From overgrazed land to forests: assessing soil health in the Caatinga biome

Author(s):Show less -

Bieluczyk, Wanderlei ; Souza, Pablo Acacio dos Santos ; de Oliveirab, Andressa Silva ; Sampaio, Regina Maria Barreto Campello ; Ferreira, Juscelia da Silva ; Dantas, Edilandia Farias ; Lambais, George Rodrigues ; Menezes, Romulo Simoes Cezar ; de Camargo, Plinio Barbosa ; de Medeiros, Erika Valente ; da Franca, Rafaela Felix ; Sampaio, Everardo Valadares de Sa Barretto ; de Freitas, Ana Dolores Santiago

• Document type: Journal article
• Source: Journal of Environmental Management; v. 374, p. 17-pg., 2025-01-10.

Abstract

Overgrazing is the primary human-induced cause of soil degradation in the Caatinga biome, intensely threatening lands vulnerable to desertification. Grazing exclusion, a simple and cost-effective practice, could restore soils' ecological functions. However, comprehensive insights into the effects of overgrazing and grazing exclusion on Caatinga soils' multifunctionality are lacking. This study examines (i) how overgrazing impacts multiple soil indicators, functions, and overall soil health (SH) and (ii) whether natural early forest growth post-grazing exclusion enhances critical soil functions for ecosystem restoration. We compared preserved dense forests, longterm overgrazed pastures (over 30 years), and young fenced-off open forests (three years old) along a longitudinal transect in the Caatinga biome: 36 degrees W (Sao Bento do Una), 37 degrees W (Sertania), and 40 degrees W (Araripina). Soil samples from the 0-20 cm layer were analyzed for thirteen physical, chemical, and biological indicators for a structured SH assessment, calculating index scores based on soil functions. Forest-to-pasture transition and subsequent overgrazing consistently compacted the soils and decreased nitrogen, carbon (C), microbial biomass C, and glomalin protein, thus degrading the soil's physical, chemical, and biological functions. Regionally, this conversion depleted 14.7 Mg C ha(-1) and reduced overall SH scores by 18%, severely impacting biological functions ( e.g.,-43% for sustaining biological activity). No significant differences in functions or SH were found between grazed pastures and open forests. SH scores and C stocks were highly interrelated (r > 0.5; p < 0.001), suggesting that C losses and SH deterioration were closely aligned. We conclude that overgrazing degrades soil multifunctionality and health across the Caatinga biome, with biological functions most severely damaged and legacies obstructing soil recovery for up to three years of grazing exclusion. Future SH studies should include open forest chronosequences with older ages and active restoration practices ( e.g., planting trees or green manure) to enhance Caatinga's ecological restoration knowledge and efforts. (AU)

• FAPESP's process: 22/07490-2 - Greenhouse gas fluxes resulting from land use and land cover changes in the Caatinga Biome: expansion of the field database and regional-scale modeling
• Grantee: Plínio Barbosa de Camargo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 20/15230-5 - Research Centre for Greenhouse Gas Innovation - RCG2I
• Grantee: Julio Romano Meneghini
• Support Opportunities: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 14/50279-4 - Brasil Research Centre for Gas Innovation
• Grantee: Julio Romano Meneghini
• Support Opportunities: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 23/18333-8 - Quantifying Soil Organic Carbon Responses to Fire at the Landscape Scale in the Amazonia
• Grantee: Wanderlei Bieluczyk
• Support Opportunities: Scholarships in Brazil - Post-Doctoral