Pasture Productivity Changes In Mongolia

Pasture Productivity Changes In Mongolia

The result of Century model gives simulated pasture biomass values at 899 grid points over Mongolia. From above figure we can distinguish summer peak biomass from 1 ts/ha to 25 ts/ha in different natural zones. In fact this figure could directly present the natural zones of the country. Climate change has had an effect on not only peak standing biomass but also spring biomass. Livestock survival capability is strongly depends on spring weather and forage resource for winter and spring.

The average spring potential biomass by the ecosystem model Century was estimated as 27-50 g/m2 in the forest steppe, 15-33 g/m2 in the steppe, 5-13 g/m2 in the Altai mountains and 3-6 g/m2 in the Gobi desert.

Biomass in April and May was decreased in the forest steppe and the steppe directly caused by precipitation changes for those months. The total pasture carrying capacity* was estimated as 44.5 million sheep unit based on average observed biomass. Based on the decreasing trend of peak biomass by 20-30 %, the total pasture capacity was calculated as 32.6 million sheep unit. Past 40 years the total pasture carrying capacity was drop down by 27 % because of biomass decrease.

Monitoring Of Pasture Condition From Space
Among several types of satellite data available for monitoring of global scale and NOAA AVHRR data has been selected primarily because of its high frequency, wide coverage for one pass and low cost compared to high resolution satellite data. NDVI value derived from NOAA/AVHRR has becoming the main tool to estimate and monitor vegetation dynamics for whole territory of Mongolia over long duration.

According to the 10 days NDVI composite images we can determine the temporal and spatial vegetation changes i.e. onset, growing pick and senescence time of vegetation growth. From the general dynamics of pasture condition we could say that better grazing time for the pasture animals begins from earlier May to latest October till suffering full snow coverage and the best grazing time is too short as, from July to August.

Vegetation dynamics
As mentioned, NDVI is most suitable data for global vegetation monitoring; we have analyzed the seasonal and long term vegetation dynamics. However, Mongolia has short summer season, as well as short duration of growing period, from June to early September. In general, the peak of vegetation growth fits in August. Depending on the climate situation of certain region, its pasture vegetation condition changes within the years and also within 10 days. The long term dynamic of August of 1982 – 2001 is showing in Fig. 2.

Fig. 2. Long term NDVI dynamics (August, 1982 – 2001)
In general, 1994 was quite wet year and 2001 was more drought year within above 20 years of study.

From NDVI dynamics we could estimate only vegetation condition of certain period. Also we could determine the vegetation condition by comparison with long term NDVI data. For example, by calculation of Vegetation condition index (VCI) could be distinguished the areas, where vegetation condition is good, where is normal and/or bad. By NDVI difference calculation we could present areas, where current NDVI is much better, better, normal and lower or much lower than long term average NDVI of corresponding period.

Natural zones
There are several types of ecosystem, like high mountain, mountain taiga, forest steppe, steppe, desert steppe, and desert, which are completely different from each other.

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