Synergistic promotion of soil fauna and water addition on dung decomposition differs among dung types in a semi-arid steppe in China

Résumé fourni par la source

Herbivore dung decomposition plays a vital role in grassland ecosystems and is affected by both dung quality and soil abiotic and biotic factors. However, less information is available on the interactive effects of dung quality, soil biota, and climate on the process. We conducted an in-situ experiment using the ‘dung and soil’ mesocosm to examine the individual and combined impacts of soil fauna and moisture on decomposition of dung from cattle and horse, the primary grazers with distinct digestive systems in the native steppes of northern China. We found that (1) soil fauna accelerated the reduction of carbon (C) and nitrogen (N) content in dung, but did not alter dung dry mass loss. (2) Water addition increased dung dry mass loss, especially for horse dung, but did not significantly alter dung wet mass and C and N contents at the early stage of dung decomposition. (3) There was a synergistic promoting effect of water addition and soil fauna on soil microbial respiration and dung mass loss, especially for horse dung at the early stages of dung decomposition. (4) Soil fauna exhibited no direct effects on the dung mass loss; instead, it influenced decomposition indirectly by modulating microbial respiration through changes in dung moisture content; and this indirect effect was contingent on dung types: significant for horse dung but absent for cattle dung. Water addition directly promoted the mass loss of horse dung but not cattle dung. These findings indicate that dung type mediates the effects of both soil fauna and moisture on decomposition processes, and suggest it crucial to incorporate herbivore types into ecosystem models for accurately predicting carbon and nutrient cycling.

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