Nitrogen inputs by rainfall, throughfall and stemflow in Brazilian semiarid

R. L. Deusdará1 2, M. C. Forti1, L. S. Borma1, R. S. C. Menezes3, J. R. S. Lima4, and J. P. H. B. Ometto1, E. R. Sousa-Neto1, K. Ribeiro1

1 Centro de Ciência do Sistema Terrestre - CCST, sala 5, 3º andar,  Instituto Nacional de Pesquisas Espaciais - INPE, Avenida dos Astronautas, 1758, 12227-010, São José dos Campos, SP, Brasil,

2 [email protected]

3 Departamento de Energia Nuclear - DEN, Universidade Federal de Pernambuco - UFPE, Av. Prof. Luiz Freire, 1000, 50740-540, Recife-PE, Brasil

4 Universidade Federal Rural de Pernambuco - UFRPE, Avenida Bom Pastor, s/n, Garanhuns - PE, 55292-270, Brasil

Abstract

The aim of this study was to quantify nitrogen inputs by the rainfall, throughfall and stemflow, assessing the canopy role in the nitrogen transfers between atmosphere and soil in a rural tropical semiarid region in the Brazilian Caatinga. Samples were collected during two wet seasons, one during an extremely dry year (2012) and one during a year with normal rainfall (2013). The ionic concentrations of N-NH4+, N-NO3-, dissolved organic nitrogen (DON) and dissolved total nitrogen (DTN) was 0.04 and 0.15, 0.07 and 0.10, 0.49 and 0.48, 0.61 and 0.73 mg l-1 in the rainfall for 2012 and 2013, respectively. The canopy enrichment for DON were 3 times for both wet seasons and for DTN were 3 and 2 times in relation to rainfall values for 2012 and 2013, respectively. There were no differences in N-NO3- between rainfall and throughfall. The enrichment for stemflow were 31, 8, 15 and 17 times for N-NH4+, N-NO3-, DON and DTN for the wet season for 2013, respectively. We report a low bulk nitrogen deposition during both wet seasons and an estimative of about 2.05 kg N ha-1 ano-1. We estimated slightly lower annual inputs than previous global estimates, likely due to the low rainfall depths that occurred during the studied years and the lack of measured data for South America. Our findings contribute to the knowledge of nitrogen deposition in the northeastern Brazil by providing information for this poorly studied tropical and semiarid ecosystem.