| Ecological environment is the basis for the survival of human society,and its quality is closely related to the construction of ecological civilization and economic and social development.Yanhe River Basin is located in the hilly and gully region of loess in China.The ecological and environmental problems such as soil erosion and soil erosion are prominent in the basin.Therefore,accurate and efficient monitoring of watershed ecological environment quality,analysis of its spatio-temporal change process,explore the driving mechanism,is an urgent need to improve the watershed ecological environment.Firstly,moving window method and entropy method were used to optimize Remote Sensing Ecological Index(RSEI).The Modified-Remote Sensing Ecological Index(M-RSEI)was constructed.Meanwhile,intermediate variable: Regional Optimized Remote Sensing Ecological Index(RO-RSEI).Then,RSEI,RO-RSEI and M-RSEI were respectively applied to the monitoring of ecological environment quality in the Yanhe River Basin in 2000,2005,2010,2015 and 2020,and the relevant results were analyzed and evaluated.Finally,the driving mechanism of ecological environment in the watershed is studied by using the geographic detector method,and CA-Markov model is used to predict the ecological environment quality in 2025 and 2030.The main findings are as follows:(1)Compared with the other two models,the M-RSEI model is more consistent with the actual situation of ecological environment quality in the Yanhe River Basin.Comparing the results of different models,it is found that the monitoring accuracy of RO-RSEI model with only moving window method is higher than that of RSEI model,but the results are still not stable,and the ecological environment quality of some regions is underestimated or overestimated.This problem can be further improved by using entropy method instead of principal component analysis method.Finally,the calculation results of the three models were compared with the announcement of ecological environment status of Shaanxi Province in2020,and the M-RSEI monitoring results were the closest.(2)During the monitoring period,the ecological environment quality of the Yanhe River Basin showed an overall upward trend,but its interannual variation was still different.The mean values of M-RSEI in the Yanhe River Basin in 2000,2005,2010,2015 and 2020 were0.481,0.520,0.491,0.537 and 0.628,respectively,and the mean values of the first four periods were all lower than 0.6,indicating that the ecological environment quality was still poor.According to the classification of M-RSEI with an interval of 0.2,the ecological environment in the southern part of the basin is better than that in the northwestern part of the basin.The environmental quality of the basin is mainly "medium",and the "good" level increases year by year,especially from 2015 to 2020,indicating that the ecological environment quality of the basin has been greatly improved during this period.The dynamic monitoring showed that the ecological environment quality in nearly half of the basin had changed obviously,with the change level being 1 and negative 1.The ecological environment center of gravity gradually moved to the northwest direction.(3)The four indexes of NDVI,WET,NDBSI and LST are suitable to evaluate the ecological environment of the basin.In 2020,the ecological environment of the basin is mainly affected by land use,temperature and elevation.The ecological environment of the basin gradually increases under the influence of elevation and temperature,and gradually decreases under the influence of slope and soil type.As indicated by the effect of detection factors,it is found that NDVI,WET and GDP factors promote the improvement of ecological environment quality,while NDBSI and LST factors inhibit the improvement,and the area with moderate rainfall,temperature and elevation is the most suitable for human habitation.By exploring the interaction of various factors,it is found that the change of the ecological environment quality of the basin is the result of the interaction of various factors,and human activities are the indirect factors affecting the ecological environment quality.When controlling the ecological environment problems of the basin,the driving factors should be considered such as terrain,human activities,meteorology,soil type,etc.The single factor should also be analyzed from many aspects.(4)CA-Markov model predicts that the ecological environment quality will be greatly improved in the future,but ecological problems still exist in some regions.Kappa coefficient was used to verify the calculated and simulated results in 2015 and 2020,and the values were0.6762 and 0.6503,respectively,with good fitting accuracy,indicating that CA-Markov model is suitable for the prediction of ecological environmental quality in Yanhe River Basin.The total area of "good" and "excellent" grade in 2025 and 2030 will be 73.44% and 76.87%respectively,while the area of "very poor" grade will decrease to 0.46% in 2030.The ecological environment quality has been improved in the northwest,Xincheng District and the lower reaches of the basin,but there are still areas with poor ecological environment quality.Therefore,the government should focus on the northwestern part of the Yanhe River Basin,the Xincheng District and the lower part of the basin. |
