ECOSYSTEM CARBON STOCKS AND CARBON SEQUESTRATION POTENTIALS OF MAIN AFFORESTATION SPECIES IN HUANGHUADIANZI WATERSHED

Afforestation projects are critical in ecosystem recovery, which actively affect the worldwide carbon circulation. Recently, two main afforestation tree species-Pinus tabulaeformis and Hippophae rhamnoides in Huanghuadianzi Watershed of Chifeng City, Inner Mongolia were investigated. With natural grasslands as a comparison, the impacts of returning from grazing to afforestation on the carbon stocks and carbon cycles of ecosystem are summarized. After returning from grazing to afforestation, the carbon stocks in both vegetation and litter generally increase with time. Without human interferences, the carbon stocks were 7147.45, 7461.67, 7509.895, 8468.375 and 8247.85 g m-2 in the 9a, 15a, 18a, 22a and 29a P. tabulaeformis forests, respectively, and were 6695.44, 6700.82, 8011.86, 8001.92, and 7981.92 g m-2 in the 9a, 15a, 18a, 22a and 26a H. rhamnoides forests, respectively. Due to interferences from intermediate logging, the carbon stock in the ecosystem of the 36a P. tabulaeformis forest was only 7702.58 g m-2. Moreover, with the returning years, the carbon stocks in soil dropped first, and then gradually increased. The ecosystem carbon stock sequestration potentials in the18a H. rhamnoides and 22a P. tabulaeformis were 1621.55 g·m2 and 2078.01 m-2, suggesting that the ecosystems investigated in this work are a chronic impressive carbon sink after returning from grazing to afforestation.