Linkages between root traits, soil fungi and aggregate stability in tropical plant communities along a successional vegetation gradient

Determining which abiotic and biotic factors influence soil aggregate stability (MWD) in tropical climates is often confounded by soil type. We aimed to better understand the influence of soil physical and chemical components, vegetation and fungal abundance on MWD of a Ferralsol along a successional gradient of vegetation in New Caledonia. Five plant communities (sedge dominated, open sclerophyllous shrubland, Arillastrum forest, Nothofagus forest and mixed rainforest) were studied. For each community, MWD, soil texture, soil organic carbon (SOC), iron (Fe) and aluminium (Al) sesquioxides, root length density (RLD), specific root length (SRL), root mass density (RMD) and fungal abundance were measured. Generalized linear models were used to predict MWD from soil and plant trait data. The best prediction of MWD combined abiotic and biotic factors. Along the gradient, Fe increased MWD, while root traits, fungal abundance and SOC modified MWD. From the sedge-dominated community to Arillastrum forest, RMD and SOC increased MWD, while between Nothofagus and mixed rainforest, it was likely that floristic composition and fungal communities influenced MWD. Plant community, the intrinsic nature of Ferralsol and fungal abundance all modified MWD. However, the specific effect of microbial communities should be addressed through a metagenomics approach to elucidate microbial interactions with plant communities.