生物多样性与生态系统生产力:为什么野外观测和受控实验结果不一致?

BIODIVERSITY AND ECOSYSTEM PRODUCTIVITY: WHY IS THERE A DISCREPANCY IN THE RELATIONSHIP BETWEEN EXPERIMENTAL AND NATURAL ECOSYSTEMS?

人们担心生物多样性的空前丧失会危及到生态系统的服务功能 ,因此有关生物多样性_生态系统生产力这一古老命题的讨论成为当今生态学的热点议题之一。 2 0世纪 90年代以DavidTilman和ShahidNaeem为代表的生态学家利用大规模的受控实验 ,对物种多样性与生态系统功能的诸多方面进行了研究 ,结果表明物种多样性导致生态系统生产力的增加。这一结果遭到以DavidWardle ,MichaelHuston和PhillipGrime为代表的生态学家的质疑 ,认为这样的结果可能是由抽样效应引起的 ,而不是生物多样性本身的作用。争论的本身在很大程度上是由于受控实验结果和野外观测不一致造成的。结合作者的实验以及文献综述 ,该文分析了生物多样性实验群落和自然发育的群落之间的异同 ,认为野外观测和受控实验结果不一致的原因 ,可能源于群落密度、均匀度及土壤营养状况的不同 ,以及由此改变了生物多样性_生态系统生产力之间的关系。这些因子在自然状况下是多变的 ,而在生物多样性实验条件下则相对一致。最后 。

The old issue of biodiversity_ecosystem function (BEF) has been rekindled in the 1990s due to the fact that the loss of biodiversity caused by the increased human impact on ecosystems may substantially alter ecological functions and jeopardize ecosystem services to humans. The contemporary biodiversity_productivity experiments started in the 1990s, in which plant species richness is deliberately manipulated and aboveground productivity of the ecosystem measured, generally demonstrate that greater plant species diversity leads to greater productivity. However, a debate has followed regarding the mechanism causing the relationship in these experimental systems and questioning whether the observed positive relationship exists in natural, unmanipulated systems. The debate has divided ecologists. One group represented by D. Tilman and S. Naeem, holds the view that there are causative relationships between diversity and ecosystem functioning. The other group led by D. A. Wardle, M. A. Huston, and J. P. Grime, believes that it is the biological characteristics of the dominant plant species rather than their number that control ecosystem productivity and biogeochemistry. One common criticism of biodiversity experiments is that there is a discrepancy in the relationship between experimental and natural ecosystems. With experiments, as well as literature survey, we present some evidence in this paper that the discrepancy may be caused by the differences in community density, evenness and soil nutrient availability between biodiversity experimental communities and natural developed communities. These three factors were relatively uniform in experimental communities, while they differ spatially in natural communities. We argue that community density, evenness, and soil nutrient availability are confounding factor in the BEF relationships and that they should be considered when drawing conclusions about the results from biodiversity_productivity experiments. We also raised the potential feedback by soil nutrient availability, which may also influence the BEF relationships.