Research On Dynamic Changes Of Ecological Environment Quality In Qinling-daba Mountains From 2000 To 2019

The mountain ecological environment is a very complex combination of multiple environmental elements,and its internal system is faced with environmental problems such as soil erosion,forest degradation,and land desertification.It plays an important role in indicating regional or global changes,and is also an important reference for reflecting a region’s ecological coordination and evaluating ecological environment construction.Based on the improved remote sensing ecological index model(NRSEI),with the help of the GEE remote sensing information processing platform,combined with Landsat remote sensing image data and soil data,spatial principal component analysis(SPCA)and geostatistical methods were used to quantitatively evaluate dynamic change characteristics of the ecological environment quality of QinlingDaba Mountains from 2000 to 2019.The spatial distribution pattern of the ecological environment quality in Qinling-Daba Mountains was analyzed from multiple perspectives(spatial migration,topography,latitude and longitude,spatial structure,landscape pattern),and the EQI ecological environment index was constructed to analyze the main factors affecting the changes in the ecological environment quality of Qinling-Daba Mountains.EQI verifies the model effect.The main conclusions are as follows:From 2000 to 2019,the cumulative contribution rate of PC1 and PC2 in the fifth-phase remote sensing data of Qinling-Daba Mountains reached more than 85%,which collected most of the information of 5indicators;Greenness(NDVI)and humidity(WI)have a positive effect on the quality of the ecological environment,while dryness(NDSI)and soil erosion(SRI)have a negative effect on the quality of the ecological environment,while heat(LST)is not obvious;Except for the LST,the other indicators have a high correlation with the newly established ecological environment index.The regression coefficient of each index has experienced a trend of first decreasing and then increasing in the past 20 years.The NDVI factor has a decisive role in the quality of the ecological environment,while the remaining factors play a complementary role.The average spatial distribution of ecological environment quality in Qinling-Daba Mountains from2000 to 2019 was 0.65,which was at a "good" level,and the ecological environment of the entire region gradually improved over the past 20 years;From 2000 to 2010,the NRSEI was in a transition from “moderate”to "good",with an average change of 35.30%,and the ecological environment quality improved significantly.The high-quality areas are concentrated in Qinling Mountains,Shennongjia Forest Area,Western Henan Mountains,Taibai Mountains and high-altitude areas in the west,covering Shennongjia,Taibai Mountain,Baotianman,Funiu Mountain and Gansu Lianhua Mountain and other national nature reserves;The lowquality areas are mainly distributed in the west,northwest low-altitude areas,the Hanzhong area and the eastern area,and are generally concentrated in the urban fringes;The range of slight rise and obvious rise between regions is large,while the range of decline is small and concentrated in high-altitude areas,and the spatial variation characteristics are more significant.The ecological environment in Qinling Mountains,Daba Mountains,Funiu Mountains,and the northwest is dominated by the "excellent" and "good" areas,while the high altitudes in the southwest and the high mountains in the central and western Qinling are converted into "poor" and "very good" areas;The improved area of ecological environment is much larger than the area of worsened ecological environment,the moving distance of high ecological environment type index is greater than that of low type index,and the spatial migration direction is mainly from the fragile ecological environment with more complex environment to the area with better ecological environment.As the altitude increases,the quality of the ecological environment first increases and then decreases.The area increases most significantly between1000 and 1500 m,and reaches a peak near 2500 to 3000 m.The ecology is poor in the range of <1000 m and >3000 m,and the upper limit of the NRSEI distribution is closely related to the altitude;on the slope,the high ecological index is mainly concentrated in the range of 10～40°,the low ecological index is between less than 10° and greater than 40°,and the human disturbance is serious under the low slope;on the aspect,the high ecological index area is located in the sunny slope and semi-sunny slopes,the low ecological index is located on shady and semi-shady slopes,and there is a big difference between sunny slopes and shady slopes.The Moran’ I value of ecological environment quality from 2000 to 2019 reached the maximum at grid2 km,and NRSEI has strong spatial heterogeneity at this scale;high-high clusters are mostly distributed near mountains with good vegetation,and low-low clusters are mainly distributed in high-altitude or urbanintensive areas,and the possibility of ecological environment deterioration in the alpine areas west of the Jialing River becomes greater;Within the optimal scale of 2 km,the optimal model is a spherical model,which is affected by both structural and random factors.In the past 20 years,the fragmentation of the QinlingDaba Mountains habitat landscape gradually decreased,and the PAFRAC,CONTAG,SHDI,and MSIEI were 1.500,55.458%,0.935,and 0.473,respectively,and the heterogeneity of different landscapes tended to be consistent at the same period.The COHESION of the two grades of "very poor" and "excellent" are 77.605%and 85.194% respectively,and the spatial aggregation degree is poor,while "poor","moderate" and "good" show obvious good spatial aggregation,and the landscape pattern presents the general characteristics of "bad at both ends,good in the middle";Habitat fragmentation gradually changed from moderate fragmentation to low fragmentation.The "very poor","poor" and "moderate" areas contributed to more than 75% of the improvement of the ecological environment in the study area,and the high fragmentation areas were mainly concentrated in some farming areas and western mountainous areas,the fragmentation of habitats in other areas is not obvious.The ecological niches of different levels of ecological index generally move to high levels,but the maximum value of the ecological niche is only 0.319,and the distribution of regional ecological environment quality in the ecosystem needs to be further improved.The analysis of influencing factors shows that NDVI has the highest spatially independent explanatory ability(83.10%),followed by climatic elements and topographic elements.The ecological environment quality is obviously restricted by natural factors,and the influence of social and economic factors is not enough to offset changes well of the regional mountain ecology;The interaction between NDVI,DMI,TPI and any factor is greater than that of a single factor,and its correlation coefficient is as large as that of NRSEI.Vegetation status,climate change and topographic features significantly affect the distribution of ecological environment quality in Qinling-Daba Mountains.Through the verification of EQI ecological environment index,it is found that the improved remote sensing ecological index NRSEI is better than the ecological environment verification index EQI.EQI is coupled with multiple target factors,and the local details are not obvious enough,and it is easily affected by the weight of a single index factor;the average value of EQI is in some years are higher than NRSEI,but the spatial stability is not as good as NRSEI;compared with EQI,NRSEI improves the expression ability of soil factors,vegetation factors and population distribution factors in the evaluation of ecological environment quality in Qinling-Daba Mountains,and has strong accuracy and superiority.