What is the general situation of China's natural environment?

China is located in the southeast of the Eurasian continent, bordering the Pacific Ocean in the southeast, deep into the hinterland of the Asian continent in the northwest and bordering the South Asian subcontinent on the Qinghai-Tibet Plateau in the southwest. This country has a vast territory, about 9.6 million square kilometers. It starts from Zengmu shoal in the south and reaches the center of Heilongjiang in the north of Mohe in the north, with a longitudinal span of 50 latitude and a length of 5500km. From the intersection of Heilongjiang and Wusuli rivers in the east to Pamirs in the west, it spans 62 longitudes and is 5200km long from east to west. In this vast land, the landform is complex, the climate is diverse and the natural resources are very rich.

I. Topography

China has complicated geological conditions. In the long process of geological historical evolution, there are various types of landforms shaped by internal and external forces, including mountains, hills, plateaus, plains, basins and other normal landforms. Among them, mountains account for about 33% of China's total land area, plateaus account for about 26%, hills account for about 10%, plains account for about1%and basins account for about 19%. The whole terrain is high in the west and low in the east, with the Qinghai-Tibet Plateau as the highest point and descending step by step from west to east, connecting Chinese mainland with the Pacific Basin through a vast continental shelf. There are two geomorphologic boundaries composed of mountains in the territory, which obviously divide the mainland into three steps. The west line is the contour line of Kunlun Mountain-Qilian Mountain-Minshan Mountain-Qionglai Mountain, along the Hengduan Mountains. On the east side is Daxinganling-Taihang Mountain-Wushan-Xuefeng Mountain Line. The highest level is the Qinghai-Tibet Plateau, with an average elevation of more than 4,500 meters and an area of about 2.5 million square kilometers. This is the highest plateau in the world. A series of continuous snow-capped mountains straddle the plateau. From north to south, there are Kunlun Mountain, Altun Mountain and Qilian Mountain, Tanggula Mountain, Karakorum Mountain, Gangdise Mountain and Himalayas. The southeast is part of the Hengduan Mountains. There are countless basins in the mountains. The second level is elevation 1000-2000 m, which consists of a series of mountains, plateaus and basins. Such as Altai Mountain, Tianshan Mountain, Qinling Mountain, Junggar Basin, Tarim Basin, Sichuan Basin, Inner Mongolia Plateau, Loess Plateau and Yunnan-Guizhou Plateau. Along the northeast line of Daxing 'anling, Taihang Mountain, Wushan Mountain and Xuefeng Mountain, it belongs to the third step, and there are northeast plains, North China plains and the middle and lower reaches of the Yangtze River from north to south. To the south of the Yangtze River, there is also a large low hill, which is generally called the southeast hill. The former is below 200m, while the latter is mostly below 500m. Only a few mountain ranges can reach or exceed1000m. The eastern part of this ladder is the continental shelf extending from the mainland to the ocean, with vast blue waves and dotted islands, and the water depth is mostly within 200m. This topographical feature, which is high in the west and low in the east, leads directly to the ocean, which is conducive to the infiltration of moist air from the ocean and the supply of a large amount of water vapor.

Second, climate.

Diversity is an important feature of China's climate. According to different temperatures, it is divided into six hot zones from south to north, including equatorial zone, tropical zone, subtropical zone, warm temperate zone, middle temperate zone and cold temperate zone. According to the water condition, it can be divided into humid area, semi-humid area, semi-arid area and arid area from southeast to northwest. There are many mountains, high mountains and the vertical distribution of climate increase the complexity and diversity of climate types. Although the climate varies from place to place, the continental monsoon climate is a common feature of China's climate, which is mainly manifested in:

1. The direction of Xia Feng changes obviously in winter.

In winter, the airflow mainly comes from high latitude, northerly wind, cold and dry; In summer, the air flow comes from the low-latitude ocean, and the wind direction is southerly, warm and humid.

2. The annual temperature difference is large, the daily temperature difference is also large, and the extreme temperature difference in winter and summer is even greater.

Compared with other parts of the world at the same latitude, especially with the western part of Eurasia, the temperature in China is much lower in winter, but higher in summer. For example, Qiqihar, Heilongjiang (47 23 ′ n), 1 month average temperature is-19.6℃, July average temperature is 22.6℃, and annual average temperature is 42.2℃. In Paris (48 58 ′ n) near its latitude, the monthly average temperature is 65438 0℃, the July average temperature is 65438 09℃, and the annual average temperature is only 65438 05.9℃. Compared with the two places, the temperature in Qiqihar in June was 22.7℃ lower than that in Paris at 5438+ 10, but it was 3.6℃ higher in July and 26.3℃ higher in annual range.

3. The regional precipitation distribution is uneven, and the annual precipitation decreases rapidly from east to northwest.

The southwest region (especially the southern slope of Himalayas) and the southeast region (especially the eastern slope of mountains in Taiwan Province Province) with the largest annual precipitation are all over 2000mm, and the driest Tarim Basin is less than 50 mm, and the seasonal distribution of precipitation is also quite different. Summer rainfall generally accounts for more than 50% of the annual precipitation, while winter precipitation is mostly below 10%, and the annual precipitation changes greatly. In the rainy south of the Yangtze River, the annual precipitation variability is also 10- 15%. For the northern and northwestern inland areas with less precipitation, the annual precipitation variability can reach more than 30%.

4. Rain and heat in the same period

That is, the season with the most precipitation is generally the season with the highest temperature, vigorous plant growth and the largest water demand.

5. Factors affecting climate characteristics in China.

(1) Latitude position

This is the basic factor that determines the solar radiation and heat conditions and affects the climate characteristics. The latitude difference between north and south of China is as high as 50 degrees. The eastern half can be divided into cold temperate zone, middle temperate zone, warm temperate zone, subtropical zone and tropical zone from north to south. In the western half, the uplift of the Qinghai-Tibet Plateau broke the relationship between the above temperature and latitude. Among these hot zones, the middle temperate zone, warm temperate zone and subtropical zone have the widest area, and the tropics also have a certain proportion. Especially the subtropical zone of China, influenced by monsoon, has become the region with the richest natural resources in the world, and is also the "storage place" of many precious, rare and endangered animals and plants in the world. The southern tropical region provides an important base for the utilization and development of tropical plant resources in China.

(2) Land and sea location

This is the fundamental reason that determines the thermal difference between land and sea, causes different temperature and pressure fields in winter and summer, and forms monsoon circulation. China lies between Eurasia, the largest continent in the world, and the Pacific Ocean, the largest ocean. Due to the different physical properties of land and ocean, the difference of surface heat leads to the different temperature and pressure fields between land and ocean in winter and summer, which leads to obvious monsoon circulation. The larger the land and sea area, the more obvious the monsoon. Therefore, China is most affected by the monsoon. In addition to the northwest inland areas separated by the Qinghai-Tibet Plateau, the vast areas in the east and south, and even a large part of the Qinghai-Tibet Plateau, are affected by the summer monsoon, showing the characteristics of monsoon climate.

(3) the influence of topography

China is high in the west and low in the east, with staggered mountains. The complex terrain has a great influence on the climate. There are many mountains in different directions, and the Qinghai-Tibet Plateau is in the southwest, which makes the climate formed by latitude position and land and sea distribution more complicated. A series of northeast and southwest mountains from Daxing 'anling and Taihang Mountains to the east of Bomi Line in Tibet play an important role in blocking the water vapor in the Pacific Ocean from moving to the northwest, while the south-north Hengduan Mountains in the southeast of Qinghai-Tibet Plateau are serious obstacles for the air flow in the Bay of Bengal from low altitude. At the same time, a series of east-west mountains in the eastern half blocked the winter cold wave from north to south, resulting in obvious differences in temperature and precipitation in different hot spots in China. In addition, various landform types also have an impact on the climate in some areas. For example, high mountains divide the climate vertically, the windward side becomes a rainy center, and the leeward side becomes a high temperature center, and so on. Due to the barrier of mountains, the climate in the northwest inland becomes more arid, but the mountains intercept more water vapor from high altitude, which can also make many patches of forests and grasslands appear in arid areas.

(4) Atmospheric circulation

This is an important factor leading to the formation of climate. Influenced by latitude, land and sea distribution and Qinghai-Tibet Plateau, China's atmospheric circulation situation is extremely complicated. Generally speaking, the operation and change of seasonal airflow in China are controlled by four active centers: Siberian high, Indian subcontinent low, North Pacific high and Aleutian low. In winter, the Siberian high covers the Asian continent, and the wind flows from the Arctic Ocean through Siberia and Mongolia in the Soviet Union to the south of China and blows to the ocean. Therefore, the wind direction in the eastern half of China is mostly northeast wind or northwest wind. Because the air is dry and cold, which strengthens the cold wave brought by the winter monsoon to our country, most of our country is generally cold and dry in winter, and it is a country with the same latitude in the world. In summer, the mainland becomes a low-pressure area, the air pressure on the ocean increases, and the air blows from the moist ocean to the mainland, so the air flow brought by the Southeast Pacific High and the Southwest Indian Ocean High prevails in Chinese mainland in summer. In addition to the Qinghai-Tibet Plateau and Northwest China, the southeast monsoon from the Pacific Ocean and the southwest monsoon from the Bay of Bengal and the Indian Ocean are blowing in most parts of China, bringing abundant rainfall to China, making the southeast half of China a region with more rainfall at the same latitude in the world.

Third, soil.

The formation and development of soil in China are related to climate, various chemical types of soil-forming weathering crust, mountain topography and vegetation types. For example, as far as the relationship between macro-climate and soil is concerned, the humid areas in eastern and southeastern China are abundant in rainfall, and the soluble salts in the soil are easily leached, so it is mainly acidic forest soil; From north to south: brown coniferous forest soil, dark brown soil, brown soil, yellow brown soil, yellow soil, red soil, latosol, latosol. In semi-arid areas, there is little rainfall, and lime is easy to remain in the soil layer, so various calcareous grassland soils appear; There are chernozem, black loessial soil and chestnut soil in the north temperate zone. There are alpine meadow soil and alpine grassland soil on the Qinghai-Tibet Plateau in the southwest. In the most arid area in the west, lime and gypsum in the soil are retained in the topsoil, and various desert soils have appeared, with a large area of saline-alkali land.

1. Red soil and yellow soil

This kind of soil includes latosol in humid tropics and red soil, yellow soil and yellow brown soil in humid subtropics.

(1) latosol and latosol

This is the soil in tropical monsoon forest and rain forest areas, which is characterized by obvious aluminum enrichment, strong acid reaction (pH 4.0-4.8) and extremely poor nutrients such as nitrogen, phosphorus, sulfur, calcium and magnesium.

(2) Red soil

This soil is developed on the acidic weathering crust in humid subtropical climate, with strong acidic reaction (pH 4.0-5.5), extremely thin surface humus and low contents of calcium, magnesium, manganese, sodium and total phosphorus.

(3) Yellow soil

This is strongly acidic soil, and its climatic conditions are wetter than red soil. Weathered crust is thin, and the contents of calcium, magnesium, nitrogen and sulfur are extremely low.

(4) Yellow brown soil

This is developed on the acidic parent material in the humid climate of north or middle subtropical zone. It is weakly acidic (pH 5.0-6.0), with the properties of brown soil to yellow soil, and most of the salt bases in the soil have been leached out.

2. Grayish brown soil

This kind of soil includes brown coniferous forest soil in cold temperate zone and dark brown soil in north temperate zone, which is strongly acidic to moderately acidic, with high replaceable aluminum content and low base saturation content, and poor potassium, sodium, calcium, magnesium, nitrogen, phosphorus and sulfur content.

(1) brown coniferous forest soil

This is developed under the deciduous forest in the cold temperate zone and distributed in the platforms, hills and mountains along the coast of Heilongjiang. It is strongly acidic or moderately acidic (pH4.5 or 5.0-6.0), with low replaceable alkali content and high replaceable aluminum content.

(2) Dark brown soil

It is developed under mixed coniferous and broad-leaved forests and distributed in the mountainous areas in the eastern part of Northeast China. The content of humus in topsoil is high, and it is moderately acidic (pH 5.0-6.0), and the saturation of salt base in topsoil is high.

3. Brown soil

This kind of soil includes warm temperate brown soil, gray forest soil and temperate eluviated black soil, which is moderately acidic to slightly acidic.

(1) brown soil

This is developed from granite parent material under deciduous broad-leaved mixed forest and deciduous oak forest, which is mainly distributed in Shandong, Liaodong Peninsula, southern Liaoning and hilly areas of Hebei in humid temperate zone, showing a slight or moderate acid reaction. Calcium content is rich, iron and aluminum are poor, while silicon dioxide content has increased.

(2) Black soil

This is developed from the natural vegetation of mixed grass meadow. Part of the soil-forming parent material of Quaternary Pleistocene clay deposits is bedrock weathered slope deposits, which are distributed in the northeast plain with temperate and semi-humid climate. The surface humus layer is about 100cm thick, with humus content of 3-6% and height of 15%. Weak acid reaction (pH 5.5-6.5). The content of nitrogen, phosphorus and replaceable calcium is high, the natural fertility is high, and the effect of water and fertilizer conservation is good.

4. Calcareous forest soil

This kind of soil is distributed in all kinds of forest soils with carbonate weathering crust from north to south in the humid area of eastern China, and it is neutral to slightly alkaline.

(1) cinnamon soil

This is formed on limestone, loess and carbonate alluvium under deciduous and broad-leaved mixed forest, and distributed in the humid and warm temperate zone with obvious dry season. It is neutral to alkaline. There is obvious calcium carbonate layer, which is rich in alkaline earth metals, alkali metals and accumulated calcium, sodium, magnesium, iron and aluminum compounds. There are many available N, P and K, and the fertility is high.

(2) Yellow cinnamon soil

This is formed in the middle of the transition from cinnamon soil to yellow soil, developed on calcareous parent material under deciduous broad-leaved forest with evergreen components, and distributed in semi-subtropical. The upper layer is slightly acidic or neutral, and the lower layer is slightly alkaline to moderately alkaline. Substituted calcium and magnesium are dominant.

(3) Black limestone soil, which is formed by decomposing plant residues under deciduous and evergreen broad-leaved mixed forests and combining with calcium, is distributed in subtropical limestone areas and presents lime reaction (pH 6.5-8.5). Topsoil organic matter is 6.0-7.0%, with high nitrogen, phosphorus and potassium content.

(4) Purple soil

This is developed from calcareous purple sand shale and distributed in humid subtropical areas south of the Yangtze River. The topsoil is slightly acidic or neutral, and the subsoil is moderately alkaline (pH 6.5-8.5). Calcium, magnesium, sodium and sulfide are rich, and phosphorus and potassium are also rich. Soil fertility is high.

(5) calcareous soil containing phosphorus

This is coral limestone distributed in the South China Sea Islands of China, where juicy evergreen sea leaf shrubs and undergrowth plants grow. Topsoil is a complex of organic matter such as phosphorus, calcium and bird droppings, which is moderately alkaline or strongly alkaline (pH 8.0-8.5). The content of organic matter in the upper layer can reach 10%, nitrogen 1.0%, total phosphorus (P2O5)30% and calcium (Cao) over 40%.

5. chernozem and chestnut soil

This kind of soil includes meadow soil formed by various carbonate weathering crusts in semi-humid and semi-arid areas, including meadow meadow soil-chernozem distributed in the central part of the Northeast Plain, chestnut soil distributed in the central and northern Inner Mongolia, meadow meadow soil-chernozem distributed in the southeastern part of the Loess Plateau with warm temperate and semi-humid climate, and soil with an altitude of 4,400-5,200 m distributed in the central and southern Qiangtang Plateau. The soil is alkaline, with a calcium layer and no gypsum.

6. Desert soil and saline-alkali land

This kind of soil includes: gray-brown desert soil in northern Xinjiang with temperate arid climate, Gobi desert and brown desert soil in Hexi Corridor in southern Xinjiang with extremely arid climate in warm temperate zone, desert saline soil in northern Tibet, Tarim Basin and other places, inland saline soil in humid or arid areas in northern China and saline soil in coastal areas. Soil contains a lot of chlorine, sodium and sulfur.

7. Meadow soil and swamp soil

This kind of soil includes meadow soil, alpine meadow soil, swamp soil and paddy soil formed by excessive precipitation conditions in various climatic zones in China.

8. Aeolian sand

This kind of soil is widely distributed in arid temperate zone and extremely arid warm temperate zone, and also distributed in semi-arid temperate zone. Because of the weak pedogenesis, the soil properties are parent materials to a great extent.

China is a mountainous country, and the phenomenon of vertical differentiation of soil types with the increase of mountain height is widespread. The vertical zonality spectrum of soil in main mountainous areas of China is listed in Table 3- 1.

Table 3- 1 Vertical Zoning Spectrum of Soil in Main Mountainous Areas of China

Table 3-1 Vertical Zone Spectrum of Soil in Main Mountainous Areas of China (Continued)-1

It can be seen from Table 3- 1 that due to the regional differences of temperature and precipitation, the structure of vertical band spectrum of mountain soil is obviously different at different latitudes and longitudes. However, the vertical band spectrum of each mountain always develops on the base band of the horizontal band at the latitude where the mountain is located, which is an integral part of the horizontal zonality and reflects the horizontal differentiation law of vegetation and soil.