Estimation of NPP based agricultural production
For Asian countries using Remote Sensing data and GIS
Abstract
The land use / land cover has been changed for many countries of Asia In last a few decades caused by the population pressure . Generally speaking, the agricultural land increased and forested land decreased. Then, the agricultural production has been increased for many years in the region. However ,there is some doubt that the region can sustain or improve the production In future . The productivity may vary depending on the environment of the land .In this study, the estimation of agricultural production reflecting the current land use/land cover is made .
The agricultural production is considered to be a part of NPP(Net Primary Production) on the agricultural land . The NPP can be estimated using PAR (Photo synthetically Active Radiation ) and NDVI, and both can be seen in the land use /land cover map. The estimation of NPP on the agricultural land of Asian countries is made . Moreover , by Integrating the result of the agricultural NPP with the statistics, the conversion efficiency of agricultural production from agricultural NPP is made. The conversion efficiency shows the status agriculture for the country.
1.Introduction
According to the Announcement, world population reaches 6 billion in October 1999.Monitoring, estimating and forecasting agricultural production are quite important for the management of world / regional or local food demand and supply balance for social security. A method to monitor and estimate agricultural production in coarse however broad frequency scale is introduced in this study.
2.Data Used
Following data were prepared and used in this study.
NDVI Data
NDVI data were used to calculate Net Primary Production in combination with Photosynthesis Active Radiation data. Monthly. NDVI data for January 1982 to December 1993 were composed from 10days composite data set of NQAA/ NASA Pathfinder AVHRR Land Data Set.
Photosynthesis Active Radiation Data
Monthly Photosynthesis Active Radiation(PAR) data for January 1979 to December
1989 were provided ,and averaged monthly PAR data using these data were prepared in order to calculate Net Primary production of 1990 to 1993 in combination with NDVI data .
Land Cover Data
Land cover data were retrieved from USGS Global Land Cover Characteristics Data Base < http:// edcwww.cr.usgs.gov/landdaac.glcc/_ na.html> .There are 6 maps in different schemes in the data base, and IGBP Legend map was used in this study.
Agricultural Production Data (Statistics)
Agricultural production data were retrieved from FAOSTAT agricultural Data
. In this study, "cereal production"was used to represent agricultural production.
3.Methodology
3.1 Estimation of Net Primary productivity
Monthly Net primary Productivity (NPP) can be estimated using NDVI and PAR data by "production efficiency approach" proposed by Go ward ( 1992)and Ruimy (1994).
NPP = eň APARdt ...........(*)
NPP: [gdm/m2time],
e:efficiency[g/MJ],
APAR: Absorbed PAR [MJ/ m2]
f APAR = -0.08+ 1.075 NDVI ......(**)
The annual total NPP can be estimated as follows:
3.2 Extraction of Net Primary Production from crop lands
After calculate NPP on whole land , Net Primary Production in cropland is extrated by overlaying USGS/IGBP legend land cover map.
3.3 Calculation of NPP - Crop conversion ratio
By adding NPP in crop lands for countery base , the relationship between NPP in croplands and cereal production is analyzed. The conversion ratio from NPP in croplands to cereal production is calculated for each country.
