Spatial And Temporal Variabilities Of Forestry Biomass And Its Response To Climate Change In China

Forests are the important part of terrestrial ecosystems.Their changes in carbon reserves have a major role in estimating terrestrial carbon sinks.Biomass is an important functional indicator of ecosystem,an important indicator of forest carbon sequestration capacity and an important parameter for assessing forest carbon budget.How to invert forestry biomass quickly and accurately is one of the focuses of current global change research.Therefore,under the background of climate change,research on the biomass of forest ecosystems in China can not only provide a theoretical basis for the study of carbon cycle processes in terrestrial ecosystems,but also provide strategies for forest management.In this study,the forest ecosystem in China from 1993 to 2012 was taken as the study area.Firstly,it described the construction process of LPJ?Lund-Potsdam-Jena?global vegetation dynamics model and satellite remote sensing data used in the study,and analyzed the temporal and spatial characteristics of forestry productivity measured by LPJ in China.Then studying the temporal and spatial distribution of carbon density based on measured data,model simulation data and satellite remote sensing data of forest ecosystem in China.Finally,the impact of climate change on forestry biomass was analyzed.Research indicates:?1?The results of the simulation by LPJ model showed that from 1993 to 2012,the NPP of forestry ecosystem had a spatial pattern decreasing from southeast to northwest in China.The average annual NPP value of the forest in China was 531.21gC·m^-2·a^-1 for the past 20 years.And it showed significantly increasing trend?r=0.44,p<0.05?.The NPP of the three major forest areas showed an upward trend.The average NPP value of the southeast forest area was the highest,followed by the NPP average of the southwest forest area,and the annual NPP value of the northeast forest area was the smallest.The linear trends of NDVI and NPP were consistent and both showed an upward trend.?2?The results of LPJ and satellite inversion showed that the forestry vegetation carbon storage and forestry biomass showed a distribution pattern of low in the northwest and high in the southeast from 1993 to 2012 in China.Among them,the average density of the forestry biomass retrieved by the satellite was 38.96Mg/hm²,while the average density of forestry vegetation carbon storage simulated by LPJ was 64.08Mg/hm²,both of which had significant differences in the northeast and south regions;In the past 20 years,forestry biomass in China generally showed a significant upward trend?r=0.80,p<0.01?.According to the measured biomass data in Chinese forest,the maximum value of the living biomass in the community was 1567.94Mg/hm²,and the maximum value of dead biomass in the community was 117.39Mg/hm² in China.With the growth of age class,the biomass of all layers in the community ecosystem has shown an increasing trend.The biomass of the community,the arbor layer and its aboveground biomass were positively correlated with the forest age,average breast diameter,average tree height and standing tree volume.The biomass of the community,the arbor layer and its aboveground biomass were negatively correlated with the stand density.?3?There was a good correlation between biomass and NPP of forest in China,and the correlation coefficient between them was 0.5?p<0.05?.Among the seven geographical regions in China,the forestry biomass in the eastern China,southern China,northern China,central China,northwest and southwest regions was positively correlated with NPP,while the forestry biomass in the northeast and northern China was negatively correlated with NPP.The correlation between forestry biomass and NPP in northwest was the best,while the correlation between forestry biomass and NPP in northern China and eastern China was lower.There were significant regional differences in vegetation carbon storage and forestry biomass in China.Vegetation carbon storage was highly distributed in the northeast forest region and southeast forest region,and was relatively low in the southwest forest region.Forestry biomass was highly distributed in the northeast forest region and southwest forest region,and was relatively low in the southeast forest region.?4?The forestry biomass had a clear response to changes in temperature and precipitation in China.In the measured biomass,the biomass of the community,the arbor layer and the aboveground biomass were negatively correlated with the latitude,positively correlated with the temperature and precipitation.The spatial inversion of forestry biomass in China was mainly positively correlated with the annual average temperature,and was mainly negatively correlated with the annual precipitation.The biomass of the three major forestry areas was positively correlated with air temperature and negatively correlated with precipitation.Among them,the relationship between forestry biomass,temperature and precipitation was significant in the southwest forest area.There was no significant relationship between forestry biomass and temperature,and there was a significant relationship between forestry biomass and precipitation in the southeast forest area.The relationship between forestry biomass,temperature and precipitation in the northeast forest area did not pass a significant test of a=0.05.The vegetation carbon storage,temperature and precipitation in the three major forest areas simulated by LPJ maintained similar characteristics in the four periods during 1993¹997,1998²002,2003²007and 2008²012.