基于生态位分化和扩散迁移过程的高寒草甸群落构建机理

Reconciling the niche theory and neutral theory to explain the mechanism of maintaining species diversity is the focus in community ecology. The aim of this project is to explain the community assembly rules based on the niche-neutral continuum, incorporating niche differentiation and dispersal processes in and between local communities. Field experiments of this project will be conducted on alpine meadow. The model of niche differentiation is analyzed by the functional trait of component species and the difference of resource exploitation, such as light, moisture, nitrogen, phosphorus etc. We measure regeneration processes of the component specie, such as propagule dispersal, settlement, in climax local community, and colonization rate of pioneer species, its migration between local communities in succession communities and disturbed gaps, to investigate the contribution of resource partitioning, regeneration and migration processes in and between local communities to maintain species richness in communities. An individual-based, spatially explicit stochastic model of sessile organisms is the basic bracket of our model. By simulating the dynamics of a metacommunity consisted of interconnected local communities, together with the parameter gat from the field experiment, we show the effect of niche breadth and migration rate on species richness and the abundance of common and rare species. We intend to expound the mechanism of maintaining specie diversity in alpine meadow at both local and metacommunity scales by investigating the real ecological process in natural community.

协调生态位与中性理论，解释群落物种多样性的形成与维持，是近年来群落生态学家所关注的焦点。本项目基于综合生态位模型与中性模型的理论框架，结合生态位分化和局域群落内、群落间的扩散迁移过程，以高寒草甸为研究对象，阐释植物群落的构建机制。利用群落组分种功能性状和对光、水、氮、磷等资源的差异利用，分析群落中生态位分化的模式；在顶极植被的局域群落内观测物种种源扩散、定居的更新过程，在演替群落及扰动斑块中观测先锋种的拓殖及其在群落间的迁移，由此确认资源划分的生态位过程和群落内、群落间的更新、迁移过程各自对群落物种丰富度及分布模式的影响。构建基于个体的空间显式模型，以局域群落的网络为集合群落，代入野外调查和样地观测所得参数，模拟生态位宽度、迁移率等对局域群落物种丰富度及稀有种、优势种相对多度的贡献，以期在确认自然群落实际生态过程的基础上，在局域群落和集合群落两个水平上阐明群落物种多样性形成与维持的机理。

基于群落组分种生态位分化和群落间的扩散迁移过程，我们将空间显式模型模拟和高寒草甸野外调查、观测相结合，在山地坡向生境梯度上、生境同质的局域群落中及资源添加的扰动生境中，探讨物种生态位适宜度和随机扰动促成的扩散迁移各自对群落物种多样性形成与维持的贡献。本项目研究得到如下主要结论：.1）物种和环境之间的关系是要依赖于物种的生态位适宜度、对量效应的响应及其统计随机性。在研究物种分布时，必须同时考虑环境的生境异质性和扩散网络的空间结构。2）通过多种异质生境结构下的系统模拟，发现在一定的生境资源条件下，多度排序等级一致性能够实现群落构建机理的识别和预测。对于具自相关结构的生境，计算其群落的等级一致性指标值，则生态位-中性连续统上存在唯一的位置与之相对应。 3）土壤水分梯度显著改变了群落中物种组成和周转。在局域群落水平上，物种丰富度均随着坡向梯度由南向北呈现增加的趋势，而在坡向生境梯度上，β多样性从阳坡到阴坡呈现先增后减趋势。4）物种丰富度随单独 N 添加量的增加而降低。禾本科对N、P元素添加较敏感，具有高的增长率，因而在光竞争中排除其它物种而取胜；N、P添加的扰动，不仅会影响群落的物种数的多少，而且会改变群落的物种组成结构，即物种-多度分布模式。5）提出了“常见-稀有连续统”概念，计测了稀有种和常见种分别对群落相似性的贡献，结果表明：常见种在维持群落结构和功能中起着关键作用，而稀有种主要是增加区域种库和局域群落的物种多样性。本项目的研究将生态位分化与扩散迁移过程结合起来，并在生境梯度和局域群落两个水平阐释了植物群落的构建过程和机制。尤其是常见-稀有连续统与生态位-中性连续统相匹配概念的提出是群落生态学研究中的首创。