Effects of biochar addition on soil fauna communities-A meta-analysis

Soil fauna is an important part of global biodiversity and plays a vital role in ecosystems. The microbial communities in soil fauna can have significant impacts on soil fertility, as microbial communities play a pivotal role in soil function by supporting ecological integrity and agricultural productivity. This study assesses the effect of biochar on soil fauna and response of microbial communities. Biochar is a highly porous organic carbon material, and the impact of biochar on microbial communities in soil fauna remains unclear. To date, no quantitative or comprehensive investigation has been undertaken to examine the effects of biochar on microbial communities in soil fauna. In this paper, we aim to quantify the effects of biochar on the abundance and diversity of soil fauna communities in various environments by conducting a meta-analysis of 24 studies and analysing 459 observations. The impact of biochar on soil fauna communities was determined by analysing the responses of soil fauna that included differences in biochar feedstock, pH and pyrolysis, application rates and application times, as well as soil fauna with different physiological characteristics (body size, presence of exoskeletons). The results showed that biochar had a neutral (non-significant) effect on the soil fauna community, with a total mean effect size (Hedge's g) = -0.04 (CI: -0.28; -0.20). Results Data validation using Egger regression showed no publication bias. Higher pH biochar and biochar from conventional pyrolysis were beneficial to soil fauna, but not significant (QM (df = 3) = 4.07, p = .25). In addition, body size of soil animals significantly reflected different sensitivities to biochar application, with Medium-sized animals benefiting the most from biochar addition (0.35; CI: 0.05; 0.65; n = 6; 56). Animals with (n = 11; 125) and without exoskeletons (n = 17; 308) also showed favourable and unfavourable responses to biochar addition, respectively. This study can provide basic data for the evolutionary pattern of animal communities during biochar soil amendment, as well as information for the comprehensive evaluation of the environmental and biological effects of biochar.