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November 2002 |
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Vegetation growth zones using NOAA-AVHRR data
Case Study
A case study carried out for the DL1 region is indicated in the existing agro-ecological zone map to present the usefulness of the new zoning technique (figure 1). This DL1 zone belongs to the dry part of the country. The dry zone of the country is classified into 5 regions namely DL1, DL2, DL3, DL4 and DL5. DL1 has a 75 percent probability annual rainfall amounting to 775 mm. The soils in DL1 are predominantly reddish brown earths and low humid grey soils. More than 50 percent of the total irrigated lands of the dry zone are situated in this region. Rice is the main crop in the irrigated lowland. There are 29 major vegetation growth zones identified inside the DL1 zone. In the existing agro-ecological zone map the whole area is classified as a dry zone region. However, in the new classification system, there are 3 zones identified within the intermediate zone out of these 29 vegetation growth zones (1<MAI <1.4). The P75 histograms for these 3 zones also significantly deviate from the histogram associated with the existing DL1 zone.
Figure 1: Agro-ecological regions and Vegetation growth
zones within the DL1 zone
Figure 2: Annual actual evapotranspiration
(a) and annual accumulated biomass (b)
across the DL1 region from June 1999 to May 2000.
During this one-year cycle study, the accumulated biomass production calculated ranges from 31255 kg/ha/year to 19741 kg/ha/year for the vegetation growth zones within DL1. The average biomass production for the dry monsoon forest is 27,820 kg/ha/year. The actual evapotranspiration values vary between 1,123mm/year to 1,472 mm/year. In the paddy cultivation areas, the average biomass development is 8,501 kg/ha/season and 7,546 kg/ha/season for the two cropping seasons of Maha (Oct. – Feb. major cultivation season) and Yala (Mar. – Aug.minor cultivation season), respectively (Fig. 2).
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