SOIL BIODIVERSITY AS THE CENTRAL ROLE OF PLANT-SOIL FEEDBACKS IN AMAZON AGROFORESTRY SYSTEMS

Abstract

Interactions between plants, microorganisms, and soil occur continuously and can have positive or negative effects, known as plant-soil-feedback (PSF), but are still poorly understood in Amazonian soils. Agroforestry systems (AFS) are crucial for food security; however, they are dependent on natural processes and ecosystem services to maintain their sustainability and productivity. Furthermore, deforestation and land-use change can intensify extreme seasonal events, such as heatwaves and heavy rain, leading to immeasurable losses for biodiversity. The objective of this project is to evaluate and apply the PSF model in Amazonian SAFs through two complementary studies. The first study will characterize the taxonomic and functional composition of the soil, as well as the composition of decomposer fungi in the litter layer, in AFS areas, primary forest, and degraded pasture during the dry and rainy seasons. Nutrient content, dissolved organic matter, and fungal community of the litter layer will also be evaluated. The soils will be characterized in depth for fertility, organic matter fractionation, total carbon, and enzyme activity involved in C, P, and S cycling. The second study will apply the PSF model in a greenhouse experiment to evaluate the effect of plant and healthy soil inoculum on the recovery of degraded soils. The assay is divided into two stages: first, soils were seeded with three native species in SAF, forest, and pasture soils, becoming inoculants for the second stage. These soils were inoculated into degraded pasture soils, and new plants were grown in co-specific and hetero-specific soils. During the second trial, plant growth rate, biomass production, and nutrient absorption will be measured, as well as quantification of 16S rRNA and ITS soil genes. The results will allow us to identify the interactions of the inoculants with different native species, identifying key processes to understand the soil-plant interactions for the recovery of degraded areas. This project is linked to the joint call FAPESP-FAPEAM "Plant-soil feedbacks in the Amazon Forest and in agricultural systems in the state of Amazonas" (Process: 20/08927-0).