Water Conservation Mechanism Of Typical Vegetation Types In North Slope Of Changbai Mountain

Changbai Mountain covers on one of the three primary forests in China and contains abundant water resources.It is an extremely important ecological function area in China.However,under the influence of global changes and human activities,Changbai Mountain is faced with a series of ecological and environmental problems,among which water resources are particularly prominent.In the existing research on water resources in Changbai Mountain,the research on the source of groundwater,exploitation and utilization is relatively much.Lack of comprehensive and overall understanding of forest ecosystem water cycle process and assessment of water conservation capacity of forest ecosystem.In the study of forest water cycle,the stable isotope of hydrogen and oxygen in water molecules is an accurate and efficient tracer.In this case,the typical vegetation types on the northern slope of Changbai Mountain(broadleaf Korean pine forest,Poplar-Birch secondary forest,Spruce-fir forest,Erman's birch forest,a tundra belt)were studied.The stable isotope techniques are combined with traditional observation methods to study the hydrogen oxygen stable isotopic characteristics of atmospheric precipitation,snowmelt water,dew water,forest ecological water,surface water and groundwater,the contribution of regional water vapor source,snow melt water in runoff and forest ecosystem,and to reveal the distribution process of forest precipitation and evaluate the water conservation capacity of forest ecosystem.It can provide theoretical and practical basis for revealing the regulation mechanism of forest vegetation on regional runoff and water resources and the construction of ecological civilization.The main results are as follows:(1)In 2020,the local meteoric water line is?D=7.09?¹⁸O-9.01of Changbai Mountain area.(2)From January to March,affected by the monsoon,the moisture mainly come from Mongolian Plateau and Siberia region in the Changbai Mountains.While the high-pressure center shifted from the Mongolian plateau and Siberia to the Western Pacific in April to august,warm and wet water vapor enhanced humidity and precipitation relatively of Changbai mountain areas.(3)From April to August in 2020,the component of Erdaobai River showed significant temporal variations.Snow meltwater played a key role in runoff,the contribution ratios to runoff between 14.1%?59.8%with the average of 42.6%,the lowest was in August,the highest was in June.The maximum contribution discharge of snowmelt water was 10.35×10⁶m³in June,the ninimum was 2.62×10⁶m³in August,total was 36.56×10⁶m³during melting period.(4)Total dew in the north slope of Changbai Mountain areas in 2020 was 48.53mm,rainfall was 336.80 mm in the same period.As an important compensation of precipitation,the role of dew on forest ecosystem will be enhanced under the background of global change and frequent abnormal climate.(5)In the process of forest precipitation in Changbai Mountain,the canopy firstly intercepts the precipitation,second layer is ground cover layer and the last layer is soil.The canopy permeability is the water body which enters the next layer after the canopy and trunk are intercepted,all of which come from precipitation.The ground cover water mainly comes from canopy permeability and trunk runoff.Soil water mainly comes from precipitation and groundwater,and the contribution of precipitation to soil water decreases with the increase of soil depth.In the precipitation event of moderate rain and light rain for three consecutive days,the contribution of precipitation to soil water does not involve deep soil.(6)In the forest ecosystem on the northern slope of Changbai Mountain,the water conservation capacity of coniferous forest and broadleaf Korean pine forest was significantly stronger than that of Poplar-Birch secondary forest and Erman's birch forest.The comprehensive water conservation capacity of four vegetation types is consistent with the order of water conservation capacity of litter layer and soil layer,which indicates that the water conservation capacity of ground cover layer and soil layer determines the comprehensive water conservation capacity of forest ecosystem.