Soil carbon dynamics: a robust indicator for sustainable land use planning in Indian Himalayas

The fragile Himalayan mountain is crucial to ensuring global ecological security by maintaining biodiversity and sequestering carbon (C) in the soil system. However, undesirable land use systems depleted the soil C reserve and threatened the ecosystem sustainability. Hence, the current study was conducted to assess the impact of different land uses viz. natural sal forest, mango orchard, rice–wheat system, and barren land on total soil C stock, C fractions and associated C, total water-stable aggregates (WSA), aggregate associated C and its preservation capacity and C management indices in 0–15 cm and 15–30 cm soil depth of foothills of Indian Himalaya. The study involved analyses such as bulk density determination, soil texture classification, particle size distribution assessment, and pH measurement. Aggregate stability was evaluated by analyzing water-stable aggregates, while soil organic carbon stocks were estimated using specific methodologies. The results revealed that the total C (24.30 g kg−1) including labile (0.15 g kg−1) and non-labile (24.15 g kg−1) pools and their preservation capacity were maximum under sal forest while the lowest under barren land. However total C under sal forest was statistically at par with the total C present under mango orchard. The C sequestration potential of sal forest was significantly higher than other land uses. The mango orchard recorded the highest WSA (71.57%) over sal forest (69.54%), rice–wheat system (68.23%), and barren land (53.55%). The highest associated C was observed in the macro aggregate class (> 2.5 mm) and the lowest was in the micro-aggregate (< 0.25 mm). The mango orchard had significantly higher aggregate associated C than other land uses, although it was statically at par with sal forest. The C management index (CMI) and C pool index (CPI) were found highest under sal forest followed by mango orchard. The labile and non-labile pools of C both were the lowest under barren land at both the soil depths. This inferred that natural sal forest generates greater C, however, continuous soil erosion depleted the soil C. The soils under mango orchards also preserved and stored considerably higher SOC over the rice–wheat system. Therefore, barren land use in the Himalayan region of India should be brought under Mango plantations for carbon restoration and climate change mitigation.