| Grasslands are an important ecological security barrier in China and an important resource for maintaining the country’s ecological security.The stability of the ecological security state of grasslands is related to the process of building ecological civilization,and plays an irreplaceable role in promoting the sustainable and stable socio-economic development of grassland areas.Located in the Tibetan Autonomous Prefecture-Qiang of Aba,northwest of Sichuan Province,the Northwest Sichuan Grassland is in the transition zone between the Qinghai-Tibet Plateau and the Sichuan Basin and has an important ecological location because it is the ecological safety barrier of the Yangtze.and the Yellow River basins and is of great importance to the region in terms of water conservation,soil and climate regulation.Translated with www.Deep L.com/Translator(free version)However,it has a complex geographical environment,frequent natural disasters and fragile ecological environment.As human social development has promoted the development of the grasslands in northwest Sichuan,it has also put pressure on the ecological environment of the region,which to some extent has an impact on the ecological security of the grasslands.Maintaining the richness of grassland resources in northwest Sichuan and protecting a good grassland ecological environment are directly related to the overall ecological security of the region and the realization of sustainable development.At present,scholars have conducted ecological security evaluation of ecologically fragile areas in northwest Sichuan,but the evaluation is based on the overall situation without refinement and delineation on a smaller spatial scale.In addition,the current grassland ecological security evaluation is mainly retrospective research,and the research on early warning models and systems has not been enriched.This study takes the grasslands of northwest Sichuan as a research object,using "3S" techniques to assess and provide early warning for the ecological security of the grassland.Based on the conceptual model of "Driving(D)-Pressure(P)-State(S)-Impact(I)-Response(R)",The study established a grassland ecological security evaluation index system in northwestern Sichuan,combined with remote sensing image data,digital elevation models,weather station data and statistical data,combined with social and economic conditions,obtained the spatial data required by the evaluation system,and improved the evaluation database.The projection tracing model was used to determine the weights of each influence factor,and then comprehensive weighting was calculated to obtain the ecological security evaluation results of the study area from 2000-2015 and graded and analyzed.On this basis,the data from 2000-2010 were made as training samples and validated with 2015 data,and a qualified gray prediction model was used to predict the future development trend of ecological security status in the study area,which finally provides decision basis and reference support for local natural resources protection and tourism planning and management with respect to the characteristics at all levels.The main conclusions of this study are as follows.(1)The study establishes the ecological security evaluation index system for grassland in northwestern Sichuan,using the projection pursuit model,constructing the projection index function and optimizing the projection direction,and finally obtaining the weights of each influence factor in the evaluation system.It is calculated that there is no great difference in the weights of each influence factor,but the weight values of population number and slope factor are higher than the weight values of other factors,both of which exceed 0.1.It can be said that the ecological security evaluation results of the study area are more influenced by slope changes and human activities.(2)The average value of the ecological safety assessment results in the study area shows an initial downward trend and then a slow increase.The average value of ecological safety assessment results in the study area was 0.6258 in 2000,and slightly decreased by 0.0009 to 0.6249 in 2005.It continued to decrease to 0.6235 in 2010,but rebounded in 2015,reaching 0.6241.The average value of each period is in a safer state,which shows that the overall state of the study area is good,although the effect of measures such as returning farmland to forest and grass is slightly lagging,but various ecological civilization construction initiatives have curbed the deterioration of the environment.(3)The study area is dominated by the safe state(V)and the safer state(IV),and the area ratio of the safe state and the safer state combined in each phase exceeds 60%of the total area of the study area,which dominates the entire ecological safety state in the study area,and the overall performance is strong resistance to disturbance and has certain self-healing ability.Although there is a certain degree of transfer in and out among the security levels,the distribution of ecological security levels in each period maintains basic stability,and the area ratio of each ecological security level in the whole study area belongs to safer state(IV)> safe state(V)> light warning state(III)>moderate warning state(II)> severe warning state(I).In terms of spatial distribution,the safe state areas are mostly distributed in the middle of the study area,where the slope changes little,the surface undulation is small,the vegetation cover is good,and the ecosystem is more stable.The safer areas are mostly distributed around the safe area,which is a transitional state between the safe state and the light warning state.The light warning area is distributed around the outer edge of the medium warning area and the severe warning area,and is also in the transition stage between the safe state and the warning state.The medium warning area is distributed in the northeast and southwest of the study area,where the elevation is high,the slope changes a lot,and the surface is undulating,and due to the scarcity of vegetation cover,low water-holding capacity and large slope,geological disasters are prone to occur and the ecosystem is unstable.The heavy warning areas are mostly distributed in the contiguous areas of moderate warning areas in the northeast and southwest of the study area.(4)The study established a gray prediction model based on the prediction grid cells and trained on the data from 2000-2010,and used the 2015 data as the validation,the final model accuracy R2 reached 0.88,and the prediction effect was good,which can be used for the prediction of the future ecological security status of the study area.The prediction results showed that the mean value of future ecological safety evaluation in the study area showed a small decline in the prediction period as a whole,from 0.6225 in 2025 to 0.6216 in 2035.but there was no great change in the overall grade distribution share pattern,only an increase and decrease in the area of each grade.From the length of the time series interval,the mean value of ecological security has a small change,and if active conservation measures are taken will provide a good positive guidance for the protection and restoration of the ecological environment in the study area. |
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