A Comparative Study Of Climate Change And Its Environmental Effects In The Northern And Southern Regions Of Qinling Mountains

Based on the data from47weather station between1960and2011, with the help ofclimate trend rate, Spline Interpolation and wavelet analysis, we analyzed the spatialdistribution, spatial and temporal variation and their periodic characteristics of temperature,precipitation, wind speed, sunshine hours, water vapor pressure in northern and southernregions of Qinling Mountains (NSQ). We also discussed the possible impact of climatechange on rainfall erosivity, potential evapotranspiration, photosynthetically active radiation,net primary productivity by the methods of Zhang Wenbo Model, Penman-Monteith Equation,Angstrm Equation, Zhang Xinshi-Zhou Guangsheng Model. Especially, we discussed thepossible cause of evaporation paradox and the decreasing trend of photosynthetically activeradiation. Besides, we analyzed the vegetation coverage change in the period of1982-2011and its response to climate change (temperature and precipitation) based on NDVI(Normalized Difference Vegetation Index) from different sensors (AVHRR and MODISsatellite).1. Temperature in northern region of Qinling Mountains (NRQ), southern slope ofQinling Mountain (SSQ), Han River Basin (HRB), Bawu Valley (BWV) and NSQexperienced increasing trend since1990s. Yearly averaged temperature was consistent withthe accumulated temperature. Temperature experienced slight decrease from1951to1993anda rapid increase since1993; The average temperature of cold seasons of January exhibited thetrends that slightly increased from1951to1985and declined since1985. Since the1990s, theincreasing range of temperature and thermal resources in the northern regions were biggerthan the southern regions, especially for annual temperature, average temperature of January,and the accumulated temperature.2. The precipitation in NSQ presented a latitudinal zonality, which was high in southernpart while low in northern part. According to the amount of rainfall, the order was BWV, HRB, SSQ, NRQ. The spatial distribution of seasonal rainfall was similar to annual rainfall, most ofrainfall concentrated in summer and autumn; The turning point of rainfall lied in1984,rainfall in the period of1960-2010showed an insignificant decreasing trend, the decreasingrate in southern part of Qinling Mountains was bigger. On the seasonal scale, rainfalldecreased in spring and autumn while increased in summer and winter; The spatialdistribution of rainfall erosivity was similar to rainfall, which was high in southern part whilelow in northern part, the order was BWV, HRB, NSQ, SSQ, NRQ; Rainfall erosivity alsoshowed a decreasing trend, the order of decreasing rate was NRQ, BWV, NSQ, SSQ andHRB.3. Surface water vapor presented a clear pattern that high in south and low in north,water vapor decreased from east to west, which had a good altitudinal and latitudinal zonality.The order of water vapor, according to amount of water content, was BWV, HRB, NSQ, SSQNRQ, the order of seasonal water vapor was summer, autumn, spring and winter; Yearlyaveraged water vapor pressure presented an increasing trend, the increasing rate was bigger inSSQ and HRB, while BWV had a deceasing trend. In spring, regionally averaged water vaporpressure increased insignificantly, BWV and NSQ had decreasing trend; In summer,regionally averaged water vapor pressure decreased insignificantly, only NSQ showedincreasing trend; In autumn, all regions’ water vapor pressure increased, the increasing rate ofSSQ and BWV was relatively bigger; In winter, water vapor pressure of most stations showedincreasing trend, which was more obvious in southern regions of Qinling Mountains; Watervapor pressure of53%stations experienced abrupt change in winter, which mainly located inthe southern regions of Qinling Mountains and the period mainly lied between1985and1988,in line with the mutation of temperature in winter. The phenomenon of mutation was notobvious in other regions; Water vapor pressure was affected by several meteorological factorsincluding temperature, wind speed, sunshine etc. Water vapor pressure correlated positivelywith precipitation, temperature, relative humidity and sunshine hours, but it had a negativecorrelation relationship with wind speed. The order of influential factor was temperature,precipitation, sunshine hour and relative humidity. Except for BWV, temperature and watervapor pressure had same change trend.4. The wind speed presented a pattern which was big in south and low in north, big ineast and small in west. According to wind speed, the order was NRQ, SSQ, HRB and BWV,the order of season was spring, winter, summer and autumn; Wind speed decreasedsignificantly in the whole region and different sub-regions during the last52years, thedecreasing rate in NRQ was the biggest and the smallest one was in the HRB. The order ofdecreasing rate was winter, spring, autumn and summer; The annual and seasonal abrupt change happened mainly in3periods, which were1969-1974,1978-1981and1990-1994, thewhole region was detected abrupt change in1981; The development of city construction andchange of observational devices had some effect on wind speed change, however, regionalcurrent change and global warming were the main reasons for wind speed decreasing.5. The sunshine hours and PAR became weaker from north part to south part, i.e. fromNRQ to SSQ, to HRB and to BWV. Sunshine hours and PAR in summer was the highest,followed by spring, autumn and winter. The distribution of sunshine hours and PAR in spring,autumn and winter showed the same spatial pattern as annual result, but in summer, sunshinehours and PAR in NRQ is also the highest, then HRB and BWV, and SSQ being the lowestone; Sunshine hours and PAR declined significantly in past52a, the declining rates becamesmaller from south and east part to north and west part of this region. Except for aninsignificant increase in spring, sunshine hours and PAR decreased in other seasons, and therate in summer was fastest, followed by that in winter and autumn. The maximum andminimum sunshine hours and PAR appeared in1960s-1970s and2000s respectively in spring,summer and autumn;89%of stations had abrupt change points of yearly and summersunshine hours and PAR, and about85%and90%of them happened between1979and1983,respectively. There were no obvious abrupt change points in spring or autumn; Climatechange (wind speed declining), fast urbanization and more aerosol emission from industrialproduction were the main reasons for the continuous decline of sunshine hours and PAR, andthe aerosol emitted from volcanoes was the main reason for fluctuation of that.6. Yearly averaged ET0was964.2mm, with the spatial distribution pattern of higher ineast and lower in west. According to the size of ET0, the order was NRQ, SSQ, HRB, BWV.Four seasons’ ET0had the same distribution characteristics as the annual ET0, the order wassummer, spring, autumn and winter.1979and1993were the change point of ET0, whichdivided ET0into two periods, ET0increased from1960to1979and then decreased from1993to2011. Between1960and1979,"Evaporation paradox" only existed in HRB and BWV, theperiods of1980-1993,1994-2011and1960-2011all had "Evaporation paradox" phenomenon.Both the last18years and the whole52years in autumn as well as the initial34years and thewhole52years in winter had "Evaporation paradox" phenomenon, which was more obviousin winter; According to the effect of meteorological elements change on ET0change, the orderwas sunshine hours, wind speed, maximum temperature, relative humidity, mean temperature,mean air pressure and minimum temperature. On the year scale, the significant decrease ofsolar radiation (sunshine hours) was the dominating factor leading to the decrease of ET0.While on the seasonal scale, the dominating factor of spring’s ET0was wind speed, the otherthree seasons were all solar radiation (sunshine hours). 7. NPP was lower in northern part and higher in southern part, according to the size, theorder was BWV, HRB, SSQ and NRQ. The ratio between maximum and minimum value wassmall which ranging from1.34to1.89; NPP increased over14.8%under the condition thattemperature and precipitation improved together, the northern region of Qinling Mountainshad more obvious increasing trend compared with the southern region. Temperate zonedeciduous broadleaved showed biggest increasing range, while temperate hassock was thesmallest one; Temperature increasing but precipitation decreasing (scenario b) was not goodfor the accumulation of NPP, thus most stations decreased instead. Subtropical and tropicalbroadleaved and deciduous forest showed biggest increasing rate, while temperate zonedeciduous broadleaved was the smallest one; NPP increased obviously in scenario c, whichwas smaller than scenario a, the northern region of Qinling Mountains increased moreobviously than the southern region. Different vegetation types showed same changing trend asscenario a, which was smaller than scenario a.8. Yearly averaged NDVI presented slight increasing trend in the period of1982-1999with the biggest increasing rate in northern slope of Ba Mountain and the smallest rate innorthern slope of Qin Mountains. Seasonal NDVI had no obvious fluctuation, however,presented slight increasing trend; Vegetation coverage between2000and2011maintainedstable, however, local regions had degradation trend. The fluctuation of NDVI can beattributed to crop productivity which influenced by temperature and precipitation; Warmingtrend in spring was the main reason for NDVI increasing, however, high temperature insummer had negative impact on growth of vegetation, temperature in autumn and winterpositively correlated with NDVI, but didn’t reach significant level; The correlationrelationship between seasonal NDVI and precipitation was not very obvious, only NDVI inautumn correlated well with precipitation in winter. In summary, winter’s rainfall fluctuationwas the main reason for NDVI variation, excessive rainfall in autumn and winter had negativeimpact on the growth of vegetation.