Climate, organic matter and clay content relationships in the Pampa and Chaco soils, Argentina

Abstract Temperature and precipitation have strong effects on soil processes. The Pampa and the Chaco are vast plains with soils mainly derived from loess. Our objective was to study the effects of temperature and precipitation of both regions on selected soil properties. Using data from soil surveys for ca. 65 Mha, we defined 40 geographic units of ca. 1.6 Mha each. Organic carbon content (g cm−3), solum thickness and clay content were averaged for each unit. Temperature, precipitation and potential evapotranspiration were obtained from climatic records. Carbon inputs to the different soil layers were estimated by calculating net primary productivity of ecosystems and partitioning coefficients of above and belowground biomass. Inputs were affected by a retention factor taking into account temperature effects on organic matter decomposition. Soil organic carbon increases with higher precipitation and decreases with higher temperature. Consequently, the organic carbon content in the top 0–50 cm soil layer is positively correlated with the precipitation/temperature ratio (potential model r2=0.693, P

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