青藏高原1982~2015年FPAR时空变化分析

Analysis of the Spatio-temporal Variation in FPAR of the Tibetan Plateau from 1982 to 2015

植被吸收利用太阳光合有效辐射比率反映了植被固碳释氧能力,根据青藏高原GIMMS NDVI3g(1982~2015年)和MODIS NDVI(2001~2015年)数据,采用非线性半理论半经验模型进行FPAR反演及时空变化分析。结果表明:①2001~2015年GIMMS NDVI3g和MODIS NDVI反演FPAR在空间分布上具有较高的一致性,相关系数为0.82(P<0.01),年际变化趋势一致至少6年的区域占80%;②青藏高原FPAR受坡度和海拔影响较大,其中15~35坡度FPAR变化最快,700~2100 m海拔区间FPAR值最大;不同坡向对应的FPAR除南坡方向偏低外其他方向差异不大。③1982~2015年青藏高原四季FPAR时空变化研究中,冬季FPAR年际变化最明显,约78.5%的区域表现为增长趋势;秋季FPAR下降区域最多,但超过71.5%区域变化不显著;④基于MODIS NDVI和GIMMS NDVI两数据反演的所有植被类型的FPAR都在2012年间出现小幅度下降趋势,且不同植被类型FPAR的年际变化趋势各不相同。

The absorbed and utilized Fraction of Photosynthetically Active Radiation(FPAR)reflects the capacity of carbon fixation and oxygen release by vegetation,which may vary over space and time in large scale.Analysis of spatial-temporal variation in FPAR is an important topic of plant ecology.Based on GIMMS NDVI3g(1982~2015)and MODIS NDVI(2001~2015)data in the Tibetan plateau,here we used the nonlinear,semi-theoretical and semi-empirical models to inverse and analyze the spatial and temporal variation in FPAR.The results showed that(1)The spatial distributions of FPAR derived from GIMMS NDVI3g and MODIS NDVI were highly consistent,with the correlation coefficient being 0.82(P<0.01).The area in which the trends of inter-annual change in the two inversion data were consistent for at least 6 years made up 80%of the studying area.(2)FPAR in Tibetan Plateau was greatly affected by slope and altitude.Changes in FPAR were fastest at slopes of 15~35 degrees and highest at altitude of 700~2100 m.The effect of slope direction on FPAR was limited.There was little difference in FPAR among different slope directions except for the south where the FPAR was relatively lower.(3)The FPAR data from 1982 to 2015 demonstrated seasonal variation.The inter-annual variation in FPAR was most significant in winter,in which FPAR in about 78.5%of the area increased.FPAR declined most significantly in the fall.(4)FPAR derived from both the MODIS NDVI and GIMMS NDVI data demonstrated a small,temporary decline in 2012.The trend of inter-annual variation in FPAR was largely different among different vegetation types.In conclusion,the FPAR data from 1982 to 2015 in the Tibetan plateau demonstrated both spatial and seasonal variation,which may have important implications for further studies concerning climate and environmental changes in the region.