Work

Soil organic carbon distribution in inselbergs of Caatinga

Year: 2026

Type: article

Abstract: This study focuses on the Caatinga, the largest seasonally dry tropical forest in South America. Climate, low primary productivity, and severe erosion result in soils with low organic carbon content. Inselbergs stand out due to their unique biodiversity and serve as bioclimatic indicators for studies on the origin of organic compounds. Soil and litter samples were collected from three inselbergs at different slope positions. Morphological, physical, and chemical properties were determined. Data revealed a variation in SOC content ranging from 1.5% to 12.8% among the three inselbergs, with the highest contents predominantly at the backslope position. SOC content showed significant correlations with clay, available water, Ca 2+ , and Mg 2+ , and a weak correlation with phosphorus. Principal Component Analysis explained 62.1% of the total variance. PC1 represented a soil fertility gradient, while PC2 was primarily associated with SOC content and cation exchange capacity. Linear mixed-effects models revealed significant effects of both slope position and site on the multivariate gradients, with the highest scores occurring at the backslope rather than following a monotonic trend along the slopes. The δ 13 C values indicated a predominantly C₃-derived organic matter source, with spatial differences in vegetation-derived carbon inputs associated with local microtopographic conditions. The accumulation of fine sediments, litter, and organic matter in depositional microsites may promote soil development, moisture retention, and nutrient enrichment, favoring vegetation establishment. Therefore, inselberg soils contribute to maintaining Caatinga biodiversity and carbon stocks.

Source: Geoderma Regional

DOI: 10.1016/j.geodrs.2026.e01128