Land-use change and agricultural intensification in the interface Amazon - Cerrado biome: Assessing impacts to soil health and greenhouse gas emissions

Abstract

The interface Amazon - Cerrado (Brazilian savannah) biomes represent one of the most important hotspots of land-use change in Brazil. The LUC of natural ecosystem into agricultural fields leads to significant soil health depletion and greenhouse gases emissions (GHG). In the Canarana microregion - northeast part of Mato Grosso state, many studies regarding effects of land-use change and land management to soil and GHG were conducted since the early 2000's; most of them under the supervisor of Dr. Paulo Brando - University of California Irvine (UCI) and/or Dr. Christopher Neill - Woodwell Climate Research Center (WCRC). We propose an integration of the data collected by the Ph.D. student and from other studies to assess the impacts of LUC and intensification to soil chemical, physical, biological parameters and GHG emissions in the region. Additional studies from the Amazon-Cerrado transition will be assembled to investigate the relation of intensification (soil use and management) and GHG emissions across different soil types. Disturbed and undisturbed soil samples were collected at Tanguro Ranch (municipalities of Canarana and Querência) in areas of native vegetation, recently deforested, single-cropped soybean, double-cropping soybean and maize and pasture. The soil depths evaluated were: 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 60-70, 80-90, 90-100, 100-150, 150-200, 200 -300, 300-400, 400-500, 500-600, 600-700 and 700-800 cm. Soil samples were used for soil bulk density, saturated hydraulic conductivity, soil porosity estimation and total soil C, N concentration and isotopic composition 13C/12C (0) and 15N/14N (0) determination. Labile C, microbial biomass C and -N, ²glucosidase, urease and dehydrogenase activities were assessed until 30 cm. Soil pH was determined in CaCl2 0,01 mol L-1. Calcium, magnesium, phosphorous (available-P) and potassium were extracted using ion exchange resin method. The exchangeable aluminum was determined by titration with KCl 1 mol L-1 and hydrogen plus aluminum by pH SMP. The inorganic N concentrations were analyzed in an automated flow injection analysis. Data analysis will be performed in two steps. First, this new information will be organized into a comprehensive database and combined with the large amount of existing data from the region. Multivariate statistics will be used to assess the different databases. Second, GHG emissions in the Amazon-Cerrado transition will be simulated using the process-oriented biogeochemical DeNitrification-DeComposition (DNDC) model. Linear mixed models will be used to quantify N2O emissions as function of soil type, use and management, local (municipality) and climate conditions (weather) and time (years) These results will contribute to a better understanding of C and N dynamics (soil, vegetation and atmosphere) and provide useful guidance for policymakers related to reducing soil degradation and GHG emissions from land change and land management.