The effect of trophic cascade on process chain in detrital food webs

营养级联对碎屑食物网过程链的影响

• 批准号: 15570013
• 负责人: MIYASHITA Tadashi
• 金额: $ 1.28万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15570013/
• 关键词: top-down effect; decomposer system; ecosystem function; spider; colembola; 生物間相互作用; 食物連鎖; 食物網; 土壌動物

This study aimed at clarifying the effect of trophic cascade on the process chain in detrital food webs by using the system consisting spider-colembola-microorganism-litter-soil animals. I investigated direct and indirect effects of the predator Neriene brongersmai, a web spider abundant in the forest-floor of the Japanese cedar, on soil ecosystems by establishing field enclosures with and without this spider. Four a priori hypotheses that I had made are as follows,1)Do spiders control the abundance of Colembola?2)Do spiders indirectly increase the biomass of soil microorganisms?3)Do spiders indirectly increase the rate of decomposition of litter?4)Do spiders indirectly increase soil animals that are not directly eaten by spiders?A land 1/2 year long experiment showed that the hypothesis 1 was supported, i.e., spiders suppressed collembolan abundance. Contrary to my expectation, the hypotheses 2 to 4 were not verified. I proposed several reasons for these negative effects, including 1)top-down effect by the spiders was not strong enough to cause trophic cascade, 2)biomass of micoorganisms had decreased in a short term by spider predation, but the rapid turnover rate made the long term biomass invariable. This study failed to demonstrate the linkage between trophic cascade and process chain, but the approaches used in this study appeared to be useful. In the future, it is necessary to conduct manipulation experiments to examine how functional group level effect is operating, and how diversity of species or guilds within a functional group influences processes linking food web and process chain.

以蜘蛛-有尾类-微生物-凋落物-土壤动物组成的系统为研究对象，探讨碎屑食物网中营养级联对食物链的影响。我调查的直接和间接影响的捕食者Neriene brongersmai，丰富的日本雪松的森林地板上的蜘蛛，土壤生态系统，通过建立现场围栏和没有这种蜘蛛。我提出的四个先验假设如下：1）蜘蛛控制着弹尾目的丰度吗？2）蜘蛛是否间接增加了土壤微生物的生物量？3）蜘蛛是否间接地增加了凋落物的分解率？4）蜘蛛会间接增加不被蜘蛛直接食用的土壤动物吗？一项为期1/2年的实验表明，假设1得到了支持，即，蜘蛛抑制跳虫的数量。与我的预期相反，假设2至4没有得到验证。本文提出了造成这些负面影响的几个原因：1）蜘蛛的自上而下效应不足以引起营养级联; 2）蜘蛛的捕食使微生物生物量在短期内下降，但快速的周转率使长期生物量保持不变。本研究未能证明营养级联和过程链之间的联系，但在这项研究中使用的方法似乎是有用的。今后，有必要进行操纵实验，以检查功能组水平的效果是如何运作的，以及功能组内的物种或行业协会的多样性如何影响连接食物网和过程链的过程。