决定森林群落优势物种种数的因素

本研究基于已发表的关于群落优势度的数据进行了全球尺度与演替序列上群落优势度差异进行了分析,并依据本文提出的资源有效性假说对其进行了解释,即有效资源的分布决定了群落的优势度格局。结果表明,全球尺度上各纬度带森林顶级群落的优势度各不相同,从寒带、温带森林的单物种占优势变化至热带森林的多物种共优势,甚至没有明显的优势物种。这与全球资源的分布格局是一致的。同样,群落在演替序列上的群落优势度也表现出一定的规律,在热带森林群落,演替序列上的物种优势从演替初始的单物种占优势逐渐变成演替后期的多物种共优势,甚至无优势种。这是由于演替序列上不断变化的有效资源所决定的。然而,与热带森林群落相反,温带或寒带森林群落经常是由单物种占优势。这是由于低的有效资源,特别是低的有效水分与温度决定的。这种表现在寒带森林中尤为明显,低的温度会极大地减少水分与养分的有效性,是造成单物种占优势的原因。另外,基于群落优势度会随着物种多样性的增加而下降的现象,我们可以得出这样的结论,较高的有效资源维持了群落较低的优势度。总之,有效资源越丰富,群落的优势度就越低,反之亦然。本文提出的资源有效性假说能够很好地解释全球与群落尺度上群落优势度的差异。

What determines the number of dominant species in forests?

In this work, the difference in number of dominant species in a community on global scale and successional trajectories was analyzed based on the published data. We explained the reasons of these differences using a resource availability hypothesis, proposed in this work, that the distribution of available resource determined the pattern of community dominance. The results showed that on global scale the number of dominant species of community varied across latitudinal forest zone,namely from single-species dominance in boreal and temperate forest to multi-species codominance, even no dominant species in tropical forest.This was consistent with the pattern of resource distribution on global scale. Similarly, in successional trajectories, the number of dominant species gradually radiated from single-species dominance to multi-species codominance, even no dominant species in tropical forest.The changing available resources in trajectories were responsible for this difference. By contrary, a community was often dominated by single species in temperate or boreal forest. This was determined by the low available resource, especially low available water and temperature. In boreal forest, low temperature greatly reduced availability of water and nutrient, which were responsible for the single-species dominance. In addition, the conclusion that high available resources sustained low dominance of community might be deduced, based on the fact that the dominance of community declined with the increasing of species diversity. To sum up, the richer the available resources were, the lower the dominance of community was, and vice versa. The hypothesis that the resource availability controlled the dominance of community could well elucidate the difference of community dominance on global and community scale.