Microbiome resilience of Amazonian forests: Agroforest divergence to bacteria and secondary forest succession convergence to fungi

Abstract

Over the past decade Amazonian rainforest has been converted to commodity production (pasture and soybean) at a rate of 6.54 M hectares per year (Kim et al., 2015). To circumvent the limitations presented by nutrient-poor soils, many farmers adopt slash-andburn practices, which use fire to quickly mineralize nutrients stored in the plant biomass and make them available for subsequent crops.

On the complexity of agroforestry systems

“…Regarding management, our results highlight the importance of generating in situ mulch containing both pruned leaves and woody material. This is in line with other studies that showed the importance of this practice for nutrient cycling from leaf litter (Froufe et al, 2019;Schneidewind et al, 2018) and woody logs for soil biodiversity (Leite et al, 2023). As our results show, the combination of nutrients and C inputs from this practice stimulates the formation of stabilised SOC stocks and, therefore, agroforestry farmers can enhance nutrient cycling and SOC storage, simultaneously.…”

“…Also, the interaction between ACI and clay is significant for pH, meaning that particularly on sandy soils, pH tends to increase in more complex systems over time which could reflect successional changes in micro-bial communities in highly complex systems. It should be noted that farmers of older, highly complex systems in our study maintained frequent pruning & mulching regimes over the years which is probably necessary to sustain resilient microbiomes (Lehmann et al, 2020;Leite et al, 2023). Hence, while our results overall suggest that complexification can increase ecosystem service provision relatively fast, the associated practices such as maintaining high diversity, density and in situ biomass cycling, should be maintained in the long-term.…”

The Microbial Community Structure in the Rhizosphere of Theobroma cacao L. and Euterpe oleracea Mart. Is Influenced by Agriculture System in the Brazilian Amazon

“…These results suggest that the AFS may have a positive effect on the abundance of nitrogen-fixing microorganisms and the availability of metabolically available nitrogen forms for both crops [ 66 , 67 , 68 ]. In this sense, the complexity of the bacterial community in the soil of agroforestry systems in the Amazon demonstrates being mostly influenced by soil nutrient availability, while the fungal community is more closely linked to variables related to above-ground plant biomass [ 69 ]. Thus, it is essential to emphasize that factors such as biogeography, climate, soil nutritional conditions, and adopted management practices, such as the use of pesticides or the degree of shading in cocoa agroforests, play a determining role in the structure of these communities that can be distinctly influenced.…”

“…Previous studies have shown that some agroforestry system models, such as cocoa systems, may share similarities with natural forests, suggesting a possible relationship between the richness and diversity of the microbial community and soil nutrient dynamics [ 66 , 82 , 83 , 84 , 85 ]. However, it has been evidenced that an increase in the diversity of associated species is not the primary determining factor for microbial group abundance and soil fertility variations [ 67 , 69 , 86 , 87 ]. Therefore, these data suggest that agroforestry systems, although sharing similarities in terms of vegetation and biodiversity with forests, may differ concerning the abundance of microbial communities and soil nutrient dynamics, depending on the geographic region, climate, associated species, and agroforestry management age.…”

Converting Low-Productivity Pasture to Well-Managed Pasture and Silvopastoral System Cause Relevant Changes in Soil Chemical and Microbiological Characteristics

“…Integrated systems are studied as a production alternative associated with conservation practices [16] to simulate the characteristics of natural ecosystems [17] and those that notably improve the soil chemical, physical, and microbiological properties [18,19]. Currently, the adoption of integrated systems in Brazil is extremely important for several reasons.…”