Distribution Of Forest Species Research Articles

Modelling Spatial Distribution of the Carob Tree (Ceratonia siliqua L.) in Azilal Province, Morocco

Factors determining forest species distribution include, in addition to external factors such as human interference and environmental management strategies, also soil and hydrological characteristics and climate conditions in any given areas. Modelling<strong> </strong>distribution has practical application in forest conservation and management, and help decision makers to develop strategies aimed at forest restoration, development of mountainous areas and the continuous and sustainable provision of forest-related services. Species distribution modelling (SDM) can be used for predicting species distribution based on tree presence records and on a number of environmental predictors. In this study we used MaxEnt for niche modelling in predicting carob (<em>Ceratonia siliqua </em>L.) trees spatial distribution in the Province of Azilal in Morocco. The results obtained show that a large area of the mountain regions is suitable for the expansion of <em>Ceratonia siliqua</em> stands. These findings will help decision makers in forest planning to better identify suitable sites for carob tree plantations and assess the potential of the exiting populations.

Tree or soil? Factors influencing humus form differentiation in Italian forests

We aim to investigate the occurrence of forest humus forms (Moder, Amphi and Mull) in relation to environmental factors describing parent material, climate and tree species. Boosted regression trees (BRTs) were applied as modeling tool to analyze data of 238 plots of the BioSoil database covering the whole Italian forest territory. Though predictive ability was not very high, especially for the Amphi form, we could gain significant insight into factors controlling humus form differentiation. In the BRT analysis, the diversity of tree species was the most important predictor for Moder and Mull models and specific plant effects were evidenced. However, our results showed that the geographic distribution of Italian forest species was influenced by soil and climate conditions, partly explaining the high weight of tree species as factor. The importance of the soil nutritional status, due to parent material properties, in driving humus form differentiation was stated, highlighting the key role played by pH and calcium content, with the hitherto understated importance of phosphorus. This study further clarified the functioning of the still poorly understood Amphi form. Reduced effective soil volume (EfVol) combined with seasonality appeared to constrain pedofauna activity in otherwise favorable and nutrient rich systems, favoring the evolution of Amphi instead of Mull forms.

불확실성을 고려한 미래 잣나무의 서식 적지 분포 예측 - 종 분포 모형과 RCP시나리오를 중심으로 -

Climate change will make significant impact on species distribution in forest. Pinus koraiensis which is commonly called as Korean Pine is normally distributed in frigid zones. Climate change which causes severe heat could affect distribution of Korean pine. Therefore, this study predicted the distribution of Korean Pine and the suitable habitat area with consideration on uncertainty by applying climate change scenarios on an ensemble model. First of all, a site index was considered when selecting present and absent points and a stratified method was used to select the points. Secondly, environmental and climate variables were chosen by literature review and then confirmed with experts. Those variables were used as input data of BIOMOD2. Thirdly, the present distribution model was made. The result was validated with ROC. Lastly, RCP scenarios were applied on the models to create the future distribution model. As a results, each individual model shows quite big differences in the results but generally most models and ensemble models estimated that the suitable habitat area would be decreased in midterm future(40s) as well as long term future(90s).

Predicting the distribution of forest tree species using topographic variables and vegetation index in eastern Acre, Brazil

Species distribution modeling has relevant implications for the studies of biodiversity, decision making about conservation and knowledge about ecological requirements of the species. The aim of this study was to evaluate if the use of forest inventories can improve the estimation of occurrence probability, identify the limits of the potential distribution and habitat preference of a group of timber tree species. The environmental predictor variables were: elevation, slope, aspect, normalized difference vegetation index (NDVI) and height above the nearest drainage (HAND). To estimate the distribution of species we used the maximum entropy method (Maxent). In comparison with a random distribution, using topographic variables and vegetation index as features, the Maxent method predicted with an average accuracy of 86% the geographical distribution of studied species. The altitude and NDVI were the most important variables. There were limitations to the interpolation of the models for non-sampled locations and that are outside of the elevation gradient associated with the occurrence data in approximately 7% of the basin area. Ceiba pentandra (samaúma), Castilla ulei (caucho) and Hura crepitans (assacu) is more likely to occur in nearby water course areas. Clarisia racemosa (guariúba), Amburana acreana (cerejeira), Aspidosperma macrocarpon (pereiro), Apuleia leiocarpa (cumaru cetim), Aspidosperma parvifolium (amarelão) and Astronium lecointei (aroeira) can also occur in upland forest and well drained soils. This modeling approach has potential for application on other tropical species still less studied, especially those that are under pressure from logging.

Variation in the population structure between a natural and a human-modified forest for a pioneer tropical tree species not restricted to large gaps.

The distribution of tree species in tropical forests is generally related to the occurrence of disturbances and shifts in the local environmental conditions such as light, temperature, and biotic factors. Thus, the distribution of pioneer tree species is expected to vary according to the gap characteristics and with human disturbances. We asked whether there was variation in the distribution of a pioneer species under different environmental conditions generated by natural disturbances, and between two forests with contrasting levels of human disturbance. To answer this question, we studied the distribution patterns and population persistence of the pioneer tree species Croton floribundus in the size and age gap range of a primary Brazilian forest. Additionally, we compared the plant density of two size-classes between a primary and an early successional human-disturbed forest. Croton floribundus was found to be widespread and equally distributed along the gap-size gradient in the primary forest. Overall density did not vary with gap size or age (F-ratio = 0.062, P = 0.941), and while juveniles were found to have a higher density in the early successional forest (P = 0.021), tree density was found to be similar between forests (P = 0.058). Our results indicate that the population structure of a pioneer tree species with long life span and a broad gap-size niche preference varied between natural and human-disturbed forests, but not with the level of natural disturbance. We believe this can be explained by the extreme environmental changes that occur after human disturbance. The ecological processes that affect the distribution of pioneer species in natural and human-modified forests may be similar, but our results suggest they act differently under the contrasting environmental conditions generated by natural and human disturbances.

Tagging and Mapping of Mixed Dipterocarp Mountain Forest at Species Level using an Airborne Hyperspectral Imager

Forest inventories describe the quantity and quality of trees and other organisms of the forest and the characteristics of the land on which the forest grows. Thus, to manage the resource of the forest systematically, the forest has to be precisely identified and classified before implementing decisions. A study on the spatial distribution of mountain mixed hill dipterocarp forest tree species in Gunung Stong Forest Reserve, Kelantan, Malaysia was conducted using an airborne hyperspectral imaging technique to identify, tag and map tree distribution at species level for future sustainable harvest and management planning. The general objective of this study is to assess the capability and usefulness UPM-AISA airborne hyperspectral sensor in Pre-Felling forest inventory while the specific objectives are to identify, map and tag individual trees in Gunung Stong Forest Reserve, Kelantan. A Sobel filter was used to enhance the image followed by a Spectral Angle Mapper (SAM) analysis to classify the individual tree species within the study plot. A digital map of tree tagging was produced with the tree species identified were Kelat (Syzgium spp), Keledang (Artrocarpos spp), Mengkulang (Heritiera spp), Tempinis (Streblus elongatus), Keranji (Dialium spp), Tulang Daing (Callerya atropurea), Meranti Sarang Punai (Shorea parvifolia), Kembang Semangkuk Jantung (Scaphium macropodum), Bintangor (Calophyllum spp), Nyatoh Minyak (Sapotaceae spp), Mersawa (Anisoptera spp), Resak (Cotylelobium spp), Sepetir (Sindora spp), Temponek (Artocarpus rigidus) and Petaling. The mapping accuracy of 89.66% was attained in the 1 ha study plot. Tree tagging using airborne remote sensing has a great potential in the Pre-F inventory and should be integrated with a GIS database management for future decision in management, development and utilization of sustainable forest resource.

Old forest edges may promote the distribution of forest species in carabid assemblages (Coleoptera: Carabidae) in Croatian forests

Boundaries between habitats are usually accompanied by transitions in the diversity and structural complexity of insect as- semblages. Edge effects on carabid beetle assemblages across forest-meadow ecotones in Dinaric beech-fir forests were determined in the Gorski Kotar region of western Croatia. Carabid beetles were sampled using pitfall traps set along gradients extending 60 m from the forest edge into its interior and 60 m into the meadow. Embedded forest edges were greater than 100 years old and had a similar composition and structure of vegetation to that in the adjacent forest. A total of 20,526 individuals belonging to 66 carabid beetle spe- cies were recorded. Carabid assemblages in the ecotones were more similar to those in the forest interiors than those in the meadows. The classical edge effect hypothesis was not supported, since the ecotones were less diverse than the meadows, while the carabid as- semblages of the forest interiors were the least diverse. Soil temperature, soil humidity and light intensity did not differ significantly between the ecotones and the forest interior. Therefore, embedded forest edges reduced the microclimate edge effect by providing stable microclimatic conditions for carabid assemblages similar to those in the forest interior. In addition, this enabled forest specialists and generalists to occur right up to the forest edge and maintain stable populations in the ecotone. On the other hand, ecotones acted as filters for certain forest generalist species and true barriers for most open-habitat species. This study confirmed that the structure and ages of the vegetation at edges may play a key role in determining the spatial pattern of carabid beetles across forest-meadow ecotones.

Future of the Main Important Forest Tree Species in Serbia from the Climate Change Perspective

Materials and Methods: Our study integrates climate change scenarios for the region of Serbia together with the current distribution of forest tree species. Evaluation was performed using forest aridity index which takes into account mean temperatures and sums of precipitation of the critical months during the growing season. Distribution data of the nine most abundant tree species in Serbia (European beech, Turkey oak, Sessile oak, Hungarian oak, Pedunculate oak, Norway spruce, Silver fir, Black and Scots pine) were taken from the National Forest Inventory. Results: Significant change of bioclimatic niches is expected for the majority of the studied tree species. The most endangered will be Pedunculate oak due to the extreme change of its habitats, while drought prone species (like pines and Hungarian oak) will be less endangered. Sessile oak, Turkey oak, Silver fir, Norway spruce and European beech will be out of their 20 th century bioclimatic niches before the end of 21 st century according to A2 scenario. Conclusion: Our results suggest that some of the most important tree species in Serbia (Sessile oak, Turkey oak, Silver fir, Norway spruce and European beech) will be endangered by the end of 21 st century. General adaption options and specific measurements for forestry sector have to be made for the region of southeast Europe due to the expected extreme change in climate.

The altitudinal belts of subalpine virgin forest on Mt. Gongga simulated by a succession model

How to accurately simulate the distribution of forest species based upon their biological attributes has been a traditional biogeographical issue. Forest gap models are very useful tools for examining the dynamics of forest succession and revealing the species structure of vegetation. In the present study, the GFSM (Gongga Forest Succession Model) was developed and applied to simulate the distribution, composition and succession process of forests in 100 m elevation intervals. The results indicate that the simulated results of the tree species, quantities of the different types of trees, tree age and differences in DBH (diameter at breast height) composition were in line with the actual situation from 1400 to 3700 MASL (meters above sea level) on the eastern slope of Mt. Gongga. Moreover, the dominant species in the simulated results were the same as those in the surveyed database. Thus, the GFSM model can best simulate the features of forest dynamics and structure in the natural conditions of Mt. Gongga. The work provides a new approach to studying the structure and distribution characteristics of mountain ecosystems in varied elevations. Moreover, the results of this study suggest that the biogeochemistry mechanism model should be combined with the forest succession model to facilitate the ecological model in simulating the physical and chemical processes involved.

Different factors affect the local distribution, persistence and spread of alien tree species in floodplain forests

Floodplain forests are characterized by high and increasing levels of invasions by plant species, but the factors that drive their spread are insufficiently understood. Using data from 708 plots surveyed twice (1998, 2008) supplemented with further data (management, stand age, distance to dispersal corridors, type of ecosystems invaded) we analyzed the factors which shape the local distribution, growth, persistence and spread of three invasive alien tree species (Acer negundo, Ailanthus altissima, Robinia pseudoacacia) in the National Park Donau-Auen in Austria. Using Generalized Linear Models (GLMs), we found that the distribution of the study species per plot is contingent on stand age (R. pseudoacacia), type of floodplain forest (A. negundo, A. altissima) and distance to the next water body (A. negundo). For all study species, colonization of new plots between both surveys is driven by short distance spread from already established invasion foci. Moreover, recipient habitats (softwood vs. hardwood floodplain forests) modify invasion success in species-specific ways. The probability of occurrence and colonization of plots located in softwood floodplain forests is higher for A. negundo, whereas A. altissima more frequently colonizes hardwood floodplain forests. Persistence of R. pseudoacacia decreases with stand age, whereas its growth rate is significantly higher in plots located in zones where management is allowed than in those which are not managed. Persistence and growth of the other two study species were not related to any explanatory variables analyzed. The on-going spread of the study species in the National Park Donau-Auen suggests that their local distribution is in disequilibrium, i.e. not all suitable habitat patches have yet been colonized. This implies that increased management efforts are necessary to reverse the spread of alien tree species in the study area and to maintain the high conservation value of this iconic area which protects one of the largest floodplain forests in Europe.

Correlation analysis of soil and species of different life forms in Baotianman Nature Reserve

The plant community renewal process is influenced by the vertical structure of forests and soil is an important factor affecting community succession. This study investigated the relationships between soil and different species of each forest layer in the Baotianman Nature Reserve. The Canonical Redundancy Analysis (RDA) was used to explore the relationship between the surface soil and deep soil and the distribution of different forest layer species. Principal Component Analysis (PCA) was conducted on the properties of the two soil layers and a Generalized Additive Model (GAM) was used to fit the relationship between the main species of trees, small trees and shrubs with each principal component. The results were as follows: (i) the surface soil and deep soil jointly explained 40.52%, 40.46%, 37.17% and 42.14% of the distribution of all species, trees, small trees and shrubs, respectively. The corresponding values in the surface soil independently were 14.68%, 17.32%, 10.61% and 17.32%, and in the deep soil independently were 18.24%, 17.22%, 18.8% and 18.84%. (ii) The 15 soil properties of PCA showed that the first four principal components represented 38.02%, 14.41%, 9.06% and 5.79% and the cumulative contribution rate was 67.28%. (iii) The GAM fitting results showed the different forest vertical layers that were associated with the four principal components: the tree layer of <italic>D</italic>² was 0.63%-9.07%, the little tree layer of <italic>D</italic>² was 1.41%-1.41% and the shrub layer of <italic>D</italic>² was 1.91%-1.91%. These results showed that soil properties play an important role on species distribution in the Baotianman Nature Reserve. The nutrient content of topsoil is greater than the deep soil, but that does not necessarily mean a stronger relationship with the forest layer species distribution than the deep soil. Future research should focus on the combined effects of the soil properties and the characteristics of the each layer species, with special attention to the role of the species in the deep soil. Different intra- and inter-layer species may compete for soil nutrients, which may promote species coexistence and resource partitioning.

Universality principle in second-order phase transition models for describing succession processes and spatial distribution of species in forests

For a description of the successional processes in forest coenoses and the spatial distribution of tree species, an approach using phase transitions models is proposed. We introduced a variable equation and phase transition models that describe processes in forest coenoses. The analysis showed that the model considering processes in the forest as second-order phase transitions is in good agreement with the field data. The model parameters can be calculated from the data of field observations and used for prognosis calculations of successional processes in a forest and the distribution of important tree species in high-altitude forests. The proposed approach to the modeling of dynamic processes in the forest as phase transitions is universal and it greatly simplifies the task of constructing models of forest dynamics.

Distribution and abundance of tree species in swamp forests of Amazonian Ecuador

Research to date on Amazonian swamps has reinforced the impression that tree communities there are dominated by a small, morphologically specialized subset of the regional flora capable of surviving physiologically challenging conditions. In this paper, using data from a large‐scale tree inventory in upland, floodplain, and mixed palm swamp forests in Amazonian Ecuador, we report that tree communities growing on well‐drained and saturated soils are more similar than previously appreciated. While our data support the traditional view of Amazonian swamp forests as low‐diversity tree communities dominated by palms, they also reveal four patterns that have not been well documented in the literature to date: 1) tree communities in these swamp forests are dominated by a phylogenetically diverse oligarchy of 30 frequent and common species; 2) swamp specialists account for &lt; 10% of species and a minority of stems; 3) most tree species recorded in swamps (&gt; 80%) also occur in adjacent well‐drained forest types; and 4) many tree species present in swamps are common in well‐drained forests (e.g. upland oligarchs account for 34.1% of all swamp stems). These observations imply that, as in the temperate zone, the composition and structure of Amazonian swamp vegetation are determined by a combination of local‐scale environmental filters (e.g. plant survival in permanently saturated soils) and landscape‐scale patterns and processes (e.g. the composition and structure of tree communities in adjacent non‐swamp habitats, the dispersal of propagules from those habitats to swamps). We conclude with suggestions for further research to quantify the relative contributions of these factors in structuring tree communities in Amazonian swamps.

Contribution of environmental filtering and dispersal limitation to species turnover of temperate deciduous broad‐leaved forests in China

AbstractQuestionsHow and to what extent do environmental filtering and dispersal limitation affect species turnover among sites in the temperate deciduous broad‐leaved forests of China? Do different life forms respond to environmental filtering and dispersal limitation in the same way?LocationSeventeen mountains (31°8′–44°22′N, to 104°42′–128°8′E) in China.MethodsWe measured the plant species composition of 495 plots. We calculated the Jaccard's similarity (SJac) of species composition, geographic distance (Dg) and environmental divergence (De) for each plot pair for trees, shrubs and herbs. Three plot pair groups were distinguished: (1) plot pairs with both plots from the same mountain; (2) plot pairs with two plots from different mountains but with a similar environment; (3) plot pairs with two plots from different mountains and with a heterogeneous environment. We analysed the relationship between SJac, Dg and De for all three groups, and performed partial redundancy analysis. We also calculated beta‐diversity of mountains, and explored latitudinal and climatic patterns of beta‐diversity.ResultsSJac decreases significantly with both De and Dg for all three plot pair groups. Environmental and geographic variables together explain 13.8%, 11.6% and 11.1% of variance in species composition of trees, shrubs and herbs, respectively. For all life forms, environment explains more variance than geography, and environment and geography have strong co‐varying effects. The beta‐diversity for each mountain decreases with latitude, but increases with mean annual temperature (MAT).ConclusionEnvironmental filtering rather than dispersal limitation predominantly regulates patterns of species turnover in the temperate deciduous broad‐leaved forests of China. Furthermore, the increases of beta‐diversity along MAT also support the effects of environment on species turnover. These results indicate that environment might influence the distribution of most species in temperate forests of China. However, dispersal limitation still independently accounts for a small amount of variance in species turnover. We therefore conclude that environmental filtering and dispersal limitation have both combined and independent effects, but environmental filtering is more important in shaping the community assembly of temperate deciduous broad‐leaved forests of China.

English

Although, human activities have caused major losses of tropical forest, there are also reports of forest encroachment and expansion into surrounding sparse vegetation types (savannah and woodland). Large savannah-woodland trees may promote forest encroachment into their surroundings by facilitating seed deposition and subsequent establishment of forest species. This work sought to determine whether large individuals of the woodland tree&nbsp;Brachystegia&nbsp;floribunda&nbsp;facilitate encroachment of montane forest tree species. To this end, environmental parameters, seed rain and seedling distribution of montane forest tree species were examined in south-east Africa. The seed rain and the numbers of tree seedlings were both higher below large&nbsp;B.&nbsp;floribunda&nbsp;trees than below: (i) small specimens of this woodland tree and (ii) in open grassland. Moreover, large individuals of&nbsp;B.&nbsp;floribunda&nbsp;modified microhabitat conditions more than small trees. Thus, large&nbsp;B.&nbsp;floribunda&nbsp;trees probably facilitate the encroachment of montane forest trees into surrounding woodlands. &nbsp; Key words:&nbsp;Brachystegia&nbsp;floribunda, tropical forest, grassland, woodlands.

Spatial distribution and environmental preferences of 10 economically important forest palms in western South America

Sustainable management strategies for tropical forest ecosystems require a detailed understanding of the distribution of tropical forest species, limitations on distribution, as well as occurrence patterns in the absence of limitations. In the Americas, many tropical palms (Arecaceae) are locally abundant keystone species that provide a number of non-timber forest products. Here we focus on 10 such species (Aphandra natalia, Attalea phalerata, Euterpe oleracea, Iriartea deltoidea, Mauritia flexousa, Oenocarpus bataua, Phytelephas aequatorialis, Phytelephas macrocarpa, and Phytelephas seemannii) found in western South America. This study aimed to determine: (i) what variables control potential species distribution, (ii) whether their distribution is spatially constrained and if so, (iii) how their potential ranges compare to their actual ranges. We built species distribution models using Maxent software with three groups of predictor variables: C (climatic), N (non-climatic environmental), S (spatial), and combinations thereof: C, CN and CNS. The CNS predictor variable combination gave superior predictive ability based on median Area Under the Curve (AUC) values and was consistent with available range maps. In contrast, individual C and CN predictor variables gave inferior AUC values and showed less similarity to range maps. We concluded that the CNS model that combined climatic, non-climatic, and spatial variables best represented the actual distribution of the 10 palm species, whereas C and CN models approached their potential distribution. Precipitation during the driest quarter and annual precipitation were the most important predictors of the potential distribution, whereas temperature of the coldest month, soil, and the Normalized Difference Vegetation Index (NDVI) were less important. We found that the actual distributions of palm species were spatially constrained, and that the spatial variables largely coincided with the dispersal barriers of the Andean Cordillera and past climatic fluctuations. The estimated potential range varied from nearly equal to the actual range, to up to 0.55×106km2 (55.1×106ha) larger than the actual range, depending on model, threshold settings, and species. We thus concluded that current palm resources in the forests of western South America have major potential for ecological expansion. These results are relevant to current palm management and resource conservation planning, as well as future strategies that will have to address climate change and increasing human disturbance.

The effect of highly variable topography on the spatial distribution of &lt;i&gt;Aniba perutilis&lt;/i&gt; (Lauraceae) in the Colombian Andes

Topography is a factor that can significantly affect the diversity and the distribution of trees species in tropical forests. Aniba perutilis, a timber species listed as vulnerable to extinction, is widely distributed in Andean forest fragments, especially in those with highly variable topography. Based on field surveys and logistic regression analyses, we studied the population structure and the effect of highly variable topography on the spatial distribution of this tree in three protected forest fragments in the central Andes of Colombia. Individuals of A. perutilis were mainly found on mountain ridges and hills with gentle slopes; no individuals were found in valleys. Using a species distribution model with presence/absence data, we showed that the available habitat for A. perutilis is significantly smaller than the extension of the fragments and much smaller than the extension of the currently protected areas. Our results have important implications for the conservation ofA. perutilis and likely for other threatened Andean tree species, which can also have locally restricted distributions due to highly variable local topography.

Modeling Forest Species Distributions in a Human-Dominated Landscape in Northeastern, USA

Mapping forest species distributions is notoriously difficult in human-dominated mixed temperate forest environments. The goal of this study is to evaluate the effectiveness of species distribution modeling techniques for estimating the distribution of forest canopy species on Cape Cod, Massachusetts, USA. Binary maps of estimated presence/absence were produced for four canopy species using a classification tree approach and a generalized linear modeling approach, both including and excluding a spatial dependence term, and the results are evaluated using several assessment measures. Secondary goals of the study are to examine the influence of past land use on species distributions at the landscape scale and to consider the effect of explicitly including information on spatial dependence. Findings suggest that these techniques are broadly applicable in such human-dominated landscapes, but that complex disturbance histories introduce significant challenges.

Growth and stable isotope signals associated with drought-related mortality in saplings of two coexisting pine species

Drought-induced events of massive tree mortality appear to be increasing worldwide. Species-specific vulnerability to drought mortality may alter patterns of species diversity and affect future forest composition. We have explored the consequences of the extreme drought of 2005, which caused high sapling mortality (approx. 50 %) among 10-year-old saplings of two coexisting pine species in the Mediterranean mountains of Sierra Nevada (Spain): boreo-alpine Pinus sylvestris and Mediterranean P. nigra. Sapling height growth, leaf δ(13)C and δ(18)O, and foliar nitrogen concentration in the four most recent leaf cohorts were measured in dead and surviving saplings. The foliar isotopic composition of dead saplings (which reflects time-integrated leaf gas-exchange until mortality) displayed sharp increases in both δ(13)C and δ(18)O during the extreme drought of 2005, suggesting an important role of stomatal conductance (g(s)) reduction and diffusional limitations to photosynthesis in mortality. While P. nigra showed decreased growth in 2005 compared to the previous wetter year, P. sylvestris maintained similar growth levels in both years. Decreased growth, coupled with a sharper increase in foliar δ(18)O during extreme drought in dead saplings, indicate a more conservative water use strategy for P. nigra. The different physiological behavior of the two pine species in response to drought (further supported by data from surviving saplings) may have influenced 2005 mortality rates, which contributed to 2.4-fold greater survival for P. nigra over the lifespan of the saplings. This species-specific vulnerability to extreme drought could lead to changes in dominance and distribution of pine species in Mediterranean mountain forests.

Consistent patterns of elevational change in tree taxonomic and phylogenetic diversity across Malesian mountain forests

AbstractAimIn order to investigate the relative importance of ecological (habitat specialization) and biogeographical (speciation, geographical dispersal limitation) processes as causes of non‐random spatial distribution of tree species in the mountain forests of Malesia, we analysed the elevational change in the taxonomic and phylogenetic diversity of tree assemblages in different biogeographical subregions.LocationMalesia (Borneo, Java, Sulawesi and the Philippines).MethodsTree inventory data of 12 old‐growth forests from a wide elevational range (650–3080 m a.s.l.) were taxonomically harmonized and standardized (50 random draws of 245 individuals each per plot), and the phylogeny of 204 genera was resolved and scaled to its evolutionary origin. The taxonomic and phylogenetic diversities were calculated using effective generic measures, and the diversity patterns analysed by regression, ordination and classification.ResultsThe primary factor determining the diversity patterns of the tree assemblages was elevation, whereas the influence of region was surprisingly low. This results in common elevational patterns in taxonomic and phylogenetic community structure across western and central Malesia. The major clades of the contemporary mountain forest trees must therefore have evolved before the formation of the Malay Archipelago in its present form (sympatric speciation). Taxonomic richness and phylogenetic diversity exhibited opposite trends with elevation. Generic richness decreased linearly with elevation; the phylogenetic structure of high‐elevation forests revealed overdispersion, indicating convergent trait evolution towards higher elevations, whereas the submontane and colline assemblages showed clustering with a considerable number of confamilials. The upper montane forests of Borneo and Sulawesi were characterized by the dominance of Southern Hemisphere conifers, which differentiated them from lower‐elevation communities.Main conclusionsOur results indicate that ecological, evolutionary and biogeographical processes (environmental filtering, sympatry and long‐distance dispersal) have shaped the contemporary community structure of Malesian mountain forests. Wallace's Line may represent a significant barrier between the lowland tree floras of Borneo and Sulawesi, but this is not true for those at higher elevations. The uniqueness of high‐elevation forests in terms of their high phylogenetic diversity and of their unusual structure calls for a high priority in conservation programmes.