| The construction and operation of highways promotes rapid socio-economic development,but at the same time disturbs the ecological environment along the highway.The Baima Snow Mountain National Nature Reserve is rich in natural resources and unique in cultural landscape,and is one of the global hotspots for biodiversity conservation.Due to the unique biodiversity of the reserve and the fragility of the ecological environment,it is extremely important to maintain the ecological safety of the reserve,and it is necessary to investigate the impact of the road crossing the reserve on the ecological environment along the route.Therefore,the G214 in the Baima Snow Mountain Reserve is used as an example to reveal the impact of highway construction and operation on the ecological environment along the route by analysing the changes in land use,landscape pattern and plant diversity at different spatial and temporal scales within 10 km of the highway.According to the construction and operation process of G214 in the protected area,the time scale of the study is divided into three stages,namely,2000-2010,the tertiary highway operation stage,2010-2015 on the basis of the original G214 construction stage,2015-2020G214 operation stage.A buffer zone of 10 km along both sides of the highway was selected as the study area,with each 1 km buffer zone as the study scale,which is within 3 km buffer zone and then every 300 m buffer zone as the study scale,to study the characteristics of changes in ecological and environmental indicators.The main findings of the study are as follows.(1)From the land use changes,the land use along G214 in Baima Xueshan Reserve is dominated by forested land,shrubland and grassland.2000-2010,during the operation phase of thetertiary highway,the area of forested land,grassland,rural settlements and arable land increased,while the area of shrubland decreased;2010-2015,during the construction phase of the G214,the area of forested land and shrubland decreased,while the area of grassland,rural settlements and arable land decreased.The area of grassland,rural settlements and arable land increases;the operational phase of the G214 from 2015 to 2020 results in a decrease in the area of wooded and shrubby woodland and an increase in the area of rural settlements and grassland.During the operation phase of the former tertiary roads,the area of shrubland mainly decreases,and during the construction and operation phase of the national roads,the area of forested land and shrubland mainly decreases in the areas along the routes,which are more seriously disturbed by the roads,while the area of grassland,rural settlements and arable land increases,and the area of water bodies and unused land changes the least,among which forested land and shrubland are the most important types transferred to rural settlements and arable land;in terms of spatial changes In terms of spatial change,the rate of spatial change in land use and the index of comprehensive degree of land use in the 1-3 km buffer zone range along the highway is the largest,which has a serious impact on land use change,an average impact on land use change in the 4-7 km buffer zone range,and no impact on land use change in the 8-10 km buffer zone range.In terms of vegetation cover changes,during the operation phase of the former tertiary highway from 2000 to 2010,the areas of medium-low cover and low cover increased and the areas of medium cover and high cover decreased;during the construction phase of the G214 from 2010 to 2015,the areas of medium cover,medium-low cover,low cover and bare land increased and the areas of high cover decreased;during the operation phase of the national highway from 2015 to 2020,the areas of medium-low cover In the operation phase of the G214 from 2015 to 2020,the areas with medium-low coverage,low coverage and bare land increase,while the areas with high coverage and medium coverage decrease;in terms of spatial changes,the serious impact of the construction and operation of the highway on the reduction of vegetation cover is in the 1-7 km buffer zone,while the vegetation cover in the8-10 km buffer zone is basically not affected by the highway.(2)The fragmentation of landscape pattern along the highway was the most obvious during the operation stage of the original tertiary highway;during the construction stage of G214,it also affected the landscape pattern,but the fragmentation of landscape pattern was weakened,and during the operation stage of G214,the fragmentation of landscape pattern improved;from the spatial changes,the highway had a serious impact on the fragmentation of landscape pattern in the 1-3 km buffer zone,especially in the 0.3-0.9 km buffer zone.The 0.9-3 km buffer zone is less severely affected than the former,and is a less severely affected area;the 4-8 km buffer zone is less affected by landscape fragmentation;the 8-10 km buffer zone is basically unaffected by the road.(3)In terms of changes in ecosystem services,during the operational phase of the form ertertiary highway from 2000 to 2010,the value of ecosystem services along the highway increased in terms of water content and soil conservation,and decreased in terms of habitat quality and NPP,with a certain downward trend;during the construction phase of the G214 from 2010 to 2015,the value of all four ecosystem services-habitat quality,water content,soil conservation and NPP-decreased.This indicates that the construction of the national highway will significantly reduce the value of ecosystem services along the highway;during the operation phase of the national highway from 2015 to 2020,NPP increases and water quality,habitat quality and soil conservation decrease.During the operational phase of the former tertiary roads,two ecosystem services,habitat quality and NPP,were mainly affected,while all four ecosystem services tended to decrease during the construction phase of the national roads.The construction and operation phases of national highways are the most severely affected ecosystem services in the region along the highway,most notably reducing the three ecosystem services of habitat quality,water retention and soil conservation.In terms of spatial variation,the construction of the highway had the most serious disturbance of ecosystem services in the 1-3 km buffer zone;the 0.3-0.9 km buffer zone had the greatest fluctuation of ecosystem services and was the most severely affected area;the 0.9-3 km buffer zone had a certain improvement of habitat quality and soil conservation and was the second most severely affected area;the 4-7km buffer zone had an average impact,while the 8-10 km buffer zone had an average impact.(4)Vegetation type and quantity along the road increased with distance from the road,and the herbaceous layer > shrub layer > tree layer,the dominant species composition of the tree layer was not affected by the road,while the dominant species of the shrub layer and herb layer were more affected by the road.The closer the sample site to the road,the lower the species richness and Shannon-Wiener index,the higher the Pielou evenness index and Simpson index,the lower the plant diversity,and the more seriously affected by the road,and the most seriously affected by the tree layer,especially the road has the greatest impact on the plant diversity within the10-300 m buffer zone.Conversely,the farther away from the road,the higher the plant diversity and the less affected by the road.In conclusion,the construction and operation of national highways in the reserve have caused changes in land use along the route,fragmenting the landscape pattern along the route and further causing changes in the value of ecosystem services,affecting vegetation growth and leading to a reduction in plant diversity.The construction of the G214 has the most serious impact on the ecological environment in the 1-3 km buffer zone,while the 4-7 km buffer zone has an average impact and the8-10 km buffer zone is basically unaffected by the highway.Within the 1-3 km buffer zone,the impact on the 0.3-0.9 km buffer zone is extremely severe,and the impact on the 0.9-3 km buffer zone is less severe. |
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