Banca de DEFESA: GABRIELLE CUSTODIO MELO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GABRIELLE CUSTODIO MELO
DATE: 05/08/2025
TIME: 09:00
LOCAL: Auditório do PPG Ciência do Solo
TITLE:

Microbiological indicators, stocks and carbon fractions in a silvopastoral system in the southern Agreste region of Pernambuco

KEY WORDS:

Organic carbon. Nutrient cycling. Microorganisms. Carbon stability. Ecosystem services.

PAGES: 82
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Microbiologia e Bioquímica do Solo
SUMMARY:

Anthropogenic activities have been and continue to be responsible for the exponential emission of carbon dioxide (CO₂), contributing to climate change. One of the strategies for mitigating atmospheric CO₂ involves carbon storage in the soil through conservation management systems, such as silvopastoral systems, which can be enhanced by the use of arboreal legumes. Understanding soil carbon stocks is directly linked to the dynamics of organic carbon and microbial activity, which are responsible for nutrient cycling and the formation of soil organic matter (SOM). Therefore, the objective of this study was to quantify nitrogen and total carbon stocks, as well as carbon associated with soil organic matter fractions, and to evaluate the dynamics of microbial activity in a silvopastoral system composed of signalgrass (Urochloa decumbens Stapf.) intercropped with the arboreal legume Mimosa caesalpiniifolia Benth. (sabiá). The study was conducted in Garanhuns, Pernambuco, Brazil, in a 9.18 ha area using a randomized block design with three replications. The systems and positions evaluated were: a silvopastoral system with four sampling points based on the distance from the double row of legumes (0, 3, 6, and 12.5 meters); sabiá monoculture; and signalgrass monoculture with and without fertilization. Soil samples were collected down to 100 cm depth (0–10, 10–20, 20–40, 40–60, and 60–100 cm) to determine carbon and nitrogen concentrations and stocks, carbon in soil organic matter fractions (SOM), microbial biomass, and basal soil respiration. Soil depth had a significant effect (p < 0.1) on microbiological indicators, carbon and nitrogen concentrations and stocks, as well as on organic carbon fractions and their respective stocks. The effects of systems and sampling positions (p < 0.1) were observed for the hot water-extractable carbon fraction and its stock at 0–100 cm. Microbial biomass carbon differed only between the 20–40 cm (189.70 mg kg⁻¹) and 60–100 cm (119.86 mg kg⁻¹) layers. Basal respiration remained low throughout the soil profile and, together with qCO₂, did not indicate oxidative stress in the microbiota. Hot water-extractable carbon showed a gradual effect with depth, as did particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), both being higher in the 0–10 cm layer compared to deeper layers. The hot water-extractable carbon stocks (0–100 cm) were highest in the fertilized signalgrass monoculture, differing only from the farthest points from the legume rows in the silvopastoral system. The humin fraction showed the highest concentrations compared to fulvic and humic acids, especially in the surface layer. Silvopastoral systems show potential for storing organic carbon at greater depths, providing favorable conditions for both microorganisms and the stabilization processes of soil organic matter.

COMMITTEE MEMBERS:
Interno - ***.952.028-** - FELIPE JOSÉ CURY FRACETTO - USP
Interno - MARIO DE ANDRADE LIRA JUNIOR
Externo ao Programa - 2346742 - ALEXANDRE CARNEIRO LEAO DE MELLO - UFRPE