【作者】 黄运峰；

【导师】 臧润国；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2013， 博士

【摘要】 热带林演替动态理论研究的主要内容是揭示确定过程和随机过程影响物种组成、空间分布及其变化速度的相对重要性。本文以海南岛刀耕火种干扰后自然恢复的10hm2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)和老龄林群落的物种组成、种群空间分布和种间关联,揭示次生演替过程中的群落构建规律。主要研究结果如下：通过比较不同演替阶段的次生林和老龄林在幼苗、幼树和成年树群落的物种组成,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。应用空间点格局方法分析不同林龄种群的空间格局变化,同时通过案例-对照设计检验密度制约效应的相互作用。结果表明：不同林龄阶段树木的空间分布格局主要以聚集分布为主,小尺度上聚集的物种随演替进行逐渐减少。小树作为案例存在额外的聚集格局的物种数显著低于幼树的,说明随着树木的生长,个体在成年树周围聚集程度在降低。小尺度上密度制约作用的强度随着次生演替进行逐渐减小,但随着尺度的增大其作用强度逐渐趋同。不同林龄的死树与成年个体存在空间相关的距离各不相同。研究结果说明密度制约在作用在次生演替群落中普遍存在,并且不同演替阶段密度制约作用存在一定差异。物种个体多度和生活史特性在不同林龄群落中的差异是影响密度制约效应格局差异的主要因素。同时,生境异质性、种子扩散限制以及种间竞争等对密度制约效应的检验存在干扰。应用点格局分析方法比较分析在不同演替群落中种间关联性,对种间独立原则进行检验。我们假设由于增加了物种丰富度导致随机稀释效应将抑制物种的相关联,从而产生近似的种间相互独立。研究结果表明,不相关的物种对占的比例将随次生演替进行而增加,种间分离的物种对占的比例将随次生演替进行而减小。小尺度上不显著的种间相互作用的物种对占的比例随次生演替进行而增大。研究结果说明在物种极为丰富的群落范围内独立实际上是一个很好的近似值。我们的结果对更好地理解物种丰富群落中的控制因子迈进了一步,同时我们提出解释为什么在物种丰富的群落中物种布局是接近独立的假设。更多还原

【Abstract】 A major challenge in studies of tropical forest successional dynamics is to reveal therelative importance of deterministic versus stochastic processes affecting speciescomposition, spatial distributions, and their rates of change. In this thesis, we explored thespecies composition, tree population patterns and interspecific spatial associations along achronosequence of secondary forest plots, which were ranging from15years to60yearssince abandonment after shifting cultivation, and as two old-growth forest plots forcomparison. The results were listed as followings:We evaluated the species composition of different size classes (seedlings, saplings andadult trees) of communities. The results showed that both species diversity for all sizeclasses and the species similarity among size classes in old-growth forests exhibitedsignificantly higher than those in secondary forests, but the proportion of species dominancein old-growth community was lower than that of secondary forests. Species similaritybetween secondary forests and old-growth forests increased with forest recovery, supportingthe view of equilibrium succession dynamics. In each recovery stage, the number ofindividuals, species richness and abundance-based coverage estimator (ACE) in seedlingcommunity were lower than those both sapling communities and adult communities.Moreover, the species compositions for seedling communities of secondary forests differedsignificantly from that of both sapling communities and adult communities, suggesting thatthe recruitments into the seedling community may be a rather unpredictable process. Ourresults suggest that the community assembly processes during secondary forest recovery aredriven by both stochastic and deterministic processes.We used spatial point pattern analysis to elucidate the changes of spatial patterns of treespecies across forest ages, and applied the random-labelling null model within a case-controldesign to estimate the mutual effects of density-dependent. The results showed that most species were aggregated in plots of different ages and the small-scale aggregated speciesdecreased during succession. The number of species that juveniles as ‘cases’ showingadditional aggregation pattern was significantly lower than that of saplings, which suggestthat the extent of gathering around the adult tress from saplings to juveniles are declining.The strength of density dependence at scale of0–5m was decreased during secondarysuccession. Furthermore, the distance of spatial correlation between dead trees and adulttrees were different across forest ages. Our findings highlight density dependence as aprevalent mechanism for regulating the population spatial structure in successionalcommunities, and indicate that there are vary effect of density dependent by which dictatedthe variance of species abundance and life history in different successional stages.Habitatheterogeneity, seeddispersal limitation and interspecific competition could be confoundingfactors in studies that seek evidence for density dependence.We used techniques of spatial point pattern analysis to conduct a comprehensive test ofthe independence assertion by analyzing the species associations in successionalcommunities. We hypothesize that stochastic dilution effects owing to increasing speciesrichness overpower signals of species associations, thereby yielding approximate speciesindependence. The results showed that the proportion of species pairs with no signifcantinterspecifc association increased with during secondary succession and that the proportionof species pairs showing segregation decreased during succession. Moreover, the proportionof species pairs with non-signifcant interspecifc small-scale interactions should increaseduring succession. This suggests that independence may indeed be a good approximation inthe limit of very species-rich communities. Our findings were a step towards a betterunderstanding of factors governing species-rich communities and we proposed a hypothesisto explain why species placement in species-rich communities approximates independence.更多还原