter Island, New York contains one of the premier oak-dominated coastal plain forests in the northeastern U.S. It represents a unique opportunity to study woody species in juxtaposed forests that differ primarily in past land-use (logging versus agriculture). We researched how contrasting land-use history affected: 1) tree species composition, size, and age structure; 2) soil chemistry and morphology; 3) the dominance of Smilax, a native invasive shrub; and 4) the historical ecology and successional pathways. Randomly located plots were sampled for vegetation and soils in the unplowed interior forest versus the maritime forest that was cleared and/or plowed for agriculture and grazing in the 18th and 19th centuries and then abandoned after 1870. The upper soil profile was examined for soil nutrients and pH, the presence/absence of a plow layer (Ap) and for soil charcoal. Tree cores (N = 130) were taken across both forest types to include the full range of species and diameter size classes to assess temporal and spatial variation in recruitment. Maritime forests are closer to the ocean shore and are dominated by Quercus velutina, Sassafras albidum, Carya glabra, and Q. alba, whereas the interior forests are dominated by Q. velutina, Acer rubrum, C. glabra, and Q. prinus. The interior forest plots appear to have continually supported forests, have soils that are somewhat doughtier and less fertile, and lack a plowed horizon, but have frequent soil charcoal as compared with the maritime forest. Formerly plowed and grazed maritime soils are more fertile and Q. alba has greater importance, while Q. velutina has lower importance. Following agricultural abandonment, the maritime forest understory became dominated by thickets of Smilax and presently has lower tree diversity than interior forests. Tree regeneration is sparse in both forest types due, at least in part, to intense browsing by white-tailed deer (Odocoileus virginianus). The interior forest exhibits a predictable successional pathway from mixed-oak to A. rubrum and Fagus grandifolia, which is not apparent in the maritime black oak forests. We believe that differences in overstory and understory composition, species diversity, and successional pathways between the two forest types can be mainly attributed to contrasting land-use history. Smilax is a super-dominant species that has profoundly influenced many ecological processes on the preserve and if left unchecked will continue to do so long into the future.

Dominance-diversity, community-coefficient and nice-width relations of woody species in Montane forests of Garhwal Himalaya, India

The synthetic characters of different plant communities are analysed. Community-coefficient for tree and shrub layer were 89.99 and 88.49%, respectively in North-West aspect of Cedrus deodara forest, probably due to maximum number of species common to both sites. Among the twelve tree species, only two viz., Cedrus deodara and Cupressus torulosa showed 100% presence amongst all the sites. The maximum equitability (10.47) value was computed in site five, because of similar type of species found in this site. Cedrus deodara (6.34) and Cupressus torulosa (5.54) had broader niches due to their presence at all the sites. Species diversity was highest (3.22) on the North West (NW) aspect of the V site and was directly related to the high density of tree species in this site. Dominance-diversity curve (d-d curve) for the tree layer and shrub layer, based on Importance Value Index (IVI) exhibited a geometric series for all forest sites except site IV, where it reflected Preston\'s log normal models. The log normal distribution of this site indicated the mixed nature of vegetation. These species are gradually loosing their niche width, density, dominance and diversity in different sites because of over exploitation and over grazing pressure on these species. In view of the great anthropogenic pressure on the plant community, conservation and management measures are required for sustainable use of these important ethnobotanical plant species and plant biodiversity protection.International Journal of Biological & Chemical Sciences Vol. 1 (1) 2007: pp. 35-42

Plant species richness and floristic composition change along a rice-pasture sequence in subsistence farms of Brazilian Amazon, influence on the fallows biodiversity (Benfica, State of Pará)

Along the Amazonian pioneer front in the Brazilian state of Pará, smallholder farmers manually clear primary rain forest every year to grow rice prior to sowing pastures that they will use for 5–20 years. Species richness and floristic composition of the weedy species were studied in 20 plots along a farming succession, from rice fields, to 1-year-old, 4–8-year-old and over 10-year-old pastures planted to Brachiaria brizantha. In the early phases of the farming cycle reduction in the average plant total species richness in 50 m 2 plots decreased from 67 to 20 species and comprised both woody and herbaceous species. The increase to 41 species further observed in mature pastures was essentially comprised of herbaceous species. Rice fields were characterised by a great floristic heterogeneity which later decreased when they were planted to pastures. PCA of plant communities ordinated plots along a gradient of increasing anthropisation that explained 23.6% of total variance. Species were classified into four ecological groups, which floristic composition and specific richness changed throughout the farming succession. Species richness and density of forest woody species decreased progressively from 32 to 7 species and from 152 to 16 individuals per 50 m 2, and only a few species such as Memora allamandiflora and Poecilanthe effusa resisted pasture conditions. Pioneer/secondary woody species of the genera Cecropia and Solanum germinated out of the forest seed bank, and seven species on average were observed in rice fields and 1-year-old pastures. At later stages (>4 years) their respective species richness decreased to three species while their density decreased sharply, from 439 to 41 individuals per 50 m 2. A few forest herbaceous species of the families Marantaceae and Poaceae and the fern species Adiantum argutum, which survived in rice fields (2 species per 50 m 2 on average), almost disappeared in the 4–8-year-old pastures. In the early phase of the intra-farming succession, a rather stable community of six species of secondary herbaceous plants on average was established. Species richness further increased to 16 in the >10-year-old pastures with addition of species such as Desmodium axillare, Phyllanthus amarus or Cyperus compressus. In accordance with the concept of Initial Floristic Composition, floristic composition at the beginning of the intra-farming succession was determined by the floristic composition of the former forest and by the nature and intensity of the initial disturbance (deforestation and burning). Further changes in species richness, floristic composition and density in the intra-farming succession are driven by the intra-farming management.

WOODY PLANT RICHNESS AND NDVI RESPONSE TO DROUGHT EVENTS IN CATALONIAN (NORTHEASTERN SPAIN) FORESTS

The role of species diversity on ecosystem resistance in the face of strong environmental fluctuations has been addressed from both theoretical and experimental viewpoints to reveal a variety of positive and negative relationships. Here we explore empirically the relationship between the richness of forest woody species and canopy resistance to extreme drought episodes. We compare richness data from an extensive forest inventory to a temporal series of satellite imagery that estimated drought impact on forest canopy as NDVI (normalized difference vegetation index) anomalies of the dry summer in 2003 in relation to records of previous years. We considered five different types of forests that are representative of the main climatic and altitudinal gradients of the region, ranging from lowland Mediterranean to mountain boreal-temperate climates. The observed relationship differed among forest types and interacted with the climate, summarised by the Thorntwaite index. In Mediterranean Pinus halepensis forests, NDVI decreased during the drought. This decrease was stronger in forests with lower richness. In Mediterranean evergreen forests of Quercus ilex, drought did not result in an overall NDVI loss, but lower NDVI values were observed in drier localities with lower richness, and in more moist localities with higher number of species. In mountain Pinus sylvestris forests NDVI decreased, mostly due to the drought impact on drier localities, while no relation to species richness was observed. In moist Fagus sylvatica forests, NDVI only decreased in plots with high richness. No effect of drought was observed in the high mountain Pinus uncinata forests. Our results show that a shift on the diversity-stability relationship appears across the regional, climatic gradient. A positive relationship appears in drier localities, supporting a null model where the probability of finding a species able to cope with drier conditions increases with the number of species. However, in more moist localities we hypothesize that the proportion of drought-sensitive species would increase in richer localities, due to a higher likelihood of co-occurrence of species that share moist climatic requirements. The study points to the convenience of considering the causes of disturbance in relation to current environmental gradients and historical environmental constraints on the community.

CARBOHYDRATE STORAGE AND LIGHT REQUIREMENTS OF TROPICAL MOIST AND DRY FOREST TREE SPECIES

In many plant communities, there is a negative interspecific correlation between relative growth rates and survival of juveniles. This negative correlation is most likely caused by a trade-off between carbon allocation to growth vs. allocation to defense and storage. Nonstructural carbohydrates (NSC) stored in stems allow plants to overcome periods of stress and should enhance survival. In order to assess how species differ in carbohydrate storage in relation to juvenile light requirements, growth, and survival, we quantified NSC concentrations and pool sizes in sapling stems of 85 woody species in moist semi-evergreen and dry deciduous tropical forests in the rainy season in Bolivia. Moist forest species averaged higher NSC concentrations than dry forest species. Carbohydrate concentrations and pool sizes decreased with the light requirements of juveniles of the species in the moist forest but not in the dry forest. Combined, these results suggest that storage is especially important for species that regenerate in persistently shady habitats, as in the understory of moist evergreen forests. For moist forest species, sapling survival rates increased with NSC concentrations and pool sizes while growth rates declined with the NSC concentrations and pool sizes. No relationships were found for dry forest species. Carbon allocation to storage contributes to the growth-survival trade-off through its positive effect on survival. And, a continuum in carbon storage strategies contributes to a continuum in light requirements among species. The link between storage and light requirements is especially strong in moist evergreen forest where species sort out along a light gradient, but disappears in dry deciduous forest where light is a less limiting resource and species sort out along drought and fire gradients.

Plant Functional Types of Woody Species Related to Fire Disturbance in Forest–Grassland Ecotones

The study of plant functional types (PFTs) has been widely emphasized when analysing plant community changes in relation to variations in climate and disturbance regime. In this study, we search for PFTs of woody species near forest–grassland boundaries in South Brazil where, due to climate, forests tend to expand over grassland but are being restricted by frequent fires. We aimed at answering the questions: (i) which plant functional types of forest woody species can establish in adjacent grassland subject to fire disturbance and (ii) which plant functional types of forest and grassland woody species are related to short-term community dynamics in frequently burned grassland. Traits were assessed in woody plants in 156 plots (6.75 m2) arranged in 12 transects across forest–grassland boundaries with different fire history in their grassland part. The analysis used a recursive algorithm to search for traits and PFTs maximally associated to spatial distance from forest limit in one analysis, and elapsed time since last fire in another. As a result, nine PFTs of forest woody species were identified that best described community patterns associated to distance from forest. Resprouting ability characterized forest plants able to colonize grasslands. PFT diversity was higher in border plots than inside forest or grassland. Four PFTs of forest and grassland woody species best described woody species community patterns in the grassland associated to elapsed time since fire. Taller individuals of single-stemmed shrubs predominated in late post-fire recovery (3–4 years), while shorter multi-stemmed shrubs in recently burned areas (3 months to 1 year). PFTs of forest trees occurred in border plots or, as established adults, in grassland, remaining unaffected by fire. We conclude that easily measurable structural plant traits, such as those used in our study, are sufficient to evaluate post-fire community dynamics. Forest PFTs in burned grassland are restricted to those with resprouting ability to survive recurrent fire events. Establishment success is highest on protected sites with lesser or low-intensity fire.