| The remaining part of plant photosynthetic activity per unit area after deducting auto trophic respiration,that is,the difference between carbon absorbed by plant photosynthesis and carbon released by respiration,is called Net Primary Productivity(NPP).NPP plays an important role in carbon cycle.It can not only reflect production capacity of vegetation,but also have the ability to fix carbon dioxide in the atmosphere.Therefore,studying NPP has important implications for global carbon cycle change and terrestrial ecosystem.In this paper,the temporal variation and spatial distribution characteristics of vegetation NPP were analyzed using MOD17A3 dataset with 1km spatial resolution from 2000 to 2014in Beijing-Tianjin-Hebei region.Based on topographic data,the correlation between NPP and topographic factors was analyzed.Based on vegetation NPP,MCD12Q1 data,Beijing Statistical Yearbook,Tianjin Statistical Yearbook and Hebei Economic Yearbook,the equivalence factor and production factor of Beijing-Tianjin-Hebei region were calculated from 2001 to 2013.The spatial and temporal distribution of per capita ecological footprint,per capita ecological capacity and per capita ecological deficit/surplus from 2001 to 2013were derived.The main conclusions are as follows:(1)The spatial distribution characteristics and temporal trends of vegetation NPP in Beijing-Tianjin-Hebei region from 2000 to 2014 were analyzed.The average annual NPP in the northern part of Beijing-Tianjin-Hebei showed gradual decrease from east to west,consistent with longitude zonality rule.The average annual NPP in the western part of Beijing-Tianjin-Hebei conforms to latitude zonality rule,decreasing from south to north.There was a high NPP area in the east of Taihang Mountain in the central part of Beijing-Tianjin-Hebei.The average annual NPP from 2000 to 2014 was mainly concentrated at 200-300 gC/(m~2·a).Vegetation NPP fluctuations in Beijing-Tianjin-Hebei region showed a trend of increase.In 2004,the average NPP of vegetation was as high as 356 gC/(m~2·a),followed by 2008,which was 313 gC/(m~2·a),and the lowest was 2001,which was 223gC/(m~2·a).(2)The interannual change rate of NPP in Beijing-Tianjin-Hebei region from 2000 to2014 was analyzed.The area of extremely significant increase of NPP reached 68%of the entire region,the significant increase of NPP was 8%,and extremely significant decrease was15%.The area with NPP increase(76%)was greater than the area with NPP decrease(24%).It can be seen that vegetation NPP in Beijing-Tianjin-Hebei region had been increasing during these 15 years.(3)TherelationshipbetweenvegetationNPPandtopographicfactorsin Beijing-Tianjin-Hebei region was analyzed.From 2000 to 2014,the change trend of vegetation NPP with elevation and slope in Beijing-Tianjin-Hebei region was consistent with that of NPP,and both showed fluctuations.Elevation and slope were important factors of vegetation NPP change,and NPP decreased with the increase of elevation and slope.(4)The equivalence factor and yield factor of Beijing-Tianjin-Hebei region were calculated from 2001 to 2013.The equivalence factors of six bio-productive land types in Beijing-Tianjin-Hebei region from 2001 to 2013 were different,and generally showed the law of water area>cultivated land(building land)>grassland>forest land(energy land).The yield factors of six bio-productive land types in Beijing-Tianjin-Hebei region varied from 2001 to2013,showing the pattern of water area>grassland>cultivated land(building land)>forest land(energy land).(5)Based on equivalence factor,the temporal variation and spatial distribution characteristics of per capita ecological footprint in Beijing-Tianjin-Hebei region during2001-2013 were analyzed.The results showed that per capita ecological footprints of Beijing-Tianjin-Hebei region changed irregularly from 2001 to 2013,but generally increased.Per capita ecological footprint in Beijing-Tianjin-Hebei region was the highest in 2013,which was 0.946 km~2,and the lowest value was 0.381 km~2 in 2002.The spatial distribution of per capita ecological footprint in Beijing-Tianjin-Hebei region complied with geographical differentiation law and generally remained stable.In most areas,per capita ecological footprint was 0.2-0.4 km~2.The per capita ecological footprint of coastal areas was higher,while the per capita ecological footprint of mountain areas was lower.(6)Based on equivalence factor and yield factor,the temporal variation and spatial distribution characteristics of per capita ecological capacity in Beijing-Tianjin-Hebei region during 2001-2013 were analyzed.The results showed that the per capita ecological capacity of various productive land types in Beijing-Tianjin-Hebei region slightly changed from 2001to 2013,and generally showed an upward trend.The ecological capacity in Beijing-Tianjin-Hebei region was the highest at 1.4227 km~2in 2012,and the lowest was 0.570km~2 in 2002.Thespatial distribution ofper capitaecological capacity in Beijing-Tianjin-Hebei region conformed to geographic differentiation laws during 2001-2013.The per capita ecological capacity in most areas was low(0.0005-0.0015 km~2).High-value area was produced in the northeast coastal area of Beijing-Tianjin-Hebei region(Qinhuangdao City),and the per capita ecological capacity was above 0.003 km~2.(7)Based on the calculation results of ecological footprint and ecological capacity,the temporal variation and spatial distribution characteristics of per capita ecological deficit/surplus in Beijing-Tianjin-Hebei region during 2001-2013 were analyzed.The results showed that ecological surplus in Beijing-Tianjin-Hebei region fluctuated significantly from 2001 to2013,but it generally showed an upward trend.From 2001 to 2013,the spatial distribution of per capita ecological deficit/surplus in Beijing-Tianjin-Hebei region conformed to geographic differentiation laws,showing irregular changes with ecological deficits in most regions.The per capita ecological deficit was 0.03-0.02 km~2.The ecological environment in Beijing-Tianjin-Hebei region markedly improved during 2001-2013,and per capita ecological surplus gradually increased.There was clear ecological surplus in Zhangjiakou-Chengde area. |
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