| Windbreak and sand fixation is the main ecological system service function of China’s northern sand control belt,and plays a very crucial role in building China’s northern ecological security barrier.It is also of great significance in maintaining biodiversity,maintaining regional ecological security and sustainable regional development,and is conducive to the healthy development of the ecosystem and sustainable regional economic development.Northwest Liaoning is located in the interlocking agricultural and pastoral areas of northern China,at the junction of the Horqin sands and the western plain of the Liao River.It is a typical desertification area with sparse vegetation,dense barren mountains,dry climate,drastic climate change and sensitive and fragile ecological environment.Since 2009,the government of Liaoning Province has implemented a series of grassland desertification control measures in the northwestern Liaoning Province,accelerated the special control of desertification and desertification in the southern edge of Horqin Sandy Land,improved the ecological environment in the northwestern Liaoning province,and reduced the damage of dust in the downwind areas.The modified wind erosion equation model(RWEQ)was used to evaluate the ecological effects of grassland desertification control measures in northwest Liaoning in order to scientifically and accurately assess their ecological effectiveness,as well as to enhance the coordination and restoration of ecosystem service functions between the upwind and downwind areas of the ecosystem,the Lagrangian Integration Orbit(HYSPLIT)model was adopted in combination with the wind direction,wind speed and soil dust particle composition components in the region to numerically simulate the flow paths of windbreak and sand fixation in northwest Liaoning,and to identify and calculate the radiation area and radiation effect of windbreak and sand fixation service.The main conclusions are as follows:(1)In 2000,the total annual windbreak and sand fixation in the study area was 11.74×10~6t,and the sand control per unit area ranged from 0 to 1.21 kg/m~2,with an average sand control per unit area of 0.25 kg/m~2;In 2010,the sand control per unit area ranged from 0 to 1.09 kg/m~2,with an average of 0.28 kg/m~2,and the total annual amount was 13.11×10~6 t;In 2020,the sand control per unit area ranged from 0 to 1.16 kg/m~2,with an average of 0.26 kg/m~2,and the total annual amount of 12.17×10~6 t.From 2000 to 2010,the average amount of windbreak and sand fixation per square meter has increased by 0.03 kg/m~2 and the total amount has increased by1.37×10~6 t;From 2010 to 2020,the average amount of windbreak and sand fixation per square meter has decreased by 0.02 kg/m~2 and the total amount has decreased by 0.94×10~6 t.During the 20-year period,the amount of windbreak and sand fixation generally increased,but in the three periods,the amount of windbreak and sand fixation showed a trend of increasing before decreasing,and the construction of windbreak and sand fixation is still a part of the northwest Liaoning region that needs to be strengthened as a priority.(2)Under the influence of climate,soil,terrain,vegetation and human activities,there are obvious differences in the service space of windbreak and sand fixation in northwestern Liaoning.Overall,"low"and"lower"levels of windbreak and sand fixation are the most widely distributed areas.The distribution of"medium"and"higher"levels of windbreak and sand fixation is the second.The distribution of"high"level windbreak and sand fixation is relatively small.In terms of spatial distribution,from 2000 to 2020,the regions with"low"and"lower"levels of windbreak and sand fixation function are mainly located in the southern edge of Horqin Sandy Land,and most regions of Tie ling City,Kang ping County and Fa Ku County are in the"low"level all year long.The regions with the function level of"medium"for windbreak and sand fixation are scattered in the northwestern part of Liaoning Province with irregular distribution and obvious changes.The areas with"higher"and"high"levels of windbreak and sand fixation function are mainly distributed near the Liao he River,Da ling River and Rao yang River basins.It is suggested to strengthen the ecological management of some inland areas in the southern edge of Horqin Sandy Land,so as to improve the overall windbreak and sand fixation service capacity in the northwest of Liaoning Province.(3)In 2000,2010 and 2020,249,216 and 195 windbreak and sand fixation service flow paths were generated in northwest Liaoning,mainly occurring in spring,with a proportion of more than 30%per year.The decrease in windbreak and sand fixation service flow paths indicates that the number of windy days in northwest Liaoning is decreasing year by year.The flow path of windbreak and sand fixation services mostly spreads from the study area to the east,northeast and southeast,mainly covering the northeast,north China and the Yellow Sea and Bohai Sea areas,and very few will spread to the northwest.There are seasonal differences in the distribution of the flow path in the service space of windbreak and sand fixation.It is transported eastward and southeast in spring,autumn and winter.Flows east and northeast in summer.Most of the radiation areas with a flow path distribution frequency of less than 3%,and areas with a distribution frequency greater than or equal to 10%are concentrated in central Liaoning Province,northwestern Jilin Province and eastern Inner Mongolia Autonomous Region.(4)In 2000,the service radiation area of windbreak and sand fixation in northwest Liaoning was 1.75×10~6 km~2,and the amount of downwind dust was reduced by 5.76×10~6 t,and the reduction of dust settlement per unit area was 122.80t/km~2.In 2010,the radiation area of windbreak and sand fixation service was 1.72×10~6 km~2,and the downwind dust reduction was 6.43×10~6t,and the reduction of dust settlement per unit area was 137.54t/km~2.By 2020,the service radiation area of windbreak and sand fixation in northwest Liaoning was 1.84×10~6km~2,and the amount of downwind dust is 5.97×10~6 t,and the amount of dust settlement per unit area is 127.71t/km~2.The provinces involved include 13 provinces(municipalities directly under the Central Government and autonomous regions),including Anhui,Beijing,Hebei,Heilongjiang,Henan,Jilin,Jiangsu,Liaoning,Inner Mongolia Autonomous Region,Shandong,Shanghai,Tianjin and Zhejiang,of which Heilongjiang and Inner Mongolia Autonomous Regions received the largest radiation effect,accounting for more than 50%of the total,while Tianjin,Beijing and Shanghai enjoyed a relatively small radiation effect,all less than 1%of the total. |
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