Carbon Sequestration Potential of Hardwickia Binata Roxb. Based Agroforestry in Hot Semi-Arid Environment of India: An Assessment of Tree Density Impact

Agroforestry is one of the most promising options for climate change mitigation through carbon sequestration. However, carbon sequestered in agroforestry system depends on various factors like type of tree species, tree density, system age, soil and climate. One of the most important factors for enhancing carbon sequestration per unit land is tree density. Hardwickia binata Roxb. has been reported as suitable agroforestry tree species with multiple benefits in arid and semi-arid region, however, the role and impact of tree density in carbon sequestration is poorly reported. This study estimated impact of tree density (D₁ = 333 tree ha^-1 and D₂ = 666 tree ha^-1) on carbon sequestration potential of 30-year-old H. binata Roxb. + Cenchrus setigerus silvipasture system in hot semiarid region of Rajasthan. The carbon sequestered in tree biomass was estimated by reported allometric equations, whereas in soil it was determined by Walkley and Black method. Results showed significant impact of tree density on carbon sequestration per unit tree and per hectare land. The average biomass carbon sequestered by a tree was significantly more (44.5%) in low density (D₁) compared to high density (D₁) system. However, total biomass carbon sequestered per hectare land was significantly more (40.8%) in high density system (31.6 ± 12.6 Mg C ha^-1. Carbon sequestered in soil organic matter was higher in both D₁ and D₁ systems compared to control (sole Cenchrus setigerus field). It ranged from 19.93 ± 0.31 Mg C ha^-1 in control to 22.94 ± 0.65 Mg C ha^-1 and 23.25 ± 0.78 Mg C ha^-1 in D₁ and D₂ respectively. The total carbon sequestered (below and above ground tree biomass and soil organic carbon) was in the order D₂ > D₁ > control.