Carbon dioxide mitigation potential and carbon density of different land use systems along an altitudinal gradient in north-western Himalayas

The present study estimated the biomass, carbon density and carbon dioxide mitigation potential of different land use systems along an altitudinal gradient in valley ecosystem showing variation in biodiversity because of changing climatic conditions. Seven different land use systems/crop rotations viz., cereal–cereal, cereal–vegetable, vegetable–vegetable, orchard + cereal–cereal, orchard + cereal–vegetable, orchard + vegetable–vegetable and pure orchard at four altitudinal gradients viz, 1,000–1,300, 1,300–1,600, 1,600–1,900 and 1,900–2,200 m above mean sea level and approximately 1°C temperature gradient were assessed. The results revealed that different land use systems have significant influence on the production of above ground biomass, below ground biomass, carbon density and carbon mitigation potential. Maximum above ground biomass (75.64 Mg ha⁻¹) and below ground biomass (23.60 Mg ha⁻¹) was accumulated in orchard + cereal–cereal system. Total biomass production of different land use systems in valley ecosystem followed the order of orchard + cereal–cereal > orchard + cereal–vegetable > orchard + vegetable–vegetable > pure orchard > cereal–cereal > cereal–vegetable > vegetable–vegetable. Rate of CO2 mitigation potential was maximum (7.81 Mg ha⁻¹ year⁻¹) in the orchard + cereal–cereal based land use system situated at an altitudinal range of 1,900–2,200 m. Maximum carbon density (90.88 Mg ha⁻¹) of both soil + plant was also observed in orchard + cereal–cereal based land use systems at 1,300–1,600 m above mean sea level.