The Carbon Sequestration Potential In Aboveground Biomass Of Qinghai Spruce Forest At Qilian Mountains

The terrestrial ecosystems are important carbon pool in the global carbon cycle, in the terrestrial ecosystems. Until 1990’s, almost 40% of terrestrial land has been exploited to make the way for cultivation land or pasture, this kind of change is basically at the expense of forest and grassland. These deforestation may have resulted in large amount of CO2 been emitted to atmosphere. If the deforestation can be reduced, the carbon loss from forest land can be reduced and furthermore, and furthermore, if the forest can be restored, more carbon in the atmosphere can be sequestrated in the forest biomass and forest soil.The Qilian Mountains situated at upper reach of inland rivers in arid and semiarid northwest part of China, the relatively vulnerable ecological environment and more than 1,000 years of disturb have resulted in profoundly decrease of forest coverage, the situation may continued in the near future. In 1986, the Qilian Mountains National Nature Reserve was established and through afforestation and reforestation practices, the severe disturbance imposed on the forest ecosystems has been reduced, the forest dominated by Qinghai spruce (Picea crassifolia) has been restored at a certain extent. It can be predicted that the restored forest has the potential to sequestrate the carbon in the atmosphere. The literature review demonstrated that the estimation about the carbon sequestration potential in the Qinghai spruce forest has not been studied, so this desertation takes the Qinghai spruce as our study species and aims to estimate the total carbon which can be sequestrated in the potential distribution area of Qinghai spruce. Some of the conclusions are:On the species distribution modeling aspect:(1) The selected environmental variables have impact on the performance of species distribution models, so the selection of key environmental variables is of the first importance during modeling. Different models use different approaches to conduct the selection, generally speaking, the Generalized Linear Model and correlated stepwise regression is the most effective methods.(2) The prediction of species potential distribution is demonstrated in the form of probability at the corresponding pixels, as a result, these unsuitable pixels for study species need to be removed based on the samples information and certain threshold value, which can be reliablely determined use Kappa index and overall classification index. (3) This research used the marginal difference index of variables (MDIV) and total difference index of variables (DIV) to evaluate the performance of species distribution models, the results demonstrated that MDIV and DIV are effective evaluation approach during species distribution modelling.(4) The species distribution models are sensitive to the climatic baseline, so for the different ecological applications, the corresponding climatic baseline need to be properly selected.On the niche and potential distribution of Qinghai spruce aspect:(1) The potential distribution of Qinghai spruce modeled by Genetic Algorithm for Rule-Set Prediction (GARP) and Maximum entropy are 4.72×105 ha and 4.86×105 ha, the actual distribution of Qinghai spruce is 1.81×105 ha, the corresponding estimation revealed that almost 61% of Qinghai spruce has been deforested.(2) The Mean temperature of warmest quarter, Precipitation of the wettest quarter, Annual solar radiation and Topographic wetness index are the most important environmental variables which influence the distribution of Qinghai spruce, the contribution of these four variables are 36.9%,28.5%,24.2% and 12.8%, respectively, the total contribution of these four variables is 91.4%.The biomass and carbon storage aspect:(1) The minimum and maximum biomass per unit of Qinghai spruce is 84.0 t/hm2 and 239.6 t/hm2 with an average of 169.8 t/hm2, the stand deviation (SD) is 22.7, the total aboveground biomass of Qinghai spruce at actual and potential distribution area are 3.3×107t and 12.79×107 t(GARP) and 12.86×107(Maxent).(2) The carbon stored at actual distribution area of Qinghai spruce is 1.73×107t, on the potential distribution areas, the storage was projected to be 6.70×107 t (GARP) and 6.74×107t(Maxent).