Study On The Effect Of The Typical Project Area Of The Three-North Shelter Forest Program On The Ecological Environment

The Three-North Shelter Forest Program is an important ecological and environmental protection project in China,which not only prevents wind and fixes sand,but also improves the local ecological environment.A large number of studies have been carried out on the ecological effects of windbreak and sand fixation,but few studies have been conducted on the ecological effects of afforestation areas on nearby microclimates.This study firstly analyzes the temporal and spatial variation patterns of land surface temperature,temperature,precipitation,and NDVI in the Three-North Shelter Forest Program from 2001 to 2017,and then analyzes the land surface temperature,evapotranspiration,albedo,temperature of forest land to open land by the method of "spatial substitution time".The regional ecological and environmental effects of the Three-North Shelter Forest Program were evaluated based on effects.The main conclusions are as follows:(1)The NDVI,surface temperature,air temperature,precipitation,multi-year average temperature and precipitation of the growing season in the Three-North Shelter Forest Program showed a fluctuating and slow increasing trend from 2001 to 2017.The study showed that the ecological environment quality was improved,and the implementation of the projects of returning farmland to forest and grass had achieved good ecological effects.(2)From 2001 to 2017,the effect of the Three-North Shelter Forest Program on the surface temperature was manifested as a diurnal asymmetry of cooling during the day and warming at night.The effect of afforestation on the surface temperature has a seasonal law.The cooling effect of the daytime surface temperature is:summer>autumn>spring>winter,and the warming effect of the nighttime surface temperature is: autumn>summer>winter>spring.The influence effect is presented as a cooling effect.(3)From 2001 to 2017,the effect of the Three-North Shelter Forest Program on evapotranspiration showed that it first increased and then weakened with the month.The maximum value is 0.05mm/d in July,and the weakening effect reaches a maximum value of-0.11mm/d in January of the following year.The effect of evapotranspiration is the strongest in summer,followed by spring and autumn,respectively,and the evapotranspiration in winter is weakened.The overall effect on albedo is a weakening effect.As the month first shows a trend of first weakening and then strengthening,it reaches the lowest value of 0.4% in July,and then the albedo effect gradually shows a strengthening effect.The maximum value is 3.4%.The albedo changes in spring,summer,autumn and winter all showed a weak decreasing trend.(4)From 2001 to 2017,the effect of Three-North Shelter Forest Program on precipitation showed that the effect of precipitation in different months showed an "n"-shaped change trend,with a maximum value of 13.845 mm in September and a minimum value of 0.448 mm in December.The effect on summer precipitation is the strongest,followed by autumn and spring,and the lowest in winter.The multi-year average value of the effect of precipitation is 7.323 mm,indicating that the Three-North Shelterbelt has a strong precipitation effect on the local area.The effect on temperature shows an "n"-shaped trend,reaching a maximum value of 2.212℃ in July and a minimum value of-0.234℃ in January.The summer temperature has the greatest impact,followed by autumn and spring,and the winter temperature has the least impact,the multi-year average value of the effect on temperature is 1.432℃.