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Land cover change and pasture estimation of Mongolia from space
Assessment of pasture condition
- Vegetation dynamics by NOAA data
NDVI value has becoming the main tool to estimate vegetation dynamics for whole territory of Mongolia. According to the monthly NDVI composite images we can determine the temporal and spatial vegetation changes i.e. onset, pick and die time of vegetation growth. From the general dynamics of pasture we can say that better grazing time for the pasture animals begins from latest April to latest October till suffering full snow coverage and the best grazing time is too short as, from July to August.
Using 13 years NDVI data we calculated the long term normal values for each months and for each year of whole Mongolia.
Figure 3. Long term normal NDVI map of Mongolia (August 1985-1997)
With comparison above maps we have distinguished normal (1985, 1987, 1988), drought (1989, 1992, 1995) and good vegetated (1990, 1991, 1993, 1994, 1996, 1997) years within 13 years.
- Vegetation zone classification
According to the vegetation zone map of Mongolia (Figure 4a) we have classified the vegetation zone map using NDVI data Figure 4b, which is highly correlated with first one (r = 0.9619). The regression function determined like,
Y = 0.078968 + 0.977887X
Figure 4. a. Vegetation zone map (source from National Atlas of Mongolia)
b. Vegetation zone classification map (classified by NDVI)
Based on time series analysis of above classified map and multi temporal NDVI data calculated the monthly spectral curves of 6 types of vegetation zones, as high mountain, mountain taiga, forest steppe, steppe, desert steppe and desert.
According to the above results we could make decision that the NOAA NDVI GAC data is available to estimate vegetation condition, in particular the pasture condition during a year. As analysis, all vegetation zones are different by NDVI values specially, in growing season (Figure 5).
Figure 5. a. Area difference of vegetation zones from original map and calculated
from NDVI
b. Spectral characteristics (yearly NDVI changes) of different vegetation
zones
We have a new technology of preprocessing of NOAA/NDVI data and producing following numbers of outputs as,
- Current NDVI map of Mongolia with summer condition score (point type at the meteorological station) and drought index (pattern type by whole country)
- NDVI difference map, in %
- Hay and Pasture map with VCI map (pattern) and biomass data (point)
- Drought index map with Pedi index (point)
- Biomass map estimated by NDVI
- Pasture carrying capacity
In other hand, the pasture vegetation condition depends not only upon natural (drought) condition, but also on human activities.
Conclusions
From the comparison of multi-date land cover map of 1992 and 1997 found that the total forest area in Mongolia including deciduous needleleaf, deciduous broadleaf, coniferous forest and all mixed forest is about 12.7%.
NOAA/NDVI monthly data set is useful information for pasture vegetation monitoring of Mongolia. The spectral characteristics of different pasture vegetation zones, derived from NOAA/NDVI was distinguishable from each other.
According to the accepted new technology for pasture vegetation condition mapping the outputs from NOAA/NDVI would be increased for the end users and also for decision makers. In this case we could estimate current situation of pasture vegetation and compare with a long term condition.
The results of study will sober to strengthen the pasture management related to the decision support system of the country, after integration with other socio-economic information.
References
- Adyasuren Ts. "Environment and Development issues in Mongolia". Ulaanbaatar, 1998.
- Batima P. Dagvadorj D. "Climate Change and its Impacts in Mongolia". Ulaanbaatar, 2000.
- Batima P., Dagvadorj D. "Mongolia National Action Programme on Climate Change", Ulaanbaatar, 2000.
- Chandra P.Giri, Surendra Shrestha. Developing land cover classification system for NOAA AVHRR applications in Asia.
- Khudulmur S, Erdenetuya M, Munkhtuya Sh. and Odbayar M, Classification and Monitoring of land cover of Mongolia. Report 1997.
- Mongolian Development Strategy Research Project: "Some issues of environment and development of pasture and animal husbandry of Mongolia", Ulaanbaatar 1999.
- Mongolia - 21 century. New policy of economy and social problems, Ulaanbaatar, 1997.
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