该文开展了全球变暖影响下青藏高原植被净初级生产力(Net Primary Productivity,NPP)对物候变化响应机制的研究。首先,基于MODIS MOD13Q1 NDVI数据集,采用动态阈值法和CASA模型分别反演了2002-2012年青藏高原植被物候和植被NPP。而后研究了青藏高原物候和NPP时空演变格局,分析了青藏高原不同生态单元、不同植被类型的NPP对物候变化的响应机制。结果表明:1)2002-2012年青藏高原高寒植被生长初期(Beginning of Glowing Season,BSG)提前(0.034 d/a),生长结束期(Ending of Growing Season,EGS)推后(0.299 d/a),生长期(Length of Growing Season,LGS)延长(0.300 d/a),植被NPP与此相应出现不同程度的增加(1.494 gC·m~(-2)/a)。 2)青藏高原植被NPP对植被物候变化的响应出现明显的区域分异。整体上青藏高原植被LGS的延长促进了NPP的增加,但由于不同地区主导气象因子的差异,两者之间的响应关系也存在明显差异。3)春季物候的提前对NPP所带来的影响明显大于生长结束期,而BGS主要靠影响春季NPP的累积进而影响全年植被NPP的总量。
英文摘要:
It is already an indisputable fact that the phenology of high-latitude areas has changed to a different extent following global warming.The research of this phenomenon is important for us to predict the response of terrestrial ecosystem to global change.However,the knowledge about the effects of phenology changes on biomass especially on vegetation net primary productivity(NPP)is hardly known.This paper took the Tibet Plateau(TP)as study area for its unique natural geographical environments and aimed to study the response mechanism between phenology and NPP.Firstly,phenology and NPP were detected respectively with dynamic threshold value method and CASA model based on MODIS NDVI dataset and meteorological data from 2002 to 2012 in the Tibet Plateau.Then,the paper described the spatio-temporal trends of phenology and NPP,and analyzed the impacts of phenology changes on NPP of different areas and vegetable types.The research also discussed the temperature and precipitation in different areas to better explain the response mechanism diversities.Conclusions can be drawn as follows:1)The beginning of growing season(BGS)of overall vegetations in Tibet Plateau has advanced during 2002 to 2012 at the rate of 0.034 d/a;the end of growing season(EGS)has delayed 0.299 d/a;the length of growing season(LGS)extended 0.300 d/a,and the annual NPP has increased 1.494 gC·m~(-2)·a~(-1) significantly.2)The extending of LGS can contribute to the increasing of NPP overall the Tibet Plateau.However this correlation is not notable and has regional differences because of the changing dominant meteorological factors.3)The advance of BGS has greater impact on NPP than the delay of EGS,and the effect of BGS mainly lies in the stimulation to the spring NPP.