Loreau M
Laboratoire d'Ecologie, Unité Mixte de Recherche 7625, Ecole Normale Supérieure, 46 rue d'Ulm, F-75230 Paris Cedex 05, France.
Proc Natl Acad Sci U S A. 1998 May 12;95(10):5632-6. doi: 10.1073/pnas.95.10.5632.
Recent experiments have provided some evidence that loss of biodiversity may impair the functioning and sustainability of ecosystems. However, we still lack adequate theories and models to provide robust generalizations, predictions, and interpretations for such results. Here I present a mechanistic model of a spatially structured ecosystem in which plants compete for a limiting soil nutrient. This model shows that plant species richness does not necessarily enhance ecosystem processes, but it identifies two types of factors that could generate such an effect: (i) complementarity among species in the space they occupy below ground and (ii) positive correlation between mean resource-use intensity and diversity. In both cases, the model predicts that plant biomass, primary productivity, and nutrient retention all increase with diversity, similar to results reported in recent field experiments. These two factors, however, have different implications for the understanding of the relationship between biodiversity and ecosystem functioning. The model also shows that the effect of species richness on productivity or other ecosystem processes is masked by the effects of physical environmental parameters on these processes. Therefore, comparisons among sites cannot reveal it, unless abiotic conditions are very tightly controlled. Identifying and separating out the mechanisms behind ecosystem responses to biodiversity should become the focus of future experiments.
近期的实验已提供了一些证据，表明生物多样性的丧失可能会损害生态系统的功能和可持续性。然而，我们仍然缺乏足够的理论和模型来对此类结果进行有力的概括、预测和解释。在此，我提出一个空间结构生态系统的机理模型，其中植物竞争一种有限的土壤养分。该模型表明，植物物种丰富度不一定会增强生态系统过程，但它识别出了两类可能产生这种效应的因素：（i）物种在地下占据空间的互补性，以及（ii）平均资源利用强度与多样性之间的正相关。在这两种情况下，该模型预测植物生物量、初级生产力和养分保持量都会随着多样性的增加而增加，这与近期田间实验报告的结果相似。然而，这两个因素对于理解生物多样性与生态系统功能之间的关系具有不同的意义。该模型还表明，物种丰富度对生产力或其他生态系统过程的影响被物理环境参数对这些过程的影响所掩盖。因此，除非非生物条件得到非常严格的控制，否则不同地点之间的比较无法揭示这一点。识别并分离出生态系统对生物多样性响应背后的机制，应成为未来实验的重点。
