| As the North-South boundary of China and the watershed between Yellow River and Yangtze River,the Qinling-Daba Mountains are characterized with complicated and transitional variations in mountain altitudinal belts.For a longtime,latitude,longitude and mountain mass effect(MEE)have been considered to affect the vertical distribution of montane vegetation or altitudinal belts.MEE refers to the thermal effect generated by the uplift block,leading to the phenomenon that the mountain altitudinal belts boundary is higher inside the mountain than outside.The quantification of MEE in the Qinling-Daba mountains should start from the mountain structure and extract the Mountain base elevation(MBE),which is the most closely topographic factor related to MEE.The quantification and digital extraction of MBE is the key to the quantification of MEE in the Qinling-Daba mountains.Mountain/plateau uplift has changed the heat distribution pattern and its surrounding areas,resulting in MEE and this is the essence of MEE of the QinlingDaba mountains.The difference of temperature between the internal and external mountain at the same altitude is an ideal index to represent the magnitude of MEE and a key index to quantify MEE.The MEE is quantified by quantifying MBE using the method based on drainage basin division to determine mountain base subareas and based on STRM-1 data with 30 m resolution.Then this study used relief amplitude,the average altitude in each subareas and slope to calculate the MBE.The geographical weighted regression(GWR)method was used to estimate the temperature,combined with MODIS land surface temperature(LST)data,STRM-1 DEM data and temperature observation data of 419 meteorological stations in the QinlingDaba mountains.Air temperature at an altitude of 1500m(the average elevation of the Qinling-Daba Mountains)in the interior of the Qinling-Daba Mountains was calculated by a fixed lapse rate and compared with that in the periphery.Solar radiation analysis method based on Arc GIS,using DEM data and spatial distribution data of sunshine duration obtained by Kriging interpolation of the sunshine duration data of 419 meteorological stations to determine parameter setting,the spatial distribution data of direct radiation,diffuse radiation and gross radiation intensity in the Qinling-Daba mountains are calculated.The linear relationship between the MBE,air temperature at an altitude of 1500 m and gross radiation intensity is analyzed quantitatively.Finally,With the altitudinal belt of vegetation data of 31 data points in the Qinling-Daba mountains collected from the literature,the correlation between the MBE,air temperature at an altitude of 1500 m,gross radiation intensity and the upper limit of altitudinal belts distribution was analyzed by using the correlation analysis method.The main results and conclusions are as follows:(1)There are 209 subareas based on drainage basin division method in the Qinling-Daba Mountains.And from east to west,MBE presents a gradual upward trend.Along latitudinal direction,the eastern and middle sections of the Qinling-Daba mountains show a trend of increasing firstly and then decreasing,that is,MBE presents a tendency of increasing from the Hanjiang Valley to the Qinling ridge and the Daba ridge.It reflects that the terrain of the Qinling-Daba mountains rises from the east to the west and from the Hanjiang Valley to the Qinling ridge and Daba ridge.However,the MBEs vary greatly in different exposures,from 1000 m to 1809 m in the southern flank of the Qinling,but only 850-1300 m in the northern flank.(2)Using GWR method established by MODIS LST data,DEM data and meteorological station observation data to estimate the temperature of the Qinling-Daba mountains,the estimation accuracy is ideal with R~2 >0.89 and the root mean squared error(RMSE)= 0.68-0.98 ?.The existence of MEE causes the temperature to presents a gradual upward trend from east to west.The growing season(May,June,July,August and September)and the average annual temperature at the altitude of 1500 m of the eastern Die mountain is 3.3?-6? higher than the western Funiu mountain,and the eastern Honggang mountain is 4.5?-8.5? higher than the western Shiyan city.From the edge of the mountain to the interior presents an obvious rising trend.Compared with the lower valleys in the Hanzhong and western of Henan,the monthly mean temperature at the altitude of 1500 m are approximately 3.85-9.28?,1.49-3.34? and 0.43-3.05? higher in the Great undulating high mountains in the western Qinling-Daba Mountains,the Great undulating middlehigh mountains in the Qinling Mountains and the great undulating middle mountains in the Daba Mountains,respectively,and the average temperature difference is about 3.50?.This causes the zonal decline rate of the temperature at the same altitude to shrink,and even causes the temperature at the same altitude in the mountain to be higher at higher latitudes than at lower latitudes.It shows that the MEE of the Qinling-Daba Mountains is obvious,which changes the zonal distribution pattern of temperature.(3)The spatial distribution of solar radiation is gradually increasing from east to west and from the edge of the mountain to the interior in the Qinling-Daba Mountains.The higher the elevation,the higher the solar radiation value.The lowest values of direct radiation,diffuse radiation and gross radiation intensity appeared in the valleys and mountain margins.And,secondly,solar radiation of the valleys outside the mountain and the areas with relatively gentle slopes is also relatively lower.The mountain slopes were elevated,and reached the highest values in the western high-altitude area of the Qinling mountain,the Daba mountain ridge,the Qinling ridge and the areas with higher elevations(such as the Taiba Mountain,Micang Mountain,Shennongjia Mountain,etc.).The gross radiation intensity in the Qinling-Daba Mountains increased by about 25000W/m~2 from the Funiu Mountain to Taibai Mountain,by about 40000-50000W/m~2,from Shiyan city to the Honggang Mountain in the east,by about 10000-25000W/m~2 from the Han river valley to the Micang Mountain in the south,and by about 25000-45000W/m~2 from the Taibai Mountain in the north.From the Han river valley to the north to the Huashan Mountain,the gross radiation intensity increased by about 10000-15000W/m~2,and about 15000-20000W/m~2 to the Shennongjia Mountain.There was a significant positive correlation between the solar radiation and the MBE,the temperature at the altitude of 1500 m.The R~2 of the MBE was greater than 0.94 and that of the temperature at the altitude of 1500 m was greater than 0.81.(4)There is no significant correlation between the upper limit of mixed evergreen-deciduous broadleaf forest belts and MBE,the gross radiation intensity in the Qinling-Daba Mountains.The upper limit of mixed evergreen-deciduous broadleaf forest belts and the temperature at the altitude of 1500 m is significantly negative(-0.716,P<0.05;-0.738,P<0.01).There is no significant correlation between the upper limit of the deciduous broadleaf forest belts and MBE,the temperature at the altitude of 1500 m,the gross radiation intensity in the Qinling-Daba Mountains.The correlation between the upper limit of the distribution of mixed broadleaf-conifer forest belt and MBE,air temperature at the altitude of 1500 m,the gross radiation intensity has significant positive correlation in the Qinling-Daba Mountains.The correlation between the upper limit of the distribution of mixed broadleaf-conifer forest belt with MBE is 0.824(P<0.05)and 0.875(P<0.01)in the Qinling Mountain and the Daba Mountain,respectively.The correlation between the upper limit of the distribution of mixed broadleaf-conifer forest belt with the growth season and annual average air temperature at the altitude of 1500 m is 0.950(P<0.01)and 0.920(P<0.01)in the Qinling Mountain,0.722(P<0.05)and 0.758(P<0.05)in the Daba mountain.And the correlation between the upper limit of the distribution of mixed broadleaf-conifer forest belt with the growth season gross radiation intensity in the Qinling Mountain is 0.810(P<0.05).This reflects the important influence of MEE on the distribution limit of the altitudinal belt in Qinling mountains and Daba mountains,especially the upper limit of the distribution of mixed broadleafconifer forest belt.It changes the zonal distribution rule of latitude and longitude of the distribution limit of the vertical belt in the mountains,and presents the non-zonal distribution,that is,the altitudinal belt of vegetation distribution height is higher in the mountains where the MEE is obvious. |
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