Change in community phylogenetic structure during tropical forest succession: evidence from New Guinea

Ecologists have recently interpreted patterns of phylogenetic distance among coexisting species as indicative of processes affecting community assembly during forest succession. We investigated plant community phylogenetic structure along a successional gradient in New Guinean lowland rain forest. We surveyed all trees with diameter at breast height ≥ 5 cm in nineteen 0.25 ha plots representing younger secondary, older secondary, and primary forest. We estimated plant community phylogeny from rbcL gene sequences to quantify change in phylogenetic structure during succession. Mean phylogenetic distance among co‐occurring trees increased with total basal area per plot, a proxy for forest age. Significant phylogenetic clustering was detected in secondary forest whereas primary forest was significantly over‐dispersed relative to null expectations. We examined the sensitivity of these patterns to various methods of branch length estimation and phylogenetic uncertainty. Power to detect community phylogenetic patterns when equal branch lengths were assumed was weak in comparison to direct molecular and time‐calibrated measures of divergence. Inferred change during forest succession was also robust to phylogenetic uncertainty so long as temporal information was incorporated in estimates of divergence. The observed patterns are consistent with processes of environmental filtering during tropical forest succession giving way to other processes in primary forests including density‐dependence.     

Edge disturbance drives liana abundance increase and alteration of liana–host tree interactions in tropical forest fragments

Closed‐canopy forests are being rapidly fragmented across much of the tropical world. Determining the impacts of fragmentation on ecological processes enables better forest management and improves species‐conservation outcomes. Lianas are an integral part of tropical forests but can have detrimental and potentially complex interactions with their host trees. These effects can include reduced tree growth and fecundity, elevated tree mortality, alterations in tree‐species composition, degradation of forest succession, and a substantial decline in forest carbon storage. We examined the individual impacts of fragmentation and edge effects (0–100‐m transect from edge to forest interior) on the liana community and liana–host tree interactions in rainforests of the Atherton Tableland in north Queensland, Australia. We compared the liana and tree community, the traits of liana‐infested trees, and determinants of the rates of tree infestation within five forest fragments (23–58 ha in area) and five nearby intact‐forest sites. Fragmented forests experienced considerable disturbance‐induced degradation at their edges, resulting in a significant increase in liana abundance. This effect penetrated to significantly greater depths in forest fragments than in intact forests. The composition of the liana community in terms of climbing guilds was significantly different between fragmented and intact forests, likely because forest edges had more small‐sized trees favoring particular liana guilds which preferentially use these for climbing trellises. Sites that had higher liana abundances also exhibited higher infestation rates of trees, as did sites with the largest lianas. However, large lianas were associated with low‐disturbance forest sites. Our study shows that edge disturbance of forest fragments significantly altered the abundance and community composition of lianas and their ecological relationships with trees, with liana impacts on trees being elevated in fragments relative to intact forests. Consequently, effective control of lianas in forest fragments requires management practices which directly focus on minimizing forest edge disturbance.     

Disturbance regime changes the trait distribution,phylogenetic structure and community assembly of tropical rain forests

A rapidly increasing effort to merge functional community ecology and phylogenetic biology has increased our understanding of community assembly. However, studies using both phylogenetic‐ and trait‐based methods have been mainly conducted in old‐growth forests, with fewer studies in human‐disturbed communities, which play an increasingly important role in providing ecosystem services as primary forests are degraded. We used data from 18 1‐ha plots in tropical old‐growth forests and secondary forests with different disturbance histories (logging and shifting cultivation) and vegetation types (tropical lowland and montane forests) on Hainan Island, southern China. The distributions of 11 functional traits were compared among these six forest types. We used a null model approach to assess the effects of disturbance regimes on variation in response and effect traits and community phylogenetic structure across different stem sizes (saplings, treelets, and adult trees) and spatial scales (10–50 m). We found significant differences in the distribution of functional traits in highly disturbed lowland sites versus other forest types. Many individuals in highly disturbed lowland sites were deciduous, spiny, with non‐fleshy fruits and seeds dispersed passively or by wind, and low SLA. The response traits of coexisting species were clustered in all sites except for highly disturbed lowland sites where evenness was evident. There were different distributions of effect traits for saplings and treelets among different forest types but adult trees showed stronger clustering of trait values with increasing spatial scale among all forest types. Phylogenetic clustering predominated across all size classes and spatial scales in the highly disturbed lowland sites, and evenness in other forest types. High disturbance can lead to abiotic filtering, generating a community dominated by closely related species with disturbance‐adapted traits, where biotic interactions play a relatively minor role. In lightly disturbed and old growth forests, multiple processes simultaneously drive the community assembly, but biotic processes dominate at the fine scale.     

Do lianas shape ant communities in an early successional tropical forest?

Almost half of lowland tropical forests are at various stages of regeneration following deforestation or fragmentation. Changes in tree communities along successional gradients have predictable bottom‐up effects on consumers. Liana (woody vine) assemblages also change with succession, but their effects on animal succession remain unexplored. Here we used a large‐scale liana removal experiment across a forest successional chronosequence (7–31 years) to determine the importance of lianas to ant community structure. We conducted 1,088 surveys of ants foraging on and living in trees using tree trunk baiting and hand‐collecting techniques at 34 paired forest plots, half of which had all lianas removed. Ant species composition, β‐diversity, and species richness were not affected by liana removal; however, ant species co‐occurrence (the coexistence of two or more species in a single tree) was more frequent in control plots, where lianas were present, versus removal plots. Forest stand age had a larger effect on ant community structure than the presence of lianas. Mean ant species richness in a forest plot increased by ca. 10% with increasing forest age across the 31‐year chronosequence. Ant surveys from forest >20 years old included more canopy specialists and fewer ground‐nesting ant species versus those from forests <20 years old. Consequently, lianas had a minimal effect on arboreal ant communities in this early successional forest, where rapidly changing tree community structure was more important to ant species richness and composition.     

Climatic correlates of phylogenetic relatedness of woody angiosperms in forest communities along a tropical elevational gradient in South America

Aims This study assesses the relationship between phylogenetic relatedness of angiosperm tree species and climatic variables in local forests distributed along a tropical elevational gradient in South America. In particular, this paper addresses two questions: Is phylogenetic relatedness of plant species in communities related to temperature variables more strongly than to water variables for tropical elevational gradients? Is phylogenetic relatedness of plant species in communities driven by extreme climatic conditions (e.g. minimum temperature (MT) and water deficit) more strongly than by climatic seasonal variability (e.g. temperature seasonality and precipitation seasonality)?Methods I used a set of 34 angiosperm woody plant assemblages along an elevational gradient in the Andes within less than 5 degrees of the equator. Phylogenetic relatedness was quantified as net relatedness index (NRI) and nearest taxon index (NTI) and was related to major climatic variables. Correlation analysis and structure equation modeling approach were used to assess the relationships between phylogenetic relatedness and climatic variables.Important findings Phylogenetic relatedness of angiosperm woody species in the local forest communities is more strongly associated with temperature-related variables than with water-related variables, is positively correlated with mean annual temperature (MAT) and MT, and is related with extreme cold temperature more strongly than with seasonal temperature variability. NTI was related with elevation, MAT and MT more strongly than was NRI. Niche convergence, rather than niche conservatism, has played a primary role in driving community assembly in local forests along the tropical elevational gradient examined. Negative correlations of phylogenetic relatedness with elevation and higher correlations of phylogenetic relatedness with elevation and temperature for NTI than for NRI indicate that evolution of cold tolerance at high elevations in tropical regions primarily occurred at recent (terminal) phylogenetic nodes widely distributed among major clades.     

Exploring the community phylogenetic structure along the slope aspect of subalpine meadows in the eastern Qinghai–Tibetan Plateau,China

Exploring the community assembly has been important for explaining the maintenance mechanisms of biodiversity and species coexistence, in that it is a central issue in community ecology. Here, we examined patterns of the community phylogenetic structure of the subalpine meadow plant community along the slope gradient in the Qinghai–Tibetan Plateau of China. We surveyed all species and constructed the phylogenetic tree of the plant community based on data from the Angiosperm Phylogeny Group III. We selected the net relative index (NRI) and evaluated the community phylogenetic structure along the five slope plants communities. We found that the phylogenetic structure varied from phylogenetic clustering to phylogenetic overdispersion with the slope aspect from north to south. In the north slope, the community phylogenetically cluster indicated that the limiting similarity played a leading role in the community assembly and the maintenance of biodiversity. Community phylogenetic overdispersion in the east, southeast, and south slopes indicated that habitat filtration was the driving force for community assembly. The NRI index of the northeast slope was close to zero, implying random dispersion. But it may be driven by the neutral process or limiting similarity, in that the community assembly process was the result of a combination of several ecological factors and thus required further study.     

Phylogenetic Structure of Tree Species across Different Life Stages from Seedlings to Canopy Trees in a Subtropical Evergreen Broad-Leaved Forest

Investigating patterns of phylogenetic structure across different life stages of tree species in forests is crucial to understanding forest community assembly, and investigating forest gap influence on the phylogenetic structure of forest regeneration is necessary for understanding forest community assembly. Here, we examine the phylogenetic structure of tree species across life stages from seedlings to canopy trees, as well as forest gap influence on the phylogenetic structure of forest regeneration in a forest of the subtropical region in China. We investigate changes in phylogenetic relatedness (measured as NRI) of tree species from seedlings, saplings, treelets to canopy trees; we compare the phylogenetic turnover (measured as β_NRI) between canopy trees and seedlings in forest understory with that between canopy trees and seedlings in forest gaps. We found that phylogenetic relatedness generally increases from seedlings through saplings and treelets up to canopy trees, and that phylogenetic relatedness does not differ between seedlings in forest understory and those in forest gaps, but phylogenetic turnover between canopy trees and seedlings in forest understory is lower than that between canopy trees and seedlings in forest gaps. We conclude that tree species tend to be more closely related from seedling to canopy layers, and that forest gaps alter the seedling phylogenetic turnover of the studied forest. It is likely that the increasing trend of phylogenetic clustering as tree stem size increases observed in this subtropical forest is primarily driven by abiotic filtering processes, which select a set of closely related evergreen broad-leaved tree species whose regeneration has adapted to the closed canopy environments of the subtropical forest developed under the regional monsoon climate.     

沿海拔梯度变化的哀牢山亚热带森林群落系统发育结构

为揭示森林群落系统发育结构在海拔梯度上的变化及其驱动因素, 本研究以云南哀牢山西坡的亚热带森林群落为研究对象, 以APG III系统为基础框架, 结合DNA条形码序列信息解决末端分类单元亲缘关系的方法, 构建了哀牢山森林群落系统发育进化树, 采用净亲缘指数(net relatedness index, NRI)和最近亲缘指数(nearest taxon index, NTI), 探讨了不同植被类型的森林群落系统发育结构和沿海拔梯度的变化规律。结果表明, 从整体的海拔变化趋势上来看, 哀牢山森林群落系统发育结构随海拔上升由系统发育聚集(phylogenetic clustering)走向发散(phylogenetic overdispersion)或聚集程度降低。在低海拔地区, 群落表现为系统发育聚集, 表明生态位理论中的生境过滤作用在群落构建和生物多样性的维持中起着主导作用; 在中海拔地区, 出现了聚集与发散两种群落系统发育结构并存的现象, 推测可能是生境过滤和竞争排斥两种生态过程共同作用的结果; 在高海拔地区, 群落的系统发育结构因选择的指数不同而出现相反的结果, NRI表现出系统发育聚集, 而NTI却表现为随机或发散, 考虑到高海拔地区的环境胁迫可能促使植物发生趋同进化, 推测其群落构建的生态学过程需要更为综合的研究。本研究揭示群落系统发育结构沿海拔梯度确实存在显著的变化, 证明在生态群落的构建过程中非随机过程起到促进乃至关键作用。     

Multi-scale phylogenetic structure in coastal dune plant communities across the globe

Aims Studies integrating phylogenetic history and large-scale community assembly are few, and many questions remain unanswered. Here, we use a global coastal dune plant data set to uncover the important factors in community assembly across scales from the local filtering processes to the global long-term diversification and dispersal dynamics. Coastal dune plant communities occur worldwide under a wide range of climatic and geologic conditions as well as in all biogeographic regions. However, global patterns in the phylogenetic composition of coastal dune plant communities have not previously been studied.Methods The data set comprised vegetation data from 18463 plots in New Zealand, South Africa, South America, North America and Europe. The phylogenetic tree comprised 2241 plant species from 149 families. We calculated phylogenetic clustering (Net Relatedness Index, NRI, and Nearest Taxon Index, NTI) of regional dune floras to estimate the amount of in situ diversification relative to the global dune species pool and evaluated the relative importance of land and climate barriers for these diversification patterns by geographic analyses of phylogenetic similarity. We then tested whether dune plant communities exhibit similar patterns of phylogenetic structure within regions. Finally, we calculated NRI for local communities relative to the regional species pool and tested for an association with functional traits (plant height and seed mass) thought to vary along sea–inland gradients.Important findings Regional species pools were phylogenetically clustered relative to the global pool, indicating regional diversification. NTI showed stronger clustering than NRI pointing to the importance of especially recent diversifications within regions. The species pools grouped phylogenetically into two clusters on either side of the tropics suggesting greater dispersal rates within hemispheres than between hemispheres. Local NRI plot values confirmed that most communities were also phylogenetically clustered within regions. NRI values decreased with increasing plant height and seed mass, indicating greater phylogenetic clustering in communities with short maximum height and good dispersers prone to wind and tidal disturbance as well as salt spray, consistent with environmental filtering along sea–inland gradients. Height and seed mass both showed significant phylogenetic signal, and NRI tended to correlate negatively with both at the plot level. Low NRI plots tended to represent coastal scrub and forest, whereas high NRI plots tended to represent herb-dominated vegetation. We conclude that regional diversification processes play a role in dune plant community assembly, with convergence in local phylogenetic community structure and local variation in community structure probably reflecting consistent coastal-inland gradients. Our study contributes to a better understanding of the globally distributed dynamic coastal ecosystems and the structuring factors working on dune plant communities across spatial scales and regions.     

Variation in liana abundance and biomass along an elevational gradient in the tropical Atlantic Forest (Brazil)

Lianas play a key role in forest structure, species diversity, as well as functional aspects of tropical forests. Although the study of lianas in the tropics has increased dramatically in recent years, basic information on liana communities for the Brazilian Atlantic Forest is still scarce. To understand general patterns of liana abundance and biomass along an elevational gradient (0–1,100 m asl) of coastal Atlantic Forest, we carried out a standard census for lianas ≥1 cm in five 1-ha plots distributed across different forest sites. On average, we found a twofold variation in liana abundance and biomass between lowland and other forest types. Large lianas (≥10 cm) accounted for 26–35% of total liana biomass at lower elevations, but they were not recorded in montane forests. Although the abundance of lianas displayed strong spatial structure at short distances, the present local forest structure played a minor role structuring liana communities at the scale of 0.01 ha. Compared to similar moist and wet Neotropical forests, lianas are slightly less abundant in the Atlantic Forest, but the total biomass is similar. Our study highlights two important points: (1) despite some studies have shown the importance of small-scale canopy disturbance and support availability, the spatial scale of the relationships between lianas and forest structure can vary greatly among tropical forests; (2) our results add to the evidence that past canopy disturbance levels and minimum temperature variation exert influence on the structure of liana communities in tropical moist forests, particularly along short and steep elevational gradients.     

Changes in liana community structure and functional traits along a chronosequence of selective logging in a moist semi-deciduous forest in Ghana

ABSTRACT

Background: Lianas are an important component of tropical forests that respond to logging disturbance. Determining liana response to selective logging chronosequence is important for understanding long-term logging effects on lianas and tropical forests.

Aims: Our objective was to quantify the response of liana communities to selective logging chronosequence in a moist semi-deciduous forest in Ghana.

Methods: Liana community characteristics were determined in ten 40 m × 40 m plots randomly and homogenously distributed in each of four selectively logged forest stands that had been logged 2, 14, 40 and 68 years before the surveys and in an old-growth forest stand (ca. >200 years).

Results: Liana species composition differed significantly among the forest stands, as a function of logging time span, while species richness fluctuated along the chronosequence. The abundance of liana communities and of reproductive and climbing guilds was lower in the logged forests than in the old-growth forest. The ratio of liana abundance and basal area to those of trees was similar in the logged forests, but significantly lower than those in the old-growth forest.

Conclusions: Logging impacts on liana community structure and functional traits were largely evident, though no clear chronosequence trends were recorded, except for species composition.     

Change in Phylogenetic Community Structure during Succession of Traditionally Managed Tropical Rainforest in Southwest China

Tropical rainforests in Southeast Asia are facing increasing and ever more intense human disturbance that often negatively affects biodiversity. The aim of this study was to determine how tree species phylogenetic diversity is affected by traditional forest management types and to understand the change in community phylogenetic structure during succession. Four types of forests with different management histories were selected for this purpose: old growth forests, understorey planted old growth forests, old secondary forests (∼200-years after slash and burn), and young secondary forests (15–50-years after slash and burn). We found that tree phylogenetic community structure changed from clustering to over-dispersion from early to late successional forests and finally became random in old-growth forest. We also found that the phylogenetic structure of the tree overstorey and understorey responded differentially to change in environmental conditions during succession. In addition, we show that slash and burn agriculture (swidden cultivation) can increase landscape level plant community evolutionary information content.     

Dispersal process driving subtropical forest reassembly: evidence from functional and phylogenetic analysis

Understanding the mechanisms of secondary succession related to forest management practices is receiving increasing attention in community ecology and biodiversity conservation. Abiotic and biotic filtering are deterministic processes driving community reassembly. A functional trait or phylogeny-based approach predicts that environmental filtering induced by clearcut-logging results in functional/phylogenetic clustering in younger forests, while biotic filtering (competitive exclusion) promotes functional/phylogenetic overdispersion in old-growth forests. From this perspective, we examined the patterns of functional/phylogenetic structures using tree community data (147 species × 170 plots). These data were chronosequenced from clearcut secondary forests to old-growth subtropical forests in the Ryukyu Archipelago, with species’ trait data (leaf and stem) and species level phylogeny. To detect clustering or overdispersion in the functional and phylogenetic structures, we calculated the standardized effect size of mean nearest trait distance and mean nearest phylogenetic distance within the plots. Functional or phylogenetic clustering was relatively weak in secondary forests, and their directional change with increasing forest age was not generally detected. Mean nearest trait/phylogenetic distance for most plots fell within the range of random expectation. The results suggest that abiotic/biotic filtering related to functional traits or phylogenetic relatedness plays a diminished role in shaping species assembly during secondary succession in the subtropical forest. Our findings of functional and phylogenetic properties might shed light on the importance of dispersal (stochastic) processes in the regional species pool during community reassembly after anthropogenic disturbance. It will also contribute to the development of coordinated schemes that maintain potential species assembly processes in the subtropical forest.     

热带北缘鹅凰嶂季雨林四种群落特征及成熟度分析

为分析我国热带北缘季雨林的不同演替阶段的群落特征,该研究对广东阳春鹅凰嶂典型季雨林中4种(A、B、C、D)不同植物群落展开调查,对群落的物种组成、多样性和空间结构等进行分析,判断成熟度差异,预测演替方向,并提出优化建议。结果表明:(1)4种群落林层单一,小径级木与下层木占主体地位,具有1～3种明显的优势树种。(2)Shannon-Wiener指数为2.72～3.74,Simpson指数为0.90～0.97,Pielou均匀度指数为0.74～0.89,各群落多样性特征差异显著。(3)4种群落乔木胸径大小比数为0.49～0.51,角尺度为0.56～0.61,混交度为0.54～0.83,林分空间结构指数为60.57～71.44,林分空间结构距离为53.15～68.53。(4)综合群落基本特征、多样性和空间结构特征的分析得出,各群落的成熟度排名为D>A>C>B。综上认为,4种群落都处于演替前期或中期,乔木个体胸径和树高发展空间较大; 群落整体处于中庸生长状态,个体均呈轻微聚集分布,树种表现为中度、强度或极强度混交,空间结构与理想林分存在一定距离。随着成熟度的增加,4种群落都继续以阳性树种作为主要优势树种进行演替,并初步具备该区域地带性顶极群落的典型植被特征; 季雨林群落物种多样性提高,并向混交度增加、空间结构优化、稳定性增强的趋势演替。该研究结果为群落构建机制和森林结构优化等提供科学依据。未来应对该区域加强监管与保护,同时应对该地区的植被生态学和生物多样性保护展开广泛监测与深入研究。     

Environmental filters shaping angiosperm tree assembly along climatic and geographic gradients

Question

Global‐scale forest censuses provide an opportunity to understand diversification processes in woody plant communities. Based on the climatic or geographic filtering hypotheses associated with tropical niche conservatism and dispersal limitation, we analysed phylogenetic community structures across a wide range of biomes and evaluated to what extent region‐specific processes have influenced large‐scale diversity patterns of tree species communities across latitude or continent.

Location

Global.

Methods

We generated a data set of species abundances for 21,379 angiosperm woody plants in 843 plots worldwide. We calculated net relatedness index (NRI) for each plot, based on a single global species pool and regional species pools, and phylogenetic β‐diversity (PBD) between plots. Then, we explored the correlations of NRI with climatic and geographic variables, and clarified phylogenetic dissimilarity along geographic and climatic differences. We also compared these patterns for South America, Africa, the Indo‐Pacific, Australia, the Nearctic, Western Palearctic and Eastern Palearctic.

Results

NRI based on a global‐scale species pool was negatively associated with precipitation and positively associated with Quaternary temperature change. PBD was positively associated with geographic distance and precipitation difference between plots across tropical and extratropical biomes. Moreover, phylogenetic dissimilarity was smaller in extratropical regions than in regions including the tropics, although temperate forests of the Eastern Palearctic showed a greater dissimilarity within extratropical regions.

Conclusions

Our findings support predictions of the climatic and geographic filtering hypotheses. Climatic filtering (climatic harshness and paleoclimatic change) relative to tropical niche conservatism played a role in sorting species from the global species pool and shaped the large‐scale diversity patterns, such as the latitudinal gradient observed across continents. Geographic filtering associated with dispersal limitation substantially contributed to regional divergence of tropical/extratropical biomes among continents. Old, long‐standing geographic barriers and recent climatic events differently influenced evolutionary diversification of angiosperm tree communities in tropical and extratropical biomes.     

The assembly of tropical tree communities – the advances and shortcomings of phylogenetic and functional trait analyses

Tropical tree communities present one of the most challenging systems for studying the processes underlying community assembly. Most community assembly hypotheses consider the relative importance of the ecological similarity of co‐occurring species. Quantifying this similarity is a daunting and potentially impossible task in species‐rich assemblages. During the past decade tropical tree ecologists have increasingly utilized phylogenetic trees and functional traits to estimate the ecological similarity of species in order to test mechanistic community assembly hypotheses. A large amount of work has resulted with many important advances having been made along the way. That said, there are still many outstanding challenges facing those utilizing phylogenetic and functional trait approaches to study community assembly. Here I review the conceptual background, major advances and major remaining challenges in phylogenetic‐ and trait‐based approaches to community ecology with a specific focus on tropical trees. I argue that both approaches tremendously improve our understanding of tropical tree community ecology, but neither approach has fully reached its potential thus far.     

Phylogenetic plant community structure along elevation is lineage specific

The trend of closely related taxa to retain similar environmental preferences mediated by inherited traits suggests that several patterns observed at the community scale originate from longer evolutionary processes. While the effects of phylogenetic relatedness have been previously studied within a single genus or family, lineage‐specific effects on the ecological processes governing community assembly have rarely been studied for entire communities or flora. Here, we measured how community phylogenetic structure varies across a wide elevation gradient for plant lineages represented by 35 families, using a co‐occurrence index and net relatedness index (NRI). We propose a framework that analyses each lineage separately and reveals the trend of ecological assembly at tree nodes. We found prevailing phylogenetic clustering for more ancient nodes and overdispersion in more recent tree nodes. Closely related species may thus rapidly evolve new environmental tolerances to radiate into distinct communities, while older lineages likely retain inherent environmental tolerances to occupy communities in similar environments, either through efficient dispersal mechanisms or the exclusion of older lineages with more divergent environmental tolerances. Our study illustrates the importance of disentangling the patterns of community assembly among lineages to better interpret the ecological role of traits. It also sheds light on studies reporting absence of phylogenetic signal, and opens new perspectives on the analysis of niche and trait conservatism across lineages.     

The effect of altitude,patch size and disturbance on species richness and density of lianas in montane forest patches

The species richness and density of lianas (woody vines) in tropical forests is determined by various abiotic and biotic factors. Factors such as altitude, forest patch size and the degree of forest disturbance are known to exert strong influences on liana species richness and density. We investigated how liana species richness and density were concurrently influenced by altitude (1700–2360 m), forest patch size, forest patch location (edge or interior) and disturbance intensity in the tropical montane evergreen forests, of the Nilgiri and Palni hills, Western Ghats, southern India. All woody lianas (≥1 cm dbh) were enumerated in plots of 30 × 30 m in small, medium and large forest patches, which were located along an altitudinal gradient ranging from 1700 to 2360 m. A total of 1980 individual lianas were recorded, belonging to 45 species, 32 genera and 21 families, from a total sampling area of 13.86 ha (across 154 plots). Liana species richness and density decreased significantly with increasing altitude and increased with increasing forest patch size. Within forest patches, the proportion of forest edge or interior habitat influenced liana distribution and succession especially when compared across the patch size categories. Liana species richness and density also varied along the altitudinal gradient when examined using eco-physiological guilds (i.e. shade tolerance, dispersal mode and climbing mechanism). The species richness and density of lianas within these ecological guilds responded negatively to increasing altitude and positively to increasing patch size and additionally displayed differing sensitivities to forest disturbance. Importantly, the degree of forest disturbance significantly altered the relationship between liana species richness and density to increasing altitude and patches size, and as such is likely the primary influence on liana response to montane forest succession. Our findings suggest that managing forest disturbance in the examined montane forests would assist in conserving local liana diversity across the examined altitudinal range.     

海南岛热带低地雨林刀耕火种弃耕地自然恢复过程中的群落构建

研究群落构建机制是群落生态学的一个重要目标, 群落动态过程中的构建规律对于了解群落演替机理有重要的作用。该文以海南岛刀耕火种干扰后自然恢复的10 hm ²热带低地雨林为研究对象, 通过比较不同恢复阶段的次生林(15年、30年和60年)和老龄林在幼苗、幼树和成年树群落的物种组成, 揭示次生演替过程中的群落构建规律。研究结果表明, 老龄林中不同径级群落的物种多样性及不同径级间的物种相似度显著高于各恢复阶段的次生林, 但优势种在群落中的比例低于各恢复阶段的次生林。随着自然恢复过程的进行, 次生林群落物种组成与老龄林的相似性也逐渐增大, 支持演替平衡理论。所有恢复阶段样地中幼苗的个体、物种丰富度和基于多度涵盖估计量(ACE)都低于幼树和成年树群落, 幼苗层物种组成与幼树、成年树也有较大差异, 说明新增到幼苗群落可能是一个难于预测的过程。研究结果说明了确定过程和随机过程共同决定了次生演替的群落构建。     

Rapid Liana Colonization along a Secondary Forest Chronosequence

Lianas (woody vines) can have profound effects on tree recruitment, growth, survival, and diversity in tropical forests. However, the dynamics of liana colonization soon after land abandonment are poorly understood, and thus it is unknown whether lianas alter tree regeneration early in succession. We examined the liana community in 43 forests that ranged from 1 to 31 yr old in central Panama to determine how fast lianas colonize young forests and how the liana community changes with forest succession. We found that lianas reached high densities early in succession, commonly exceeding 1000 stems/ha within the first 5 yr of forest regeneration. Lianas also increased rapidly during early succession in terms of basal area but did not show evidence of saturation within the 30 yr of our chronosequence. The relative contribution of lianas to total woody plant community in terms of basal area and density increased rapidly and reached a saturation point within 5 yr (basal area) to 15 yr (density) after land abandonment. Our data demonstrate that lianas recruit early and in high density in tropical forest regeneration, and thus lianas may have a large effect on the way in which secondary forests develop both early and throughout succession.