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VEGETATION - 2000

Lake Maggiore - Italy, 3-6 April 2000


Vegetation Action & Demonstration Plan for desertification monitoring in China

Christian CREPEAU SCOT
Partners of the study
CNDMC: The China National Desertification Monitoring Centre (CNDMC) is a scientific organisation which is responsible to the Academy of Forest Inventory Planning (AFIP) and the Forest Information Centre (FIC), which are themselves responsible to the Forest State Administration.
CARSA: China Association for Remote Sensing Application.
Xinjiang Autonomous Region Authority
CNES, SCOT

Paper (pdf file, 2.26 M)

This study aims to demonstrate the contribution of Vegetation data for monitoring land cover in areas threatened with desertification in China and to identify the optimum conditions to allow Chinese users to use Vegetation data and derived products in an operational mode. Two study areas, threatened with desertification, have been chosen by the CNDMC: Inner Mongolia: 46°N, 97°E - 31°N, 123°E (3.6 millions km²) and Xinjiang : 49°N,73°E - 34°N,97°E (3.4 millions km²).

Actions carried out

Acquisition, processing and photo-interpretation of VGT data concerning the 1998 and 1999 agricultural seasons. These data were provided by the CTIV in the form of ten-day synthesis (S10).

Validation using ground survey data collected by the CNDMC and production of chronological and differential NDVI-VGT maps.

Acquisition and processing of several AVHRR images concerning the 1998 summer (Inner Mongolia area) in the form of ten-day synthesis provided by the Beijing receiving station.

Large ground survey campaign (750 sites) during the 1998 summer and delivery to SCOT of a climate and cartographic data base (road network, drainage network) concerning the two study areas.

First Results

In inner Mongolia. In the area where the NDVI value is the highest, land cover is composed of annual crops, generally planted with trees or of dense rangeland type with woody species. Crops are alternated in tight bands. In the area where the NDVI value is low (Korqin desert) the soil is generally sandy and land cover is of rangeland type with local xerophytic woody species or leguminous plants adapted to drought.

The quality of the NDVI layer is excellent in spite of some technical problems (insufficient cloud masking, too large coastal buffer).

In Xinjiang. Land cover data provided to SCOT by Xinjiang Region Authority show that vegetation vertical distribution illustrates the existence of different climates: high mountain tundra (between 4 100 and 3 200 m), grazing lands (from 3 500 to 2 300 m), forested belt (2 800 à 1 600 m), altitude steppes (2 400 to 1 300 m), steppelike and/or bushy or woody vegetation (from 1 300 to 300 m), grassland and crops on piedmont areas.

In irrigated areas, NDVI values are very high in August (in dark green). These areas are mainly located in the Tien Shan and Heerku Shan northern side and the piedmont basins where irrigated crops are prevailing (Northern Manas and southern Yanqi). Glaciers, rocks, altitude or piedmont lakes are in pink. Arid areas are in yellow and hyper-arid areas in light orange.

Between the green mountainous area and the green piedmont area, there is an area for which NDVI values are lower. This area, located at the foot of the mountains, is covered by dry xerophytic vegetation.

The quality of VGT geometry and radiometry allows to identify very small features.

Conclusions

To develop the VGT data market in Asia, a second phase should be dedicated to the development of new methodologies able to produce desertification indicators using VGT data plus climatological and socio-economical data. This new phase should take advantage of the important operational capabilities of the Chinese partners, in technical and logistical terms.