COS 312-4 - Soil fungal and arbuscular mycorrhizal communities in response to soil phosphorus gradient in managed subtropical grasslands

Abstract: The kingdom fungi in the soil are highly diverse that support plant fitness and provide an array of ecosystem functions and services. Arbuscular mycorrhizal fungi (AMF), as one of the most abundant and widespread symbiotic fungal community occurring in various ecosystems, helps to improve plant production by mobilizing soil nutrients (e.g., notably phosphorus), improving soil structure, and enhancing tolerance to soil biotic and abiotic stresses. Prior research has revealed that AMF has potential to facilitate soil phosphorus (P) uptake (e.g., converting recalcitrant inorganic and organic P compounds into bioavailable forms) and therefore reduce phosphorus loss through runoffs and leaching by promoting plant-soil interactions. However, less is known about how soil P (including both total and available P) affects fungal and AMF diversity and community, which could feedback to further regulate P cycling. In this study, we aim to explore how AMF communities respond to different soil phosphorus levels and to determine what factors contribute to their response. Our study area, Archbold Biological Station’s Buck Island Ranch in Florida, USA, consists of subtropical grasslands managed for beef cattle production and was fertilized annually with N, P, and K from the early 1970’s to 1987, resulting in long-term build-up and legacy of soil P. Representative rhizosphere soil samples were taken from sites with high, medium, and low soil P levels and were analyzed for soil characteristics, fungi community, and AMF species predictions using ITS 1 primer. Our results showed that fungi community composition and diversity were similar across high (136.0 ±16.1 mg/kg), medium (101.0 ± 9.01 mg/kg), and low (67.7 ± 5.77 mg/kg) soil total P levels. However, AMF showed differences in their relative abundance along the soil P gradient. Specifically, our preliminary results showed significant positive correlations between relative abundance of AMF and soil total P concentration. Redundancy Analysis (RDA) ordination showed that total P, Mehlich-1 P, pH, and soil moisture had significant correlations with the fungal communities, in which total P showed the strongest effect on fungal community composition. For AMF, total P, Mehlich-1 P, and pH had significant correlations with AMF community. Our results suggest that AMF community and composition are more responsive to soil P gradient in managed subtropical grasslands, with high relative abundance at high P soils. Understanding AMF community relationship with soil P level and environmental variables could enhance our understanding of AMF-soil symbioses and help to guide the management of AMF and sustainability of agroecosystems.