Stability of soil organic carbon pools affected by land use and land cover changes in forests of eastern Himalayan region, India

Abstract

Forests are among the largest terrestrial carbon pools that are most vulnerable to land use and land cover change (LULC). Therefore, it is essential to manage forest ecosystems to enhance soil organic carbon (SOC) pools and soil functionality. The present study was carried out to analyze C stability and change in SOC stock under different forest types in the eastern Himalayan region of India. Topsoil (0–15 and 15–30 cm) samples from six dominant forests i. e. tropical wet evergreen, montane subtropical, temperate, Quercus, bamboo, and shifting cultivation (Jhum) lands were collected and analyzed for selected soil properties and SOC stock. Active (very labile + labile), slow (less labile), and passive (non-labile) C fractions were also analyzed to determine the stability of the SOC pool under the LULC scenario. Results show that the percentage contribution of active C to total organic carbon in topsoil was highest in a temperate forest (74.1%) while lowest in a bamboo forest (48.1%). Unlike, slow C (18.4%) and passive C (26.6%) were highest in Quercus forest. Pearson correlation analysis shows significant positive relation of active and slow C pool with SOC and total nitrogen concentration. The estimates of SOC stock (0–30 cm) were significantly higher in temperate forests (132.7 Mg C ha−1). However, the conversion of natural forests to bamboo forest and jhum land reduced SOC stock by 29% and 68%, respectively. C lability index shows higher labile C in jhum land while recalcitrancy index was highest in a bamboo forest. Our study concluded that LULC change significantly altered the stability and stock of SOC in natural forests. Owing to a higher percentage of slow and passive C pools, Quercus forests play a major role in C sink management.