| Global warming is a hot topic all over the world.Vegetation,as an important part of terrestrial ecosystem,is sensitive to climate warming.Mountainous areas also are sensitive to climate change,and their warming trend and vegetation response are controlled by topography and complicated.It is of great significance to study the spatial distribution pattern of mountain vegetation and the topographic differentiation effect of its change under the background of climate change.The Qinling Mountains,with huge altitude differences,steep in the north and slow in the south,and shady in the north,sunny in the south,makes it a natural test ground for studying climate change and vegetation response.In this paper,taking the hinterland of the Qinling Mountains in Shaanxi Province as the study area,using meteorological observation data,remote sensing images and DEM data,we reveal the topographic differentiation characteristics of temperature and vegetation changes in the Qinling Mountains and the topographic effects of climate change on vegetation,in order to provide a scientific basis for coping with climate change,protecting ecological environment and adjusting suitable areas for agriculture and forestry in the Qinling Mountains.The major progresses and results of this study are as follows:(1)There are differences between the northern and the southern slopes,seasonal asynchrony and altitude dependence in the temperature change trend of the Qinling Mountains from 1959 to 2016.(1)Over the last 58 years,the Qinling Mountains have been warming,and the annual temperature tendency rate is 0.26?/10 a.The rising trend of temperature in the northern slope is greater than that in the southern slope,with the tendency rates of 0.29?/10 a and0.25?/10 a,respectively.The abrupt change of warming occurred earlier in the northern slope(in 1994)than in the southern slope(in 1997).(2)The temperature tendency rates of four seasons in the Qinling Mountains are spring(0.33?/10a)> winter(0.30?/10a)>autumn(0.27?/10a)> summer(0.08?/10a).The contribution rate of spring temperature change to annual average temperature is the largest,reaching 35.60% in the northern slope and 32.31% in the southern slope.The temperature difference between winter and summer showed a significant decreasing trend,and both the northern and southern slopes had a decreasing abrupt change in 1976.(3)With the increase of altitude,the average annual temperature increases,while the temperature difference between winter and summer decreases.The difference between northern and southern slopes of temperature variability mainly exists in low altitude areas,and the difference between northern and southern gradually decreases with the increase of altitude.(2)The spatial distribution of vegetation coverage and its changing trend over the last 17 years had obvious topographic differentiation effect in the Qinling Mountains.(1)The overall vegetation coverage of the Qinling Mountains is 84%,75% on the northern slope and 86% on the southern slope.The vegetation coverage on the southern slope of the Qinling Mountains is greater than that on the northern slope in areas with an altitude of less than 2000 m,while that on the northern slope is greater than that on the southern slope in areas with an altitude of more than 2000 m.The shady slope on the southern slope of the Qinling Mountains is the area with the highest vegetation coverage,while the shady slope on the northern slope is the area with the lowest vegetation coverage.(2)From 2000 to 2016,the vegetation coverage in the Qinling Mountains showed an overall upward trend,with an average regional change rate of 0.027/10 a.The vegetation coverage in the southern slope increased more than that in the northern slope,with change rates of 0.031/10 a and 0.015/10 a,respectively.From the perspective of altitude differentiation,the vegetation coverage in low-altitude areas has a decreasing trend,while that in middle-altitude areas has an increasing trend over the last 17 years.The vegetation coverage in the northern slope of high-altitude areas above 2000 m is relatively stable,but in the area of 2500-3100 m in the southern slope,there is an obvious decreasing trend.From the aspect differentiation,the increasing area of vegetation coverage is mainly distributed on the sunny slope of the northern slope,while the decreasing area is mainly distributed on the sunny slope of the southern slope and the shady slope of the northern slope over the last 17 years.(3)Climatic factors and topographic factors have interactive synergistic effects on the spatial distribution of vegetation in Qinling Mountains.(1)The spatial distribution of NDVI on the northern and southern slopes of the Qinling Mountains is mainly controlled by heat factors.The influence of climate factors are in order as follows: the hottest month temperature,annual average temperature,the coldest month temperature,annual precipitation,relative humidity and drought index.(2)The topographic differences of the explanatory power of climate factors on the spatial distribution of NDVI in the Qinling Mountains are as follows: The northern slope is stronger than the southern slope,the high altitude area is stronger than the low altitude area,and the sunny slope is stronger than the shady slope.(3)The topographic factors and climate factors have interactive synergistic effect on the spatial distribution of NDVI in the Qinling Mountains.Altitude,slope,aspect and climate factors all show a mutual enhancement relationship.Among them,altitude and climate factors play a major synergistic role in enhancing the spatial distribution of NDVI on the northern and southern slopes of the Qinling Mountains.(4)Climate warming leads to the change of vegetation adaptive area pattern in the Qinling Mountains.(1)Before the abrupt change of temperature,the southern slope of the Qinling Mountains contains five suitable vegetation zones,which are warm temperate evergreen broad-leaved mixed forest,warm temperate deciduous broad-leaved forest,temperate coniferous forest,cold temperate subalpine coniferous forest and alpine shrub meadow.Compared with the southern slope,there is no evergreen broad-leaved mixed forest zone on the northern slope of the Qinling Mountains,but after the abrupt change of temperature,a suitable area of evergreen broad-leaved mixed forest zone appears in the eastern part of the Weihe River on the northern slope of the Qinling Mountains.(2)After abrupt temperature change,the suitable area of warm temperate deciduous evergreen mixed forest and warm temperate deciduous broad-leaved forest expanded,while the suitable area of temperate coniferous and broad-leaved mixed forest,cold temperate coniferous forest and alpine shrub decreased.After the abrupt change of temperature,the altitude of the suitable areas of all vegetation types showed an upward trend,and the range of the suitable areas of vegetation belts in high altitude areas was higher than that in low altitude areas.(5)Under RCP4.5 and RCP8.5 scenarios,the Qinling Mountains keep warming,the vegetation distribution pattern may change,and the distribution area and altitude of suitable areas of various vegetation types will change to varying degrees.Under the scenarios of RCP4.5 and RCP8.5,suitable areas of subtropical evergreen broad-leaved forest would appear in the northern and southern slopes of the Qinling Mountains in the next 50 years.The area of vegetation belt in low altitude area continues to expand,while the area of vegetation belt in high altitude area continues to shrink.Subtropical evergreen broad-leaved forest and warm temperate deciduous broad-leaved evergreen mixed forest may replace temperate coniferous and broad-leaved mixed forest,thus developing into the largest vegetation type in the suitable area of the Qinling Mountains.Under RCP4.5 scenario,the average distribution altitude of vegetation belts in low altitude areas showed a continuous upward trend,while that in high altitude areas was relatively stable.Under the RCP8.5 scenario,the average altitude of each vegetation belt showed a continuous upward trend. |
PDF Full Text Request