Development of methodology to estimate regional net primary productivity (NPP) using modified Monteith model

方法：利用改进的CASA模型对干旱区植被进行调整，估算了亚洲地区2000年的实际NPP。也就是说，我使用的fAPAR估计NDVI-fAPAR回归线，我得到了我自己的现场实验。通过将月数据改为日数据，改进了土壤水分估算模型。本文应用Chikugo模型从气候资料中估算气候潜在NPP。使用的数据集如下：GPCC降水。NCEP/NCAR全球再分析产品用于温度和PAR，FAO土壤图用于土壤质地，NOAA/AVHRR USGS 1 km AVHRR全球陆地数据集用于NDVI。使用Thornthwaite方法计算潜在蒸散量。植被类型来自NOAA GVI。假定荒漠化地区的实际净初级生产力将低于气候潜在净初级生产力。结果：与GLASOD的土壤退化图相比，亚洲植被退化图在从中国到中亚的退化区域具有较好的对应性。然而，在高海拔地区，似乎有一种趋势，显示出相对较低的潜在NPP。由于该方法仅使用了一年的数据集，因此有必要对多年数据集的方法进行改进。

lt was attempted to identify the potential area affected by desertification using the data of year 2000 in Asia.Methods : I estimated actual NPP using improved version of CASA model to adjust dry land vegetation. Namely, I used fAPAR estimation by NDVI-fAPAR regression line which I obtained by my own field experiments. Soil moisture estimation model was improved by changing datasets used from monthly to daily one. Chikugo model was applied to estimate climatologically potential NPP from climatologic datasets. The datasets used are as follows ; GPCC precipitation. NCEP/NCAR Global Reanalysis Products for temperature and PAR, FAO soil map for soil texture, and NOAA/AVHRR USGS 1km AVHRR Global Land Dataset for NDVI. Potential evapotranspiration was calculated using Thornthwaite's method. The vegetation type was derived from NOAA GVI. It is assumed that actual NPP would be below climatologically potential NPP in desertified areas. Thus, first, drylands was derived and then the area where actual NPP is less than potential NPP in drylands was derived and mapped (Asian vegetation degradation map).Results : Compared to soil degradation map of GLASOD, Asian vegetation degradation map corresponds well at the degraded regions from China to Central Asia. However, it seems to have a tendency to show relatively low potential NPP in high elevation areas. It is necessary to improve the method using multi-years datasets, because this analysis used only one year dataset.