Grassland Degradation And Its Response To Climate Change In The Qinghai-Tibet Plateau

The Qinghai-Tibet Plteau has an average elevation of above 4000m,sometimes known as‘the Roof of the World'.Alpine grassland is the most widely distributed ecosystem in Qinghai Tibet Plateau,which accounts for 60%of the total area of Qinghai Tibet plateau.As an important part of grassland ecosystem,Qinghai Tibet Plateau is a sensitive area of climate change and an ecological fragile zone.Climate change is impacting the alpine ecosystem seriously in recent years.The plateau is warming and drying.The negative effect of warming and drying on grassland is greater than positive effect,which is a threat to grassland degradation.Therefore,it is very important to study the degradation of grassland and its relationship with climate change.In this paper,we analyzed the characteristics of climate change,grassland vegetation dynamics,grassland degradation and the response of grassland dynamics to climate change in 1981-2013.The main results were as follows:?1?The grassland in Qinghai Tibet Plateau is warming and drying.The annual mean temperature had a significant upward trend with a rate of 0.35?·10yr^-1,the annual precipitation trend increased slightly but not significantly,the annual potential evapotranspiration has a significant upward trend with a rate of 8.2mm·10yr^-1.?2?Alpine meadow had the highest vegetation coverage?NDVI?value,followed by alpine steppe and alpine desert steppe.Grassland annual maximum vegetation coverage?NDVI?had no significant trend and the variation coefficient was small.Mean value of grassland annual maximum vegetation coverage?NDVI?in 1981-2013 decreased from southeast to northwest.Grassland annual maximum NDVI have increased in south and northeast,decreased in north and west,but most of the area did not pass the significance test.?3?The grassland degraded area of the Qinghai-Tibet Plateau accounted for 41%of the total area of the grassland.The proportion of lightly,moderate,serious and extremely serious degraded area was 22%,8%,6%and 5%respectively.Compared with the historical average,lightly degraded grassland had a tendency to turn to moderately,seriously and extremely seriously degraded grassland in current situation.Serious and extremely serious degraded grassland was mainly distributed around the Qaidam basin.?4?The response of the Qinghai-Tibet Plateau grassland to the monthly climate change is greater than the inter-annual response.The area of NDVI significantly related?P<0.05?to temperature,precipitation and potential evapotranspiration in the Qinghai-Tibet Plateau accounted for 15%,7%and13%of the total area of the grassland respectively annually,which accounted for 38%,30%and 35%monthly.There was time lags between NDVI and the reponse to climate.The proportion of regional area which is significant with temperature,precipitation and potential evapotranspiration in maximum correlation coefficient were 78%,71%and 78%respectively.