Soil carbon and nitrogen dynamics in agroforestry land use systems of north-western Himalayas: implications for environmental sustainability
摘要
The soil organic carbon is critical in determining the sustainability, ecosystem services and atmospheric stability of any land use system. In this study, SOC and nitrogen pools across ten types of land use systems (LUSs) in the mid-hills of the northwestern Himalayas were estimated, namely sole cropping (SC), natural forest (NF), agri-silvi-horticulture (ASH), agri-silviculture (AS), fruit-based agroforestry system (FB), fodder-based agroforestry system (FTB), bamboo-based agroforestry system (BB), melia-based agroforestry system (MB), poplar-based agroforestry system (PB), and silvi-pasture (SP) at three different soil depths i.e., 0–20 cm (D1), 20–40 cm (D2) and 40–60 cm (D3). Based on the labile and non-labile C fractions, various indices like lability index, carbon pool index and carbon management index were worked out. It was found that the active carbon pool was greater in NF (4.30 mg g−1), followed by the FB (4.17 mg g−1). The maximum passive carbon pool was found in NF (13.01 mg g−1), followed by the SP system (11.41 mg g−1). The SP system had the lowest value of lability index (LI:0.24), and the highest (LI:1.35) was reported from the FB. The maximum carbon management index (CMI) was also reported in NF (184.08), followed by the BB (161.35). Ammonical and nitrate nitrogen were reported maximum in NF, i.e., 6.93 mg kg−1 and 4.34 mg kg−1, respectively. On average, the carbon and nitrogen pool declined at deeper soil depth, irrespective of the land use. Findings of this study demonstrated that agroforestry LUSs in the north-western Himalayas have a remarkable ability to sequester significant amounts of carbon and nitrogen in the soil thus provide a solid basis for adopting agroforestry practices to promote eco-friendly agriculture in a sensitive Himalayan region.