Study On Evaporation Dispersion And Its Influencing Factors In The Coniferous And Broad-leaved Mixed Forest In Jinyun Mountain Chongqing

This article takes coniferous and broad-leaved forest land as the research object in the ecological protection station of the Jinyun Mountain National Nature Reserve,and continuously monitors the environmental factors of the ecosystem from May to July 2017,at the same time,simultaneous measurements were made on the flow rate of soil and soil evaporation in the foothills,masson pine and Chinese fir in order to calculate the evaporation volume of the mixed forest of Jinyun Mountain.improving the capacity of forest water resources regulation in the region,and revealing the evapotranspiration of the Jinyun Mountain forest the regulatory mechanism.(1)Sichuan hawthorn is a binodal curve with a peak value of 4.10 mmol/(m2·s).Pinus massoniana and Chinese fir are unimodal curves.The transpiration rate in July was slightly higher than that in May and June.The average daily transpiration rate was 1.38 mmol/(m2·s)for Chinese fir,1.48 mmol/(m2·s)for Pinus massoniana,and 2.11 mmol/(m2·s)for Sichuan Shanshan.The deficit of vapor pressure difference and air temperature had the greatest impact on the transpiration rate of stand tree species,and there was a negative correlation between the relative humidity of air and the three tree species.The results showed that there were significant differences in stomatal opening between leaves of the broad-leaved trees,and the transpiration rates of the needle and broad-leaved trees were significantly different under photosynthesis.(2)The variation of the flow rate between the three tree species showed a single-peak curve fluctuation on a daily basis,showing a typical single-peak daytime high night-time trend,the peak size and the interval size.There are significant differences.The average daily liquid flow rate was 11.29 g/(m2·s)>7.07 g/(m2·s)>3.10 g/(m2·s)of Chinese fir in Sichuan Mountain,and the average daily flow rate of three species under different weather conditions.The rates are sunny>cloudy>rainy.The start-up time for mass flow of Masson pine was 7:00-8:00,which was relatively later than that in Sichuan,and the start-up time of Fir-tree flow was the latest,and the evapotranspiration of the forest in May,June and July was 94.17mm,104.45mm,and 144.11mm,respectively.The sap flow velocity of each tree species was positively correlated with PAR,VPD,Tc,w,Ta and other factors,and was significantly negatively correlated with the relative humidity of air.These differences are not only closely related to the physiological structure and functional properties of the plant itself,but also constrained by changes in the stand structure and external environmental factors.(3)The total soil evaporation was 94.35mm.The soil evaporation in each month showed a unimodal curve,and the soil evaporation in June was the smallest.In July,the peak value of soil evaporation was twice that in May,and the average daily evaporation was 2.4 mm.The error between the measured value and the simulated value is 11.7%.Positive correlation with Tc and PAR,negative correlation with air humidity.(4)The total evapotranspiration of the coniferous and broad-leaved mixed forest in Jinyun Mountain during the period from May to July was 437.08mm,and the total transpiration of the stand was 342.73mm,accounting for 75%of the total evaporation.Photosynthetic radiation,temperature and humidity,soil temperature and humidity,vapor pressure,and wind speed are all factors that mainly affect the evaporation of coniferous and broad-leaved mixed forests.