General situation of nature

Gansu Province is located at the intersection of the Loess Plateau, Inner Mongolia Plateau and Qinghai-Tibet Plateau, belonging to the Yellow River Basin, the Yangtze River Basin and the Inland River Basin. Structurally, it mainly belongs to Ordos platform, Alashan-Beishan platform, Qilian mountain fold system and Qinling fold system. Generally speaking, the landform is a mountainous plateau with high terrain and complex landform types, which can be roughly divided into six terrain areas.

(1) Longnan Mountain. It roughly includes the mountainous areas south of Weishui, Lintan and east of Diebu, and is the western extension of Qinling Mountains. This area is mountainous, with high mountains and deep valleys, diverse vegetation types and dense river networks, which is the main distribution area of forest resources in the province.

(2) Loess Plateau in central Gansu. Located in the central and eastern part of Gansu Province, it starts from the junction of Gansu and Shaanxi in the east and reaches Wushaoling in the west. The loess plateau is formed by the accumulation of loess-like materials transported by Quaternary wind, and its thickness is generally 50 ~150m. Due to the action of flowing water, gravity, undercurrent erosion and wind erosion (the most important one is flowing water erosion), loess gully landforms and loess gully landforms have been formed. The typical landforms between ditches are platforms, hills and headlands, which are mostly distributed in the east of Liupanshan at present. After thousands of years of erosion, the western part of Liupanshan has become a typical loess hilly and gully region.

(3) Gannan Plateau. It belongs to the corner of the eastern margin of the Qinghai-Tibet Plateau, with a relatively high terrain, with an average elevation of more than 3,000 meters. It is a typical plateau area and mountainous landform. This area is an important animal husbandry base in Gansu Province, with vast grass beaches and rich aquatic plants.

(4) Hexi Corridor. It is located at the northern foot of Qilian Mountain and the southern foot of Beishan Mountain, starting from Wushaoling in the east and reaching the junction of Gan Xin in the west. It is a long and narrow strip inclined from east to west and from south to north. Altitude1000 ~1500m. It is 1000 km long and varies in width from several kilometers to more than1000 km. Here, the terrain is flat, the land is vast, the light and heat are sufficient, the water resources are abundant, and oases are distributed along inland rivers. Its oasis agriculture is the main commodity grain base in Gansu Province.

(5) Qilian Mountain. Located in the south of Hexi Corridor, it is more than 1000 kilometers long, and most of the ridges are above 3500 meters above sea level. A few peaks are covered with snow all year round, and modern glaciers are developed. It is a natural solid reservoir in Hexi Corridor, with obvious vertical distribution of vegetation in mountainous areas, from low to high, desert, grassland, forest, alpine desert and ice and snow.

(6) Beishan. Located in the north of Hexi Corridor, the east-west length is 1 1,000 kilometers, and the altitude is 1 1,000 ~ 3,600 meters. It consists of a series of denuded mountains such as Mazong Mountain, Heli Mountain and Longshou Mountain. Adjacent to Tengger Desert and Badain Jaran Desert, the wind is high and the sand is high, and the rocks are exposed, showing the desert Gobi landscape.

② Climate

Gansu province goes deep inland, spanning three climatic zones: tropical zone, warm temperate zone and north sub-temperate zone. In addition, the height difference of the terrain determines three basic characteristics of the climate in Gansu Province: first, the air is dry and the continental climate is obvious; Second, the vertical changes of meteorological elements are obvious; Third, the climate types are diverse.

The average annual sunshine hours in Gansu Province gradually increase from southeast to northwest, with the range of 1700 ~ 3400 hours. Most parts of the province are rich in solar energy resources, and the spatial distribution of annual total solar radiation is consistent with that of sunshine, increasing from southeast to northwest, with an amplitude of 4800 ~ 6400 MJ/m2, with a difference of 1500 MJ/m2.

The temperature in all parts of the province has changed greatly. The annual average temperature decreases from southeast to northwest, and decreases from rivers and valleys to the top of the mountain at the same latitude, with a range of 0℃ ~ 15℃. The annual average temperature in Hexi Corridor is 5℃ ~10℃; The climate in the central part is cool, with an annual average temperature of 5℃ ~ 9℃, while the climate in Longnan is warm, with an annual average temperature of 9℃ ~ 15℃, which is the highest in the province. Gannan Plateau has a cold climate, and the annual average temperature 1℃ ~ 7℃ is relatively low. Longdong has no severe cold in winter and no intense heat in summer, and the climate is mild, with an average annual temperature of 7℃ ~ 10℃.

The daily average temperature in the province is ≥ 0℃, and the accumulated temperature ≥ 10℃ is almost the same as the annual average temperature, decreasing from southeast to northwest, and decreasing from river valleys to the top of the mountain at the same latitude. The areas with the most abundant heat resources are the south of Longnan Mountain and Guazhou-Dunhuang Basin, while the areas with insufficient heat resources are Gannan Plateau and Qilian Mountain.

The frost-free period in southern Longnan is the longest, with an average of about 250 days. It takes about 200 days in northern Longnan, 65,438+060 ~ 65,438+020 days in Longdong and Yellow River basins, 65,438+040 ~ 65,438+060 days in central and Hexi corridors, and the shortest in Gannan Plateau and some alpine mountainous areas, generally about 50 days.

On the whole, the spatial distribution trend of annual average precipitation in Gansu Province is decreasing from southeast to northwest, with the range of 35 ~ 8 10 mm, and the annual average precipitation in Kangxian County in the southeast is 802.3 mm, while that in Dunhuang County in the northwest is only 39 mm In the same area, there is more precipitation at high altitude and less precipitation at low altitude. There are more windward sides than leeward sides in mountainous areas.

The distribution trend of annual evaporation in Gansu is opposite to that of annual precipitation, and it gradually increases from southeast to northwest. The average annual evaporation in Hexi Corridor is 2000 ~ 3000mm, that in Qilian Mountain is 1600 ~ 180mm, that in the middle is 1300 ~ 2000mm, that in Longdong is 1200 ~ 1700mm, and that in Longnan is.

Agricultural meteorological disasters in Gansu Province are frequent, mainly including drought, hail, frost, flood, dry-hot wind, strong wind and sandstorm.

(3) Hydrological water system

The rivers in Gansu Province belong to the 12 drainage system of the Yellow River, the Yangtze River and the inland river basins. There are six river systems in the Yellow River basin, namely, the main stream of the Yellow River, Taohe River, Huangshui River, Weihe River, Jinghe River and Beiluo River, two in the Yangtze River basin and four in the inland river basin, namely, Sugan Lake, Shule River, Heihe River and Shiyang River. According to the investigation of surface water resources in Gansu Province by Gansu Hydrological Station 1984, among the 52 rivers in Gansu Province 152, there are 79 rivers with annual runoff exceeding1000000 cubic meters, including 36 in the Yellow River basin, 27 in the Yangtze River basin and 16 in the inland river basin. There are 12 rivers with annual average runoff exceeding 10 billion cubic meters, and the order of runoff is Yellow River, Bailong River, Taohe River, Huangshui River, Baishui River, Datong River, Weihe River, Jinghe River, Xihanshui River, Heihe River, Jialing River and Daxia River.

The depth and regional distribution of river runoff are generally consistent with the distribution of annual precipitation, that is, it is larger in the east and south and decreases to the northwest. Due to the influence of underlying surface, the distribution of precipitation is different in some areas. Under the same precipitation conditions, the runoff in mountainous areas is deep, while the runoff in hills, plains and valleys is small. The runoff in the rocky mountain forest area is deep, and the runoff in the Loess Plateau is small. From east to west, the south of Liupanshan-West Qinling-Qilian Mountain line (including the mountain itself) is rich in water, while the north is poor in water and arid.

The natural resources of groundwater in the whole province are14719.8 billion cubic meters/year (duplication has been deducted). Among them, the Hexi Corridor basin is 4,783.7 million m3/ year (accounting for 32.50%), the intermountain basin in the north of Hexi Corridor is 39 million m3/ year (accounting for 0.03%), the intermountain basin in the east valley is 798,654.38+100,000 m3/ year (accounting for 5.42%), and the diving in the Loess Plateau is 9,986,543.8+100,000 m3. The natural resources of groundwater in Longnan mountainous area are 6,325.5 million cubic meters/year (accounting for 42.97%), and in hilly area of Hexi mountainous area, it is 16. 17 1 100 million cubic meters/year (accounting for 10.99%). Although the proportion of groundwater in these two sub-regions is relatively large, it has been included in river runoff and belongs to river runoff.

The uneven distribution of precipitation and runoff in region and time leads to the sharp contradiction of water use. Hexi region is vast in land and short of water resources, which restricts the development of land resources. The central region has less rainfall, less water and more land, low water and high water, which is difficult to use; Drought is frequent in the growing period of crops, and concentrated rainfall forms a large area of soil erosion. There is little water and soil in Longnan mountainous area, which is scattered and difficult to use.

(4) Soil

Soil is an important part of land resources, the basic means of production for agriculture, and the most basic, extensive, important and irreplaceable natural resource for human survival.

Gansu province spans 1 1 geographical latitude from north to south, and extends nearly 16 geographical longitude from east to west. Large and medium-sized landforms include West Qinling, Loess Plateau, Inner Mongolia Plateau and Qinghai-Tibet Plateau, which belong to Yangtze River, Yellow River and inland river. Different climatic conditions and vegetation types form different types of soil. There are 13 soil types and 60 soil types in the national soil classification, and there are 12 soil types and 37 soil types in Gansu Province.

(1) yellow brown soil. It is distributed in the valleys and shallow hills at the southern foot of Qinling Mountains in Gansu Province, and is located in the southeast of Wenxian County, Wudu District, Kangxian County, Huixian County and Chengxian County in Longnan City. The altitude is below 1 100 meters, which belongs to the subtropical climate in North Asia, and the vegetation is mainly evergreen broad-leaved forest and deciduous forest. There is no lime reaction in the whole soil profile, and the soil pH value is 5.5 ~ 6.7.

(2) brown soil. It is mainly distributed in the Zhongshan area of Qinling Mountains in Gansu Province, with an altitude of 1400 ~ 2200m. With the increase of altitude, the temperature drops, forming a warm temperate climate in mountainous areas, with soil pH value of 5.0 ~ 7.0, and most natural vegetation is secondary forest.

(3) Dark brown soil. It is distributed in the humid and semi-humid climate zone in the temperate zone of Qinling Mountain, Gansu Province, with an altitude of 2,600-3,600 meters, rising gradually from southeast to northwest. Natural vegetation is coniferous mixed forest or coniferous forest, and undergrowth shrubs include rhododendron, honeysuckle and alpine embroidered chrysanthemum. There is no lime reaction in the whole soil profile. Generally, the surface layer is acidic, and the middle and lower layers are weakly acidic, with occasional inversion.

(4) cinnamon soil. It is mainly distributed in forests and scrub grasslands in the southern mountainous areas of Tianshui City, Longnan City, Dingxi City and Pingliang City, Gansu Province. With the decrease of altitude, it gradually transits to the Black loessial soil Belt. The natural vegetation types in cinnamon soil zone belong to temperate zone, warm temperate zone deciduous broad-leaved coniferous and broad-leaved mixed forest, forest grassland and shrub grassland, and most of the forests are ruined, mainly secondary forests. The occurrence of calcium carbonate in the whole soil profile is related to the parent material and zonality factors, and the soil pH value is greater than 7.

(5) Gray cinnamon soil. Mainly distributed in the vertical belt spectrum of Qilian Mountain, West Qinling Mountain (within the Yellow River Basin), Liupanshan Mountain and other mountainous areas, it is zonal soil formed under forest and grassland vegetation in arid and semi-arid areas. Except for layer A, the whole section of the soil has lime reaction, and the soil pH value is 6.5 ~ 7.5.

(6) black soil. Distributed in the mountainous area of Zhongshan, Gansu, with an altitude of 2300 ~ 3000 meters. Vegetation is a transitional zone of shrub, weed meadow or forest meadow grassland. The soil has a dark black or dark gray humus layer; The thickness is 30 ~ 100 cm, extending downward in a tongue shape, with granular or granular structure, and there is no obvious adhesive film on the surface of the structure. There is no lime reaction in the whole soil profile, and the soil pH value is 6.5 ~ 7.5.

(7) chernozem. It is mainly distributed in the west Qinling Mountains of Gansu Province, the eastern Qilian Mountains and the Gannan Plateau, and it is zonal soil developed under grassland and meadow grassland vegetation. In the temperate semi-arid and semi-humid climate, the parent materials of soil formation are mostly loess sediments and residual slope deposits. Point-like, mycelium-like and point-like calcium carbonate aggregate on the structural surface, and the soil pH value is 7 ~ 8.5.

(8) chestnut soil. Mainly distributed in Qilian Mountain, Wushan Mountain and other low hills or foothills, with an altitude of 2,300 ~ 2,800 meters, it belongs to temperate arid and semi-arid grassland soil, and the vegetation is mostly composed of herbs. Chestnut soil is saturated with salt base, and the pH value is mostly 7.5 ~ 8.5, and the middle and lower soil is the highest.

(9) black soil. It is mainly distributed in the loess tablelands of Qingyang City, Pingliang City, Dingxi City, Lanzhou City, Baiyin City, Linxia Hui Autonomous Prefecture, Longnan City and other cities (states), and the hilltops and gentle slopes, sloping fields and bay palm lands in the loess hilly areas are scattered on the second and third steps of rivers and valleys. The climate belongs to temperate semi-arid and semi-humid climate; The vegetation at 900 ~ 2500m above sea level is hay field and forest grassland; There is lime reaction in the whole soil profile, and the soil pH value is 7.5 ~ 8.5.

(10) brown calcium soil. It is mainly distributed in the west of Hongba River in Hexi Corridor, Gansu Province, at the northern foot of western Qilian Mountain and the northern slope of Altun Mountain, with an altitude of 2100 ~ 3000m. The texture is mostly sandy loam and clayey loam, the profile is mostly gravel, and the lower part is coarse bone. The whole profile of the soil shows a strong lime reaction, and the soil pH value is 8.5 ~ 9.0.

(1 1) calcareous soil. It is distributed in the eastern part of Hexi Corridor in Gansu Province (from Peijiaying in Gulang County in the east to Hongyazi in Gaotai County in the west), Zhangye City, Wuwei City and the yellow mounds, low hills, valley terraces and alluvial plains in Lanzhou City, Baiyin City and Dingxi City in the middle. The vegetation is a desert grassland dominated by early shrubs and drought-tolerant Artemisia, and the soil pH value is 8.0 ~ 8.5.

(12) gray desert soil. It is mainly distributed at the northern foot of East Qilian Mountain in Hexi Corridor, the low hills at the southern foot of Heli Mountain and Longshou Mountain, the top of piedmont alluvial fan, the end of Wuwei Basin and Gulanghe alluvial plain, and the area north of Mi Jiashan in Jingtai County, with an altitude of 1500 ~ 2300m. Vegetation belongs to xerophytic small semi-shrub desert type, with coverage 15% ~ 25%. There is lime reaction in the whole soil profile, and the soil pH value is 8.0 ~ 9.0.

(13) gray-brown desert soil. It is widely distributed in the piedmont Gobi zone and the sloping plain of gravelly Gobi at an altitude of 1300 ~ 2500m in Hexi Corridor, accounting for 22.8% of the total soil area in Gansu Province, and it is the largest soil type in Gansu Province. Vegetation is a drought-tolerant shrub with deep roots and thin flesh. The pH value of the soil is 8.0 ~ 9.0, and the soil is dry and firm.

(14) brown desert soil. It is mainly distributed in the gravel Gobi area with an altitude of 1 150 ~ 1400 meters in Guazhou-Dunhuang basin at the western end of Hexi Corridor. The climate is extremely dry, the annual average temperature is 9℃ ~ 12℃, the annual average precipitation is less than 50 mm, and the vegetation is sparse and single, mostly xerophytic and ultra-xerophytic deep-rooted fleshy species, with coverage less than 5%. There is lime reaction in the whole soil profile, and the soil pH value is above 8.0.

(15) loessial soil. It is widely distributed in the plateau edge, low hills and slopes of the Loess Plateau in Gansu Province, and often staggered with black loessial soil, calcareous soil and red clay. It is the main soil type in the loess area of Gansu Province. Among them, cultivated loessial soil accounts for 22.2% of cultivated soil in Gansu Province. The altitude is generally 1500 ~ 1800 meters. Generally, the content of organic matter in topsoil is less than 1.0%, and the content of calcium carbonate is about 10%. Although there is a strong lime reaction, there is no accumulation of calcium.

(16) red clay. It is widely distributed in hilly gully, gully, gully slope and toe of loess plateau in Gansu province, and also distributed in low mountain canyons and hilly slopes in Hexi desert area. There is no obvious grade differentiation in the whole profile, and the whole soil shows a strong lime reaction, and the soil pH value is 8.0 ~ 9.0.

(17) Newly accumulated soil. It is mainly distributed on the banks of rivers and valleys in Longdong, Longnan and the central loess area, on floodplain, super floodplain and gentle first-class terrace, and alluvial fans in front of the mountain are also distributed. There is no obvious humus layer in the whole soil profile; However, the sedimentary layer is obvious, and deep gravel layer often appears in the lower part of the profile.

(18) cracked soil. It is mainly distributed in the arid desert sand dunes of Zhangye City and Jiuquan City in Hexi, or in the closed low-lying areas of ancient alluvial plains, with almost no vegetation growth or only sporadic shrubs. The parent material of this soil contains a lot of salt, which is alkalized to varying degrees in the process of soil formation. Once the land is reclaimed for irrigation, salinization will become more and more obvious.

(19) aeolian sandy soil. It is mainly distributed in the desert and wind-blown sand area of Hexi, which is extremely short of organic matter and available nutrients, with single particles and no structure, mainly fine sand and medium sand, and is prone to drought, wind erosion, water leakage and fertilizer leakage. Cultivated aeolian sandy soil has low fertility and is one of the low-yield soils.

(20) Rock soil. Most of them are distributed in sunny slopes of calcareous mountains, eroded rocky mountains in Longnan, eroded rocky mountains in arid desert of Central China and Hexi. Rocky soil is located in steep mountainous area, and the slope is generally above 25. It is of little value in agriculture and animal husbandry or can only be used for seasonal grazing, so it is difficult to use it.

(2 1) coarse bone soil. The distribution area is interlaced with stony soil. Coarse bone soil has a layer of loose clastic soil, which is thicker than stony soil and has better hydrothermal conditions, but it is difficult to be used in agriculture and can be used for grazing in some areas.

(22) meadow soil. Most of the low depressions distributed at the edge of alluvial fan in the foothills of Gansu, the lower part of alluvial fine soil plain, and the flood plain, low terrace of riverbed and spring flood zone along the edge of alluvial fan along the river form a composite area with swamp soil, meadow saline soil and forest-shrub meadow soil. The basic layer of the whole soil profile consists of humus layer and rusty mottled layer. Humus layer has a large number of granular structures, and the lower part is redox layer and latent layer. Organic matter content > 3%.

(23) Mountain meadow soil. Belonging to zonal soil, it is located on mountain brown soil in vertical band spectrum, and is specifically distributed in the gentle mountain ridge watershed and valley zone in west Qinling and Longnan mountainous areas of Gansu Province. The altitude is 2000 ~ 3000 meters. The vegetation types are mainly grassland meadow and shrub meadow. The soil-forming parent materials are residual and loess parent materials.

(24) Forest irrigates meadow soil. It is mainly distributed in the riverbed, river bank and fan edge areas in Hexi desert area, especially in the low-lying areas of plain reservoirs such as Shule River, Heihe River, Danghe River, Changma River, Beidahe River, etc., mostly on the edge of meadow and sandstorm, and often forms a compound area with meadow soil. The organic matter content is low, and the salt accumulation (surface aggregation) in the soil is weak, and the soil pH value is 8.5 ~ 9.0.

(25) classical soil. This kind of soil is scattered in Gansu Province, mainly distributed in Hexi Corridor and Chuanba Valley in the east of the river. Deep soil layer and fertile soil are important foundations for developing agricultural production in Gansu. After long-term irrigation, cultivation and fertilization, the surface of fluvo-aquic soil is increasing, the groundwater level is relatively decreasing, and the process of soil wetting and salinization is gradually weakening.

(26) Marsh soil. The fan-edge low-lying land and valley-belt waterlogging land distributed in Gannan Tibetan Autonomous Prefecture, Jiuquan City, Zhangye City, Dingxi City, Tianshui City, Longnan City and other cities (states) are mostly discontinuous, forming a composite area with subalpine meadow soil, peat soil, meadow soil and saline soil.

(27) peat soil. Concentrated in Gannan Tibetan Autonomous Prefecture above 3400 meters above sea level; Zhangye city is also distributed, in the mountainous area of Qilian Mountain depression, more than 3000 meters above sea level. Organic matter content is more than 20%.

(28) Saline soil. Mainly distributed in the arid climate area of Hexi Corridor, the area of saline soil gradually expands from east to west and from south to north, and the salt content gradually increases. In addition, the saline soils in Baiyin and Lanzhou are scattered in closed basins and depressions; Wuwei City is located in Minqin Lake area in the lower reaches of Shiyang River. Jinchang is located in the northern part of the city and the southern half depression; Zhangye City is mainly distributed in the middle reaches of Heihe River, north of Zhangye City-Gaotai County-Linze County; Jiayuguan city is located at the outer edge of the spring overflow area; Jiuquan City is mainly distributed in the middle and lower reaches of Shule River, Guazhou and Dunhuang in the lower reaches of Yumen Town, and Jiuquan City and Jinta County in Heihe River Basin are also widely distributed. The pH value of saline soil is 8.0 ~ 8.6, and the pH value of soil with salt accumulation layer is higher than that of soil without salt accumulation layer. The pH value of alkaline saline soil is 8.7 ~ 9.2.

(29) Paddy soil. It is mainly distributed in Chuanba area in the valley south of Qinling Mountains, specifically in Wudu District, Wenxian County and Kangxian County of Longnan City. Soil pH is 7.4 ~ 8. 1.

(30) Fill with silt. Irrigation areas along the Yellow River in Gansu Province are mainly distributed in the valleys, terraces and plains of the Yellow River or its tributaries in Lanzhou, Baiyin, Linxia Hui Autonomous Prefecture, Qingyang, Pingliang and Tianshui. The content of soil organic matter is above 65438 0%.

(3 1) irrigate desert soil. It is distributed in the oasis irrigation area of Hexi Corridor in Gansu Province, and it is cultivated by ancient irrigation. The organic matter content of topsoil is generally >1.5%; Generally speaking, the content of calcium carbonate in soil is 5% ~ 20%. During irrigation in summer and autumn, calcium carbonate clay particles move down, evaporation is strong in spring and summer, and calcium carbonate salts gather.

(32) Alpine meadow soil. It is distributed in the mountainous areas with an altitude of 3,000 ~ 4,000 meters in Shandong, the central Qilian Mountains in Gansu and the Qinling Mountains. The vegetation is mainly cold-tolerant and wet-loving meadow plants, covering 70% ~ 90%, which is the summer grassland in pastoral areas.

(33) Subalpine meadow soil. It is mainly distributed in Shandong, the central Qilian Mountains in Hexi, and the Qinling Mountains in Gannan Plateau with an altitude of 3,000 ~ 3,500 meters. It is a good summer and autumn grassland in pastoral areas, which is connected with alpine meadow soil and chernozem. The temperature, rainfall and evaporation are slightly higher than those in alpine meadow land area.

(34) Alpine grassland soil. They are mainly distributed in the high mountain areas with an altitude of 3500 ~ 4 100 meters in the west of Qilian Mountain in Hexi and the east of Altun Mountain, that is, parts of Sunan Yugur Autonomous County in Zhangye City, Subei Mongolian Autonomous County in Jiuquan City and Aksai Kazak Autonomous County, all of which are pastoral counties. Vegetation is a low-temperature tolerant xerophyte with coverage 15% ~ 70%, which is the main summer grassland in pastoral areas. The whole profile of the soil is a strong lime reaction, and the pH value of the soil is 8.0 ~ 8.5.

(35) Subalpine grassland soil. It is mainly distributed in the west of Qilian Mountain in Hexi (scattered in the middle and east), the east of Altun Mountain and the arid area on the sunny slope of Qinling Mountain, with an altitude of 3000 ~ 3500 meters. The vegetation is a dry grassland with a coverage of 30% ~ 70%. Due to the decrease of height and the increase of temperature, the freezing and thawing effect is weakened correspondingly, and the vegetation coverage is also increased. Soil organic matter accumulated more, the content was above 2.5%, and the soil pH value was 8.0 ~ 8.7.

(36) Mountain desert soil. It is only distributed in Qilian Mountain, Altun Mountain, Houtangzi Five Springs, Nan 'anba and Yangshan in the extremely arid area of Gansu, with an altitude of 3,500-4,200m. The terrain is alluvial fan at the foot of mountain, mountain basin or steep mountain slope. The desert vegetation is dominated by xerophytes and super xerophytes, with a coverage of 5% ~10%; The higher the altitude, the more sparse the vegetation, and there is basically no vegetation above 4200 meters above sea level. The organic matter content is less than 0.5%, the calcium carbonate content is more than 10%, and the soil pH value is 8.0 ~ 8.8.

(37) Alpine desert soil. Sporadic distribution in Qilian Mountain, Qinling Mountain and Gannan Plateau (high in the west and low in the east, high in the sunny side and low in the shady side) at an altitude of 3900 ~ 4800 meters. The vegetation is mainly lichen and moss, and the coverage is 1% ~ 5%. The organic matter content is extremely low, about 0.2%, and the soil pH value is 7.0 ~ 8.5.

(5) Vegetation

Gansu province has a vast territory, complex natural conditions such as climate and soil, and rich plant species. There are 2359 species of seed plants 125 families, 765 genera, 70 species of bryophytes, 36 families, 64 genera and ferns 15 families. Gramineae, Compositae, Leguminosae, Ranunculaceae, Rosaceae, Cyperaceae, Scrophulariaceae, Chenopodiaceae and Labiatae are widely distributed in Gansu Province, and often become the constructive species of various vegetation, which is also the main plant resources in Gansu Province.

There are more than 20 kinds of food crops planted in Gansu Province, including winter wheat, spring wheat, barley, corn, highland barley, buckwheat, millet, sorghum, rice, potatoes and various beans. Among them, wheat is the most important food crop in Gansu province, which is distributed all over the province; The heat in most areas can also meet the growth of corn; Miguduo is a small autumn crop, which is usually replanted after wheat harvest.

Cash crops mainly include cotton, oilseeds, hemp, castor, sesame, beet, sunflower, tea, tobacco and hops. Flax, rape, sunflower, beet, cotton, etc. The planting area exceeds 654.38 million mu; Tea can only be planted in parts of Longnan; Cotton is distributed in the warm temperate zone in the lower reaches of Hexi inland river.

(6) Mineral resources

Gansu province is rich in mineral resources, with developed strata, complex geological structure, strong magmatic activity and diverse rock masses. Among the main minerals, more than 20 kinds of minerals, such as coal, rare earth, tungsten, molybdenum, tin, antimony, mercury, vanadium, titanium, magnesite, barite, fluorite, graphite and building decorative stone, have advantages in the world. Some bulk minerals, such as iron, manganese, aluminum, copper, zinc, sulfur, phosphorus, oil, natural gas, uranium and other resources are also quite large. The mineral resources in the province are 4 1, ranking first in the country 10. There are eight kinds of mineral resources in China, which account for more than 50% of the total reserves, namely nickel, platinum group (6 kinds) and cast clay. At present, there are 53 kinds of minerals that have been developed and utilized, including nickel, zinc, magnesium, tungsten, cobalt, antimony, platinum group, rare earth minerals, indium, thallium, cadmium, selenium, tellurium, talc, asbestos, associated sulfur, magnesite, ordinary fluorite, minerals for cement ingredients, bentonite, clay for molds, serpentine for decoration, salt mines and so on.