Soil Organic Carbon Stocks and Humic Substances in Extremely Acid Soils,Sierra Norte de Oaxaca,Mexico

摘要

The accumulation of organic matter(OM)in the decomposition is a characteristic feature of terrestrial ecosystems,and studies of OM will enable us to develop further management systems that sustain soil productivity.One of the more complex regions of Oaxaca is the Sierra Norte region that is situated at the northeast of the state,with an extension of 9,400 km~2.This study was conducted in the surroundings of Santa Cruz Tepetotutla,located in the catchment of Perfume river in the northern range of Oaxaca state(17°38'-17°40'N,and 96°32'-96°33'W).The lithology of the study area is represented mainly by mica-chlorite schists.This zone is characterized by abrupt topography with slopes ranging between 10 and 50°.The climate has been classified as hyper-humid,transitional temperate one,mean annual precipitation is 5800 mm and mean annual temperature(MAT)is 16.5°C.Vegetation along the gradient consists of a mosaic of undisturbed forest communities displaying an overall elevational arrangement,generally arranged by altitude,of premontane and montane forests.In this paper we present the characterization of the pools of organic carbon reserves,forest floor properties and the humic substances of the soils situated in an altitude gradient.