Search

Deforestation threatens the integrity of the Amazon biome and the ecosystem services it provides, including greenhouse gas mitigation. Forest-to-pasture conversion has been shown to alter the flux of methane gas (CH4 ) in Amazonian soils, driving a switch from acting as a sink to a source of atmospheric CH4 . This study aimed to better understand this phenomenon by investigating soil microbial metagenomes, focusing on the taxonomic and functional structure of methane-cycling communities. Metagenomic data from forest and pasture soils were combined with measurements of in situ CH4 fluxes and soil edaphic factors and analysed using multivariate statistical approaches. We found a significantly higher abundance and diversity of methanogens in pasture soils. As inferred by co-occurrence networks, these microorganisms seem to be less interconnected within the soil microbiota in pasture soils. Metabolic traits were also different between land uses, with increased hydrogenotrophic and methylotrophic pathways of methanogenesis in pasture soils. Land-use change also induced shifts in taxonomic and functional traits of methanotrophs, with bacteria harbouring genes encoding the soluble form of methane monooxygenase enzyme (sMMO) depleted in pasture soils. Redundancy analysis and multimodel inference revealed that the shift in methane-cycling communities was associated with high pH, organic matter, soil porosity and micronutrients in pasture soils. These results comprehensively characterize the effect of forest-to-pasture conversion on the microbial communities driving the methane-cycling microorganisms in the Amazon rainforest, which will contribute to the efforts to preserve this important biome.

Abstract: Estimating primary productivity over time is challenging for plant ecologists. The most accurate biomass measurements require destructive sampling and weighing. This is often not possible for manipulative studies that [...]

The complex interactions between plant roots and soil microorganisms are, broadly, well described. Yet the patterns of microbe–microbe interaction and their association with the root functional traits are less known especially in plant communities at the edges of agricultural landscapes. To address this gap, we measured the active soil microbial communities with and without the presence of plant roots, using in situ root exclusions, in four plant communities at the edges of agricultural fields: undisturbed natural deciduous forests (FOREST1), coniferous forests (FOREST2), rehabilitated agroforests (AGROFOREST) and perennial herbaceous grass buffers (GRASS). Amplicon‐based analysis of 16S rRNA and ITS transcripts was used to evaluate soil bacterial, archaeal and fungal communities, and their interactions, with 'roots' and with 'no roots'. Plants roots were measured for a suite of functional traits and explored in association with microbial community composition. Significant differences in bacterial and archaeal but not fungal diversity were observed between soil plots with 'roots' and with 'no roots'. Network analysis illustrated intra and inter kingdoms co‐occurrence patterns respond to the presence of plant roots, with GRASS exhibiting distinct patterns in comparison to tree‐dominated soils. A shift in microbial hub from bacterial to fungal was observed with the exclusion of roots; Planctomycetes (OM190)_10 was replaced by Archaeorhizomyces in AGROFOREST site. Microbial taxa strongly correlate with root traits especially specific root length, root diameter and root tissue density indicating root traits are predictors of microbial community composition. This study validates the vital role of root traits in predicting plant–microbe interactions and highlights the key role of fungi in microbial interkingdom interactions when roots are absent. These findings have significant ecosystem level implications, with the rising interest in associated biodiversity in and at the edges of agricultural landscapes, this work suggests that plant community selection for specific root traits may drive microbial community structure and ecosystem services. [ABSTRACT FROM AUTHOR]