Carbon Pools and Fluxes in Grassland Systems on Sodic Soils of Northern India

This study analyses vegetation carbon pools and fluxes and soil carbon storage in grassland systems on sodic soils in northern India. The grassland systems on highly sodic soils show low species diversity and single-species dominance. The plant species composition and soil conditions influence above-ground and belowground carbon pools and fluxes in different grassland systems along a range of soil pH from 8.0 to 10.2. The soil organic carbon content is low ranging from 3.42 to 0.51 g kg⁻¹ across soil depths. The carbon pool (Mg C ha⁻¹) in the primary producer compartment of the grassland ecosystems at Bichian was 4.945–1.721 above-ground biomass and 4.336–1.40 belowground biomass. The carbon flux through total net primary productivity ranged from 0.954 to 0.375 Mg C ha⁻¹ year⁻¹. The organic carbon storage (up to 1-m soil depth) in soils of the natural grassland ecosystems at Bichian was 24.713–16.649 Mg C ha⁻¹ over a period of 15 years of vegetation protection. By integrating trees with the naturally occurring grassland systems on highly sodic soils at Bichian, the soil organic carbon content increased by 15–57 %. After long-term protection of grassland vegetation on a sodic soil at Karnal, the soil carbon pool in 0–30-cm soil depth was 6.683 Mg C ha⁻¹(year 1982) and 13.91 Mg C ha⁻¹ (year 2006). The microaggregates (250, 53 and <53 μm) formed a large fraction of soil aggregates and protected most of the soil organic carbon. In the biologically reclaimed sodic soil at Karnal, the total carbon storage in soil (SOC + SIC) up to 1-m soil depth was 89.511 Mg C ha⁻¹. Thus, the protection of native grassland vegetation on sodic soils has the potential for carbon sequestration by increasing plant biomass production and improving soil organic matter. Implementing practices to build up soil carbon stocks in grasslands could lead to considerable mitigation, adaptation and development benefits.