CHAPTER V
SATELLITE IMAGE MONITORING OF ELM OPEN WOODLAND IN THE KORQIN SANDY LANDS

Six scenes of the Thematic Mapper Digital Imagery were purchased from the China Remote Sensing Satellite Ground Station (scene codes 120/29, 120/30, 121/29, 121/30, 122/29, 122/30). These images cover the whole of Korqin and were taken during summer from 1996 to 1997. For the monitoring of the vegetation coverage over the years in Kezuozhong Banner, imagery of the years 1988 and 1994 were also purchased.

The images cover a range of 430 km by 305 km, from 118.0° to 123.5° Eastern longitude and from 42.66° to 45.33° Northern latitude, that is, from Shuangliao City in the east to the western border of Balin Youqi Banner in the west, and from the southern border of Kulun Banner in the south to Taonan City in the north. The effective area included is 189000km².

The hardware used to process the images include a Sun work station with its peripherals and PC computers. Used software includes ERDAS, ARC/INFO and PhotoShop as the main ones.

5.1 General situation of the Elm open woodlands

5.1.1 The central-northern sub-region

In the central-north region (Kezuozhong Banner, Tongliao County, Tongyu County) revegetation efforts have obtained evident results, but simultaneously a large area of natural open woodland disappeared. In Kezuozhong Banner, for example, the area covered by sand dunes has been reduced due to planting/sowing of grasses, shrubs, and trees. The natural Elm open woodlands in the west and east of the county were destroyed during the period 1988–1994. The Elm open woodland in the Zhurihe Pasture (in the west of the banner) has been reduced to a shrub-like vegetation due to over-grazing, while the vast Elm open woodland on the sand-sheet around Wusitu, in the southeast of the banner, have been reduced to degraded patches.

5.1.2 The Southern Sub-region

On the sand-sheets and sand dunes in the southern part of the Korqin Sandy Lands (Kezuohou Banner, Kulun Banner, Naiman Banner), the Elm open woodlands and shrub woodlands have been almost completely destroyed, with only a few remaining relicts, in the northern part of Kezuohou Banner, and most of them degraded to shrub-like vegetation.

5.1.3 Among the mountains and on the Piedmont to the East of the Khing'gan Mountains

Large areas of elm woodlands still exist in the northwestern part of the Korqin. In the more mountainous areas, the open woodlands follow the valley bottoms. In the vast piedmont areas to the east of the Khing'gan Mountains, there also exist large stretches of elm woodland. However, conversion activities for farming and pasture are seriously encroaching upon the elm woodlands in the central plain area of Kezuozhong Banner. Newly reclaimed agricultural areas show on the images a mottled distribution of farmland and elm woodland.

The average proportion of elm open woodland in the north and northwestern part of the Korqin, i. e. in Zhalute banner, Kezuozhong Banner, Tongyu County and Keyouzhong Banner, is 12.55% according to the satellite maps measurements.

5.2 Monitoring and comparison of Elm open woodlands in Kezuozhong Banner

5.2.1. Comparison between situation 1988 and 1994

The digital data used for between-years comparison are from 1988 to 1994.

Table 5.1: Comparison results of satellite image monitoring of open woodland and grassland in Kezuozhong Banner between 1988–1994.

Note: the figures in brackets are county statistics in the same year.

From the table it can be observed that the area of the natural elm open woodland in the Kezuozhong Banner was reduced by half (from 134, 120 ha to 68,400 ha) over the 6 years from 1988 to 1994. Most of it was converted into grassland and farmland. The area of presently (1998) existing natural elm open woodland amounts to 45,450 ha, while that of shrub woodland to 22,950 ha.

The figures of the official county statistics differ from the monitoring results, since the former were estimated (not measured) and take into consideration only woodlands with a coverage of more than 30%.

5.2.2 Distribution over the different townships in the banner

The preserved natural woodland in the banner amounts to 26,000 ha according to banner statistics of 1994. The natural woodlands (defined as with about 30% coverage or more) are principally elm-based. They are occasionally mixed with mountain apricot and other shrubs (bush clovers) in the denser ones.

Table 5.2: Distribution of natural elm woodland in the banner