决定植物群落物种丰富度的环境因素和生物因素

发布时间：2018-09-01 06:04

【摘要】：物种丰富度沿环境梯度变化的决定因素一直是生态学研究的重点之一,理解物种丰富度的一般性决定因素对物种保护尤为重要。影响物种丰富度的因素大体包括两个方面:环境因素和生物因素。关于物种丰富度的环境决定因素,已有很多种假说被提出但是只有一小部分对物种丰富度有潜在的预测能力。环境异质性假说和能量假说中的生产力假说都是被频繁讨论的对象,但仍没有一个共识性结论。除了被广泛证据支持的物种丰富度与环境异质性之间的正相关关系,负相关和单峰型相关也有被报道。同样,生产力对物种丰富度有着强烈的影响,但也没有统一性的模式。如何理解这种多元化的物种丰富度与环境异质性关系模式,这些模式的变化是否与生产力水平有关?另外,环境因素对物种丰富度的影响并不一定是直接的,也可能是通过影响其它生物因素间接地改变物种丰富度,尤其是在小尺度上。这些生物因素不仅包括生物间相互作用,还包括区域物种库组成和群落总个体数等。物种丰富度与这些生物因素到底有着怎样的关系?物种丰富度-环境异质性关系和物种丰富度-生物因素关系,这两种关系哪个更具有一般性?本文将从这些问题入手结合计算机模拟、野外实验及统计推断等手段探究植物群落物种丰富度沿环境梯度变化的决定因素。通过基于个体的空间显式的竞争-拓殖权衡模型,我们发现物种丰富度-环境异质性关系模式取决于群落所处的生产力水平:在生产力水平很高或很低时,物种丰富度与环境异质性正相关;而在中度生产力水平物种丰富度与环境异质性的关系为单峰曲线。这表明生产力水平是影响物种丰富度-环境异质性关系模式的一个重要因子。所有的植物群落都是一个个个体组成的,我们通过对种-个体数累积曲线S=C(1-e~(-ZJ))的进一步拓展,提出一个新的公式S=C*(1-exp(-(pa*E+pb/J+pc)*J)),然后代入源于模型的数据进行多元非线性回归以验证其有效性。结果表明:对于空间环境均匀的群落这个公式可以有效地解释物种丰富度的变化(P0.01,R~2=0.9464),即植物群落物种丰富度的变化可以被群落总个体数(J)、均匀度(E)和物种库大小(C)联合解释。但是对于空间环境异质的群落这个公式对物种丰富度的解释能力很低。同时,这个公式有效地解释了物种丰富度沿坡向梯度的变化(P0.01,R~2=0.7667):物种丰富度沿阳坡-阴坡梯度的增加是由于均匀度和群落总个体数沿阳坡-阴坡梯度的上升。当生境的空间环境均匀时,物种丰富度-生物因素关系更具有一般性,即环境因素对植物群落物种丰富度的影响主要是通过群落总个体数(J)、均匀度(E)或物种库大小(C)间接实现的。然而,当生境的空间环境异质时,物种丰富度与环境因素的关系更有一般性,即环境异质性对物种丰富度有直接的影响。由此可见,生物因素对物种丰富度的解释能力取决于空间环境是否均匀。我们的研究为局域群落物种丰富度沿环境梯度的变化提供了一个新的视角。
[Abstract]:The determinants of species richness along environmental gradients have always been one of the focuses of ecological research. Understanding the general determinants of species richness is particularly important for species conservation. Various hypotheses have been proposed but only a small percentage have potential predictive power for species richness. Both the environmental heterogeneity hypothesis and the productivity hypothesis in the energy hypothesis are frequently discussed, but there is still no consensus conclusion. Negative and unimodal correlations have also been reported. Similarly, productivity has a strong impact on species richness, but there is no uniform pattern. How to understand the relationship between species richness and environmental heterogeneity, and whether the changes in these patterns are related to productivity? In addition, environmental factors have a strong impact on species richness. The impact is not necessarily direct, but may be indirect, especially at a small scale, through the impact of other biological factors, including not only the interactions between organisms, but also the composition of regional species pools and the total number of individuals in communities. Which of these two relationships is more general? This paper will explore the determinants of plant community species richness along environmental gradients by means of computer simulation, field experiments and statistical inference. Explicit competition-colonization trade-off model shows that the relationship between species richness and environmental heterogeneity depends on the productivity level of the community: species richness is positively correlated with environmental heterogeneity at high or low productivity levels; and the relationship between species richness and environmental heterogeneity at moderate productivity levels is a single peak curve. This indicates that productivity level is an important factor affecting the pattern of species richness-environmental heterogeneity. All plant communities are individual. We propose a new formula S = C* (1-exp (-(pa*E+pb/J+pc)*J) by further extending the species-individual cumulative curve S = C (1-e~(-ZJ)) and then substituting it from the model. The results showed that the formula could effectively explain the variation of species richness (P 0.01, R~2 = 0.9464) for communities with uniform spatial environment, i.e. the variation of species richness in plant communities could be explained jointly by the total number of individuals (J), evenness (E) and the size of species pool (C). At the same time, the formula effectively explained the variation of species richness along slope gradient (P 0.01, R~2 = 0.7667). The increase of species richness along sunny-shady gradient was due to the increase of evenness and the total number of individuals along sunny-shady gradient. When the spatial environment of the habitat is uniform, the relationship between species richness and biological factors is more general, that is, the influence of environmental factors on species richness of plant community is mainly realized indirectly by total community number (J), evenness (E) or species pool size (C). However, when the spatial environment of the habitat is heterogeneous, species richness and environmental factors are more common. The relationship between elements is more general, that is, environmental heterogeneity has a direct impact on species richness. Thus, the ability of biological factors to explain species richness depends on whether the spatial environment is homogeneous.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：Q948

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