Understanding the effect of three decades of land use change on soil quality and biomass productivity in a Mediterranean landscape in Chile

Abstract

Land-use and land-cover change (LUCC) can deeply alter soil quality (SQ), affecting important productivity functions like vegetation biomass. A further understanding of the history of LUCC is essential to explain natural or anthropic landscape cover. The Mediterranean region of central Chile has historically been affected by LUCC impacts on the vegetation gradient of the landscape, which ranges from natural cover to anthropic cover like grazing pastures and crop lands. The main objective of this study is to define the historical impact of LUCC on SQ in a Mediterranean landscape in central Chile. To conduct the study, historical LUCC trends between 1975 and 2011 were analyzed. A Soil Quality Index (SQI) was developed to comparatively assess six types of land use (Annual Crops, Perennial Crops, Grazing, Espinal, Dense Espinal and Native Forest); and finally, SQI was interpolated at landscape scale using the soil-adjusted vegetation index (SAVI) as an auxiliary variable. SAVI was selected to represent indirect information on vegetation biomass productivity. The results indicate that most LUCC dynamics were observed in the Espinal woodland, where agriculture and grazing activities have been developed historically. The SQI showed significant SQ deterioration when Native Forests (SQI=0.82) degrade and are transformed by anthropic interventions like Annual Crops (SQI=0.27), Perennial Crops (SQI=0.34) or Grassland (SQI=0.36). However, a slight improvement in SQ compared to the other land uses was identified in the Dense Espinal (SQI=0.46). Finally, the quality model at landscape scale showed clear differences in SQI values for all landscape covers.