Zhao Songqiao(Chao Sung-chiao)
The extremely arid desert zone is distributed widely in China,located westwardfrom the Holan Shah up to the Sino-Russian border and northward from the KunlunShan up to the Sino-Mongolian boundary.It has an area of about 1.9 million sq.km,occupying one fifth of total land area of China.There are now about 60 millionmow of cropland in the desert zone of China,with about 200 million mow of stillunused arable land which accounts for nearly 30% of total unused arable land inChina.In this desert zone,land and mineral resources as well as solar and windenergy are very bountiful,with a considerable amount of water and biologicalresources too;all of them have great capability for further and better development.The desert zone of China is chiefly characterized by the following physical fea-tures:(1)The climate is extremely dry.Sunshine and solar radiation are very richwith generally more than 3400 hours of sunshine and 130-155 k.cal/cm2 of solarradiation annually.Winters are long and severe,and thermal variations,bothannual and diurnal,are very great.Strong winds blow frequently.(2) Geomorphologically thedesert zone of China is essentially composed of the Alashan Plateau andthree great inland basins-the Junggar,the Tarim and the Qaidam.As a whole,theground surface is level or undulating,with rather coarse materials,chiefly sands and gravels.(3)Practically no perennial river fed by local runoff exists.Thereflow in the zone only intermittent streams and a few larger rivers which areoriginated in the surrounding high mountains.The distribution of ground waterresource is quite variated and unbalaneed:very rich along perennial river channelsanti high mountain piedmont plains,while very poor in most other parts of thezone.(4)The most widely distributed soils are yermosols,xerosols and solonchaks,allwith soil profiles poorly developed,soil moisture and humus content very low,parentmaterials rather coarse,and salt content very high.(5)The desert vegetation is verysparse,generally less than 20-30% in coverage,with large tracts less than 5%.Thedesert vegetation is ecologically mainly composed of shrubs,half-shrubs and small half-shrubs and floristieally mostly of chenopodiaceae,compos ite and zygophyllaceae.In the desert zone of China,major diversifying physical attributes in terrainanalysis are landforms and ground surface materials.Seven major terrain typesare indentified in the first-level terrain types:clay and silt level terrain,sandy level terrain (sandy desert or Shamo,accounting for about 30% of totaldesert area),stony,gravel level terrain (Gobi,accounting for about 25% oftotal desart area),Denundational mountain and hill,Erosional high mountain,Ni-val apine,Oases (planted Vegetation).First and second-level terrain classificationsystem is tentatively proposed as table 1.Four natural regions are indentified in the desert zone of China:The AlashanPlateau temperate desert,The Junggar basin temperate desert,The Tarim basinwarm-temperate desert and The Qaidam high Plateau Desert.This paper takes the Jiayuguan,the Turpan basin,The Minfeng and Tajnar-lake areas as examples,they respectively represent four natural regions in thedesert zone of China,and analyzes terrian type based on landsat imageries.From above-discussed sample studies in landsat imagery,it seems good and quickresults might be obtained for terrain analysis and mapping in the desert zone of China if we use simultaneously an advanced remote lsensing technique and the traditional ground-truth investigation.
