Legacy effects overprint tree diversity effects on soil fungal communities in oil palm-enrichment plantations

Financially profitable large-scale cultivation of oil palm monocultures in previously diverse tropical rain forest areas constitutes a major ecological crisis today. Not only a large proportion of the aboveground diversity is lost, but the belowground soil microbiome is massively altered with importance consequences for soil health and functions. Intermixing oil palms with native tree species promotes vegetation biodiversity and stand structural complexity in plantations, but the impact on soil fungi remains unknown. Here we analyzed the diversity and community composition of soil fungi three years after tree diversity enrichment in an oil palm plantation in Sumatra (Indonesia). We tested the effects of tree diversity, stand structural complexity indices and soil abiotic conditions on the diversity and community composition of soil fungi. We hypothesized that the enrichment experiment alters the taxonomic and functional community composition, promoting soil health and functions. Fungal community composition was affected by soil abiotic conditions (pH, N and P), but not by tree diversity and stand structural complexity indices. These results suggest that intensive land-use and abiotic filters are a legacy to fungal communities, overruling structuring effects of the vegetation at least in the initial years after enrichment plantings.