The Method System And Case Study Of A Vulnerability Assessment Of Mountain Ecological System In Semi-arid And Arid Areas

Arid and semi-arid mountain ecosystem is an important biological habitat and biodiversity center in northern China,with water conservation,windbreak and sand fixation,soil conservation,scientific research and other ecological service functions.However,under the influence of global change and human activities,due to the endogenous vulnerability and instability of mountain ecosystems,it shows obvious ecological vulnerability.Therefore,how to improve the stability of mountain ecosystems in arid and semi-arid areas is the key to protect the ecological environment,This requires a study of the corresponding technical approach system to provide guidance for the effective management of regional ecosystems.The aim of this study is to construct a framework system for estimating the vulnerability of mountain ecosystems in arid and semi-arid areas based on the VSD model and taking the Helan Mountain in Ningxia as an example.The main contents of the study include the identification of the main exposure sources in the region,the sensitivity and adaptability of the ecosystem after being disturbed,the interrelationship between the exposure,the sensitivity and the adaptability,and the temporal and spatial distribution of the regional ecological vulnerability.The results are as follows:(1)Ecological environment improved obviously in Helan mountain of Ningxia.From the time point of view,from 1988 to 2013,regional ecological environment was recovered from mainly severe vulnerable to moderately vulnerable,the ecological vulnerability classification index decreased from 7.4 to 5.3.The total area of the ecological fragility of each grade in the study area was 1770 km2,the comprehensive dynamic degree was 77%,And the overall trend of transition from high vulnerability to low vulnerability.Among them,the severe fragile area of the largest change,accounting for 38.3%of the total area of the study area,mainly into moderate fragile areas,reducing the area accounted for 42.4%of the total area.The basic non-graded areas in the region are transformed into extremely vulnerable areas.(2)From the spatial pattern,the ecological fragility of Helan Mountain in Ningxia showed a low distribution pattern.In 1988,the ecological fragility level and the slope grade showed a regular occurrence of the low middle height between the two ends.The severe and extremely vulnerable areas occurred in the range of 25°-40°.2013 is similar to 1988.Indicating that there was no significant change in the spatial distribution of ecological vulnerability levels over time.And the results of the superposition of the elevation also show a similar occurrence law,that is,low altitude and high altitude local vulnerability level less,the maximum value of the basic range of 1500-2000m.(3)The evaluation system of mountain ecosystem vulnerability in arid and semi-arid areas has certain guiding significance.The ecological environment of the study area is improved and the ecological fragility is obviously reduced,which is consistent with the change of the ecological environment of Helan Mountain after the establishment of the Helan Mountain National Nature Reserve in Ningxia.It shows that the framework model constructed in this study has practical significance,The relationship between exposure,sensitivity and adaptability of mountain ecosystems is described accurately.Thus providing effective technical support for the management of mountainous systems in arid and semi-arid areas.