Temporal And Spatial Variation Of Vegetable Net Primary Productivity And Influence Of Climate Change And Human Activity In Qilian Mountains

Human activities have caused a significant increase in the concentration ofgreenhouse gases, which leads to global warming. However, the vegetation has anirreplaceable role in mediating the global carbon balance, slowing the increase in theconcentration of atmospheric carbon dioxide and other greenhouse gases, andmaintaining the stability of the global climate. The net primary productivity of thevegetation can reflect the capacity which the vegetation fixes on atmospheric CO2. Itis generally accepted that the net primary productivity of the vegetation is animportant part of matter and energy translocation in terrestrial ecosystems. We mustestimate the net primary productivity of the vegetation in regional or global scaletimely and accurately, and analyze the temporal and spatial variation. More detailedstudies are needed to fully understand the linkages between the net primaryproductivity of the vegetation and other related factors. It is very important tounderstand carbon cycle in regional or global scale. The studies can provide importantscientific basis in developing and utilizing natural resources in regional or global scalereasonably. Qilian Mountain which is China’s famous mountain ranges owns abundantwater conservation forest and snow and ice water resources. It is is an importantguarantee to maintain ecological balance in the northwest basin. Based on MOD17A3datasets in Qilian Mountain from2000to2010, the methods of GIS, ZhouGuangsheng model and residual analysis are employed to analyze variability of thevegetation. The results are as follows:(1) Vegetation NPP ranges from12.76to2995.28g C/(m2a), with the averageof198.12g C/(m2a) in Qilian Mountains during2000-2010. The distribution ofannual NPP decreases from east to west. Annual NPP which is more than410gC/(m2a) mainly distributes in North Slope of the eastern Lajishan and Wushaoling inRegion One. In most areas of Region One and Two, annual NPP varies between210and410g C/(m2a). Annual NPP varies from12.76to210g C/(m2a) in the west ofRegion Two and most areas of Region Three.(2) Compared with2000, annual NPP increase in most parts of Qilian Mountainsin2010, which accounts for92.93%of the total area of the study. The increasingrange of annual NPP in Qilian Mountains mainly varies between0and50, accounting for72.58%of the total area in Qilian Mountains. The trend of annual NPP mainlyincreases, which accounts for92.98%of the total area of the study. The variation from0to30%of annual NPP is in the most part of Region One and Two, whereas thevariation (over30%) occupies in the south of Region Two, southeast of Region Threeand the junction of them in the southeast. In Region One, the variation of annual NPPis less than0, indicating that the vegetation degenerates gradually in the region.(3) The potential annual NPP ranges between68.82and215.52g C/(m2a),with the average of151.94g C/(m2a) in Qilian Mountains during20002010. Itis less than actual annual NPP. In the context of climate warming, annual NPP exhibitsa gradually increasing trend in most parts of central and western Qilian Mountains,indicating that the climate changes are conducive to the recovery and growth incentral and western regions. However, impacted of climate change toward a warm anddry, annual NPP has been a decreasing trend in parts of Wushaoling (9.44%of thetotal area).(4) There is a high correlation between precipitation NPP, including actual andpotential annual NPP, indicating that precipitation is the most influential factor on theNPP of Qilian Mountains. The correlations between Potential annual NPP and annualNPP are significant at the0.01level.(5) The studies show that human activities contribute to ecological environmentin Qilian Mountains by the residual method in the recent11, especially in the easternand northern of Region One and Two. However, the vegetation degrades west andsouth of Region Two and Three. Although large-scale ecological protection andconstruction has achieved certain results since2000, the positive impact of humanactivities on vegetation is showing a decreasing trend. The change rate of annual NPPresiduals is-0.054from2000to2010, indicating that ecological protection andconstruction project implementation lack sustainable action.