Relationships Between The Tibetan And Qiang Settlements' Habitat Differentiation And Climate Change In The Upper Reaches Of The Min River,China

The regional response of climate changes and corresponding human adaptation are the frontiers of ecological and environmental issues.Study on the relationship between the habitat differentiation and climate change is a comprehensive integration of mountain climate change,mountain environment response and settlement habitat change.This useful information can provide new exploration for recognizing the law of the mountain environmental change and serve as the sustainable development of mountainous areas.The Upper Reaches of the Min River is a special region where the arid valley landscape and multi-national culture coexist.Therefore,based on the unique geographical background of the arid valley in the Upper Reaches of the Min River,this thesis selected the two sensitive ecological zones(i.e.,the arid valley boundary and the lower timberline)and the minority settlements habitat as research objects,and took the mountainous climate change,the displacements of the arid valley boundary and lower timberline,and the settlement habitat variation as the main research thread.Using the method of niche and Geodetector,the response of the arid valley boundary and lower timberline to mountainous climate change were clarified,and the settlement habitat characteristics and their change regulation in the arid valley were revealed.Finally,the related mechanisms between the displacements of the arid valley boundary / lower timberline and settlement habitat variation under the climate change background were revealed.The main research contents and achievements are as follows:(1)The climate in the Upper Reaches of the Min River tended to warm-humid and the mountainous characteristic lines tended to lower elevation.Based on analysis of the meteorological data from 1999 to 2013 provided by National Meteorological Information Center,the climate change in the Upper Reaches of the Min River during the past 15 years tended to warm-humid.Specifically,the temperature,precipitation,and evaporation increased,and the sunshine duration and relative humidity showed decreasing trends at the rates of 0.008 °C/a,2.25 mm/a,5.51 mm/a,8.72 h/a,and 0.19 %/a,respectively.Meanwhile,under the background of the warm-humid tendency of climate,both the arid valley boundary and the lower timberline moved to lower elevation at the speed of-0.76±0.26 m/a and-0.46±0.15 m/a,respectively.It indicated that the combination of water and heat in the basin showed a favorable trend to the growth of vegetation.Quantitative study on the relationship between the arid valley boundary / the lower timberline and climate showed that: The arid valley boundary's displacement was significantly correlated with the variation of annual sunshine duration variation(P=0.010<0.05)and the lower timberline's displacement was significantly correlated with the variation of annual average relative humidity(P=0.031<0.05).Moreover,based on Geodetector,the displacements of the arid valley boundary and lower timberline were mainly affected by annual sunshine duration variation and annual precipitation variation,with an influencing power of 0.277 and 0.244,respectively.(2)Characteristics of settlement habitat in the arid valley of the Upper Reaches of the Min RiverThere were 858 settlements in the arid valley of the Upper Reaches of the Min River,which were mainly distributed at the elevations ranged from 1201 m to 3100 m,and the geographical radius of settlement niche ranged from 170 m to 520 m.Based on the assessment of habitat suitability,the settlements with suitable and sub suitable habitat accounted for 71% of the total number of settlements in the study area,and the habitat suitability of Qiang settlement was slightly superior than that of the Tibetan settlement.Through the analysis of Geodetector,the annual evaporation was the dominant climatic factor affecting the suitability of settlement habitat in the arid valley in the basin scale,with an influencing power of 0.126.For the Tibetan settlement and Qiang settlement,the main climatic factors affecting their habitat suitability were respectively annual precipitation and annual evaporation,and the factors' influencing power were 0.092 and 0.133,respectively.(3)Relationship between settlement habitat variation and mountainous characteristic lines' displacementDuring 1999~2013,the average elevation of settlement decreased from 2249 m to 2245 m,the radius in geography of settlement niche decreased from 406 m to 383 m,and the habitat suitability index of settlement increased by 0.003 in the arid valley of the Upper Reaches of the Min River.Further analysis showed that: in many meteorological elements,the key factors influencing the displacement of gravity center of the settlement niche were the annual average relative humidity variation and annual precipitation variation with an influencing power of 0.137 and 0.187,respectively.Meanwhile,annual precipitation variation and annual evaporation variation were the major factors affecting the habitat suitability of settlement in arid valley and their influencing power were 0.159 and 0.150,respectively.For the relationship between the evolution of settlement habitat and the arid valley boundary / the lower timberline in the basin scale,the variation of settlement habitat suitability showed a significant positive correlation with the lower timberline's displacement(P=0.026<0.05),and the vertical displacement of gravity center of the settlement niche showed a significant negative correlation with the displacement of the arid valley boundary(P=0.046<0.05).(4)Response of habitat suitability to climate change in the Upper Reaches of the Min RiverCompared with 1999~2013,the major trend of climate change in the Upper Reaches of the Min River in 2014~2050 would be warm and humid.By 2020,2030 and 2050,the possible increase in the temperature of the basin would be 0.28 °C,0.68 °C and 1.48 °C,respectively.Meanwhile,the possible increase of precipitation is 9 %,14 % and 15 %,respectively.Moreover,the habitat suitability values in 2020,2030 and 2050 would increase by 0.008,0.014 and 0.018,respectively,and the suitability of settlement habitat would be gradually improved.