Interkingdom plant-microbial ecological networks under selective and clear cutting of tropical rainforest

Abstract

Recent studies have revealed that interkingdom relationships in below-aboveground metacommunity may contribute to ecosystem functions more than species diversity. While effects of deforestation on aboveground interactions have been well studied, the responses of interactions among plant, soil bacterial and fungal communities to deforestation are pooly understood and their effects on vegetation restoration remain unknown. We sequenced soil 16S rRNA and ITS genes from the primary forest without logging history and secondary forests that had been clear cut or selective cut and left to recover for up to 50 years in the typical tropical rainforest in Hainan Island. Soil bacterial-fungal, plant-bacterial and plant-fungal associations were illustrated via ecological network analysis, and their correlations with plant composition, soil and litter properties were examined to explore the links to ecosystem functions.A higher negative proportion of bacterial-fungal interactions was found in selective cut sites while a higher positive proportion presented in clear cut sites. The changes after selective cut was related to tree composition and reductions in nitrogen and phosphorus content from soil and litter, indicating increased competition for nutrients, decoupling of communities and niche differentiation. The bacterial-fungal interaction changes after clear cut was associated with decrease in tree biomass and soil carbon content while increase in litter carbon content, implying increased co-operation in nutrient strategies and community homogenization. This ecological implications of bacterial-fungal interaction after clear cut was also applicable to plant-microbial interaction showing modular structure and strong across-module associations and significant correlations with litter carbon and soil nitrogen availability, which was indicative of a particular collection of microbial members under given plant species driving by changes in carbon and nitrogen content. Overall, the responses of bacterial-fungal and plant–microbe interactions to selective cut may in term promote the recovery of plant diversity during forest restoration, whereas these responses to clear cut may hinder the recovery of plant community diversity, and more costly restoration approaches based on different tree species planting will be required. This study suggested that the interkingdom interactions in below-aboveground metacommunity are indicative of changes in tree composition and soil fertility during the restoration of logged forest, and changes in such interkingdom interactions could in turn influence plant diversity and soil nutrients transformation.