Simulating the Impact of Land Use Change on Soil Organic Carbon Turnover through Modelling in the Outer Himalayas

Abstract

newline Land-use change affects important ecosystem functions including carbon sequestration, climate regulation, land degradation etc. Our study area in the Outer Himalayas showcased varied landscapes, making it an interesting place to explore and was investigated for various land use systems and their transitions. LULC change was mapped to analyze temporal changes (2000 and 2023) in study area using visual image interpretation technique and multi-sensor satellite data of LANDSAT for respective years. A decrease in area under agriculture (300 sq km), forests (1061 sq km) and waterbodies (16 sq km) while an increase under bareland (1282 sq km) and riverbeds/builtup (95 sq km) was observed. Soil samples were collected from the land use change sites as well as from their adjacent sites where no land use change was observed for studying the impact of land use changes on soil carbon, biological activity and nutrient status at different depths. The dominant textural class was sandy loam. Soil pH was lowest in forest land and highest in wasteland use. Agricultural land use had the highest EC followed by wastelands and forests. Forest land use exhibited highest levels of available nutrients, Total Nitrogen,Cation Exchange Capacity, Water Holding Capacity followed by agricultural land use and the minimum content was observed in wastelands. Forested areas exhibited relatively stable soil aggregates. However, transitions to agriculture and wasteland resulted in notable decrease in MWD values. Carbon pools viz. oxidizable organic carbon, soil microbial biomass carbon, permanganate oxidizable carbon, total organic carbon, and total carbon, exhibited a consistent decreasing trend with depth. They were highest under forests and decreased on its transition to other land uses. The microbial count and enzymatic activities also followed the similar pattern. The erodibility indices were found to be minimum in forests followed by agriculture and wastelands. A depth wise decline in properties was also observed except soil pH