| In the context of global change,large-scale land use/cover changes have caused a series of ecological and environmental problems,which have seriously threatened regional food security and ecological security.As a unique mountain system in China,the Qinling-Daba Mountains have high ecological sensitivity.Under the combined action of human activities and climate change,problems such as changes in land use structure,landscape destruction,and non-point source pollution in river basins have resulted in the fragmentation of ecosystem functions.As an important ecological security barrier in China and the largest contiguous destitute area in China,the Qinling-Daba Mountains are currently in a period of intense conflict between ecological protection and poverty alleviation.And the scale effect of its ecological environment quality and driving mechanism is analyzed,in order to provide a scientific basis for the ecological protection construction of Qinling-Daba Mountains,and also provide a theoretical reference for the sustainable development of mountain ecosystems.Based on the land use data of 2000,2010 and 2020,this paper analyzed the land use change and terrain gradient difference in Qinling-Daba mountains from the perspectives of quantity,spatial pattern,transfer and topographic differentiation.The spatial-temporal changes of ecoenvironmental quality and the ecological effects of land use from 2000 to 2020 were analyzed based on remote sensing ecological Index(RSEI).From the perspective of ecological zoning,seven factors,including elevation,slope,population density,annual temperature,annual precipitation,land use degree and soil type,were selected to analyze the scale difference of driving mechanism of ecological environment quality in Qinling-Daba mountains,and to identify the ecological dominant areas.The results show that:(1)Cultivated land,forest land and grassland are the main land use types in Qinling-Daba mountains.During the study period,the total area of these three land types accounts for more than 95% of the total area of the whole region.There are regional differences in quantity change and transfer.As a whole,cultivated land decreased,woodland grassland increased,and grassland increased or decreased.Land transfer was particularly obvious from 2010 to 2020,and 30,177km2 of farmland was converted to forest and grassland,and 300,80km2 of ecological degradation(forest land and grassland converted to arable land)occurred in the whole region,of which the land transfer was most obvious in Shaanxi and Henan provinces.(2)There are obvious differences of terrain gradient in land use in Qinling-Daba mountains.The area with low elevation and small slope is the dominant area of construction land and water body distribution.Woodland and grassland have strong adaptability to terrain difference.The transfer index of construction land and water decreased with the increase of elevation and slope.Under the influence of ecological protection construction,cultivated land is transferred to woodland and grassland in hilly areas.Affected by the demand of production and living,woodland and grassland tend to be transferred to arable land in plain basin area.(3)In the study period,the ecological environment quality pattern of Qinling-Daba mountain area showed a state of high in the middle and low in the east,and the ecological environment improved continuously.From 2000 to 2010,the area of ecological environment quality in Qinling-Daba mountains improved by more than 50%,mainly in Sichuan and Hubei provinces.From 2010 to 2020,more than 95 percent of the region’s ecological and environmental quality was improved,with only sporadic areas experiencing degradation.In terms of the ecological effect of land use,forestland and grassland can help to improve the ecological environment,while the increase of cultivated land area will have some negative effects.The implementation of Qinling-Daba mountain ecological protection project plays a positive role in the improvement of ecological environment,and the ecological environment quality in the area of returning farmland to forest and grassland is obviously higher than that in the area of not returning farmland.(4)There are scale differences in the causes of spatial differentiation of eco-environmental quality in Qinling-Daba mountains.At the regional scale,altitude and annual average temperature were the primary factors affecting ecological environment quality.From the perspective of ecological subregion,the ecological environment quality of haidong-Gannan alpine meadow grassland ecological subregion is mainly affected by population density.The ecological environment quality of minshan-Qionglai Spruce forest-Alpine meadow-evergreen broad-leaved forest ecological subregion was mainly affected by altitude,annual average temperature and soil type.The ecological environment quality of the mixed deciduous broadleave-coniferous and broadleave-mixed forest in the Qinling Mountains was mainly affected by altitude,annual average temperature and annual average precipitation.The ecological environment quality of micangshan-Dabashan deciduous broadleave-conifer and broadleave-conifer mixed forest and three Gorges Reservoir ecological sub-area were mainly affected by altitude and annual average temperature.The ecological environment quality of mountainous evergreen deciduous broad-leaved forest subregion in southwest Henan and agricultural ecological subregion in hilly basin of upper Hanjiang River are mainly affected by land use degree.When the altitude,annual mean temperature and land use degree interact with other factors,their effects are significantly enhanced,resulting in regional differences of ecological environment in the Qinling-Daba mountains.(5)The relationship between eco-environmental quality and driving factors is linear and nonlinear.In the area with altitude < 3,200 m and slope <35°,the eco-environmental quality increases with the increase of altitude and slope,and the eco-environmental quality of some sub-regions decreases in the area with altitude > 3,200 m and slope >35°.There is a negative linear relationship between annual temperature and ecological environment quality.There are nonlinear relationships among population density,annual precipitation,land use degree and eco-environmental quality.The ecological environment quality of man-made land area is lower than that of alpine soil area.In general,the areas with medium and large slope,medium and high altitude,low population density,low annual temperature,low land use degree and alpine soil constitute ecological advantage areas.The ecological environment quality of haidong--Gannan Alpine meadow grassland sub-area and Minshan--Qionglai Spruce fir forest-Alpine meadow--evergreen deciduous broad-leaved forest sub-area was higher than the average level of Qinling-Bashan mountains.The ecological environment quality of the mountainous evergreen deciduous broad-leaved forest subzone in southwest Henan province,the agricultural ecological subzone in the hilly basin of the upper Hanjiang River and the ecological sub-zone of the Three Gorges Reservoir are lower than the average level of the Qinling-Daba mountains. |
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