Assessment of carbon storage under rainforests in Humic Hapludox along a climosequence extending from the Atlantic coast to the highlands of northeastern Brazil.
An understanding of the stock of soil organic carbon (SOC) in the umbric epipedon of Oxisols located in the tropical forests surrounded by a semi-arid region is limited but essential because of their importance in the global cycle of carbon (C). The purpose of this study was to assess the effects of climatic (temperature and rainfall), soil organic matter (SOM) composition and litter on the stability of C in surfaces and subsurfaces in five Humic Oxisols along a 475-km climosequence from 143 to 963ma.s.l. in a tropical environment in northeastern Brazil. We assessed vertical changes in SOC; soil total nitrogen (N); C from the microbial biomass; δ(13)C, δ(15)N and the humified composition of SOM; the composition of the humin (HUM) fraction by Fourier Transform Infrared (FTIR); and Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) at depth. The elemental and isotopic composition of the litter samples were analyzed in all areas studied. The results indicated that the current climate and recalcitrant organic compounds are not preponderant factors in the formation of the umbric epipedon, as suggested by the partial influence of temperature and rainfall on SOM. In addition, SOM was dominated by easily decomposable compounds, as indicated by the predominance of aliphatic C-H groups in the HUM fraction in the FTIR spectra; by the thermal oxidation through DSC-TG, which revealed that approximately 50% of the HUM was composed easily decomposable compounds; and by the high proportion of organic C present in the microbial biomass. Values of δ(13)C showed a predominance of C3 plant-C in SOM whereas δ(15)N patterns indicated that N dynamics differ among the profiles and drive the accumulation of C. These findings can help to characterize the susceptibility of these soils to changes in climate and land use and the implications for the sequestration of soil C.
Departamento de Agronomia, Universidade Federal Rural de Pernambuco, Av. Dom Manoel de Medeiros, s/n, 52171-900 Recife, PE, Brazil. Electronic address: janeksaraujo@gmail.com.
Jane Kelly Silva
JKS
Araujo
Departamento de Agronomia, Universidade Federal Rural de Pernambuco, Av. Dom Manoel de Medeiros, s/n, 52171-900 Recife, PE, Brazil. Electronic address: valdomiro.souzajunior@ufrpe.br.
Valdomiro Severino
VS
de Souza Júnior
EMBRAPA Solos/UEP Nordeste, Empresa Brasileira de Pesquisa Agropecuária, Rua Antônio Falcão 402, 51020-240 Recife, PE, Brazil. Electronic address: flavio.marques@embrapa.br.
Flávio Adriano
FA
Marques
School of Environmental Sciences, University of Guelph, 50 Stone Road East, N1G 2W1 Guelph, ON, Canada. Electronic address: pvoroney@uoguelph.ca.
Paul
P
Voroney
Instituto de Ciências Agrárias, Universidade Federal Rural da Amazônia, Av. Presidente Tancredo Neves 2501, 66077-830 Belém, PA, Brazil. Electronic address: regilene.angelica@ufra.edu.br.
Regilene Angelica
RA
da Silva Souza
Deep carbon; FTIR; Litter; Microbial biomass; Semi-arid; Soil nitrogen