Study On Ecological Security Evaluation Of Yuanmou Dry-hot Valley Region

Natural eco-environment is fragile in dry-hot valley region ikm severe human disturbances and frequent eco-environmental problems,so regional ecological security is facing serious threats.Quantitative study on ecological security evaluation of dry-hot valley region is helpful to clarify regional ecological security situation,its change process and development trend,to reveal main obstacle factors and obstacle formation mechanism,and to provide theoretical basis for ecological risk prevention and ecological environment protection in dry-hot valley,so as to promote ecological environment governance for local environment and the Yangtze river basin.Taking Yuanmou dry-hot valley(the whole Yuanmou county)as a case study,land use,landscape pattern,ecological systemservice value and vegetation coverage were studied and analyzed by using 3S technology,landscape ecology,geospatial analysis,mathematical model and multivariate statistical analysis.Then,a landscape ecological security model was constructed with landscape pattern indexes,vegetation coverage degree and ecological system service value as main parameters,so as to analyze temporal and spatial heterogeneity of landscape ecological security.A DPSIR framework model was used to build a comprehensive ecology security index system,the entropy weight matter-element model to study correlation level of evaluation indexes and comprehensive ecological security,a comprehensive index model to study DPSIR classification indexes and development trend of comprehensive ecological security.An ecological security barrier model was built to reveal evaluation index obstacles and their changes,and to find main obstacles and forming mechanism of regional conprehnesive ecological security.The remote sensing images of 2008 and 2016 were interpreted by remote sensing and GIS technology.It analyzed characteristics and changes of land use structure and landscape pattem.The study showed that land types were dominated by grassland,forestry and cultivated land in the study area.A majority of land use types had a greater degree of change,but the overall level was smaller and land use index had a slight change.The areas of cultivated land,forestry and construction land increased,while that of grassland,unused land and water area decreased.Grassland had the largest conversion areas to other landuse types.The conversion of construction land from other landtypes and that of unused land to other landtypes were obvious.Regional landscape pattern became complex for shorten area differences of landscape types and deepened landscape fragmentation degree.Spatial pattern and temporal evolution of vegetation coverage of Yuanmou dry-hot valley region from 2008 to 2016 were explored by using geospatial analysis and multivariate statistical methods,and elevation factors effect on vegetation coverage was analayed by the geographical regression model.The results showed that spatial pattern of vegetation coverage was highly consistent with terrain differentiation of the study area.The overall vegetation coverage was low,and high vegetation coverage proportion in the middle-high mountain areas greatly reduced,indicating that vegetation ecological environment in this area degraded.The area ratio of increased vegetation coverage and that of decreased vegetation coverage was 10:9,which showed the change of positive vegetation coverage was slightly higher than that of negative vegetation coverage,but dramatical change area of increase was larger than that of decrease.The dry-hot valley was very sensitive to the precipitation difference caused by elevation difference.The significant shortage of precipitation in the dry year made the differences between water and evaporation caused by elevation difference more obvious to vegetation coverage.The effect of elevation factors on vegetation coverage after 2012 significantly reduced,indicating that human interference factors strengthen its force.The article studied status and changes of ecological system service value from static value and dynamic value from 2008 to 2016.The results showed that forest land had largest static service value proportion in the study,grassland,followed by cultivated land,water body,and unused land,and construction land had greatest negative effect on ecosystem static service value.Static value of ecosystem service got slightly improvement,and dynamic value of ecosystem service was much lower than static value at the the corresponding period.However,change rate of ecosystem service dynamic value was much higher than that of ecosystem service static value,indicating that although the importance of ecosystem service value was not attached fully at the present stage,but with the development of economic and social development,dynamic value would significantly improved.A landscape ecological security evaluation model was constructed by using landscape pattern index,ecological system service value as parameters and vegetation coverage,and temporal and spatial evolution characteristics of landscape ecological security were analyzed.The value of landscape ecological security pattern index(LESP),landscape ecological quality index(LEQ)and landscape ecological security degree(LESD)belonged to the critical safety value range,which indicated that regional landscape ecological security was in a state of critical safe.Yuanmou's ecological security degree had a globally and locally positive correlation.The high-high value areas were clustered in the eastern and southern of the middle-high mountain areas and low mountains around the river dam,and the low-low value accumulation areas mainly distributed in the northern and western of the dry-hot valley and the middle-low mountain.The low-low value accumulation areas were broken obviously in the low mountains around the river dam and the middle-low mountainous areas along the Jinshajiang river,which reflected landscape fragmentation in this area.Terrain and geomorphology,climate,hydrology and other structural factors played a decisive role in the spatial distribution of landscape ecological security,while unstructured factors effect such as unused land development,cultivated area growth,urban expansion and natural forest protection,returning farmland to forests and other human factors,enhanced their impacts on spatial distribution of landscape ecological securityBased on DPSIR model as a theoretical framework,an evaluation index system of integrated ecological security was established.An entropy weight matter-element model and an integrated index model were used to evaluate comprehensive ecological security.An obstacle degree model was used to quantify the obstacle degree and to analyze mechanism of the evaluation index.The study showed that comprehensive ecological security of the study area had undergone four stages which were " conversion to extreme unsafety","conversion to less safety","conversion to critical safety" and "conversion to relative safety",indicating that comprehensive ecological security level continued to improve,but it still did not really enter the state of "good" level.The results of time series analysis showed that although comprehensive ecological security index in the next five years would get a slightly slow growth,comprehensive ecological security would remain in the state of conversion to "good" level for a long time.From 2005 to 2015,main obstacle types of comprehensive ecological security had changed,which can be divided into three stages:from 2005 to 2008,main obstacles of comprehensive ecological security were economic development level;from 2009 to 2011,cultivated land quality and agricultural production conditions gradually became main obstacles,followed by economic factors;from 2012 to 2016,population factors gradually became main obstacle type,followed by cultivated land quality.Comprehensive ecological security of the study area was mainly controlled by the insecurity of the native natural environment.As economic,social and land problems gradually improve,population factors became key obstacle.We must reduce population's pressure on ecological security through ecological migration and industrial transformation,realizing the transformation of ecological security quality,so as to ensure regional sustainable development.The paper had some innovations in spatial and temporal characteristics of landscape ecological security and quantitative evaluation of comprehensive ecological security in dry-hot valley.