Legacy Effects Overshadow Tree Diversity Effects on Soil Fungal Communities in Oil Palm-Enrichment Plantations

Abstract

Financially profitable large-scale cultivation of oil palm monocultures in previously diverse tropical rain forest areas constitutes a major ecological crisis today. Not only is a large proportion of the aboveground diversity lost, but the belowground soil microbiome, which is important for the sustainability of soil function, is massively altered. 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 fungal diversity. 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, overshadowing the structuring effects of the vegetation, at least in the initial years after enrichment plantings.

Early Effects of Fertilizer and Herbicide Reduction on Root-Associated Biota in Oil Palm Plantations

“…Here, we show that soil and root mineral nutrients were unaffected in the initial phase, one year after the start of the experimental treatments. This result agrees with other short-term studies, where management was stopped or reduced [51][52][53] and might have been expected because it is well known that agricultural soil usage has long-lasting legacy effects [54,55]. For example, recovery of N cycling takes almost a decade [56,57].…”

“…However, the opposite that recovery of AMF is one of the earliest effects in the root-associated fungal community is a novel result. This effect appears to be specific to roots since the presence of AMF in soil was unaffected in plots of oil palm plantations after discontinuing fertilization [54]. The observed recovery in AMF abundance has the potential for shifts in ecosystem functions since mycorrhizal fungi play a prominent role in plant nutrition and increase plant protection from pathogens [64,65].…”

Diversity and Ecological Guild Analysis of the Oil Palm Fungal Microbiome Across Root, Rhizosphere, and Soil Compartments

“…Development of next generation sequencing approaches has provided opportunities for culture-independent analysis of microbiomes for fine-level resolution of the diversity and composition of plant-associated microbiomes, characterization of the factors which shape community composition, and to reveal microbial interactions which affect plant health (Hilton et al, 2021). Several studies have used culture-independent approaches to investigate how plantation management (Ballauff et al, 2020) and the conversion of native forest to oil palm cultivation impacts the soil microbiome. Soil bacterial and fungal communities are impacted by oil palm cultivation (Lee-Cruz et al, 2013;Tripathi et al, 2016), including reduced abundance of ectomycorrhizal fungal associates of dipterocarp trees (McGuire et al, 2015), and increased abundance of AMF (Krashevska et al, 2015;Sahner et al, 2015).…”

Host plant richness and environment in tropical forest transformation systems shape arbuscular mycorrhizal fungal richness

“…In soils of south-east Asian forest conversion systems (Borneo, Sumatra, Malaysia) massive shifts in whole fungal community composition were found but the relative abundance of Glomeromycota appeared to be little affected (Kerfahi et al, 2014;McGuire et al, 2015;Brinkmann et al, 2019). For example, McGuire et al (2015) found an overall decrease in fungal species richness (-30%) in plantation soil but a higher abundance of Glomerales in soils of oil palms than in primary or regeneration forests, while other studies using similar fungal amplicon-based sequencing techniques found no clear effects on AMF abundances (Kerfahi et al, 2014;Brinkmann et al, 2019;Ballauff et al, 2020).…”

“…For example, McGuire et al. (2015) found an overall decrease in fungal species richness (-30%) in plantation soil but a higher abundance of Glomerales in soils of oil palms than in primary or regeneration forests, while other studies using similar fungal amplicon-based sequencing techniques found no clear effects on AMF abundances ( Kerfahi et al., 2014 ; Brinkmann et al., 2019 ; Ballauff et al., 2020 ).…”