CARBON AND NITROGEN IN SOILS AND HUMIC FRACTIONS OF DIFFERENT PEDOFORMS IN THE ATLANTIC FOREST BIOME

Marisa De Cássia Piccolo,Victoria Maria Monteiro Mendonça,Marcos Gervasio Gervasio Pereira,Gilsonley Lopes Santos

doi:10.5380/rf.v50i3.64171

Marisa De Cássia Piccolo, Victoria Maria Monteiro Mendonça + Show 2 more

Open Access

https://doi.org/10.5380/rf.v50i3.64171

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Abstract

Relief is a soil formation factor that can modify the distribution of soil organic matter (SOM) fractions in a landscape. The objective of this study was to evaluate the effect of the relief on SOM fractions, considering their distribution in different topographic positions, segments, in two pedoforms (concave and convex) in areas covered with forest in the Atlantic Forest biome. The two pedoforms were selected in adjacent areas and divided into segments considering the topographic variation. The carbon and nitrogen origins were evaluated in the extract up to 100 cm of depth. Soil samples from the 0-5, 5-10, and 10-20 cm layers were collected for chemical characterization and fractioning (granulometric and chemical) of the SOM. The soil density in the 0-5 and 5-10 cm layers was determined to calculated the carbon stocks. The isotopic composition showed predominance of 13C. The highest organic carbon and particulate carbon contents were found in the convex pedoform. The distribution of humic fractions showed that the larger part of the humidified carbon was in the humin fraction. The humin and fulvic acid fractions were higher in the convex pedoform. The carbon stocks were, in general, higher in the convex pedoform, decreasing as the soil depth increased; and nitrogen stocks presented no differences. The higher carbon and nitrogen contents were found in the convex pedoform and in the lower region of the concave pedoform.

Highlights

Soil organic matter (SOM) transformations are essential to improve or maintain the soil attributes in tropical forests
The 13C and 15N contents found in the segments (Figure 3) showed that both pedoforms were covered by C3 plants, since the 13C contents were between -28 and -24, indicating few or absence of C4 species in the environments and that the segments present predominance of C3 plants
The contents decreased up to 100 cm depth and were the highest contents found in the segments of the convex pedoform, with intermediate found for S-III

Summary

Introduction

Soil organic matter (SOM) transformations are essential to improve or maintain the soil attributes in tropical forests. The SOM promotes processes that maintain the soil productive capacity due to its effects in the edaphic attributes (MARTINS et al, 2015). The different topographic forms, known as pedoforms, cause variations in soil and landscape attributes. They affect pedogenetic processes and the diversity of plant species by affecting the distribution of water (transport and storage), sediments, dissolved matter, light incidence, and soil moisture, determining horizontal and vertical distribution of soil attributes and the dynamics of SOM fractions (GODINHO et al, 2013).

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