Srivastava Diane S, Cardinale Bradley J, Downing Amy L, Duffy J Emmett, Jouseau Claire, Sankaran Mahesh, Wright Justin P
Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada.
Ecology. 2009 Apr;90(4):1073-83. doi: 10.1890/08-0439.1.
The flow of energy and nutrients between trophic levels is affected by both the trophic structure of food webs and the diversity of species within trophic levels. However, the combined effects of trophic structure and diversity on trophic transfer remain largely unknown. Here we ask whether changes in consumer diversity have the same effect as changes in resource diversity on rates of resource consumption. We address this question by focusing on consumer-resource dynamics for the ecologically important process of decomposition. This study compares the top-down effect of consumer (detritivore) diversity on the consumption of dead organic matter (decomposition) with the bottom-up effect of resource (detrital) diversity, based on a compilation of 90 observations reported in 28 studies. We did not detect effects of either detrital or consumer diversity on measures of detrital standing stock, and effects on consumer standing stock were equivocal. However, our meta-analysis indicates that reductions in detritivore diversity result in significant reductions in the rate of decomposition. Detrital diversity has both positive and negative effects on decomposition, with no overall trend. This difference between top-down and bottom-up effects of diversity is robust to different effect size metrics and could not be explained by differences in experimental systems or designs between detritivore and detrital manipulations. Our finding that resource diversity has no net effect on consumption in "brown" (detritus-consumer) food webs contrasts with previous findings from "green" (plant-herbivore) food webs and suggests that effects of plant diversity on consumption may fundamentally change after plant death.
营养级之间的能量和养分流动受到食物网的营养结构以及营养级内物种多样性的影响。然而，营养结构和多样性对营养传递的综合影响在很大程度上仍不为人知。在此，我们探讨消费者多样性的变化对资源消耗速率的影响是否与资源多样性的变化相同。我们通过关注生态上重要的分解过程中的消费者 - 资源动态来解决这个问题。本研究基于28项研究报告的90项观测结果，比较了消费者（分解者）多样性对死有机物质消耗（分解）的自上而下效应与资源（碎屑）多样性的自下而上效应。我们没有检测到碎屑或消费者多样性对碎屑现存生物量测量的影响，对消费者现存生物量的影响也不明确。然而，我们的荟萃分析表明，分解者多样性的降低会导致分解速率显著下降。碎屑多样性对分解有正面和负面的影响，没有总体趋势。多样性的自上而下和自下而上效应之间的这种差异对于不同的效应大小指标是稳健的，并且不能用分解者和碎屑操纵之间实验系统或设计的差异来解释。我们发现资源多样性对“棕色”（碎屑 - 消费者）食物网中的消耗没有净效应，这与之前“绿色”（植物 - 食草动物）食物网的研究结果形成对比，表明植物多样性对消耗的影响在植物死亡后可能会发生根本性变化。
