Land-use and topographic effects on soil carbon and nitrogen fractions across contrasting land-use systems in the wet temperate northwestern Himalayas

Résumé fourni par la source

Soil organic carbon (SOC) and nitrogen (N) dynamics are strongly influenced by land-use systems (LUS) and topographic variability, particularly in fragile Himalayan ecosystems, where climate and vegetation interact across steep environmental gradients. However, information on SOC fractions and N pools in the wet temperate northwestern Himalayas remains limited. Therefore, the present study investigated the effects of LUS (agriculture, agroforestry, horticulture, and barren land), topography (valley and mountain), and soil depth (0–20, 20–40, and 40–60 cm) on SOC fractions, carbon pool index (CPI), carbon management index (CMI), and N fractions in the high-hill wet temperate region of Himachal Pradesh, India. The results revealed significant (p<0.05) variation in SOC fractions and nitrogen pools among LUS and topographic positions. Agroforestry had the highest total organic carbon, active carbon pool, passive carbon pool, and soil nitrogen density, followed by horticulture, whereas barren land exhibited the lowest values. Among the topographies, the valley ecosystem had the highest active carbon pool (9.08 mg g -1 ), whereas the mountainous topographies had the highest passive pool (9.04 mg g -1 ). Soil depth significantly (p < 0.05) influenced carbon distribution, with Cfrac1, Cfrac2, and Cfrac3 decreasing by 45.7%, 45.8%, and 34.5%, respectively, whereas Cfrac4 increased by 84.8% from D 1 to D 3 . The CPI and CMI were significantly (p<0.05) higher under agroforestry and horticulture systems, indicating greater carbon accumulation and changes in carbon lability. Overall, the findings indicate that land-use system, topographic position, and soil depth jointly influenced soil carbon and nitrogen distribution, with tree-based systems showing greater carbon and nitrogen accumulation than conventional agriculture. These findings highlight the potential of agroforestry as a sustainable land-use option for maintaining soil carbon and nitrogen in wet temperate Himalayan ecosystems.

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