FPAR(fraction of photosynthetically active radiation absorbed by the canopy)是植被冠层阻截太阳光合有效辐射的比例,是遥感估算陆地生态系统植被净第一性生产力(NPP)的重要参数。利用Monte Carlo方法模拟光子在植被冠层中的辐射传输过程,以植被冠层二向反射分布函数的模拟来验证模拟的正确性;在此基础上对400—700nm光合作用波段范围内的植被叶片吸收光子辐射比例的FPAR进行模拟。FPAR的Monte Carlo模拟结果,揭示了FPAR与太阳天顶角及植被冠层参数之间的关系。
Based on light-use efficiency model, an MODIS-derived daily net primary production (NPP) model was developed. In this model, a new model for the fraction of photosynthetically active radiation absorbed by vegetation (FPAR) is developed based on leaf area index (LAI) and albedo parameters, and a pho- tosynthetically active radiation (PAR) is calculated from the combination of Bird's model with aerosol optical thickness and water vapor derived from cloud free MODIS images. These two models are inte- grated into our predicted NPP model, whose most parameters are retrieved from MODIS data. In order to validate our NPP model, the observed NPP in the Qianyanzhou station and the Changbai Mountains station are used to compare with our predicted NPP, showing that they are in good agreement. The NASA NPP products also have been downloaded and compared with the measurements, which shows that the NASA NPP products underestimated NPP in the Qianyanzhou station but overestimated in the Changbai Mountains station in 2004.
根据野外调查和实验分析研究了江西省千烟洲人工针叶林下狗脊蕨(Woodwardia japonica)群落的生物量、细根生物量、净初级生产力(Net primary productivity,NPP)、比叶面积(Specific leaf area,SLA)和叶面积指数(Leaf area index,LAI)等。通过叶片参数和地上生物量的相关关系建立了狗脊蕨单株地上生物量估算模型,分别为W1=0.021H1.545(R2=0.790)和W1=2.518(D2H)0.616(R2=0.894;H为株高,D为地径)。人工针叶林下灌草层地上生物量为367.8g.m-2(52～932g.m-2),凋落物为1631g.m-2(672～2763g.m-2),分别占乔木层地上生物量的4.7%(1.55%～13.2%)和20.7%(7.6%～32.1%)。狗脊蕨群落地上生物量和NPP分别为266.6g.m-2和88.67g.m-2.a-1,其中狗脊蕨种群占73.7%;地下生物量为212.6g.m-2。狗脊蕨的SLA和叶干物质含量(Leaves day mutter con-tent,LDMC)分别为144.0cm2.g-1和31.99%,二者之间呈显著负相关;最佳叶面积估算模型为S=21.9226-0.152L2+0.0009L3(9.0≤L(叶片长度)≤23.5;1.4≤W(叶片宽度)≤5.9)。狗脊蕨种群的LAI为1.8。土壤含水量对狗脊蕨生物量有显著影响。群落生物量与土壤有机质和全氮含量正相关。
