Trophic cascades, reciprocal predator–prey effects that alter changes of nonadjacent trophic level, are mostly demonstrated for aboveground ecosystems. However, the role of trophic cascade effects in detrital food webs has been less explored.  

In terrestrial detrital food webs, Collembola, an important component of soil meso‐fauna, are a significant prey source for spiders. Collembola also play a significant role in decomposition processes by feeding on plant litter and stimulating microbial activities. It is not known how nitrogen (N) deposition and potential feedbacks could influence trophic cascades in simplified spider–Collembola detrital food webs. 

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to examine how simulated N decomposition influenced the trophic cascade effects of spiders on leaf litter decomposition. They experimentally manipulated the abundance of spiders with two foraging strategies, sit-and-wait (SW) and actively hunting (AH), in microcosms with Collembola.
They found that spiders, irrespective of foraging strategies, indirectly reduced litter decomposition rates but only under N addition conditions, which was likely due to the combined effect of spiders and N reducing Collembola abundance. 

The combined effects of N and spider predators on Collembola abundance triggered significant reductions in litter decomposition and subsequent trophic cascades. 

“We show that changes in N concentration can impact the trophic cascade effects of spiders in the detritus‐based food web by changing densities of Collembola”, said Dr. LIU Shengjie, the first author of the study. 

“Spider foraging strategies had different impacts on Collembola suppression”, added LIU. 

The study entitled “Nitrogen addition changes the trophic cascade effects of spiders on a detrital food web” has been published in Ecosphere.  

Contact 

YANG Xiaodong Principal Investigator  

Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China     

E-mail: yangxd@xtbg.ac.cn