Determining factors of soil organic carbon in the sclerophyll ecosystem of central Chile

The sclerophyllous forest of Central Chile, a Mediterranean-type ecosystem, is facing increasing vulnerability, exacerbated by anthropogenic pressures and drought conditions that have intensified over the past decade.

The objective of this study was to determine, at both regional and local scales, the factors influencing soil organic carbon (SOC), considering the integrated soil-vegetation system. Biophysical conditions such as primary productivity (PP), soil properties (SP), terrain physiography, and climate were considered.

At the regional scale, predictive variables for PP were selected using remote sensing techniques, including the Enhanced Vegetation Index (EVI) and the Normalized Difference Water Index (NDWI) in the spring period. Additionally, climatic variables (maximum, mean, and minimum temperature in spring and annual precipitation between 2001 and 2021) and physiographic variables such as exposure, slope, elevation, and topographic position index (TPI) were included. Statistical analysis was analyzed using a Random Forest model.

At the local scale, a forest inventory has been made, and soil samples were taken at a depth of 20 cm in 45 field plots of 400 m², located in multi-species shrub vegetation (>4m in height). Concentrations and stocks of SOC were quantified, along with physical properties (texture, field capacity, and macroaggregates), chemical properties (pH, organic matter content, total nitrogen, and C/N ratio), and microbial activity estimated through basal respiration. Biomass, nitrogen content, and C/N ratio of leaf litter also measured. Statistical analysis was performed using a stepwise regression.

Preliminary results indicate that the most significant variables in predicting SOC were EVI, slope, elevation, total nitrogen, DA, LAI, coverage of the tree stratum, and vegetation height at the corresponding spatial scale.