Spatial and temporal analysis of beta diversity in the Barro Colorado Island forest dynamics plot, Panama

Background: Ecologists are interested in assessing the spatial and temporal variation in ecological surveys repeated over time. This paper compares the 1985 and 2015 surveys of the Barro Colorado Forest Dynamics plot(BCI), Panama,divided into 1250(20 m × 20 m) quadrats.Methods, spatial analysis: Total beta diversity was measured as the total variance of the Hellinger-transformed community data throughout the BCI plot. Total beta was partitioned into contributions of individual sites(LCBD indices), which were tested for significance and mapped.Results, spatial analysis: LCBD indices indicated the sites with exceptional community composition. In 1985,they were mostly found in the swamp habitat. In the 2015 survey, none of the swamp quadrats had significant LCBDs.What happened to the tree community in the interval?Methods, temporal analysis: The dissimilarity in community composition in each quadrat was measured between time 1(1985) and time 2(2015). Temporal Beta Indices(TBI) were computed from abundance and presence-absence data and tested for significance. TBI indices can be decomposed into B = species(or abundances-per-species) losses and C = species(or abundances-per-species) gains. B-C plots were produced; they display visually the relative importance of the loss and gain components, through time, across the sites.Results, temporal analysis: In BCI, quadrats with significant TBI indices were found in the swamp area, which is shrinking in importance due to changes to the local climate. A published habitat classification divided the BCI forest plot into six habitat zones. Graphs of the B and C components were produced for each habitat group. Group 4(the swamp) was dominated by species(and abundances-per-species) gains whereas the five other habitat groups were dominated by losses, some groups more than others.Conclusions: We identified the species that had changed the most in abundances in the swamp between T1 and T2.This analysis supported the hypothesis that the swamp is drying out and is invaded by species from the surrounding area. Analysis of the B and C components of temporal beta diversity bring us to the heart of the mechanisms of community change through time: losses(B) and gains(C) of species, losses and gains of individuals of various species. TBI analysis is especially interesting in species-rich communities where we cannot examine the changes in every species individually.

A Survey of Mycorrhizal Colonization in the 50-ha Korup Forest Dynamic Plot in Cameroon

A study was carried out in the 50-ha Korup Forest Dynamic Plot in South West Cameroon, to evaluate the diversity of mycorrhizal associations as well as to determine the effect of habitat types on the type of mycorrhizal association. A total of 781 individual trees belonging to 51 families, 165 genera and 252 tree species, were sampled from the four habitat types found in the plot: low drier, hill slope, ridge top and wetland complexes. In each habitat type, all stems ≤ 1 cm depth at breast height had already been tagged, measured, mapped and identified to the species level. Root samples were collected, cleared, stained and examined microscopically for mycorrhizal type. Of the total number of species sampled, 248 (98.41%) formed mycorrhizal associations with only 4 (1.59%) being non mycorrhizal. For mycorrhizal trees, 232 (93.55%) formed exclusively arbuscular mycorrhiza, 10 (4.03%) formed ectomycorrhiza, while 6 (2.42%) formed both ecto- and arbuscular mycorrhiza. The ridge top harbored the least number (152) of mycorrhizal trees while the low drier area harbored the most number (266) of mycorrhizal trees. Although habitat effect was not significant in influencing mycorrhizal colonization of tree species, some tree species did show aggregated patterns in particular habitats.

Drivers of the differentiation between broad-leaved trees and shrubs in the shift from evergreen to deciduous leaf habit in forests of eastern Asian subtropics

In eastern Asian subtropical forests,leaf habit shifts from evergreen to deciduous broad-leaved woody plants toward higher latitudes.This shift has been largely explained by the greater capacity of deciduous broad-leaved plants to respond to harsh climatic conditions(e.g.,greater seasonality).The advantages of deciduous leaf habit over evergreen leaf habit in more seasonal climates have led us to hypothesize that leaf habits would shift in response to climate changes more conspicuously in forest canopy trees than in forest understory shrubs.Furthermore,we hypothesize that in the forests of the subtropics,plants at higher latitudes,regardless of growth form,would better tolerate seasonal harsh climates,and hence show less differentiation in leaf habit shift,compared to those at lower latitudes.To test these two hypotheses,we modelled the proportion of deciduous broad-leaved species and the incidence of deciduous and evergreen broad-leaved species in woody angiosperm species compositions of ten largesized forest plots distributed in the Chinese subtropics.We found that the rate of leaf habit shift along a latitudinal gradient was higher in forest trees than in forest shrubs.We also found that the differentiation in leaf habit shift between trees and shrubs is greater at lower latitudes(i.e.,warmer climates)than at higher latitudes(i.e.,colder climates).These findings indicate that specialized forest plants are differentially affected by climate in distinct forest strata in a manner dependent on latitudinal distribution.These differences in forest plant response to changes in climate suggest that global climate warming will alter growth forms and geographical distributions and ranges of forests.

2018年浙江古田山24公顷亚热带常绿阔叶林动态监测样地林冠结构与地形数据集

林冠结构与地形因子共同影响着森林重要物种资源及生境的时空变化,而针对我国地带性森林生态系统高精度林冠结构和地形数据集极为缺乏。基于近地面遥感平台获取的激光雷达数据,可以获取精确的林冠结构和地形数据。本研究以位于钱江源国家公园核心保护区的24公顷亚热带常绿阔叶林动态监测样地为研究对象,对该区域2018年基于近地面遥感技术获取的激光雷达点云数据进行计算分析及质量控制,获取该样地的林冠结构和地形数据。通过实时动态测量(RTK)的地面数据对数字高程模型(DEM)进行精度检验和验证,表明DEM的高程中误差为0.07米,数据具有较高精度。古田山24公顷亚热带常绿阔叶林动态监测样地为典型的中亚热带低海拔常绿阔叶林,本数据集可以为亚热带常绿阔叶林生物多样性监测和研究提供数据支撑。

祁连山青海云杉林叶面积指数的空间异质性

叶面积指数(leaf area index,LAI)在山地森林具有高度的空间异质性。基于大样地尺度的山地森林叶面积空间异质性的研究较少,而且不涉及LAI对地形的响应研究。基于LAI的空间异质性和地形因子的相关性,确定取样尺度,可为提升区域尺度上LAI的空间遥感精度提供依据。本研究依托祁连山大野口流域10.2 ha(340 m×300 m)的青海云杉林动态监测样地,使用CID CI-110植物冠层数字图像分析仪对样地内255个20 m×20 m样方进行五点法LAI测定,分析LAI的空间异质性特征和空间分布格局及其与地形因子的相关性。研究结果表明:(1)LAI具有中等变异性,指数模型是变异函数的最佳理论模型,具有强烈的空间自相关,变程为16 m,南—北方向上是LAI分布的优势格局。(2)LAI的空间分布格局相对简单,具有一定的斑块性,LAI为0.56~1.43的斑块所占面积最大。(3)LAI与海拔和坡度均呈极显著负相关(P<0.01),与坡度和曲率的相关性均不显著(P>0.05)。(4)青海云杉林的LAI空间异质性与尺度和方向有关,部分地形因子对LAI存在着显著影响。研究结果可为青海云杉林生态过程分析以及遥感技术反演LAI参数提供依据。

Functional traits of tree species with phylogenetic signal co-vary with environmental niches in two large forest dynamics plots

Aims While using phylogenetic and functional approaches to test the mechanisms of community assembly,functional traits often act as the proxy of niches.However,there is little detailed knowledge regarding the correlation between functional traits of tree species and their niches in local communities.We suggest that the co-varying correlation between functional traits and niches should be the premise for using phylogenetic and functional approaches to test mechanisms of community assembly.Using functional traits,phylogenetic and environmental data,this study aims to answer the questions:(i)within local communities,do functional traits of co-occurring species covary with their environmental niches at the species level?and(ii)what is the key ecological process underlying community assembly in Xishuangbanna and Ailaoshan forest dynamic plots(FDPs)?Methods We measured seven functional traits of 229 and 36 common species in Xishuangbanna and Ailaoshan FDPs in tropical and subtropical China,respectively.We also quantified the environmental niches for these species based on conditional probability.We then analyzed the correlations between functional traits and environmental niches using phylogenetic independent contrasts.After examining phylogenetic signals of functional traits using Pagel’sλ,we quantified the phylogenetic and functional dispersion along environmental gradients within local tree communities.Important Findings For target species,functional traits do co-vary with environmental niches at the species level in both of the FDPs,supporting that functional traits can be used as a proxy for local-scale environmental niches.Functional traits show significant phylogenetic signals in both of the FDPs.We found that the phylogenetic and functional dispersion were significantly clustered along topographical gradients in the Ailaoshan FDP but overdispersion in the Xishuangbanna FDP.These patterns of phylogenetic and functional dispersion suggest that environmental filtering plays a key role in structuring local tree assemblages in Ailaoshan FDP,while competition exclusion plays a key role in Xishuangbanna FDP.

Biomass increment and mortality losses in tropical secondary forests of Hainan, China

Secondary forests, created after heavy logging,are an important part of China's forests. We investigated forest biomass and its accumulation rate in 38 plots in a tropical secondary forest on Hainan Island. These secondary forests are moderate carbon sinks, averaging1.96–2.17 t C ha-1 a-1. Biomass increment is largely by medium-sized(10–35 m) trees. Tree mortality accounts for almost 30% of the biomass and plays a negligible role in biomass accumulation estimates. Mortality rate is highly dependent on tree size. For small trees and seedlings, it is related to competition due to elevated irradiance after logging. Regarding prospective biomass and rates of accumulation, recovery is not as rapid as in secondary forests of cleared land. Therefore, tropical forests are susceptible to logging operations and need careful forest management.

Coarse woody debris features of a warm temperate deciduous broad-leaved forest,northern China

Stocking and structural composition of a deciduous broad-leaved forest were determined to predict coarse woody debris quantity by quantifying the empirical relationships between these two attributes.The most ecologically significant families by stem density were Salicaceae,Betulaceae,Fagaceae,and Aceraceae.P opulus davidiana was the most dominant species followed by B etula dahurica,Quercus mongolica,and Acer mono.The four species accounted for 69.5%of total stems.Numerous small-diameter species characterized the coarse woody debris showing a reversed J-shaped distribution.The coarse debris of P.davidiana,B.dahurica,and Q.mongolica mainly comprised the 10–20 cm size class,whereas A.mono debris was mainly in the 5–10 cm size class.The spatial patterns of different size classes of coarse woody debris were analyzed using the g-function to determine the size of the tree at its death.The results indicate that the spatial patterns at the 0–50 m scale shifted gradually from an aggregated to a random pattern.For some species,the larger coarse debris might change from an aggregated to a random distribution more easily.Given the importance of coarse woody debris in forest ecosystems,its composition and patterns can improve understanding of community structure and dynamics.The aggregation pattern might be due to density dependence and self-thinning effects,as well as by succession and mortality.The four dominant species across the different size classes showed distinct aggregated distribution features at different spatial scales.This suggests a correlation between the dominant species population,size class,and aggregated distribution of coarse woody debris.

Fine-scale activity patterns of large-and medium-sized mammals in a deciduous broadleaf forest in the Qinling Mountains,China

The composition of animal species and interactions among them are widely known to shape ecological communities and fine-scale(e.g.,<1 km)monitoring of animal communities is essential for understanding the relationships among animals and plants.Although the co-existence of large-and medium-sized species has been studied across different scales,research on fine-scale interactions of herbivores in deciduous broadleaf forests is limited.Camera trapping of large-and medium-sized mammals was carried out over a 1 year period within a 25 ha deciduous broadleaf forest dynamics plot in the Qinling Mountains,China.Fourteen species of large-and medium-sized mammals,including six carnivores,six ungulates,one primate and one rodent species were found.Kernel density estimations were used to analyse the diel or 24 h activity patterns of all species with more than 40 independent detections and general linear models were developed to explore the spatial relationships among the species.The combination of overlapping diel activity patterns and spatial associations showed obvious niche separation among six species:giant panda(Ailuropoda melanoleuca David),takin(Budorcas taxicolor Hodgson),Reeves’s muntjac(Muntiacus reevesi Ogilby),tufted deer(Elaphodus cephalophus Milne-Edwards),Chinese serow(Capricornis milneedwardsii David)and wild boar(Sus scrofa Linnaeus).Long-term fine-scale monitoring is useful for providing information about the co-existence of species and their interactions.The results demonstrate the importance for fine-scale monitoring of animals and plants for improving understanding of species interactions and community dynamics.

The Spatial-Temporal Heterogeneity of Understory Light Availability in a Temperate Forest of North China

The spatial-temporal variation of understory light availability has important influences on species diversity and community assembly.However,the distribution characteristics and influencing factors of understory light availability have not been fully elucidated,especially in temperate deciduous,broad-leaved forests.In this study,the understory light availability was monitored monthly(May–October)in a temperate deciduous,broad-leaved forest in Henan Province,China.Differences in the light availability among different months and habitat types were statistically analyzed using Kruskal–Wallis method,respectively.Partial least squares path modeling(PLS-PM)was used to explore the direct and/or indirect effects of stand structure,dominant species and topographic factors on the light environment.Results showed that there were differences in light environments among the four habitat types and during the studied six months.The PLS-PM results showed that the stand structure and the dominant species were negatively correlated with the light environment,and the path coefficient values were−0.089(P=0.042)and−0.130(P=0.004),respectively.Our result indicated that the understory light availability exhibit a distinct spatial and temporal heterogeneity in temperate deciduous,broad-leaved forest of north China.The characteristics of woody plant community,especially the abundance of one of the dominant plant species,were the important factors affecting the understory light availability.

近地面激光雷达点云密度对森林冠层结构参数提取准确性的影响

基于激光雷达技术获取冠层结构为森林生态学研究增加了新的维度。搭载于多旋翼无人机的近地面激光雷达相比于固定翼有人机的机载激光雷达,能够更加灵活高效地获取森林群落样地高密度点云。但在实际操作中,往往出现局部低密度点云数据,影响了冠层结构参数提取的准确性。使用4块森林动态样地的近地面激光雷达点云数据;利用航带分解方法分析各样地低密度样方成因;采用点云抽稀模拟算法计算并拟合偏差曲线,对比不同样地、参数和取样尺度间的点云密度对冠层结构参数提取准确性的影响;根据偏差曲线计算各条件下保证参数提取准确性的最低点云密度。结果发现:1)低密度区域主要受地形或(和)近地面遥感设计规划的影响。地形复杂的测区(西双版纳和古田山样地),遥感规划难度大,整体难以获取高密度点云(在30点/m^(2)左右),容易在沟谷和高海拔处出现低密度样方。平坦测区(长白山两块样地)虽可获取高密度点云(均超过150点/m^(2)),但欠佳的遥感规划设计导致长白山1测区北部出现1hm^(2)低密度区域。2)冠层参数提取准确性随点云密度减少而迅速降低,呈负指数幂函数关系。这一变化趋势在不同参数和尺度间差异较大,但在各样地间无显著差异。3)根据偏差曲线拟合结果,点云密度达到16点/m^(2)可以实现5—20 m取样尺度下冠层结构参数提取准确度达95%。综上,为更好的将近地面激光雷达技术应用在森林生态学研究中,应注重外业遥感作业方案的合理性,充分考虑地形的影响,在源头把控数据质量;如果数据存在低密度点云的情况,应适当放宽取样尺度并慎重提取对点云密度较为敏感的冠层结构参数。

海南霸王岭热带山地雨林6 hm^(2)森林动态监测样地物种组成与群落特征

【目的】分析海南霸王岭热带山地雨林6 hm^(2)森林动态监测样地物种组成与群落特征,为深入理解热带天然林生物多样性维持机制提供基础依据。【方法】基于森林动态监测样地的群落调查数据,对样地内胸径(DBH)≥1 cm的所有木本植物进行了调查和统计,从物种组成特征、数量特征、科属地理成分、主要优势树种的径级结构和空间分布格局等方面入手,分析群落物种组成和特征。【结果】1)样地中物种丰富,组成复杂多样。6 hm^(2)样地内DBH≥1 cm的植物共有407种40783株个体,分属79科215属;平均植株密度为0.68株/m^(2),平均物种数为67.83种/hm^(2)。2)植物区系具有典型的热带植物区系特点。热带分布的科、属分别占样地总科、属的68.35%和88.83%。3)群落更新良好。样地内所有物种全部个体的径级分布呈典型的倒“J”型。4)优势树种的种群空间分布格局以聚集分布为主,不同物种表现为不同的空间格局类型且具有明显的空间尺度依赖性。【结论】本研究提供了海南霸王岭热带山地雨林6 hm^(2)森林动态监测样地内的物种组成和群落结构等基本信息,可为热带天然林物种共存机制、生物多样性与生态系统功能关系等方面的研究提供基础依据,也可为海南旗舰物种海南长臂猿的有效保护和海南热带雨林国家公园建设等奠定研究基础。

黄山常绿阔叶林群丛数量分类及物种多样性格局——以10.24 hm 2森林动态监测样地为例

零散的植物群落调查不符合群落分布既有连续性、又存在间断性的特点。近年来兴起的森林动态监测样地研究平台为植被分类研究提供了新途径。以黄山10.24 hm^(2)森林动态监测样地为研究对象,以地形因子和物种重要值为变量,使用多元回归树、指示种并结合冗余分析将监测样地划分为3个群丛;甜槠在3个群丛中均为重要值最高的物种,森林动态监测样地属于甜槠群系。采用α-多样性指数对该局域尺度下各群丛物种多样性进行分析,并首次引入PER-SIMPER推断黄山常绿阔叶林群落的构建机制。结果表明:群落内的群丛分类主要受海拔和凹凸度的影响,坡度与坡向对群丛分类的影响较小;生态位和扩散过程共同主导黄山植物群落的构建;不同群丛间的物种多样性存在差异,分布于低海拔山脊的群丛α-多样性与分布于山谷的群丛α-多样性存在显著差异。该研究结果为当地森林植被管理与保护提供了决策依据。

沿纬度梯度的3个热带森林动态监测样地的兽类和鸟类红外相机监测

2017年6月至9月和2018年5月至9月,利用红外相机分别对位于西双版纳的纳板河流域国家级自然保护区、西双版纳国家级自然保护区和泰国Khao Yai国家公园的三个热带森林动态监测样地的地面活动兽类和鸟类进行了监测。每个样地分别布设49台红外相机,共拍摄到66种野生动物,包括6目13科24种兽类,7目15科41种鸟类以及1种两栖类。监测结果在一定程度上反映了保护区内野生动物种类,可为基于动态监测样地的生态学和保护生物学研究提供参考。

西双版纳热带森林动态监测样地--树种组成与空间分布格局

西双版纳热带雨林是中国生物多样性最丰富的生态系统之一,西双版纳也被公认为国际上重要的生物多样性保护的热点地区之一。2007年,在中国科学院生物多样性委员会、加拿大Alberta大学和中国台湾东海大学等相关单位的支持下,由中国科学院西双版纳热带植物园和西双版纳州自然保护区管理局在西双版纳州勐腊县补蚌村的望天树(Shorea wantianshuea)林中建立了一块面积为20hm2的热带森林动态监测样地,该样地是中国森林生物多样性动态监测网络建设的重要组成部分之一,其建设技术是按照美国史密森热带研究所的热带森林研究中心(Center for Tropical Forest Science,CTFS)1980年在巴拿马Barro Colorado Island建立50hm2样地的技术规范进行的。我们逐一测量并记录了样地中所有树干胸径大于1cm树木的胸围,并对其挂牌标记、鉴定种名和确定坐标位置。并应用Ripley’sL-Function分析了样地内4种上层优势种和12个稀有种的空间分布格局。研究结果表明:样地内共含有胸径≥1cm的乔木95834株,其中已经鉴定的有95498株,占总个体数的99.65%;有乔木种类468种,隶属于213个属和70个科;另外有336个个体没有鉴定出来,仅占总个体数的0.35%。上层乔木中的望天树重要值排名第2,但具有最大的胸高断面积;中、下层的假海桐(Pittosporopsis kerrii)个体数最多,占样地内已鉴定乔木个体总数的21.90%。样地内4个上层优势种的小径阶个体数量较多,而大径阶个体数量较少,径阶分布呈倒"J"型,因此这4个种群可以维持自我更新。在分布格局上,样地内的4个上层优势树种的幼树和中龄树以聚集分布为主,而成年树则以随机分布为主。另外,大多数稀有物种也表现出聚集分布的格局。

长白山次生杨桦林样地：物种组成与群落结构

长白山次生杨桦林是该地区阔叶红松林经皆伐和火烧等破坏后恢复形成的主要次生林类型之一,是阔叶红松林次生演替系列中的重要阶段。参照巴拿马巴洛科罗拉多岛(Barro Colorado Island,BCI)50hm2热带雨林样地的技术规范,于2005年在长白山北坡的自然保护区内建立了一块5hm2的次生杨桦林长期监测样地,对样地内所有胸径≥1cm的木本植物进行了详细的定位调查。对样地的物种组成与群落结构的分析表明:次生杨桦林样地物种组成丰富,共包括16科28属44种;区系特征明显,北温带成分占主要部分;样地内被监测的树木个体数为20101,不包括分枝的独立个体数为16565;优势树种明显,从个体数、平均胸径、胸高断面积和重要值等分析来看,演替先锋树种白桦(Betula platyphylla)和山杨(Populus davidiana)在群落中占有绝对优势地位,但从径级结构来看,它们的更新却非常差,随着演替的进展,这些先锋树种将逐渐走向衰亡;阔叶红松林中的主要树种如红松(Pinusko-raiensis)和紫椴(Tilia amurensis)等已经在次生杨桦林中占有了一定的比例,林下更新良好,逐渐进入林冠层并最终取代杨桦等成为该森林的优势种;从物种的空间分布格局来看,演替先锋树种和阔叶红松林中的主要树种并没有表现出明显的聚集性分布格局,而其它的小乔木和灌木树种则表现出明显的聚集性分布格局,但与地形并没有表现出明显的相关性,相关结论还需要进一步分析。

鄂西南亚热带常绿落叶阔叶混交林优势种群的结构与动态特征

【目的】分析鄂西南森林动态样地内优势种群的结构及动态特征,为进一步深入研究亚热带常绿落叶阔叶混交林的更新动态及生物多样性维持机制奠定基础。【方法】参照热带森林科学中心森林动态监测样地(大样地)建设与监测技术规范,于2014年在湖北木林子国家级自然保护区的亚热带常绿落叶阔叶混交林中建立15 hm^2大样地,调查并鉴定胸径大于1 cm的所有木本植物,分析其种群结构及动态特征。【结果】在垂直结构上,物种丰富度和个体多度都随着树木高度层次的降低而升高;在径级结构上,物种丰富度和个体多度都随着径级增大而降低,呈倒"J"形分布趋势;按所分布的径级数量不同可将群落内的物种分为10类,多数物种主要分布于小径级范围,但优势种群则集中分布于某个径级或均匀分布于各径级,表明优势种群可能有集中更新和连续更新2种方式;在胸径小于10 cm的径级内翅柃最占优势,而在其他径级内壳斗科物种占主要优势;群落中大部分种群有超过60%个体分布在最低的2个垂直层次内,且有超过85%的个体胸径小于10 cm,表明其具有良好的更新趋势,群落总体上处于进展演替中;对群落中径级和高度级上都占优势的25个种群的动态分析表明,16种属进展种群,3种属近期处于稳定状态但远期将趋于衰退状态,2种属衰退状态,4种属进展期与衰退期相间出现及个体数量存在波动的种群。【结论】鄂西南亚热带常绿落叶阔叶混交林群落树体较小,大径级和高度级树木种类及个体较少,绝大多数优势种群及群落总体均处于进展演替阶段,群落具有良好的自然更新。

喀斯特常绿落叶阔叶混交林土壤磷钾养分空间异质性

在木论国家级自然保护区内喀斯特常绿落叶阔叶混交林内建立500 m×500 m长期监测样地,采用经典统计学和地统计学方法研究喀斯特森林土壤磷钾养分含量及其空间变异特征。结果表明:研究区土壤全磷(TP)、全钾(TK)、速效磷(AP)、速效钾(AK)含量分别为(1.60±0.76)g/kg、(5.42±2.74)g/kg、(5.74±3.63)mg/kg、(5.20±2.96)mg/kg;磷钾养分含量均为中等变异,变异强度为AP>AK>TK>TP。研究区土壤TP、TK、AP、AK变异函数值的最佳拟合模型均为指数模型,决定系数均很高(0.671-0.995),TP、AP呈中等强度空间自相关,TK、AK呈弱空间自相关。TP、AP的变程较长,分别为336.00 m和373.50 m,空间连续性较好,TK、AK变程较短(33.30 m、64.50 m),空间依赖性较强。土壤TP表现为坡下(含洼地)含量高,坡上含量较低;AK表现为坡中含量高于洼地含量;AP、TK呈斑块破碎化分布。海拔、坡度和地面凹凸度是土壤磷钾养分空间异质性的主要影响因素。喀斯特常绿落叶阔叶混交林土壤磷钾养分存在不同空间异质性和空间关联性,这为小流域尺度上土壤养分管理、可持续利用策略、喀斯特退化生态系统生态恢复提供理论依据。

不同尺度上环境因子对常绿阔叶林群落的谱系结构的影响

群落的谱系结构是反映作用于群落组成的各种生态过程的综合指标。通过研究群落的谱系结构,能够有效地推断形成群落谱系结构的生态过程。该文从环境因子(海拔、地形、pH、土壤湿度和土壤元素等)对群落谱系结构的影响这一视角出发,采用圆形随机取样,在半径为5、25、50、75和100m5个尺度上,深入研究了古田山24hm2永久样地群落的谱系结构。研究发现:古田山样地在所有研究尺度上(半径>5m)都表现为谱系聚集,随着尺度的增加,群落的聚集程度呈现出先增加后下降的格局。采用多元线性回归模型分析环境因子对群落谱系结构的影响时发现:随着尺度的增加,环境因子对群落谱系结构的影响逐渐增强;在小尺度上,环境因子对谱系结构没有显著影响,这可能是由于小尺度上近缘种之间较强的竞争排斥作用所致。当尺度达到100m半径时,高海拔区域表现出谱系发散格局,而低海拔区域保持谱系聚集,这可能是由于古田山样地海拔较高的地带生境异质性较强和较大的干扰所致。该研究在所有的尺度上都表现出显著的谱系聚集,与中性理论所预测的群落是物种的随机组合、无谱系结构相反,因而为生态位理论提供了证据。

云南高黎贡山中山湿性常绿阔叶林的群落特征

森林植被与其生存环境相互制约、相互依存，一直处于不断的发展变化之中。对森林植被的动态进行监测，通过考察植被的组成、结构、功能与其生境关系的时空变化过程，揭示它们之间相互作用的规律，并在此基础上对森林植被及其生境的演变方向和机理进行科学研究并作出综合评价，有利于森林植被的有效保护和管理（李玉媛，2003）。