Litterfall sustains soil fertility and nutrient reallocation to the soil and atmosphere. Litter decomposition governs carbon and nutrient cycling in terrestrial ecosystems. However, the interactions between soil fauna and litter diversity are poorly understood.

In a study published in Journal of Ecology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Wuhan Botanical Garden (WBG) of the Chinese Academy of Sciences tackled a bottleneck in the understanding of litter mixture effects on litter decomposition. They highlighted the importance of inclusion of soil fauna and shed light on the decomposition of litter mixtures. 

The researchers carried out a global meta-analysis to elucidate how soil fauna influenced litter mixture decomposition rate based on 55 published studies with 873 fauna inclusion/exclusion comparisons in field litterbag experiments.

They tried to reveal the averaged outcome of global decomposition of litter mixtures in the presence or absence of soil fauna, and also explored the interaction between soil fauna effect and precipitation during decomposition of litter mixtures.  

They found that, in their dataset including litterbag studies with different mesh sizes, litter mixture did not enhance litter decomposition globally. Plant species mixing enhanced litter decomposition when soil fauna was present, whereas plant species mixing reduced decomposition in the absence of soil fauna. 

Furthermore, the researchers investigated how variation in precipitation influenced the interaction between soil fauna and litter diversity. They found that the soil fauna effect in litter mixtures increased at reduced precipitation levels. At high precipitation levels (>2,000 mm/year) the litter mixture effect was positive in the absence of soil fauna but non-significant in the presence of fauna. 

"Our results highlight the importance of soil fauna in promoting decomposition of litter mixtures," said Gbadamassi Dossa, a corresponding author of the study. 

The researchers further proposed that the influence of climatic factors such as precipitation on the interactions between soil fauna and litter species in mixtures during decomposition should be investigated in more depth. 

Soil fauna accelerate litter mixture decomposition. (Image by Gbadamassi Dossa)