Carbon sequestration of sand-fixing plantation of Haloxylon ammodendron in Shiyang River Basin: Storage, rate and potential

Forest plantation can sequestrate atmospheric CO2 and slow down global warming effectively. However, its carbon sequestration capacity and rate vary significantly across different climate regions and tree species. Haloxylon ammodendron sand-fixing plantation, a unique ecological shelter forest in desert areas of Asia, has not only the ecological functions of reducing wind speed and controlling soil erosion, but also those of improving soil quality and increasing the carbon storage of the desert ecosystem. To reveal the effect of H.ammodendron plantation on carbon sequestration of the desert ecosystem, 3, 10, 25 and 35 a H.ammodendron plantations were selected in the lower reaches of Shiyang River Basin by using a space-for-time method, and their characteristics, rates, and potential of carbon sequestration in the vegetation succession were studied. The results showed that the biomass and ecosystem carbon storage of the H.ammodendron plantations increased first and then decreased with the afforestation years. The average carbon fixation rates of vegetation and its ecosystem in 10 a were 0.274 and 0.434 kg C/m2·a, respectively, which were significantly higher than those of other three successional stages in desert areas. With the increase in plantation ages of H.ammodendron, the soil organic carbon (SOC) density in topsoil continued to increase. SOC density in 3, 10, 25 and 35 a were 1.03, 1.60, 2.27 and 2.48 kg C/m2, accounting for 71.0%, 36.9%, 71.4% and 76.8% of the carbon density in vegetation-soil ecosystem, respectively. Soil carbon pool was the main part of the carbon pool in ecosystem. The results of carbon benefits project (CBP) estimation show that the total carbon storage of H.ammodendron sand-fixing plantations in Shiyang River Basin is 0.18 Tg C, and the maximum carbon sequestration potential is 0.84 Tg C, and the maximum carbon emission potential is 1.95 Tg C on 0–100 a time scale. On the time scale of 0–100 a, the carbon efficiency of H.ammodendron sand-fixing plantations in Shiyang River Basin showed a rapid growth (0–20 a) - slow decline (25–40 a) - rapid decline (50–100 a). In order to increase the organic carbon storage and maintain the stability of the desert ecosystem, the H.ammodendron sand-fixing plantations should be constructed largely and conserved scientifically in Shiyang River Basin.