Distribution Patterns Of Tree Species Research Articles

Disturbance sensitivity shapes patterns of tree species distribution in Afrotropical lowland rainforests more than climate or soil.

Understanding how tropical forests respond to abiotic environmental changes is critical for preserving biodiversity, mitigating climate change, and maintaining ecosystem services in the coming century. To evaluate the relative roles of the abiotic environment and human disturbance on Central African tree community composition, we employ tree inventory data, remotely sensed climatic data, and soil nutrient data collected from 30 1-ha plots distributed across a large-scale observational experiment in forests that had been differently impacted by logging and hunting in northern Republic of Congo. We show that the composition of Afrotropical plant communities at this scale responds to human disturbance more than to climate, with particular sensitivities to hunting and distance to the nearest village (a proxy for other human activities, including tree-cutting and gathering). These findings contrast neotropical predictions, highlighting the unique ecological, evolutionary, and anthropogenic history of Afrotropical forests.

Adaptive Distribution and Vulnerability Assessment of Endangered Maple Species on the Tibetan Plateau

Climate change has had an almost irreversible impact on the distribution patterns of tree species on the Tibetan Plateau, driving some vulnerable species to the brink of extinction. Therefore, it is important to assess the vulnerability of tree species in climate-sensitive areas under the following three IPCC-CMIP6 scenarios: SSP126, SSP370, and SSP585. The MaxEnt model was used to predict adaptive distribution for one endangered (Acer wardii W. W. Smith (A. wardii)) and six vulnerable maple plants on the Tibetan Plateau under current and future conditions. We then evaluated their vulnerability using the landscape fragmentation index. Our results showed that the current adaptive areas of vulnerable maple species were mainly distributed in the southeast of the Tibetan Plateau. The dominant factors affecting adaptive areas were temperature annual range (BIO7) for Acer sikkimense Miq. and Acer sterculiaceum Wall.; annual precipitation (BIO12) for Acer cappadocicum Gled.; precipitation of driest month (BIO14) for Acer pectinatum Wall. ex G. Nicholson, Acer taronense Hand.-Mazz., and A. wardii; and subsoil clay fraction (S_CLAY) for Acer campbellii Hook.f. & Thoms. ex Hiern (A. campbellii) Under the three future scenarios, the adaptive areas of maple on the Tibetan Plateau area shifted to the northwest, and habitat suitability increased in the northwestern part of the adaptive areas. In the SSP370 scenario, all seven species showed an increase in adaptive areas, while certain species decreased in some periods under the SSP126 and SSP585 scenarios. The status of the endangered maple species is likely to be even more fragile under the three future scenarios. A. wardii and A. campbellii are more vulnerable and may face extinction, requiring immediate attention and protection. In contrast, the vulnerability of the remaining five species decreased. In conclusion, this study provides recommendations for conserving vulnerable maple species on the Tibetan Plateau. Our data support understanding the distributional changes and vulnerability assessment of these tree species.

Tree species on environmental gradients in subtropical forest of northwest Belize, in the Maya Lowlands

We studied species composition and spatial distributions of tree species, and the underlying topography and soil, in subtropical forests of northwest Belize, a region in the Maya Lowlands. Our goal was to learn how much the spatial distributions of species vary and are predictable over the landscape. The study was done in old-growth, subtropical moist forest on limestone-derived topography and soil. We identified to species all trees ≥10 cm DBH in 209 400-m2 plots. For each plot, we characterized topographic setting and analyzed soil nutrients and texture. We recorded 3,984 individual trees of ∼140 tree species and used the 3,775 individuals of the 69 species occurring in ≥5 plots in multivariate analyses, including Nonmetric Multidimensional Scaling (NMS). NMS showed that 73% of the variation in species composition per plot was associated with the first three ordination axes. Sixteen out of the 34 quantitative variables we measured were correlated at R 2 > 10% with the axes. Of the categorical variables, Topographic Class was strongly associated with species composition, and USDA Texture Class less so. Of the 69 focal tree species, the abundances of 21 were correlated at R 2 > 10% with one or more axes of the NMS ordination. Importantly, these 21 species accounted for 68% of all individual trees sampled in the 209 plots. Twenty-three species were indicators of particular topographic and soil classes. We conclude that patterns of tree species distribution are strongly and predictably associated with different topographic and soil conditions in this landscape. In the past, the ancient Maya could have used this type of predictable plant–soil relationship to optimize their agriculture. In the future, our results are a basis for predicting local shifts in tree species distributions due to climate change.

Climatic distribution of tree species in the Atlantic Forest

AbstractSpecies under milder climates (e.g., warm and wet) tend to experience lower variability in temperature and rainfall regimes and might occur in narrower climatic ranges than species that tolerate harsher conditions (e.g., cold or dry climates). Thus, tree species that occur under harsh conditions should have a broader climatic range, being a small subset of the flora. Here, we assess the influence of climate on species distribution of 1138 tree species from the Atlantic Forest biodiversity hotspot. We investigate their range (or niche breadth), and the “center of gravity” index (or niche optima), along with gradients of mean annual temperature and climatic water deficit (CWD). We further identified those species associated with conditions on different ends of temperature and moisture gradients. We found a small subset of species occurring under colder temperatures or under drier conditions, and these species had a wider niche breadth. The warm or wet‐affiliated species had narrower ranges along with the temperature and the CWD gradients, respectively. Moreover, species affiliated to warm and those to moister conditions had greater densities near their occurrence limits, thus they may be more susceptible to climate changes. We conclude that global climate changes will affect the incidence and abundance distribution patterns of tree species along this threatened biodiversity hotspot, mainly those with narrow niches and within the limit of its distribution.Abstract in Portuguese is available with online material

Palm Species Traits Determine Soil Nutrient Effects on Seedling Performance

Environmental gradients influence plant establishment, survival, and functional traits. Along the Panama Canal Isthmus there is a strong rainfall gradient with an underlying mosaic of soil types ranging in soil nutrient availability. In this region, tree species distribution patterns are correlated with soil phosphorus availability and rainfall patterns, but how understory plant species such as palms relate to these factors is less clear. We hypothesized that due to greater resource use efficiency and optimal biomass allocation, specialist species will have greater seedling performance growing in home soil and sites compared to species not occurring there. To test this hypothesis, we used two specialist species (Chamaedorea tepejilote and Geonoma congesta) and two generalist species (Geonoma cuneata var. cuneata and Chamaedorea pinnatifrons), and for these four species we measured traits on seedlings and assessed their performance in shade house and field transplant experiments using five soils. Soils were sourced from five sites which varied in nutrient availability and rainfall, and were distributed along lowland tropical forests of the Panama Canal Isthmus. In the shadehouse experiment, leaf functional traits were determined by species rather than soil nutrient availability. However, in the shadehouse experiment, seedling biomass allocation, and relative growth rate were determined by interactions between species and soil, with weak support for home-site advantage for one of the species. In the field transplant experiment, seedling survival was strongly related to dry season water availability. However, species tended to have high survival at home sites and other sites with higher dry season rainfall. Together, results from these experiments suggest that understory palm species seedling performance are determined by species-specific responses to the combination of soil nutrient and water availability. This indicates that while soil nutrients influence seedling biomass allocation, dry season water availability determines both specialist and generalist seedling survival and therefore distributions along the soil nutrient and moisture gradient.

Tree diversity, distribution and regeneration in major forest types along an extensive elevational gradient in Indian Himalaya: Implications for sustainable forest management

Elevation plays a pivotal role in determining the diversity and distribution of biodiversity in mountainous landscapes, and therefore macroecological assessment of forest tree vegetation is crucial for developing scientifically-informed forest policy and management. In this study, we investigated the diversity, distribution pattern and regeneration status of tree species growing in major forest types in Jammu and Kashmir – a region located in Indian Himalaya. We carried out stratified random sampling of tree vegetation in the 12 major forest types selected along an extensive elevational gradient (350–3450 masl) in the study area. We recorded 36 forest tree species taxonomically distributed among 33 genera and 21 families, with Pinaceae as the most dominant family. Along the elevational gradient, tree species richness was greater in the low-altitude forest types dominated by broad-leaved trees and showed a declining trend with few or a single species in the forest types at high-altitudes. Based on the distribution pattern of tree species within the forest types, four distinct forest communities were recognised in the study area. In terms of elevational range size, Pinus roxburghii showed widest distribution occurring from 450 to 1650 masl, almost reaching to the Quercus incana distribution limit in Jammu. The tree regeneration status, based on seedling/tree ratio, revealed higher values for the Shiwalik Chir-Pine (650–1150 masl), Lower Western Himalayan-Banj oak (1200–1850 masl), and Fir forest types (2150–3150 masl). Across the forest types, we recorded an average sapling/tree ratio of 3.5 ± 0.89, tree density of 238 Nha−1, and basal area of 29.11 m2 ha−1. Among all the tree species, Abies pindrow showed highest regeneration performance and co-occurring well with other tree species at higher elevations (2150–3150 masl). We observed a significant positive correlation between adult tree density with those of seedling and sapling density. By making available an empirical assessment of diversity and distribution of forest tree species, and more importantly their current regeneration status, our findings will facilitate better monitoring and management of the forest ecosystems in this Himalayan region. Our study can help in developing sustainable management strategies for the existing ecologically-healthy forest areas in the region. Also, the findings will guide the ecosystem restoration of the degraded forest landscapes in the study area and provide useful insights for forest management in similar mountainous landscapes elsewhere.

Distributional Characters of Warm-Temperate Evergreen Broadleaf Tree Species Growing in Urban Park -Focused on Duryu Urban Park in Daegu-

Present study aims to find out how evergreen tree species planted in urban parks spread to nearby wild areas. We accomplished field investigation at the Duryu Park area, Daegu, where located a transitional zone between the warm-temperate and the cool-temperate zones. From 2018 to 2019, a total of 32 floristic-sociological releves were made. Distribution patterns of tree species connected into habitat conditions were explored by canonical correspondence analysis (CCA). 10 tree species dispersed spontaneously in the study area were recognized; Nandina domestica, Euonymus fortunei, E. japonicus, Quercus acuta, Q. glauca, Q. phillyraeoides, Elaeagnus pungens, Ligustrum japonicum, Osmanthus heterophyllus, and Ilex cornuta. Most of these trees were the preferentially ornamental plants introduced in the park since 1977 and mainly bird dispersal seeds. Q. glauca and L. japonicum appeared the most predominant dispersion. Their micro-habitats are the much humid and warmer stands of the deciduous broad-leaved forests mainly. We concluded that urban gardening has been also an important agent to recover the native vegetation if introducing potential natural vegetation (PNV). The habitat-based PNV in the Daegu area arose as a critical issue for further understanding.

Abundance, frequency and distribution pattern of tree species in recorded forest area of Western Himalaya

The forest in India have a long history of human induced modifications through intensive forest management that began in the colonial period but continued afterwards to meet the wood-based demand until the forestry goals shifted towards conservation efforts. All this greatly influenced the plant community structure. We attempt to describe the abundance and distribution pattern of trees in recorded forestland of Western Himalaya using the National Forest Inventory database. A total of 3549 sample plots laid across different forest types were analyzed to reveal the abundance, frequency and distribution pattern of 226 tree species/genus using various indices i.e. abundance by frequency ratio, Morisita index and variance mean ratio. Twelve tree species and Eucalyptus genus were found to be most abundantly found tree species in recorded forest area of Western Himalaya. Ten tree species were found to have regular distribution pattern, one hundred ninety-two were contagiously distributed while twenty-five were randomly distributed. Results derived from huge datasets helps in establishing firm statements with quoted significance value. Myrica esculenta and Aegle marmelos were found among the most abundantly occurring tree species whereas Myrica esculenta, Syzygium cumini and Pyrus pashia, were among the most relatively frequently occurring wild fruit yielding tree species. These species (apart from fodder tree species) can be considered in social forest and joint forest management programs in forest fringe villages/areas to enhance and sustain the provisional ecosystem services in Western Himalaya.

阿尔泰山萨彦岭4种优势树种径向生长对气候因子的响应

气候变化深刻地影响森林树木的生长，而树种对气候变化敏感度的差异可能影响了气候变化下的森林生态系统响应。因此，研究优势树种间生长对气候变化的敏感度差异，对正确认识气候变化下林分生长动态及分布格局十分重要。基于树木年代学的方法，研究了阿尔泰山萨彦岭西伯利亚落叶松（Larix sibirica）、西伯利亚红松（Pinus sibirica）、西伯利亚冷杉（Abies sibirica）以及西伯利亚云杉（Picea obovata）4种优势树种的径向生长-气候关系。结果显示：（1）西伯利亚冷杉径向生长与上一年10-11月、当年1-9月的干旱指数、2-4月的降水显著正相关，与1月的平均温和最高温呈显著负相关关系，与当年4、6月份的水汽压正相关；（2）西伯利亚落叶松径向生长与上一年8月和当年8月的平均温、最高温以及当年8月的最低温显著负相关，而与当年6月的最低温则正相关，与8月份的水汽压显著负相关；（3）西伯利亚红松径向生长与3月降水、7月最低温、上一年10月的水汽压显著正相关；（4）西伯利亚云杉径向生长与6月平均温、最高温、水汽压正相关，与上一年10-11月、当年2-4月和9月的干旱指数正相关，同时与3、4月的降水量显著正相关。西伯利亚冷杉和西伯利亚云杉、西伯利亚云杉和西伯利亚落叶松、西伯利亚云杉和西伯利亚红松对于特定气候因子表现出相似的响应结果，与年表间相关性的结果一致。但差异也是明显的，西伯利亚冷杉和西伯利亚云杉对区域水分变化敏感，而西伯利亚落叶松和西伯利亚红松主要对区域温度变化敏感。综上所述，气候变化下，该区域优势树种对气候变化响应的差异可能导致区域林分动态和格局的改变，因此，多树种径向生长-气候关系研究有助于正确反映森林动态。研究结果可以为区域森林管理与生态保护工作提供理论依据。;Climate change has a profound impact on the growth of forest trees, and the sensitivity of different tree species to climate change may influence the response of forest ecosystem under climate change. Therefore, it is extremely important to study the differences in the growth sensitivity among dominant tree species to climate change, to correctly understand the growth dynamics and distribution pattern of tree species stand under climate change. Based on the standard method of dendrochronology, we selected the tree-ring width index of four dominant tree species, including Larix sibirica, Pinus sibirica, Abies sibirica and Picea obovate on the Sayan Range of the Altai Mountains, Russian. We focused on the characteristics of standard chronologies and the relationships between the standard chronologies and the six climatic factors. The results showed that (1) there was a significantly positive correlation between radial growth of A. sibirica and PDSI from October to November of the previous year and from January to September of the current year, precipitation from February to April, and the mean and maximum temperature in January. Additionally, vapour pressure in April and June of the current year was positively correlated with radial growth. (2) The radial growth of L. Siberian was negatively correlated with the mean temperature, maximum temperature, minimum temperature and vapour pressure in August of the current year, the mean temperature and maximum temperature in August of the previous year, and positively correlated with the minimum temperature in June. (3) The radial growth of P. sibirica was significantly and positively correlated with the precipitation in March and the minimum temperature in July, also the vapour pressure in last October. (4) The radial growth of P. obovate was positively correlated with the mean temperature, maximum temperature and mean vapor pressure in June, PDSI from October to November of previous year and from February to April and September of current year. Our findings showed that there were similar results of tree radial growth-climate factors between species. But there were differences between tree species that A. sibirica and P. obovate was sensitive to regional water, while L. Siberian and P. sibirica was mainly sensitive to regional temperature. The difference of the response of dominant tree species to climate change in this region may lead to the change of regional stand dynamics and pattern under climate change. Therefore, the research on radial growth-climate relationship of multiple tree species is helpful to correctly reflect the forest dynamics. The results of this study can provide theoretical basis for regional forest management and ecological protection.

Seasonal patterns of gas exchange and water relations in juveniles of two Neotropical savanna tree species differing in leaf phenology

Ecophysiological studies on Neotropical savanna trees have shown that there is a resistance gradient of seasonal water stress in deciduous and evergreen species. Some species perform like drought avoiders, characterized by high transpiration rates during the wet season that can be sustained by evergreen deep rooted species during the dry season. Nevertheless, water deficit in superficial soil layers, fire damages and nutritional requirements could differentially affect juveniles of both phenological types determining their spatial patterns of distribution (evergreen species sparse in open grasslands and deciduous species gathered in groves). This study examined seasonal variations in water relations and photosynthesis in juveniles of two tree species differing in leaf phenology: Curatella americana (evergreen) and Cochlospermum vitifolium (deciduous). We wanted to test the hypothesis that the improved ability of evergreen deep rooted species like C. americana to colonize open savannas is related to drought tolerance and a conservative gas exchange pattern in juveniles that photosynthesize even during the dry season, while one might expect a water spender and avoider character in propagules of deciduous species like C. vitifolium that are active mostly during the rainy season. The studied species showed high transpiration rates during the rainy period, indicating little water availability limitations on surface soil layers. Even so, both species exhibited a distinctive decrease in stomatal conductance towards the end of the rainy season, an indication of water availability restrictions and/or a response to higher air evaporative demands in the shallow rooted juveniles. At the peak of the dry season, C. americana presented comparable transpiration rates with wet season measurements, indicating that the studied juveniles had reached more permanent (or stable) water sources at soil depths of 30 cm (approximate maximum root lengths measured). Yet, C. americana showed a significant decrease in water potentials from wet to dry seasons, and osmotic adjustment as a drought tolerance mechanism. Overall, the evergreen functional type (juvenile plants of C. americana) showed tolerance to water deficit, maintaining functional leaves in the dry season. On the other hand, in absence of a water deficit, juveniles of C. vitifolium showed higher photosynthetic rates that could be translated into high growth rates in wet habitats. However, the low water deficit tolerance of the juveniles of C. vitifolium seems to be the main handicap for its colonization potential of the open savanna environment. In conclusion, as predicted, the greater tolerance to water deficit of the evergreen studied species suggests that resistance to water stress determines the observed distribution pattern of tree species in the study area, where only the evergreen ones colonize the open savanna, acting in its adult stages as a focus for the recruitment of woody species.

Estrutura da comunidade e diversidade de espécies arbóreas em uma floresta subtropical no sul do Brasil

Abstract: Local and regional environmental variations lead to different species composition, creating transitional areas. An example is the Araucaria and Seasonal forest in southern Brazil. Our objectives were (1) to describe the tree community structure and composition of a subtropical forest in southern Brazil and (2) to compare the floristic relationships between two forest typologies (Araucaria and Seasonal forest) in order to characterize the study area and the distribution patterns of tree species. We conducted a survey at Chapecó National Forest (in southern Brazil) in an area of 1.2 ha, where all individuals ≥ 30 cm of circumference at breast height were sampled. Community structure was described using the traditional phytosociological parameters. The floristic relationships were obtained by comparing our results with compiled data from other scientific papers through cluster analyses using an unweighted average linkage method, based on Jaccard similarity coefficient. We sampled 809 individuals belonging to 61 species and 28 families. The richest family was Fabaceae and Coussarea contracta (Walp.) Müll.Arg. was the most abundant species. Taxonomic diversity was 3.06 and the evenness was 0.74. The floristic similarity revealed that species composition of our study area is more similar to Seasonal forest. Species composition is related to environmental factors such as great thermal amplitude and seasonality. This subtropical forest is well structured, highly diverse and extremely important for the local and regional biodiversity conservation.

Distribution pattern of tree species from tropical to temperate regions in Makawanpur district, central Nepal

Tree species are the dominant component of forest ecosystems which influence most structural and functional attributes of these ecosystems. This study aims to document distribution pattern of forest types and their composition from tropical region at Hetauda (550 m asl) to temperate region above Simbhangyang (2500 m asl) of Makawanpur district, central Nepal. The carbon stock in the living biomass of tree species was estimated using an allometric equation while the biodiversity index was calculated using Shannon-Wiener Biodiversity index. A total of 62 species of trees belonging to 51 genera was recorded. Shorea forest was dominant in lower elevation while Quercus forest, Alnus-Rhododendron, Quercus-Lyonia and Quercus-Symplocos forests at higher elevation. Similarly, Castanopsis tribuloides has the widest distribution range (570 m to 2240 m asl) followed by Shorea robusta, Lagerstroemia parviflora, Trichilia connaroides, Syzigium jambos, Castanopsis indica, Schima wallichii etc. The highest number of tree species was recorded at 550 m elevation. Estimated carbon stocks were ranged from 0.85 — 53.37 t/ha with the mean value 24.98 t/ha. The values of Shannon-Wiener Biodiversity index ranged from 1.23— 2.78. There was positive relationship between carbon stock and biodiversity index (R2 = 0.40, p = 0.03). People have been practicing community forest management to support sustainability of harvesting in the study area.Banko JanakariA Journal of Forestry Information for NepalVol. 28, No. 1, 2018, page: 20-25

Patterns of tree species variation across southern South America are shaped by environmental factors and historical processes

The southern portion of South America, which encompasses high and exceptional lineage diversity, is well-suited to studies addressing the interaction between biogeography and local environmental conditions and how this historical process and environmental variables affect distribution patterns. We here assessed the role of environmental variables and spatially autocorrelated processes in driving tree species distribution patterns in the whole southern South America forests. We compiled a dataset containing 110,087 occurrence records of 3183 species distributed into 742 sites across six countries and 13 biomes. We modeled the influence of both environmental and spatial variables related to geographic distribution limitations on the variations of species composition through partial canonical redundancy analysis. We built such models for each of our four datasets: the whole extratropical area of South America; Atlantic and Pampa Biomes; dry communities east of the Andes; and communities west of the Andes. Both spatial and environmental variables affect tree species composition in the southern region of South America, although a major role is played by the “pure” spatial fraction. This greatest significance of spatial structures reinforces the importance of historical process for this region and the floristic dissociation existing between the tropical and extratropical portion of South America. We argue that the southern South American forests (especially their temperate portion) should not be lumped into the Neotropical Floristic Province, an idea of utmost importance for the conservation of these high-diversity austral forests.

Functional trait and community phylogenetic analyses reveal environmental filtering as the major determinant of assembly of tropical forest tree communities in the Western Ghats biodiversity hotspot in India

BackgroundImproved understanding of the processes shaping the assembly of tropical tree communities is crucial for gaining insights into the evolution of forest communities and biological diversity. The climate is thought to be the first order determinant of abundance and distribution patterns of tree species with contrasting traits such as evergreen and deciduous leaf phenology. However, the relative role of neutral, and niche-based processes in the evolution of these patterns remain poorly understood.MethodsHere, we perform an integrated analysis of the data on tree species abundance, functional traits and community phylogeny from a network of 96 forest plots, each 1 ha in size, distributed along a broad environmental gradient in the central Western Ghats, India. Then, we determine the relative importance of various process in assembly and structuring of tropical forest communities with evergreen and deciduous leaf phenology.ResultsThe deciduous leaf phenological trait has repeatedly evolved among multiple distantly related lineages. Tree communities in dry deciduous forests were phylogenetically clustered and showed a low range and variance of functional traits related to light harvesting, reproduction, and growth suggesting niche-based processes such as environmental filtering play a vital role in the assembly of tree communities in these forests. The external factors such as human-mediated disturbance also significantly, but to a lesser extent, influences the species and phylogenetic turnover.ConclusionsThese findings revealed that the environmental filtering plays a significant role in assembly of tree communities in the biologically diverse tropical forests in the Western Ghats biodiversity hotspot.

Effects of topography and spatial processes on structuring tree species composition in a diverse heterogeneous tropical karst seasonal rainforest

Aggregated patterns of tree species originate either from the physical forcing of habitat heterogeneity or from community processes. In both cases, spatial structuring plays a functional role in ecosystems. This study examines the spatial patterns of tree species, and discusses the degree to which variation in species distribution patterns depends on topographic variation. We first analyzed the spatial distribution patterns of tree species by using the univariate pair correlation function. We used redundancy analysis to identify the main structures explained by the measured topographic variables. Then, we used variation partitioning in combination with Moran’s eigenvector maps and seven topographic variables to determine the relative importance of the effects of pure topographical, pure spatial, and spatially structured environmental processes on spatial patterns of tree species composition in a large-scale stem-mapping plot located in a diverse heterogeneous tropical karst seasonal rain forest of south China. Although aggregated distribution was the dominant pattern for tree species as we expected in this tropical karst forest, the degree of aggregation was lower than in other tropical or subtropical forests. Most species showed random patterns after controlling for habitat heterogeneity in a parametric heterogeneous Poisson process null model. The seven topographical variables explained about 16.7%, 31.0% and 47.2% of the total variance in species abundances by redundancy analysis for cell sizes of 10m×10m, 20m×20m and 50m×50m, respectively. The pure spatial component was most important at the three spatial scales, which accounted for about one-third of total variance in species composition, while the spatially independent habitat contributed a negligible effect. This indicated that the overall evidence for topographic controls of the tropical tree species spatial pattern was strong, but the explanatory power of the topographic variables was negligible compared to the total variation of pure spatial processes, especially the broad-scale space. The results suggest that topographical and neutral progresses jointly contribute to the maintenance of species composition, and their relative importance varies with spatial scale in the Nonggang tropical karst seasonal rain forest.

Assessment of tree species diversity and its distribution pattern in Pachamalai Reserve Forest, Tamil Nadu

ABSTRACTAn increased understanding of the importance of forest diversity for ecosystem services such as medicine, wood, climate control, etc., has lead to greater interest in the study of forests. This study aims to analyze the diversity, composition, and distribution pattern of tree species in Pachamalai Reserve Forest in the Eastern Ghats of Tamil Nadu State. Data were collected in the quadrant method, where 10 × 10 m2 plots at different altitudes from 230 to 930 m with 50-m regular intervals were plotted. A total of 73 tree species belonging to 35 families with the density of 1,372 individuals were enumerated from 3 ha. Overall, the most dominant tree species family was Fabaceae (21 species). The highest number in terms of density of tree species was observed for Pongamia pinnata and the most dominant on the basis of basal area was Tamarindus indica. The species inventory was calculated by Shannon-Weiner index (3.916), Simpson index (0.0206), and Margalef index (9.9667). With the increasing altitudinal gradient, the maximum species richness was observed in the middle elevation zone from 580 to 780 m. The results from the study could be helpful for monitoring and sustaining the forest resources, and important in preventing the loss of biodiversity and mitigating climate change.

Spatial patterns of tree species distribution in New Guinea primary and secondary lowland rain forest

AbstractQuestionsHow do spatial patterns of tree distribution and species co‐occurrence differ between primary and secondary tropical rain forests? What signatures of ecological processes might be discerned by comparing the spatial patterns of trees between primary and secondary forest plots?LocationTropical rain forest vegetation, lowlands of Papua New Guinea.MethodsAll trees over 5 cm DBH were surveyed in two non‐replicated 1‐ha plots situated in primary and secondary forest. Grid location, DBH, height and species identity were recorded for all surveyed trees. Analysis of the spatial pattern and the autocorrelation of tree sizes and identities were used to assess the structure of the forest found within the plots. Functions combining Ripley's K and the individual species–area relationship were applied to study the spatial distribution of trees and species diversity.ResultsThe spatial distribution of common species, and all stems collectively, was aggregated in the secondary forest plot but not different from random in the primary forest plot. Diameter and height were also strongly spatially auto‐correlated in the secondary forest plot but not in the primary forest plot. Conspecific aggregations were more common in the secondary forest plot. Finally, the secondary forest plot was characterized by the presence of diversity‐repelling species and lower diversity than the primary forest plot, where diversity‐accumulating species were present.ConclusionsWe attribute the weaker autocorrelation of tree size in the primary forest to the development of size hierarchies throughout the course of stand aging. The conspecific aggregation and low local diversity within the secondary forest plot are likely caused by dispersal limitation during a brief period of establishment after disturbance. The higher local diversity of the primary forest can be explained by the reduction of species aggregation through increased mortality of conspecifics. This is caused by strong intraspecific competition, supporting the spatial segregation hypothesis (interspecific spatial segregation).

Inventory of trees in tropical dry deciduous forests of Tiruvannamalai district, Tamil Nadu, India

Sanjay-Gandhi D, Sundarapandian S. 2014. Inventory of trees in tropical dry deciduous forests of Tiruvannamalai district, Tamil Nadu, India. Biodiversitas 15: 169-179. Diversity and distribution patterns of tree species were inventoried in 20 one hectare plots in SathanurReserve Forest of Tiruvannamalai district, Tamil Nadu, India. These plots were grouped into three sites based on their location in thereserve forest and the level of disturbance. Site I (8 plots) near to the road and agricultural lands, Site II (8 plots) away from the road andhuman settlements and site III (4 plots) along the canal-side where the terrain contain rocks here and there. A total of 60 speciesbelonging to 48 genera and 29 families were enumerated including 13,412 stems (≥3.2cm DBH size class). The species richness in thestand (plot) varied from 7 ha-1 to 28 ha-1 and the stand density varied from 336 ha-1 to 1075 ha-1. Albizia amara (7999) was the dominantspecies in terms of density, basal area and IVI in all the study plots except plot no.16, where Chloroxylon swietenia was dominantindicates a mono-species dominated forest ecosystem. The mean values of Shannon and dominance indices were 1.406 and 0.411respectively. Diameter class-wise distribution showed L-shaped curve, a sign of good regeneration status. Cattle grazing and illegal fuelwood collection have been observed to pose huge pressure to the integrity of this tropical dry forest, still it have substantial tree speciesdiversity similar to many other dry forests in India and elsewhere.

Disturbance and clonal reproduction determine liana distribution and maintain liana diversity in a tropical forest.

Negative density dependence (NDD) and habitat specialization have received strong empirical support as mechanisms that explain tree species diversity maintenance and distribution in tropical forests. In contrast, disturbance appears to play only a minor role. Previous studies have rarely examined the relative strengths of these diversity maintenance mechanisms concurrently, and few studies have included plant groups other than trees. Here we used a large, spatially explicit data set from Barro Colorado Island, Panama (BCI) to test whether liana and tree species distribution patterns are most consistent with NDD, habitat specialization, or disturbance. We found compelling evidence that trees responded to habitat specialization and NDD; however, only disturbance explained the distribution of the majority of liana species and maintained liana diversity. Lianas appear to respond to disturbance with high vegetative (clonal) reproduction, and liana species' ability to produce clonal stems following disturbance results in a clumped spatial distribution. Thus, clonal reproduction following disturbance explains local liana spatial distribution and diversity maintenance on BCI, whereas negative density dependence and habitat specialization, two prominent mechanisms contributing to tree species diversity and distribution, do not.

Topography related habitat associations of tree species traits, composition and diversity in a Chinese tropical forest

Several studies have demonstrated that topography, as a proxy for resource availability, plays an important role in shaping tree species distribution patterns in tropical forests. Here we take a functional approach by assessing changes in plant functional traits along topographical gradients in a 20-ha forest dynamics plot in Xishuangbanna, southern Yunnan, China. We hypothesized that observed changes in trait composition and diversity along the topographic gradient should reflect tree life-history strategies linked to resource (water and nutrients) availability. We measured and compiled data of the maximum height, leaf area, seed mass and wood density of 334 tree species in 500 subplots (20×20m). We found that species composition and diversity changed significantly along the topographical gradient. This change was accompanied by increasing community average seed mass and wood density, and decreasing leaf area and tree maximum height with higher elevations and steeper slopes. Higher slopes and ridges were being dominated by tree communities that, possibly due to environmental filtering, converged on a combination of traits characteristic of slow growth and low turn-over. Lower slopes and valleys, on the other hand, were dominated by tree communities that showed high trait evenness and divergence, and tree species characterized by traits indicative of fast growth and turn-over, i.e. competition for resources may be responsible for complementary trait combinations and resource use in this habitat type. Our study shows that functional traits can provide a mechanistic understanding of the processes shaping tropical tree community assembly along topographical gradients and supplements information obtained using species composition and diversity data. Some practical outcomes of our study include: (1) plant species compositional trends in tropical forests can be predicted with GIS technology, focusing on topographical gradients; (2) forest communities on ridges may become more dominant and expand in the future due to increasing drought severity; (3) a considerable number of tropical tree species may currently be under threat of local extinction due to topographically biased deforestation trends and (4) trait based survey approaches improve our understanding of the mechanisms behind species compositional trends.