Experimental Study On Estimating The Snow Water Equivalent Of Canopy Intercepted By Snow Cover Area Of Tianshan Spruce

Tianshan spruce is the main body of Tianshan forest ecosystem.It has the ecological functions of water conservation,wind and sand fixation,and biodiversity protection in arid areas.It plays a very important role in the process of Tianshan hydrological ecology.The research on canopy snow interception is of great scientific significance for forest management and climate change in snow forest areas in winter.The snow water equivalent of canopy interception is equal to the quality of canopy interception divided by the projection area and snow density of canopy.Snow water equivalent is an important indicator of snow water resources and an important input parameter in hydrological simulation,which can directly reflect the water resources in snow.It is of great significance to obtain the snow water equivalent information accurately and comprehensively for improving the calculation accuracy of water resources in Tianshan Mountain.In order to obtain the snow water equivalent of the canopy interception of Picea schrenkiana,a set of experimental methods were designed:Taking the seedlings of Picea schrenkiana as the research object,the experiment of snow interception was carried out on the seedlings of Picea schrenkiana by simulating snowfall.The snow cover area of Picea schrenkiana was obtained by digital camera,and the snow water quality of the canopy was obtained by high-precision balance.Then the relationship between the snow cover area of Picea schrenkiana schrenkiana seedlings and the snow water equivalent and snow water quality of the canopy interception was established.Then,after a snowfall,the Dajiang rotor UAV was used to take aerial photos of the 8hm2 Tianshan spruce forest sample plot at low altitude.Using the above model and the data from the sample plot review in summer,the snow water equivalent of the Tianshan spruce canopy interception was estimated,so as to provide the ground measured data and high-precision estimation model for the snow and snow water equivalent of the Tianshan spruce canopy interception.The main research results are as follows:(1)In order to establish the relationship between the snow cover area of spruce seedlings and the snow water equivalent and the snow water quality,the maximum likelihood classification method was used to extract the snow cover area of spruce seedlings,The snow cover area is consistent with the snow water equivalent and the snow water mass fitting curve of the canopy interception in multiple simulated snowfall experiments,and the curve is basically quadratic:y=21.235x~2-1.457x(R2=0.9925)and y=10.278x~2-0.7048x(R2=0.9925).(2)Based on the simulated snowfall experiment of spruce seedlings,a set of scientific experimental method is proposed to accurately estimate the snow water equivalent of canopy interception through the snow cover area,which can provide ground data support and data supplement for remote sensing inversion of snow water equivalent.(3)In this study,DJI phantom 4 Pro v2.0 UAV was used to take aerial photos of8 hm2 forest sample plot of Tianshan spruce with 4K camera on the UAV to obtain image data in visible light band,Based on the field data and the orthophoto image obtained from the pre-processing,the Tianshan spruce in the forest sample was divided into three grades:large,medium and small.The snow cover area was calculated and the total snow water quality of the canopy was estimated by using the snow water quality model obtained from the simulated snowfall experiment,Finally,according to the formula of snow water equivalent of canopy interception,the snow water equivalent of canopy interception of sample plot is 21 cm(the result is larger).