The Stability Of Patchy Vegetation In The Desert-Oasis Transition Zone In The Middle Reaches Of Heihe River Under Human Disturbance

The desert-oasis transition zone in the middle reaches of the Heihe River is located at the junction of the Badain Jaran Desert and the Zhanglingao Oasis,and plays an extremely important role in resisting the dangers of wind and sand and maintaining the stability of the oasis.Due to some unreasonable human activities such as woodcutting and grazing by the local people,the desertification continued to expand and the ecological environment in the transition zone deteriorated further.In recent years,in order to prevent wind and fix sand and improve the regional ecological environment,local people have carried out a large number of replanting of sand-fixing vegetation in the transition zone.However,under this kind of human disturbance(mainly to replant sand-fixing plants),the evolution direction of regional vegetation stability has become the primary concern of the academic community.In this paper,the desert vegetation in the desert-oasis transition zone is taken as the research object.Based on the analysis of the dynamic changes of the vegetation landscape,the changes of the vegetation stability in the transition zone are evaluated from the perspective of time and space.At the same time,combined with the changing characteristics of regional environmental factors,the relationship between environmental factors and vegetation stability changes was analyzed.To further accurately assess the trend of regional vegetation stability under human interference,and provide a theoretical basis for the protection of natural vegetation in the area and the reasonable spatial allocation of artificial vegetation communities.The conclusion of the study is as follows:(1)According to the information on the change of the patch area and the bare patch area of the vegetation in the study area(Haloxylon ammodendron,Nitrarias sphaerocarpa thorn and Calligonum chinense),the vegetation area shows an increasing trend.Among them,the annual increase rate of Calligonum chinense was relatively large,which was 10.94%;the area of bare land showed a decreasing trend,with an annual decrease rate of 5.28%;from the analysis of landscape transfer matrix,it can be seen that the area of bare land converted to Haloxylon ammodendron was the most prominent during the study period.Up to 2.57 hm~2.The conversion of bare land into Nitrarias sphaerocarpa and Calligonum chinense was relatively large,0.04 hm~2 and 0.42 hm~2,respectively.In summary,the area of vegetation in the study area increases year by year,and the area of bare land decreases year by year.The ecological environment has been repaired to a certain extent.(2)From the time scale analysis of the vegetation stability in the study area,the stability ratio in 2019 is closest to the community stability point of 20/80.That is,the order of plant stability from strong to weak in the study area in different periods is:2019 a vegetation>2012a vegetation>2014 a vegetation.It shows that this kind of human disturbance is conducive to the enhancement of the stability of vegetation,but the process of enhancing stability has a lag;from the number of plant species appearing in the study area,the number of species appearing in the study area in 2012,2014 and 2019 There are 5 species,6 species and 9 species respectively,and the migration of plant species over time shows an increasing trend.It further illustrates that reasonable replanting of artificial vegetation Haloxylon ammodendron is beneficial to the stability of the desert-oasis plant community and the increase in the number of plant species.(3)From the analysis of the spatial stability of vegetation in the study area,we can see that the trend of vegetation stability in the study area in 2014 and 2019 is consistent,both of which show a change in the stability of the vegetation community from south to north and from west to east.trend.And on the south side of the plot,vegetation stability is the strongest.This may be closely related to the geographical location of the study area.(4)The effect of surface particle size restoration in the study area is:2019 a vegetation>2014 a vegetation>2012 a vegetation.Full description:Under reasonable human interference,the soil texture in the vegetation zone of the desert-oasis transition zone in the middle reaches of the Heihe River will be improved.(5)The meteorological factor that has the greatest impact on vegetation stability in the study area from 2012 to 2019 is air temperature,and the soil factor that has the greatest impact on vegetation stability is the soil water content of the 0-10 cm soil layer.(6)From 2012 to 2019,the wind and sand activity in the study area changed from wind erosion activity to wind accumulation activity.The enhancement of vegetation stability is the main reason for this phenomenon;and the topographical characteristics of the study area are the reasons for the local differences in the spatial distribution of the intensity of sand erosion.