Study Of The Alpine Meadow Yield Monitoring And The Dynamic Of Vegetation Carbon Sequestration In The Source Region Of Yangtze, Yellow And Lancang Rivers

The source region of Yangtze, Yellow and Lancang Rivers, which is a part of Tibetan Plateau, is sensitive to global climate change. Researches on grassland producing status and carbon storage of the study field play a significant role in making rational strategy on grassland utilization responding to global climate change. In this study, the correlation between rangeland surface temperature and NDVI was analyzed on the base of land surface temperature (LST), normalized difference vegetation index (NDVI), fresh weight, dry weight as well as coverage measured in field; the precision verification of grassland yield was processed by means of cross-validation; the yield of alpine meadow in the source of the three rivers from 2003 to 2009 was calculated and inversed. In the end, vegetation carbon sequestration and spatial distributions of alpine meadow in study area were estimated through building relationship between the optimal models and NDVI.The main results are as follows:(1) From 2003 to 2007, the maximum value of 8 days mean temperature is in June or July, while it appeared in May between 2008 and 2009. The relationship between alpine meadow NDVI and LST showed that the fitting degree of conic function got the highest (R2=0.5563, P<0.01).(2) Combining filed measured data collected in 145 plots, by using cross-validation, four inversion models between alpine meadow NDVI and fresh weight, dry weight and coverage were compared. It showed that cross-validation had higher fitting precision on calculating of fresh weight and dry weight, while exponential function had higher precision on inversing coverage: Based on the above model, the model was improved firstly in this study. According to the relationship between grassland growth and NDVI, water and heat, the multi-factor model was established, and performed better than the single factor model.(3) By using alpine meadow yield inversed by optimum models combine R:S of vegetation, this assay first time estimated the ANPP (aboveground net primary productivity) carbon sequestration capability of the study field in alpine meadow area. The carbon distribution was as the list,0.77Tg C(1Tg=1012g),0.76Tg C,0.87Tg C,0.77Tg C,0.75Tg C,0.75Tg C,0.91Tg C, which has a trend of increase.This result indicates that if use soil surface temperature as the response to climate change, the environment condition in study area is good for vegetation growth, though the whole global becomes warmer. It is found that during 2003 and 2008, the annual average temperature and rainfall increase while soil surface temperature decreased. In spite of the vegetation yield carbon storage was estimated and its increasing trend was found in this assay, over 86% of it exists underground and only little part of the aboveground carbon storage can be used. Therefore, the ecological significance of carbon storage is far more important than the practical significance of grazing utility.