Agricultural intensification systems enhance microbial activity and necromass contribution to soil carbon sequestration in tropical agroecosystems

• Ano de defesa: 2025
• Autor(a) principal: Pimentel, Marcelo Laranjeira [UNESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Fungal necromass; Managed pasture; Carbon sequestration; Integrated agricultural systems; Sustainable agriculture
• Link de acesso: https://hdl.handle.net/11449/259620

The Amazon region, a critical global carbon (C) sink, is increasingly threatened by agricultural expansion, causing soil disturbances that impact microbial activity, soil aggregation, and C dynamics. In the southern Amazon, Brazil, the potential of agricultural systems to sequester carbon (C) and improve soil health through microbial necromass remains largely unexplored. The scarcity of studies on the dynamics, contributions, and responses of microbial necromass in tropical systems highlights a critical gap, limiting not only the advancement of sustainable soil management strategies but also the Amazon region's contribution to mitigating the effects of global climate change. This study investigated the effects of agricultural intensification systems - crop succession (CS), crop-livestock integration (ICL), crop-livestock-forest integration (ICLF) and managed pasture (MP), after 11 years, on microbial activity, aggregate stability and C storage via microbial necromass in southern Amazonia. Soil samples were collected from 0.0-0.05, 0.05-0.1, 0.1-0.2 e 0.2-0.3 m depth. The results showed that more intensified systems, such as ICL, ICLF and MP, increased the content of C and N, with emphasis on the increase in microbial biomass carbon (MBC), enzyme activity and microbial quotient, indicating greater microbial efficiency in the use of C. In addition, MP and ICLF showed greater stability of soil aggregates, evidenced by the increase in glomalin and average diameter of aggregate weight. Microbial necromass (MNC) was identified as a critical component in C sequestration, with a greater contribution from fungal necromass (>70%) in all systems. The ICLF system had the highest necromass accumulation coefficient (NAC), and biological and chemical factors such as MBC, acid phosphatase, β-glucosidase, arylsulfatase, phosphorus, cation exchange capacity, N and C, were determinants in the formation of MNC. These findings highlight the fundamental role of integrated systems and well-managed pastures in improving soil health, promoting nature-based solutions and carbon sequestration in the southern Amazon, Brazil, contributing to more sustainable and efficient agricultural practices.