Impacts of land use and land cover changes on nitrous oxide emissions in the Brazilian semiarid

Kelly Ribeiro1, Eráclito Rodrigues de Sousa-Neto1, Paulo José Duarte-Neto2, Jean Pierre Henry Baulbaud Ometto1, Rômulo Menezes3, Willian José Ferreira1.

1Centro de Ciências do Sistema Terrestre – CCST, Instituto Nacional de Pesquisas Espaciais – INPE, São José dos Campos, SP, Brazil

2Departamento de Estatística e Informática, Universidade Federal Rural de Pernambuco - UFRPE, Recife, PE, Brazil

3Universidade Federal de Pernambuco - UFPE, Recife, PE, Brazil

Abstract

Arid and semiarid lands cover about 30% of the earth surface and may be increasing due to global change. Furthermore, semiarid zones are poorly understood and their contribution to the budges of atmospheric gases such as nitrogen oxides are extremely sparse. In Brazil, semiarid lands totalize 980,133 km2, which has a population of ~22.6 million inhabitants. This semiarid region undergoes natural lengthy periods of drought that cause losses in crop and livestock productivity, having severe impact on the population. Due to the regions vulnerability to climate change, livestock has emerged as the main livelihood of the rural population, being the precursor of the replacement of native vegetation by grazing areas. This study aimed to measure nitrous oxide emissions (N2O) from two different soil covers: a native forest and a pasture in the municipality of São João, Pernambuco State, in the years 2013 and 2014. N2O measurements were made by using static chamber techniques. Nitrous oxide emissions ranged from -1.0 to 4.2 mg m-2 d-1 and -1.22 to 3.4 mg m-2 d-1 in the pasture and native forest, respectively, and they did not significantly differ from each other. Emissions were significantly higher during dry seasons and correlated with high temperatures. In this study, soil gas fluxes seemed to be more influenced by climatic and edaphic conditions than by soil cover in the semiarid regions.