Research On Ecosystem Carbon Density And Its Distribution Characteristics Under Different ’Grain For Green’ Models In Hilly Area Of South Ningxia

The vegetation restoration measure of returning farmland to forest（grass） had a significantimpact on regional land use/cover, thereby affecting regional ecosystem carbon densitydistribution and carbon cycle process in the southern Ningxia Province of loess hilly region.Focusing on contributing to the evaluation of the effects of vegetation restoration andre-vegetation on environmental and ecological construction efficiency in this region, throughfield investigation and analysis in lab, this thesis studied ecosystem carbon densities and theirdistributions under different ’Grain for Green’ models and different plant species of carbondensities and their distributions under same model. The better ’Grain for Green’ model and plantspecies was suggested. The main conclusions were as follows:（1） The total carbon densities in the ecosystem dominated by plantations of Prunus sibiricaand Larix gmelini were85.10and106.12t C·hm^-2, respectively and the former was significantlygreater than the latter. The distribution patterns of carbon sequestration were basically consistentin the order of soil> arbor> herb layer. The carbon density of soil layers of Prunus sibirica andLarix gmelini plantations were accounted for73.47%and82.11%of the entire stored carbonwithin each of the respective ecosystem, while arbor layer accounted for12.39%and20.50%,herb layer accounted for1.28%and2.13%. It was concluded that Larix gmelini plantationecosystem is a greater carbon sink relative to Prunus sibirica plantation ecosystem. Therefore,moderate development of Prunus davidiana plantation may help fixing more ecosystem carbon.（2） The total carbon density in the plantations of Hippophae rhamnoides, Caraganakorshinskii, and Prunus davidiana were63.29,52.82, and77.78t C·hm^-2, respectively. Thedistribution pattern of carbon sequestration was basically consistent in the order of soil>shrubs> herb layer. The carbon density of soil layer of Hippophae rhamnoides, Caraganakorshinskii and Prunus davidiana plantations accounted for88.56%、87.79%and87.44%of theentire stored carbon within each of the respective ecosystem, while shrub layer accounted for10.18%、11.25%and12.16%, herb layer accounted for1.26%、0.97%and0.40%. It seems thatPrunus davidiana stands had a better carbon sink relative to Hippophae rhamnoides andCaragana korshinskii. The moderate development of Prunus davidiana stands may help fixingmore carbon. （3）The ecosystem carbon density of ten years old artificial Medicago sativa grassland was61.39t C·hm^-2. As the main part of the ecosystem carbon density, Soil layer carbon density(56.42t C·hm^-2) accounted for91.90%of the ecosystem carbon density, followed by Medicagosativa(4.17t C·hm^-2), accounted for6.79%, other weeds only accounted for1.30%.