Treeline Distribution And Its Response To Climate Change In Tibetan Chayu County

Plateau ecosystem plays an important role in the global ecosystem.Dueto its fragile ecosystem,climate change and other external interference hashad a serious impact on it.Treeline ecotone is an important dividing line invertical mountain,and it is very sensitive to climate change and otheroutside interference. To define the impact of global change on TibetanPlateau treeline ecotone has become effective premise of ecologicalprotection.Study area Chayu county is at the southeast corner of the TibetanPlateau.According to research the data(1972-2001) from44meteorologicalstations surrounding Chayu county,we know that:a.From the average annualtemperature of the tree line area showed a gradual upward trend warming upto0.6℃,and after1990, there had been a warming active period.b.Thewarming trend of June-September growing season was apparent,warmingabout1℃.c.The warming rate of the average temperature in the coldestmonth was higher than the average temperature in the warmest month.d.Theannual precipitation of study area showed a gradual decrease trend in this30years.Combine remote sensing technology and ground research,then take thegeographic information system as a tool for spatial analysis.According toanalysis three times (1973,1988,2001) of NDVI data in the study area,weknow that the NDVI increased under the impact of increasing temperature inthis30years.That means tree line position changed.On this basis,usedecision tree classification method to classify the vegetation of the studyarea.The results obtain the support from the aerial photographs of the sameperiod.Based on the above analysis of the results showed that: 1.Treeline position and the annual mean temperature had a quadraticrelationship.From1973to2001, the average annual temperature risen0.6℃, and at the same time the tree line position had26.01%of the regionon the rise,and the biggest increased about189m.2.Climate warming had also changed the shape of the tree line,the treeline of1988had the most complex shape in three times.3.With the increase of mean annual temperature,tree line position didnot continue to rise,but the rate of increase of the tree line position sloweddown.That treeline response to climate change is the most sensitive at thebeginning of the temperature increasing.4.With the reduction of the annual rainfall of study area,tree lineposition had risen.Through the research shows that global warming has already had animpact on the Tibetan Plateau tree line and the Tibetan Plateau ecosystem.