| In the context of global warming,land and marine ecosystems changed significantly.The change of vegetation is not only the ecological signal of plants responding to climate change,but also a scientific foundation for predicting and assessing the impacts of future climate scenarios on ecosystems.On the basis of literatures about the impacts of climate change on vegetation searched from digital libraries such as the China National Knowledge Infrastructure(CNKI),VIP Chinese Journal Database(VIP)and Web of Science(Wo S),and from printed journals from real libraries,this thesis synthesizes the change of vegetation responded to climate change in China during the last 65 years(1950-2015)using available records of vegetation change and meta/statistical analyses.The main conclusions are as follows:(1)A total of 1105 Chinese and English publications on the evidence of climate change impacts on vegetation in China were collected.Among them,433 publications(159 valid publications)were collected based on ground observations of plant phenology changes and 70 publications(42 valid publications)were based on remote sensing observations.There were further valid publications of 15 on species observations on the ground,14 on community change and 25 on vegetation change,and 454 publications on remote sensing-based vegetation observations(122 valid publications).Publications on the changes of net primary productivity based on ground observations and remote sensing observations were 34(17 valid publications)and 60(14 valid publications),respectively.(2)Phenophase change records based on ground observations demonstrate that the trend and the range of phenophase changes were different among species and vegetation.The phenological trends of woody species in main vegetation divisions were coincident with each other,but the range of changes varied among vegetation divisions.The herbaceous plants,however,showed very different phenological trends among vegetation divisions.Different plant species in the same vegetation zone showed also different phenological change trends.There was a significant difference in the leaf discoloration period between garden plants,fruit trees and natural plants in woody plants.The growth season of garden plants and natural plants was significantly different.The flowering period of crop plants and natural herbs in herbaceous plants had significant differences.The spring/summer phenophases(first leaf and first flowering)of woody plants had 87.4% records showing earlier trends,with a mean advance time across all vegetation zones of 2.786 d/10 a.The autumn phenophases(beginning and end of leaf coloring)showed later trends in 71.5% records,along with an average delay of 1.903 d/10 a.The growth season had extended by 2.120 d/10 a in average in 57.7% records.The flowering date and maturity date of herbaceous plants had strong trends of advance along with 3.383 d/10 a and 1.570 d/10 a,respectively,in average.Other phenophases such as the sowing date,green-up date,wilting date and growth period had parallel trends of advance/shorten and delay/extension.Spatial variations of changes of China's phenophases had significant differences,especially for the woody plants.The periods of first leafing and first flowering showed increased advance trends from the southwest to the northeast,but the periods of beginning and end of leaf coloring showed decreased delay trends from the northwest to the southeast.In most regions the growth season extended,but in some regions shorten.The representative species,wheat(Triticum aestivum),Robinia pseudoacacia,Ulmus pumila and Melia azedarach,showed significant spatial variations in their key phenophase changes.Effects of temperature and precipitation on plant phenology varied by region and species.The phenophases of woody plants in China was mainly affected by temperature.When the mean annual temperature increased,the phenophases of first leaf,first flowering,beginning of leaf coloring,end of leaf coloring and growth season had parallel trends of advance/shorten and delay/extension in different vegetation zones.The phenophases of herbaceous plants in China was mainly affected by precipitation.The phenophase of sowing date was advanced,the green-up date,flowering date,maturity date and the wilting date were delayed,and the growth period was shortened along with increased mean annual precipitation.(3)Phenophase change records based on remote sensing observations demonstrate that the start of season had 68.5% records showing earlier trends,with a mean advance of 1.268 d/10 a.The green-up date had 90.3% records showing earlier trends,with a mean advance of 9.379 d/10 a.The end of season had 65.1% records showed later trends,along with an average delay of 0.758 d/10 a.The growth season had extended by 0.984 d/10 a in average accounting for 65.2% records.Different vegetation types had different phenophase changes.For the end of growing season,the forest land and grassland showed a delayed trend and the farmland showed an early trend.The prolonged growth season of the grassland was significantly(p<0.05)higher than that of the farmland.(4)Species,community and vegetation change records based on ground observations demonstrate that climate warming led to changes in vegetation area,species diversity index and species distribution range.Such changes depended on many factors such as vegetation type,altitude and species.The cropping boundary,structure and regime in China had changed too.The crop boundary of wheat shifted to the northwest,and that of rice moved northward.In most parts of Heilongjiang Province,rice was planted instead of corn and wheat,and the area of crops with multi-crop annually continued to expand.The tree-lines of some natural forests shifted upward,especially in the Changbai Mts in Northeastern China.Areas of prammophyte vegetation and crops had continuously increased,and the area of desert had reduced.(5)Vegetation change records based on remote sensing observations demonstrated that annual variation rates of the Normalized difference vegetation index(NDVI)of grassland,forest and farmland showed increasing trends,and the annual variation rate of NDVI of grassland was significantly(p<0.01)higher than that of forest.(6)Synthesis of farmland and grassland net primary productivity changes based on ground observations showed that crop yields were increasing.The crop yields in the Jiang-Huai region,eastern Gansu Province and eastern Jilin Province continued to increase.The forage yield of pasture varied from region to region.The forage yield of alpine Stipa steppe in Xinghai County of Qinghai Province increased significantly(p<0.05),while the hay yield in Ningxia and Three River Source Region showed a decreasing trend.(7)Based on remote sensing observations,the vegetation productivity changes of China and in key areas of the Qinghai-Tibet Plateau,Inner Mongolia Plateau,Loess Plateau,Northeast China and Southwest China showed that the net primary productivity of vegetation in China was mainly increased.Only in a few regions such as central Inner Mongolia,Urumqi and parts of Yunnan Province,the net primary productivity of vegetation had a decreasing trend. |
PDF Full Text Request