Soil Organic Carbon Dynamics Across Various Land Use Systems Along Elevational Gradients in the North-eastern Himalayas

Aims: To study soil organic carbon content across different land use systems along four elevational gradients in the Himalayan Region of West Bengal. Place and Duration of Study: Kalimpong and Darjeeling districts of West Bengal, India, between April to June 2019. Methodology: Six major land use systems were selected spanning an altitudinal gradient of 400-500 m, 900-1000 m, 1400-1500 m, and 1900-2000 m, ensuring that each land use system was represented at every elevation. The land use systems included: 1. open cropland with rice, maize, winter vegetables, and pulses; 2. mandarin orchard; 3. large cardamom-based agroforestry under alder and Albizia species; 4. ginger-based agroforestry with mixed shade trees; 5. tea plantation under Albizia species; and 6. undisturbed forest. Results: Undisturbed forests had the highest OC content (21.74 g kg-1), followed by tea plantations (19.28 g kg-1), large cardamom (17.86 g kg-1), ginger-based agroforestry (15.98 g kg-1) and mandarin orchard (13.94 g kg-1). While, open crop fields had the lowest OC content (10.92 g kg-1) across various elevational gradients. Soil organic carbon showed a positive correlation with elevation and a decrease with soil depth. At higher elevations, high soil moisture and relative humidity enhance the production of above- and below-ground biomass, increasing soil organic carbon content, while lower temperatures reduce microbial decomposition, further promoting organic carbon sequestration. Conclusion: These findings provide crucial insights for researchers and policymakers, providing valuable information to assist in decision-making for sustainable land use management.