Conversion of rainforest to rubber plantations impacts rhizosphere soil mycobiome and alters soil biological activity

In Asia, large swathes of rainforest have been converted to rubber plantations, with major consequences for biodiversity and ecosystem services. However, the impact of this land use conversion on rhizosphere soil mycobiome has not yet been addressed. This study aims to investigate how rhizosphere soil fungal communities and their associated biological activity (soil respiration, soil methane (CH4) and potential soil enzyme production) are impacted by the conversion of rainforest to rubber plantations. Fungal richness and community composition in rhizosphere soils collected from natural rainforests, immature rubber, and mature rubber plantations were analyzed using paired-end Illumina sequencing. The conversion of natural rainforest to rubber plantations significantly altered fungal community composition of specific functional groups (saprotrophs, pathogens and mycorrhiza). We observed significant loss of saprotrophic and ectomycorrhizal fungi in natural rainforests, but enrichment of plant pathogenic fungi in immature rubber plantations. The mechanism underlying the effects of forest conversion on changes of fungal communities is related to reductions in soil pH, total nitrogen (N) and ammonium (NH4) in rubber plantations. Conversion to rubber plantation also resulted in decline of soil respiration rates and less potential for cellulase and chitinase productions. The significant negative correlations between fungal richness and soil respiration in mature rubber plantations indicated high competition among fungi and low nutrient availability in this system. We demonstrate the negative consequences of the conversion of rainforest to rubber plantations on soil biological activity and significant changes in fungal community composition that could threaten long-term ecosystem functions.