ORGANIC MATTER IN AREAS UNDER SECONDARY FORESTS AND PASTURE

Carlos Eduardo Gabriel Menezes,Lúcia Helena Cunha Anjos,Marisa De Cássia Piccolo,Marcos Gervasio Pereira,Roni Fernandes Guareschi,Fabiano Carvalho Balieiro,Maria Elizabeth Fernandes Correia

doi:10.1590/01047760201723032333

Abstract

ABSTRACT The objective of this study was to evaluate the soil carbon stock (Stock C) and bulk density, the chemical and granulometric fractions of the organic matter and the isotopic signal of the soil δ13C in forest fragments and a mixed managed pasture (MMP). The study was carried out in the municipality of Pinheiral, State of Rio de Janeiro. The evaluated areas were: fragment of secondary forest in initial stage (SFIS) with 20 years of regeneration; fragment of secondary forest in intermediate stage (SFINS), with 25 years of regeneration; advanced secondary forest fragment (SFAS) with 60 years of regeneration and mixed pasture managed (MHP). The attributes related to soil carbon showed significant responses to the effects of land degradation / recovery processes, especially for the following indicators: total organic carbon, organic matter stock and particulate organic matter. No significant alterations for humic substances, and prevalence of the humin fraction was found. The most significant changes in δ13C values occurred up to the depth of 60 cm. In the grassland area, at 0-10 cm, 67% of the carbon stock comes from C4 plants, reducing in the subsequent layers. In SFINS and SFAS areas, at 0-10 cm, the contribution of C3 plants was significant, with minor changes in depth.

Highlights

Deforestation for agricultural crops, followed by pastures in bustling relief regions, that is, with deep and dissected narrow valleys, can give rise to a landscape with different degrees of degradation, and the main indicators of this process are the decreases in the capacity of soil water retention, low soil stability favoring an increase in the erosion process, and reductions in fertility levels and soil capacity to store carbon (MACHADO et al, 2010; MACEDO et al, 2008; GUARESCHI et al, 2014)
Similar results are presented in the studies of Coutinho et al (2010) and Oliveira et al (2008), which did not find a significant difference for bulk density (Bd)
This pattern may be due to the small recovery time of the secondary forest, that is, its regeneration has not yet been able to reduce the impacts on the Bd caused by the pasture area that preceded it

Summary

Introduction

Deforestation for agricultural crops, followed by pastures in bustling relief regions, that is, with deep and dissected narrow valleys, can give rise to a landscape with different degrees of degradation, and the main indicators of this process are the decreases in the capacity of soil water retention, low soil stability favoring an increase in the erosion process, and reductions in fertility levels and soil capacity to store carbon (MACHADO et al, 2010; MACEDO et al, 2008; GUARESCHI et al, 2014). Guareschi et al (2014) has verified that the plant successions in the areas of forest under pasture promote the improvement of the physical and chemical attributes of the soil through the addition of organic matter. According to Schedlbauer and Kavanagh (2008), reductions in soil carbon content from conversion of rainforest to pasture can often be restored through the development of secondary forests. Coutinho et al (2010) when evaluating the impact of pasture substitution by eucalyptus plantation and secondary forest area, did not observe differences in soil C stocks in the forest and eucalyptus areas compared to a pasture area. Substantial losses of soil carbon resulting from the conversion of tropical forest into pasture can often be restored through the development of secondary forest (SCHEDLBAUER; KAVANAGH, 2008)

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