The Study Of The Vegetation Dynamic In Eco-Climatic Regionalization Of Changbai Mountains

In this study, climate data, topography data and soil data were used to reeal regionaleco-climatical zones of the Changbai Mountains. Vegetation dynamics, the trend of climateand the relationship with climate in different eco-climatical zones in the Changbai Mountainsand the Changbai Mountain Nature Reserve based on the GIMSS NDVI and SPOT/VGTNDVI data, respectively. Quantitative relationship between NDVI and climatic factors wereexamined by ridge regression and spatial lag model. The main factors that had influence onNDVI were evaluated. The time lag of the NDVI response to the climate in differenteco-cliamtic zones were discussed. Finally, the characteristic of vegetation phenology indifferent eco-climatical zones and its relationship with climate change were discussed basedon the slope method. This study provided a case of vegetation dynamic and the response toclimate change in region scale based on the blackgrond of global environmental change. Theconclusions are summarized below.1) Based on the characteristic of the stuy areas,≥10℃accumulated temperature, thenumber of days of≥10℃accumulated temperature, the average temperature of the coldestmonth and the average temperature of the hottest month as the index of temperature wereselected. The thornthwaite index and precipitation were selected as water index. Combinedwith landform and soil types, the eco-climatical zones were differentiated in ChangbaiMountains. The study area included three eco-cliamtic zones, i.e., the southern warm humidzone, middle mid temperature humid zone and northern mid temperature subhumid zone. Theresulted eco-climatical regionalization was consistent with other result.2) The NDVI in Changbai Mountains increased during1982-2006, and the areas NDVIincreased account for93.3%of the study areas. Comparison with three eco-climatical zones,the sequence of the increased areas of NDVI accounted for the whole study areas were:northern mid temperature subhumid zone> middle mid temperature humid zone> southernwarm humid zone. Seasonal analysis indicated that there was double peak for the NDVIincrease. The increase of NDVI was in spring and autumu. The NDVI variation was minimumand even dcreased in July and August. For the three eco-climatical zones, the increase slopeof NDVI was higher in mid temperature than in warm temperature in spring and autumu, andthe decrease slope of NDVI was higher in warm temperature than that in mid temperature.3) From the trend analysis in Changbai Mountains, there was increase for temperatureand decrease for precipitation. The trend was significance (p<0.05). There was more increasein high altitude for the temperature and more decrease in humid zone for the precipitation.Wavelet analysis indicated the periodicity of temperature not only has long time scale changebut also short time scale change. The periodicity of precipitation presented different scale, butthe main change periodicity was7years,15years. Blow the10years scale, there was morecomplex in short time scale, and it was more frequently alternative of the dry and wet.Relationship between NDVI and climatic factors indincate temperature stronger correlatedwith NDVI than precipitation.4) The NDVI in Changbai Mountain Nature Reserve increased during past decade. Theseasonal variation characteristic was the same as the Changbai Mountains. From therelationship between NDVI and climatic factors, with altitude rised, the relationship between NDVI and temperature became stronger, and the relationship between NDVI and precipitationbecame weaker.5) The ridge regression and spatial lag regression were used to select the main climaticfactor which had influence on NDVI and to create the relationship between NDVI andclimatic factors. The above analysis indicate that the most influences on NDVI wereminimum temperature, precipitation and wind velocity. The NDVI has time lag of10-20daysin response to minimum temperature,20-40days response to precipitation, and0-10dayresponse to wind velocity. The time lag of response of NDVI to climatic factors presentedseasonal characteristic, with short time lag in spring and long time lag in summer. At the sametime, the time lag took on the spatial heterogeneity. The time lag of NDVI response totemperature became shorter as the latitude raised; the time lag of NDVI to response toprecipitation became longer in the wetter region. With the altitude rised, the time lag of NDVIto temperature became shorter, and the time lag of NDVI to precipitation became longer.6) The general characteristics of vegetation phenology in Changbai Mountains showedthat the start of season advanced and the end of season delayed. For the three eco-climaticzones, the advanced days were0.642day/yr (warm temperature humid zone, p<0.05),0.429day/yr (middle temperature humid zone, p<0.05) and0.371day/yr (middle temperaturesubhumid zone, p<0.05). For the three zones, the delayed trend of end of season in warmtemperature humid zone was significance. For the different vegetation types, the phonologicalevent presented diversity. The change of forest phenology was more obvious than theglassland and farmland. Correlation analysis indicated that temperature had stronger influenceto the vegetation phenology than precipitation. The start of season negatively correlated withtemperature. The length of season had stronger correlation with10℃accumulatedtemperature, which indicated the increasing10℃accumulated temperature possible causedthe longer length of season.