Soil fauna regulates litter decomposition and soil organic matter transformation, acting as both litter and microbial feeders. Whether these feeding modes shift along environmental gradients remains unclear. We tested if microbivory increases with decreasing litter quality and in colder climates, both factors limiting detritus digestion by fauna. Using stable isotope composition (δ¹³C, δ¹⁵N) of 7,408 soil invertebrate samples from 228 forest sites across temperate to tropical biomes, we determined δ¹⁵N values are positively associated with litter C:N ratio and mean annual temperature, indicating a shift from detritivory toward microbivory under low litter quality with additional modulation by climate. In contrast, δ¹³C values showed no consistent association with litter C:N ratio or climate, reflecting context dependent microbial carbon routing. Our findings highlight litter quality as the primary driver of the detritivory-to-microbivory shift in soil fauna, with implications for predicting changes in climate and plant communities on carbon cycling in terrestrial ecosystems

Soil fauna regulate litter decomposition and carbon redistribution in soil, acting as both litter and microbial feeders. However, whether these feeding roles shift along environmental gradients remains unclear. We tested whether microbivory increases in cold climates and with lower litter quality – both factors limiting detritus digestion by fauna. Using stable isotope composition (δ¹³C, δ¹⁵N) of 7,263 soil invertebrate samples across temperate and tropical forests, we found that litter carbon percentage positively correlated with trophic level, indicating higher microbivory in low litter quality systems. This effect was more evident in mesofauna, while macrofauna showed an ability to incorporate more recalcitrant plant carbon. Climate type had no general effect on feeding strategies. Our findings suggest low litter quality shifts soil animals from detritivory to microbivory, highlighting the importance of litter quality over climate in shaping soil food webs. Understanding these shifts is crucial for predicting litter decomposition and global carbon cycling

Soil fauna regulate litter decomposition and carbon redistribution in soil, acting as both litter and microbial feeders. However, whether these feeding roles shift along environmental gradients remains unclear. We tested whether microbivory increases in cold climates and with lower litter quality – both factors limiting detritus digestion by fauna. Using stable isotope composition (δ¹³C, δ¹⁵N) of 7,263 soil invertebrate samples across temperate and tropical forests, we found that litter carbon percentage positively correlated with trophic level, indicating higher microbivory in low litter quality systems. This effect was more evident in mesofauna, while macrofauna showed an ability to incorporate more recalcitrant plant carbon. Climate type had no general effect on feeding strategies. Our findings suggest low litter quality shifts soil animals from detritivory to microbivory, highlighting the importance of litter quality over climate in shaping soil food webs. Understanding these shifts is crucial for predicting litter decomposition and global carbon cycling

Soil fauna regulates litter decomposition and soil organic matter transformation, acting as both litter and microbial feeders. Whether these feeding modes shift along environmental gradients remains unclear. We tested if microbivory increases with decreasing litter quality and in colder climates, both factors limiting detritus digestion by fauna. Using stable isotope composition (δ¹³C, δ¹⁵N) of 7,408 soil invertebrate samples from 228 forest sites across temperate to tropical biomes, we determined δ¹⁵N values are positively associated with litter C:N ratio and mean annual temperature, indicating a shift from detritivory toward microbivory under low litter quality with additional modulation by climate. In contrast, δ¹³C values showed no consistent association with litter C:N ratio or climate, reflecting context dependent microbial carbon routing. Our findings highlight litter quality as the primary driver of the detritivory-to-microbivory shift in soil fauna, with implications for predicting changes in climate and plant communities on carbon cycling in terrestrial ecosystems