Can Soil Organic Carbon Pools Indicate the Degradation Levels of Pastures in the Atlantic Forest Biome?

Abstract

In Brazil, a large part of the Atlantic Forest was deforested in pastures, which were developed on the basis of natural fertility and organic matter content of the new deforested soil. However, as time went by the organic matter content in these areas have been decreasing causing soil degradation. The objective of this study was to evaluate the organic matter as a quality indicator of Ultisols in different levels of pasture degradation in the region of Governador Valadares-MG. Four sites of pastures were chosen at different levels of degradation, observed visually, two capoeiras in different stages of natural recovery and forest site (reference). Soil samples were collected at three depths (0.00-0.05, 0.05-0.10 and 10-0.20 m) in two seasons of the year (rainy and dry seasons) in the middle third of the landform with three replicates. The following attributes were determined: soil organic C, free light fraction, particulate organic matter, particulate organic C, mineral-associated organic C and dissolved organic matter. The experimental results showed that the soil organic matter appeared efficient in discriminating soil quality between degraded forest/pasture, as well as between degraded capoeira/pasture. But, it was not sensitive to discriminate within levels of degraded pastures. Among the organic matter pools studied, the most sensitive soil quality indicators were: particulate organic matter and dissolved organic matter, in the following degraded order verified from these indicators: forest < capoeira 1 = capoeira 2 < pastures (1, 2, 3 and 4).

Field-based quality indicators in degraded pasture of the Atlantic forest biome

“…For the determination of soil coverage rate (Soil Cov. Rt ) in the Pastures areas 1, 2, 3 and 4, the "measuring tape" method was used (Rocha Junior et al, 2014b), where a 50-m graduated tape was stretched horizontally at the top end of the portion. Each meter determining a reading which indicated the vegetation type found at intervals of 1 m was recorded.…”

“…On the other hand, in the Vale do Rio Doce, an important water resource of the State of Minas Gerais, agricultural activities have caused the region to become quite degraded within the Atlantic Forest biome (Rocha Junior et al, 2014a;Silva et al, 2010). Few studies have been conducted on strategies to mitigate the pastures degradation of the Vale do Rio Doce region (Baruqui et al, 1985;Favero et al, 2008;Lima et al, 2008;Rocha Junior et al, 2014a;Rocha Junior et al, 2014b), thus increasing the environment, economic and social damage. To reverse the process of degradation, it is important to develop low cost and simple techniques to assess the impact of grassland management on soil quality, which can be easily used by qualified extension workers and producers (Lisbôa et al, 2016).…”

Soil Cover and Chemical and Physical Attributes in Oxisol in the Atlantic Forest Biome

“…The substitution for crop cover has caused negative changes in soil properties and consequently led to the degradation of large areas, causing a decline in their quality (ROCHA JUNIOR et al, 2014). However, the loss of soil quality has been attributed not only to the conversion of vegetation (forest/agriculture), but above all, to the management adopted in the area after the substitution (WENDLING et al, 2005).…”

“…The reduction of TOC in the areas submitted to farming or livestock can be attributed to the increase in erosion besides the increased acceleration of mineralization of soil organic matter from its disturbance or due to the lower amount of organic intake in managed systems compared to native forests (PORTUGAL et al, 2007;ROCHA-JUNIOR et al, 2014).…”

“…The determinate physical soil attributes were: soil density, set by volumetric ring method (BLAKE; HARTGE, 1986); total porosity, obtained by the ratio between soil density and particle density (1-Ds/Dp); soil texture by the slow stirring method (RUIZ, 2004); clay dispersed in water (CDW); and the degree of flocculation (FD) according to EMBRAPA (1997); and stability of aggregates set by wet path with subsequent calculation of DMG (RUIZ, 2004).…”