Study Ontemporal And Spatial Dynamic Change Of Vegetation And Its Response To Climate In Northeast China

Global climate change is becoming a focus social problem,not only an ecosystem question.As one of the most sensitive climate areas,the dynamic vegetation changes of northeast area of China play an important role on global climate change.First,the vegetation parameters of Global Inventory Modeling and Mapping Studies(GIMMS)Normalized Difference Vegetation Index(NDVI)3rd generation(GIMMS3g)data(NDVI,phenology and net primary productivity(NPP))was used to reflect the dynamic change combined with the precipitation,sunshine and other data.The characteristics of vegetation variation and its response on climate changes were analyzed from different perspectives.Second,the GIMMS3g data was reconstructed by eliminating noise,and obtaining the meteorological data(temperature and precipitation).The NDVI data of 1982-2013 was collected to analyze the vegetation Seasonal and annual changes,the NDVI characteristic of vegetation species response on temperature and precipitation.Third,GIMMS NDVI data was constructed by the asymmetric Gauss model to research the growth of vegetation from the start date to the end of growth in order to capture the parameters of vegetation growing season.The temporal and spatial variation characteristics of different types of vegetation phenology,temperature and precipitation response characteristics and hysteresis of temperature and precipitation were analyzed from the start growing time to end time.Finally,the improved CASA model,calculate vegetation NPP in Northeast China,and the use of data-modl7a3 verified,discusses the Northeast geography of different vegetation types and different climatic regions of NPP temporal and spatial variation characteristics and response to climate change.The study adopts three important indicators which could reflect vegetation dynamics,discusses the response of different vegetation types when temporal and climate change from a different perspective in Northeast China,thus better understand the bio-atmosphere's material and energy exchange processes,provide the scientific evidences for predicting vegetation types trends.This study reached the following conclusions:(1)The trends of vegetation's NDVI in the Northeast are almost negative in the past 32 years;The trends of NDVI are different in different seasons,negative in winter,spring and summer,but positive in autumn.The trends of NDVI are different in different types of vegetation,obviously positive in Underbrush in the past 32 years(0.0013 unit/year,P<0.001);negative in Meadows,Alpine vegetation,Broadleaf forest and Swamp(-0.0004 unit/year,P<0.001;-0.0009 unit/year,P<0.001;-0.0004 unit/year,P<0.05;-0.0007 unit/year,P<0.001);but no obviously change in Grassland,Shrub Cultivated vegetationn,Coniferous forest,Coniferous forest.The trends of all of vegetation's NDVI in the Northeast are positive in 1982 to 1999,but no significant change in 2000 to 2013 except Meadow and Grassland which are obviously positive.The trends of vegetation's NDVI are negative in totally in the past 14 years.(2)The stduy shows that the Forest's NDVI have a positive correlation with annual temperature in spring,but no significant correlation with precipitation;the Forest's NDVI have no correlation with annual temperature and precipitation in summer;the Forest's NDVI only have a positive correlation with precipitation in the mountains in autumn;the NDVI have a positive correlation with annual temperature,but negative correlation with precipitation.(3)The average vegetation NPP is 390.3 gC/m~2/year in the Northeast,the total NPP is 476.9 × 1012 gC/year.The NPP is low in west and southwest,high in east and north,reduced gradually from northeast to southwest in space.The average NPP and total NPP is Significant different between different vegetation types in the Northeast,the sequence of average NPP is Theropencedrymion>Broadleaf forest>Swamp>Coniferous forest>Shrub>Alpine vegetation>Meadow>Cultivated vegetation>Underbrush>Grassland,the sequence of total NPP is Broadleaf forest>Cultivated vegetation>Coniferous forest>Meadow>Grassland>Shrub>Swamp>Theropencedrymion>Underbrush>Alpine vegetation.(4)The average NPP of Underbrush,Meadow,Grassland,Shrub,Broadleaf forest,Cultivated vegetation,Swamp,Coniferous forest shows a increasing tendecy,the Underbrush's NPP increasing rate is 6.63gC/m~2/yr2(P<0.01),the Meadow's NPP increasing rate is 3.26gC/m~2/yr2(P<0.05),the Grassland's NPP increasing rate is 3.9gC/m~2/yr2(P<0.05),the Shrub's NPP increasing rate is 2.91gC/m~2/yr2(P<0.01),the Broadleaf forest's NPP increasing rate is 2.73gC/m~2/yr2(P<0.05),the Cultivated vegetation's NPP increasing rate is 3.32gC/m~2/yr2(P<0.05),the Swamp's NPP increasing rate is 4.91gC/m~2/yr2(P<0.01),the Coniferous forest's NPP increasing rate is 4.32gC/m~2/yr2(P<0.05).But the increasing of NPP is not a straight-up process,the different types of vegetation's NPP have completely different response to different climatic factors in some abnormal climate year.(5)The different types of vegetation's NPP have different correlation between annual temperature and precipitation.All of types of vegetation's NPP have positive correlation with annual temperature in spring.The NPP has positive correlation with annual temperature in summer except Grassland.The NPP has positive correlation with annual temperature in autumn,obviously in Meadows,Shrub,Broadleaf forest,Cultivated vegetation.The NPP has negative correlation with annual temperature in winter,obviously in Meadow and Swamp.Sum up,the Underbrush,Meadows,Grassland's NPP have positive correlation with annual temperature.Throughout the year,grass,meadow,grassland NPP was positively correlated with temperature,other vegetation types were negatively correlated,positive and negative correlations are both not significant.(6)In the study area,the growing season(SOS)gradually delayed from south to north,the end of the growing season(EOS)gradually advance,and SOS in plain is significantly later than in the mountain region.Different vegetation's SOS,EOS have different trends in the past 32 years,the SOS of Grass,Meadow,Grassland,Shrub,Swamps,Coniferous forest shows advance trend,but the SOS of Alpine vegetation,Broadleaf forest,Cultivated vegetationn,Theropencedrymion shows deferred trend.The EOS of all of vegetation types shows deferred trend,obviously in Theropencedrymion and Coniferous forest,relatively moderate in Grass,Meadow,Grassland,Shrub,Swamps,Alpine vegetation,Broadleaf forest,Cultivated vegetationn.(7)For the time,the SOS have negative correlation with annual temperature in spring,SOS will advance when annual temperature rise,obviously in Forest,but not in Grassland.But the EOS have positive correlation with annual temperature in summer and autumn,EOS will defer when annual temperature rise.SOS has a certain lag response to precipitation,but the response to temperature is more intense.EOS has a certain lag response to temperature,but the temperature is decisive to EOS in september to november.