Seasonal effect of land use type on soil absolute and specific enzyme activities in a Brazilian semi-arid region

Tropical environments are considerable contributors to overall soil carbon loss to the atmosphere. Land use effects on soil chemical attributes have been well documented mainly in humid environments; however, less attention has been paid to the changes in soil enzymatic activities in dry ecosystems that is a sensitive indicator in ecological processes, due to its importance in soil dynamics and microbial activity. The present study is part of interdisciplinary project that investigated the effect of land cover type and seasonal variation on absolute and specific enzymatic activities per unit of soil organic carbon (SOC) and per microbial biomass carbon (MBC). We assessed five different land use type (Tropical dry forest-TDF, protected area with Angico -ANA, protected area with Ipê-TAB, Scrub area-SCR and agricultural area with maize-M) and five areas of each land use in three layers: 0-0.05, 0.05-0.10 and 0.10-0.20 m. The samples were collected at rainy season 1 in April 2014 (RS1), dry season October 2015 (DS) and rainy season 1 April 2016 (RS2). The conversion of the preserved area provided a reduction in absolute enzymatic activities, especially in the SCR and M. The reductions were of 76% for β-glucosidase, 95% for urease and 72% for acid phosphatase. The specific enzymatic activities per unit of MBC increased with the change of soil use, except in M. The enzymatic activity per unit of SOC in the TDF area was higher in relation to the other areas evaluated, except for specific activity of acid phosphatase. The land use type influenced the absolute and specific soil enzyme activities, but not show a clear trend of seasonal effect.