Long‐Term Land‐Use‐Driven Changes in Nutrient Storage (Macro and Micro), Biological Health, and Carbon Pools in the Eastern Himalayas, India

Abstract

Long‐term land‐use transitions significantly alter soil nutrient dynamics, microbiological functions, and carbon (C) pool distributions in the soil profile. This study assessed the long‐term effects of converting a 50‐year‐old primary forest into cultivated land‐use systems, namely, agriculture (AGLU), horticulture (HOLU), and agroforestry (AFLU), over a period of 20–26 years in the Eastern Himalayas, India. The soil was taken to a depth of 1.0 m, with increments of 0.15 m until 0.60 m and 0.20 m until 1.0 m. The evaluation was carried out to assess macro‐ and micronutrient storage, microbial biomass, enzymatic activities, and total and fractionated organic carbon (C) pools. The depletion of nutrients (macro: −52.6% to −59.2%, micro: −20.4% to −61.6%) and biological properties (SMBC: −40.7%, enzymes: −25.5% to −40.2%) was the most severe in the top soil (0.15 m) under agricultural land use. In contrast, AFLU and HOLU retained higher nutrient levels and C‐pools, both in surface (0–15 cm) and subsoil layers (15–100 cm). Cultivation significantly (p < 0.05) reduced soil organic carbon and its fractions in both surface and sub‐surface soils when compared to primary forest (FOLU). The degradation index confirmed greater resilience of tree‐based systems compared to seasonal cropping. These findings support the promotion of agroforestry and perennial horticulture, which can help restore degraded soils in upland ecosystems.