Response Of The Water Conservation Function To Vegetation Dynamics In The Qinghai-Tibetan Plateau

With the increasing demand for global water resources and general deterioration of the ecological environment of the Qinghai-Tibetan Plateau,changes to the water conservation functions of ecosystems and the impact mechanisms have attracted great attention.Currently,the research on water conservation has mainly focused on a single biome type,in particular,forests.Few studies explore the differences in water conservation functions of different biome types.Research on this topic mostly utilizes field investigations and sample plot settings to explore the differences in water conservation capacity of a small number of tree species,but these methods are limited in time and space.This study took the Qinghai-Tibetan Plateau as the research area,and carried out the dynamic monitoring of vegetation space-time,vegetation phenology and water conservation capacity in the region by using MODIS products.Based on the principle of water balance,the water conservation quantity was estimated,and the response of water conservation function of different biome types and its influencing factors were explored.Finally,the issue of how to improve and manage the water conservation function is discussed.The results are as follows:(1)From 2000 to 2015,the vegetation of Qinghai-Tibetan Plateau improved slightly,with the slope values concentrated in-0.20-0.20.The vegetation fluctuated greatly in spring,improved greatly in summer,grew stably in autumn,and was in poor condition in winter.Grassland was the main vegetation improvement area,accounting for 11.36%,followed by forests,other woody vegetation and croplands.The significant improvement areas are mainly distributed in the northeast of Qinghai-Tibetan Plateau,while there is no significant change in other areas.Under the influence of climate,the length of vegetation growing season is shortened.The frequency of vegetation change is increased,and the sensitivity and vulnerability of vegetation to external environmental changes are strengthened.Therefore,reducing excessive interference from external factors is essential for vegetation protection.(2)From 2000 to 2015,the water conservation capacity of the Qinghai-Tibetan Plateau showed a slight downward trend,with slope values concentrated in-0.02-0.02,and the degraded areas were mainly located in the southeast and southwest.The water conservation function decreased gradually from southeast to northwest.The regions with high and relatively high water conservation functions were mainly distributed in the southeast of the Qinghai-Tibetan Plateau.The regions with low water conservation function were mainly located in the northwest and the Qaidam Basin.The water conservation service function in this area mainly comes from grassland ecosystems.Grassland,desert,water body and wetland ecosystems are the main ecosystems that cause the change of water conservation functions in Qinghai-Tibetan Plateau.(3)The correlation area accounts for 69.660%between vegetation and water conservation in Qinghai-Tibetan Plateau.The water conservation functions are closely related to vegetation density and biome types,and the degrees of the response of the water conservation capacities of different biome types are different.With the gradual increase of the leaf area index,the overall water conservation function showed a trend of strengthening and then weakening,and the water conservation functions of different biome types showed their own unique changing trends.To greatly improve the water conservation service function of the Qinghai-Tibetan Plateau,the management and planting of vegetation should be conducted according to the optimal vegetation coverage area,vegetation quantities and biome types.(4)The water conservation function of the Qinghai-Tibetan Plateau is not only closely related to vegetation growth,but also restricted by climate and terrain factors.Precipitation indirectly affects vegetation growth by affecting the change of water conservation.Therefore,in the work of improving and managing the water conservation function of the Qinghai-Tibetan Plateau,it is necessary to comprehensively evaluate the water conservation function and clarify the water conservation process,so as to provide more scientific and effective management measures for the sustainable development of the ecological environment.