作 者 ：刘梦雪,刘佳佳*,杜晓光,郑小刚
期 刊 ：生态学报 2010年 30卷 24期 页码：6935~6942
Keywords:species abundance distribution, chi-square test, goodness of fitting, sub-alpine meadow,
摘 要 ：物种多度分布是群落生态学研究的核心内容。通过对青藏高原东部亚高寒草甸3种不同生境草本植物群落的抽样调查，结合16个物种多度分布模型的两种曲线拟合优度检验得出如下结果：多种不同模型可以拟合同一生境的物种多度分布。相比于其他可拟合模型，几何级数模型在3种生境中两种拟合优度检验方法下的平均拟合效果是最好的，拟合优度值均在最优拟合优度值10左右波动。次优模型鉴于不同生境不同的检验方法表现不一。除了几何级数模型外，Sugihara分数模型在最小二乘法的拟合方法下，也可以拟合3种生境的物种多度分布。研究结果表明，仅用拟合优度检验区分产生不同物种分布格局的模型和机制是不可靠的，需要做进一步的检验性实验研究。
Abstract:Species coexistence mechanisms and species abundance distribution patterns at different time and spatial scale have been and may continue to be key research issues in community ecology, whereas species abundance distribution (SAD) or relative species abundance distribution (RSAD) curve is the common way to describe the species diversity distribution patterns in a community. Species abundance distribution curves have also been used to distinguish different mechanisms for species coexistence. Although there are many different models proposed to predict and explain species abundance distribution patterns and some of them have also been tested in real ecological communities, no general statistical criteria has been proposed to evaluate the power of the models to explain and predict the observed SAD or RSAD. In this paper, we compare the goodness-of-fit indexes of 16 different models for the SADs of plant communities and explore the underlying mechanism of community assembly in sub-alpine meadows in the eastern Qinghai-Tibet Plateau. Taking advantage of Ulrich′s Fortran program for the study of relative abundance distributions, which is named RAD, we fitted 16 different models of species abundance distribution (i.e. geometric model, sugihara fraction model, random fraction model, particulate niche model, etc.) to randomly simulated data sets which were collected in three different types of habitats (north-facing slope, level field, and south-facing slope) by means of two different methods (corrected least square test and chi-square test). We draw the conclusion that more than one model can fit the same data set of the observed species abundance distributions in three habitats. Compared with the other fitted models, the geometric-series model is the best for these three types of habitats in two methods of goodness-of-fit test. The value of fitness index of the geometric-series model always fluctuates around the best fit value 10. In addition to the geometric model, Sugihara fraction model can also fit the observed species abundance distributions in all three habitats but only according to the method of corrected least square test. The goodness-of-fit of other models depend on the types of habitat and the methods of goodness-of-fit test involved. As a result, simple curve-fitting of species abundance distribution might not be treated as the unique criterion for testing the models and their corresponding hypotheses as the mechanisms of community assembly Species traits affecting demographic rate (such as biomass, cover and height) and multiple methods of the goodness-of-fit test should be considered in the comparison of models. Furthermore, searching for a generally optimal model might be one of the future research hot spots because it can play an important role in explaining community structure together with the underlying process in ecological communities. While using multiply models and multiply test methods in our study offers a practicable approach to sift or build a general optimal model and also provides a possibility of producing a unified theory of biodiversity.
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