营养级联效应是理解群落结构和生态系统功能的基础。前期研究表明，在典型的三级食物链中，牧食食物网中的捕食者能通过减少猎物数量或改变其行为而促进植物生长，即捕食者的“绿色世界”效应(Green-world effect)；而碎屑食物网中的捕食者则通过减少分解者数量、降低土壤养分有效性、从而抑制植物生长，表现出“灰色世界”效应(Brown-world effect)。
中科院成都生物研究所孙书存研究员课题组赵川博士等在青藏高原东部典型的高寒草甸，通过野外微宇宙控制试验，模拟构建土壤有机质→蚯蚓→步甲三级食物链，研究了土壤食物网中捕食者诱导的营养级联效应及其生态系统功能。研究发现：步甲并没有改变蚯蚓的数量，而是迫使蚯蚓向深层土壤转移，从而间接地提高了下层土壤的孔隙度和有效养分含量，并最终增加了植物地上生物量。该结果表明，碎屑食物网中的捕食者可以通过改变猎物的行为特征而促进植物生长。这一结果与生态学传统理论的预测相反，揭示了捕食者影响植物生长的一种新机制。
该研究结果已发表于动物学研究领域的期刊Journal of Animal Ecology。
该研究得到了国家自然科学基金和全球变化重大研究计划项目的资助。（生物谷 Bioon.com）
生物谷推荐的英文内容
Journal of Animal Ecology DOI: 10.1111/1365-2656.12058
Predatory beetles facilitate plant growth by driving earthworms to lower soil layers
Chuan Zhao1, John N. Griffin2, Xinwei Wu3, Shucun Sun1,3,*
1. Theory suggests that predators of soil-improving, plant-facilitating detritivores (e.g. earthworms) should suppress plant growth via a negative tri-trophic cascade, but the empirical evidence is still largely lacking.
2. We tested this prediction in an alpine meadow on the Tibetan Plateau by manipulating predatory beetles (presence/absence) and quantifying (i) direct effects on the density and behaviour of earthworms; and (ii) indirect effects on soil properties and above-ground plant biomass.
3. In the absence of predators, earthworms improved soil properties, but did not significantly affect plant biomass. Surprisingly, the presence of predators strengthened the positive effect of earthworms on soil properties leading to the emergence of a positive indirect effect of predators on plant biomass.
4. We attribute this counterintuitive result to: (i) the inability of predators to suppress overall earthworm density; and (ii) the predator-induced earthworm habitat shift from the upper to lower soil layer that enhanced their soil-modifying, plant-facilitating, effects.
5. Our results reveal that plant-level consequences of predators as transmitted through detritivores can hinge on behaviour-mediated indirect interactions that have the potential to overturn predictions based solely on trophic interactions.
6. This work calls for a closer examination of the effects of predators in detritus food webs and the development of spatially explicit theory capable of predicting the occurrence and consequences of predator-induced detritivore behavioural shifts.
