natural conditions

Fujian province belongs to a part of South China fold system in geotectonics. The strata in this area are well developed, magmatic activity is frequent and geological structure is complex.

Since Mesozoic, the crust of Fujian Province has been rising continuously. Weathered crust materials develop into various types of soil on the hillside. In basins, valleys and low-lying areas, plains and river terraces are formed by the accumulation of foreign sediment materials, and various types of soils are also formed by surface materials.

The distribution of rocks in Fujian Province has obvious regularity. Sedimentary rocks are mainly distributed in the west of the middle mountain area of Fujian, volcanic rocks are mainly distributed in the middle mountain area of Fujian and its east, metamorphic rocks are mainly distributed in Wuyishan vein, central valley of Fujian and southwest of Fujian, and igneous rocks are exposed all over the province.

Many strata from Upper Proterozoic to Quaternary are exposed in Fujian Province. Sedimentary rocks formed before and in the Early Paleozoic have undergone different degrees of metamorphism. Sedimentary rocks, metamorphic rocks and volcanic rocks are evenly distributed in the whole province. Stratigraphic division in different periods in the province has obvious characteristics. Late Proterozoic metamorphic rocks are dominant in the north and northwest, which belong to trough-shaped thick-bed deposition. Shallow metamorphic rocks, sedimentary rocks and extrusive rocks, especially the late Paleozoic paraplatform deposits, are exposed in the middle and southwest of China. The eastern part of Zhenghe-Dabu line is dominated by a large area of late Jurassic-early Cretaceous continental volcanic rocks with complex rock types and a thickness of more than 10,000 meters. Upper Tertiary and Quaternary strata are all over the province, but developed in coastal areas.

The rocks exposed on the surface of the whole province are subjected to strong chemical weathering and biological action under hot and humid or warm and humid climate conditions, forming lateritic red soil, red soil and yellow soil. The distribution characteristics of main rocks and sediments are as follows.

1. limestone

Limestone in Fujian Province is distributed in three strata: the Huanglong Formation of Middle Carboniferous is dominated by limestone mixed with dolomite, mainly distributed on both sides of Nanxingxi-Hufang uplift belt in southwest Fujian; The strata of Chuanshan Formation in Late Carboniferous are mainly limestone with pure structure and a small amount of dolomite, which are mainly distributed in the vast areas south of Shunchang and Nanping and west of Dehua and Nanjing. Qixia Formation of Lower Permian contains siliceous nodules.

Due to the hot and humid climate, limestone exposed on the surface of the whole province developed into calcareous soil containing CaCO3 through weathering and pedogenesis. Calcareous soil is dominated by clay, and the vegetation coverage is good. However, once the vegetation is destroyed, the soil organic matter will decompose rapidly, the drought will become more serious, the fertility will decline rapidly, and it is very difficult to restore vegetation.

2. Purple calcium argillaceous clastic rocks

Purple-red calcareous argillaceous clastic rocks are distributed in the Upper Cretaceous strata, which are a set of coarse clastic rocks, purple-red, argillaceous calcareous cementation and contain more gravel. After the rock is formed, purple soil covering the parent rock is formed under the action of weathering and pedogenesis, and the soil contains a small amount of CaCO3. Purple soil has shallow soil layer and loose structure, which is easy to cause soil erosion and low fertility. Steep slope land should be mainly afforestation, which can be gently reclaimed as agricultural land and orchard.

3. Other sedimentary rocks

In addition to the limestone and purplish red calcareous argillaceous clastic rocks mentioned above, young soils have developed, and other large sedimentary rocks (including normal sedimentary rocks and pyroclastic rocks) have formed common soils, such as latosolic red soil, red soil and yellow soil, under the action of weathering, denudation and pedogenesis.

4. Intrusive rocks

Since the late Proterozoic, there have been magmatic activities in all major stages of structural evolution in Fujian Province, mainly Caledonian, Variscan-Indosinian, Yanshan and Himalayan. The exposed area of intrusive rocks in Fujian Province is 403 16.4 square kilometers, accounting for about 33% of the national territory. It ranks among the best in South China and is the main parent rock of lateritic red soil, red soil and yellow soil in Fujian Province. Among the intrusive rocks in each period, the early and late Yanshanian intrusive rocks have the largest scale. Intrusive rocks are complete in variety and diverse in lithology, among which acidic and intermediate-acidic rocks are absolutely dominant. Acidic and moderately acidic rocks account for 97.42%, moderately acidic rocks account for 2.44%, and ultrabasic rocks and basic rocks account for 0. 14%.

5. metamorphic rocks

Since the Late Proterozoic, Fujian Province has suffered many strong tectonic movements and magmatic activities, and rocks have undergone metamorphism with different properties in various tectonic cycles, forming metamorphic rocks with different metamorphic genetic types, including regional metamorphic rocks, contact metamorphic rocks and structural (fault) metamorphic rocks. However, judging from the scope and intensity of metamorphism, the regional metamorphism of rocks in the early Paleozoic and before was the largest, forming Caledonian regional metamorphic rocks (including migmatite) with an exposed area of about 27,000 square kilometers.

Discharge rock

There are various types of eruptive rocks in Fujian Province, including ultrabasic rocks, basic rocks, intermediate rock, intermediate-acid rocks and acidic volcanic rocks (including subvolcanic rocks) and their corresponding pyroclastic rocks, which are the main parent rocks of lateritic red soil, red soil and yellow soil in Fujian Province. It is widely distributed in space, but Jiufeng Mountain-Daiyun Mountain and its eastern region are obviously more than the western region. Late Proterozoic extrusive rocks are distributed in northwest and west Fujian, Carboniferous and Late Triassic-Early Jurassic extrusive rocks are distributed in west Fujian, middle Fujian and north Fujian, Late Jurassic-Early Cretaceous extrusive rocks are widely distributed in the whole province, and Daiyun Mountain is the most developed in the eastern region. Cenozoic eruptive rocks are scattered, concentrated in the coastal areas of southern Fujian and Mingxi and Ninghua areas in western Fujian. Late Jurassic-Early Cretaceous volcanic activity was the largest in intensity and scale, with an exposed area of 38,000 square kilometers.

7. Quaternary sediments

Quaternary strata are distributed in all parts of Fujian province, and the types of sediments with different origins are relatively complete. Among them, the whole province develops residual and slope deposits, covering the bedrock of mountainous hills; The materials transported and deposited by external forces such as rivers are mainly concentrated in coastal plains, both sides of valleys and intermountain basins. In coastal plain areas, in addition to sediments transported by rivers, there are marine, bay and lake sediments. Due to frequent neotectonic movements, river terraces are widely exposed. Holocene sediments constitute the first terrace, and Pleistocene sediments constitute the second terrace or above. The sediments of the first terrace are gray and grayish black, the second terrace is yellow, the third terrace is red, and the fourth terrace is brown and brownish yellow.

Compared with the residual and slope deposits covering the bedrock on the hillside, the sediments in coastal plain, intermountain basin and valley plain are thicker and are important parent materials for soil development. The soil developed in these areas is the best in Fujian Province, and high-yield fields are distributed in these areas.

(2) topography

Fujian province is located in the southeast of Eurasia plate, dotted with towering peaks, valleys and basins. The basic topographical features are as follows.

1. The terrain descends from northwest to southeast, and the cross section is slightly saddle-shaped.

There are two mountain areas in the west and middle of the province that run obliquely in the northeast direction: the west is the mountain area of western Fujian with Wuyishan as the main body; Zhonglie is a mountain system in central Fujian, which consists of Jiufeng Mountain, Daiyun Mountain and Bopingling Mountain. These two mountain belts are interconnected valleys and basins, which are often called Fujian Zhongda Valley. The eastern coast is hilly, terrace and plain.

2. There are many mountains and few plains.

The mountainous area is 64,800 square kilometers, accounting for 53.38% of the total land area of the province; Hilly terraces cover an area of 365,438+10,000 square kilometers, accounting for 25.53% of the total land area of the province; The water surface area of the plain is 25,600 square kilometers, accounting for 2 1.09% of the total land area of the province, and it is known as "eight mountains, one water and one farmland".

3. The water system is developed and the river network density is high.

The total length of rivers in China is about 1.3 thousand kilometers, and the density of river network exceeds 0. 1 kilometer per square kilometer. Minjiang River is the largest river in the province, with a total length of 577 kilometers and a drainage area of 6 1 10,000 square kilometers. The main rivers are mostly perpendicular to the mountain, and the tributaries are parallel to the mountain, forming a typical one-way grid water system in the outlet area. It is a mountainous river with many canyons and rapids, and the river bed gradient is large, mostly exceeding five ten thousandths. China has a large amount of precipitation, considerable runoff and abundant water resources.

4. The coastline is tortuous, with numerous harbors and scattered islands.

The total length of Fujian's land coastline is 3752 kilometers, second only to Guangdong Province. The coastline is mostly jagged, and the degree of twists and turns ranks first in the coastal provinces of China. There are 0/25 ports/kloc-in the whole province, and there are 6 super-large deep-water ports from north to south, including Shacheng Port, Sandu 'ao, Luoyuan Bay, Meizhou Bay, Xiamen Port and Dongshan Bay. These ports go deep inland and alternate with peninsulas. There are more than 65,438+0,500 islands along the coast, among which Haitan, Jinmen, Rinan and Mazu are the larger islands. The original Xiamen Island and Dongshan Island each had seawalls connected with the land, forming a peninsula.

(3) Climatic conditions

Fujian province belongs to subtropical maritime monsoon climate, roughly bounded by Fujian-Zhongshan belt, which is divided into two major climatic zones: the South Asian tropical climate zone along the southeast coast of Fujian and the Central Asian tropical climate zone in the northeast, northwest and southwest of Fujian. Due to the ups and downs of mountains in the province, the topography is complex and diverse, and influenced by non-zonal factors such as topography and geomorphology, the regional differences and vertical differentiation of hydrothermal conditions are obvious, thus forming a variety of local microclimates, providing superior natural conditions such as water and heat for the development and utilization of cultivated land. Generally speaking, the climate in Fujian Province is characterized by obvious monsoon climate, the same season of rain and heat, abundant heat, abundant rain and sunshine, and frequent meteorological disasters.

1. monsoon

Summer in Fujian Province is controlled by subtropical high, and southerly winds blow from the southeast ocean, which is wet and rainy, with frequent typhoons, and the temperature in north and south areas is generally high. In winter, controlled by cold and high pressure, the northerly wind of the mainland is strong, dry and rainy, the temperature is high in the south and low in the north, and the temperature difference between north and south is large; At the turn of spring and summer, cold and warm air flows are intertwined, the climate is hot and humid, and the spring rain is continuous; In summer and autumn, the weather is sunny and hot, and it seldom rains. The prevailing monsoon climate has created four distinct seasons, cold and dry in winter and warm and humid in summer, which is manifested in the four distinct seasons in the central subtropical region, while it is hot and cool in the southern subtropical region, and the winter is extremely inconspicuous.

2. Heat and sunshine

The annual average solar radiation in Fujian Province is 427 ~ 532 kJ/cm2, which increases with the terrain descending from northwest to southeast. The seasonal variation of solar radiation is basically consistent with the temperature variation. The temperature is the highest in July and August, and the solar radiation energy is the strongest. The monthly average temperature is 25℃ ~ 29℃, and the monthly average solar radiation is 54.5 ~ 67 kJ/cm2. The month with the lowest temperature and relatively weak solar radiation energy is 165438+ 10 to February of the following year, with the monthly average temperature of 1 1.65℃ and the monthly average solar radiation of 20.9-29.3 kJ/cm2. The annual average temperature in the whole province is14.6℃ ~ 210.3℃, the average temperature in the hottest month is around 28℃, and the average temperature in Leng Yue is 6.2℃ ~ 13. 1℃, which shows the law of decreasing from the coast to the inland, from the south to the north, and from low altitude to high altitude. The accumulated temperature of ≥ 10℃ in the whole province is 5000℃ ~ 7800℃, and the frost-free period is 235 ~ 365 days. There are obvious regional differences in heat conditions in the whole province. The annual average temperature19.5℃ ~ 210.2℃, the accumulated temperature ≥ 10℃6500℃~ 7800℃ and the frost-free period of more than 350 days are not only beneficial to the growth and multiple cropping of crops, but also suitable for development. The average annual temperature 17.5℃ ~ 20.3℃, the accumulated temperature ≥ 10℃ is 5000℃ ~ 6500℃, and the frost-free period is 260 ~ 300 days, which is not suitable for the normal growth of temperate economic crops. Due to the influence of mountainous landform, the vertical differentiation of heat in Fujian Province is very obvious, and the local climate is even more changeable. The heat in the whole province decreases with the elevation. Every time the altitude rises 100m, the temperature drops by 0.4℃ ~ 0.5℃ in winter and 0.6℃ ~ 0.7℃ in summer, and the accumulated temperature drops by 220℃ ~ 250℃ ≥ 10℃, which leads to the existence of a small area of a county or even a township in the middle subtropical mountainous area due to the great difference in altitude. For example, the southern part of the middle subtropical zone is a double-cropping rice area below 600 meters above sea level, a single-cropping rice mixed sowing area of 600-800 meters, and a single-cropping rice area above 800 meters; In the northern part of the subtropical zone, the area below 300 ~ 400 meters is a double-cropping rice area, the area below 300 ~ 500 meters is a single-cropping rice area, and the area above 500 meters is a single-cropping rice area.

The annual sunshine hours in Fujian province are 1700 ~ 2300 hours, which is lower than the national level. The spatial distribution of sunshine hours shows the characteristics of decreasing from southeast to northwest, and decreasing with the elevation. Sunshine hours are 2000 ~ 2300 hours in the southeast coast, 1800 ~ 2000 hours in the northwest inland, and 1700 ~ 1800 hours in mountainous agricultural areas. According to the seasonal distribution, 70% ~ 75% of sunshine hours are concentrated in March ~1October, which is suitable for the season when warm crops are flourishing. Among them, the sunshine hours from March to June are 520 ~ 560 hours, accounting for 26% ~ 28% of the whole year; The sunshine hours in July ~ 65438+1October are 860 ~ 940 hours, accounting for 43% ~ 47% of the whole year; 165438+ 10 to February of the following year, the sunshine hours are 500-600 hours, accounting for 25%-30% of the whole year.

Step 3 precipitate

Affected by the maritime monsoon climate, Fujian Province has abundant rainfall, with an average annual precipitation of 65,438+0,000 ~ 265,438+000 mm, of which 80% of the areas have an average annual precipitation of 65,438+0,500 ~ 265,438+000 mm. Affected by local circulation caused by topographic relief, the precipitation in the whole province varies with the local circulation. The annual precipitation in southeast Fujian coastal area is 1.000 ~ 1.700 mm, and that in northwest Fujian is 1.700 ~ 2.000 mm. Wuyishan and Jiufeng Mountain are the rainy centers in Fujian Province. The annual precipitation is as high as 1900 ~ 2 100 mm, Daiyun Mountain and Bopingling are sub-rainy centers, with the annual precipitation reaching 1700 ~ 1900 mm, with uneven seasonal distribution of rainfall and distinct wet and dry seasons in the province. The rainy season is from March to June, and the rainfall accounts for 50% ~ 60% of the annual rainfall. The rainfall in this period has the characteristics of wide rain area, heavy rainfall, long rain period, large intensity and small interannual variation. During this period, due to long-term rainfall, soil waterlogging often occurs, which affects the later production and normal growth of spring-sown crops. The rainfall from July to September accounts for 20% ~ 40% of the annual rainfall. Due to the influence of typhoon, the rainfall in this period showed the characteristics of great fluctuation during the year. In typhoon years, there are often storms and floods caused by typhoons. In non-typhoon years, sunny, hot and dry weather controlled by subtropical high and local thunderstorm weather limited by convergence zone often occur. Coastal areas are usually sunny and dry with little rain. If it is associated with autumn drought, the drought is more serious, while the inland areas are often regulated by high temperature and thunderstorms. The dry season is 10 to February of the following year, and the precipitation accounts for 15% ~ 20% of the annual precipitation. Autumn drought often occurs, but it has little effect on crop growth.

4. Meteorological disasters

Disaster weather is frequent in Fujian province, and the main meteorological disasters are drought, flood, wind, cold and hail, especially drought and flood. The temporal and spatial distribution of drought disasters in the whole province presents the following characteristics: ① There are many droughts and severe droughts in the southeast coast, and the frequency of drought decreases from southeast to northwest, and the drought is alleviated. The east of Fuzhou-Nan 'an-Pinghe line is a perennial drought area, with an average annual drought of 1.5; The west and north of Zherong-Dehua-Wuping line are light drought areas, with an average annual drought of1; The middle zone between the two lines is a sub-arid area. ② Summer drought is dominant, followed by autumn and winter drought. Generally, summer drought accounts for 40%, autumn and winter drought accounts for 38%, and spring drought only accounts for 22%. ③ The large-scale drought lasts every 1 1 year/week, corresponding to the sunspot activity cycle. There are mainly plum rains and typhoon floods in the province. Meiyu mostly occurs in the plain areas along the Minjiang River and Tingjiang River, and typhoon floods mostly occur in coastal areas, especially in the lower reaches of Jinjiang River and Jiulong River. The wind disasters in the province mainly include coastal gale, gale and cold air activities caused by typhoon and gale in local strong convective weather, among which typhoon and gale are the most destructive. The cold damage in Fujian mainly includes late spring cold, plum rain cold and autumn cold, among which autumn cold is the most harmful to agricultural production and an important climatic factor affecting the yield of late rice in Fujian Province, and autumn cold in the north is more serious.

(4) Hydrological conditions

Fujian Province is one of the provinces rich in water resources, with developed water system and dense streams. The total water resources are119.7 billion cubic meters. However, the spatial and temporal distribution of water resources is extremely unbalanced, which leads to frequent droughts and floods.

1. Surface water

The surface water resources in Fujian Province are mainly atmospheric precipitation, but the seasonal variation of precipitation is obvious and the regional distribution is uneven. The normal annual runoff depth decreases from northwest to southeast. The average annual water yield of the whole province is 900,000 ~1160,000 cubic meters/square kilometer, and the average annual runoff depth is 500 ~1500mm, among which the runoff depth in Minjiang river basin and the mountainous area of northeast Fujian is 800 ~1400mm, and the coastal areas are 600 ~ 900mm, with few islands. The water system is distributed in a lattice, with short river flow but abundant water. There are 29 inland river systems and 663 rivers in Fujian Province, with a total length of 13569km, including 597 rivers with a basin area of more than 50km. There are 0/2 first-class rivers/kloc-with an area of over 500 square kilometers. Minjiang River has the largest flow, followed by Jiulong River. The average annual flow of each river is 2706.82 cubic meters per second, and the total water volume is 853.57 cubic meters.

2. Groundwater

The groundwater resources in Fujian Province are relatively large, totaling 40.77 1 100 million cubic meters/year, and most of them are bedrock fissure water. According to the depth of 65.438+000 meters, its storage resources are 34.4 billion cubic meters/year. Due to the control of topography, structure, lithology and atmospheric precipitation, the distribution of groundwater abundance is uneven. According to the measured data of the whole province 1950 ~ 1979, the natural recharge of shallow groundwater in the whole province is 25.4 billion cubic meters. There is often a lack of hydraulic connection between basins, and each basin constitutes an independent hydrogeological unit; Groundwater in mountainous areas is extremely uneven, mainly karst water; Quaternary loose accumulation layer and karst basin in plain area are the main water-rich areas in Fujian Province, with abundant groundwater resources, while groundwater in bedrock area is relatively poor. According to the average low flow method, the natural resources of groundwater in the whole province are 65.438+0.79 billion cubic meters per year, of which karst water and loose accumulation layer groundwater are about 2.696 billion cubic meters per year, which are shallow buried and low in salt content, and most of them can be developed and utilized.

(5) Soil resources

According to the data of the second soil survey, the soil types in Fujian Province can be divided into five types: Fe-Al soil, primitive soil, semi-hydrated soil, saline-alkali soil and artificial soil. There are 65,438+04 lateritic red soil, red soil, yellow soil, stony soil, coarse bone soil, purple soil, lime soil, newly accumulated soil, aeolian sandy soil, fluvo-aquic soil, mountain meadow soil, coastal saline soil and so on.

1. laterite

Lateritic red soil and red soil belong to Fe-Al soil, which are the products of desilication and Fe-rich Al soil under subtropical climate conditions. Due to the vigorous biological circulation and strong weathering and leaching in the process of soil formation, a large number of soil basic substances are leached, and iron and aluminum oxides are relatively rich, showing the same characteristics as salt base saturation, such as low acidity, poor nutrients, weak fertilizer conservation and supply performance, etc. Red soil is the most widely distributed zonal soil in the southeast coastal areas of Fujian Province. It is mainly distributed in coastal hilly platforms, river terraces and coastal islands below 200 ~ 400 meters above sea level in Zhangzhou, Xiamen, Quanzhou and Putian, among which Zhangzhou and Quanzhou have the largest distribution area, accounting for about 80.22% of the total red soil area in Fujian Province. The main soil types for planting laterite are Songkhla, laterite and black Songkhla. Red soil is the largest and most widely distributed soil type in Fujian Province, mainly distributed in hilly areas and river valley platforms in Longyan, Sanming, Nanping, Ningde and Fuzhou, among which Longyan, Sanming and Nanping have the largest distribution area, accounting for 63.67% of the total red soil area in Fujian Province. The main types of soil for cultivating red soil are red soil and red mud sand.

2. Paddy soil

Paddy soil belongs to artificial soil, which is a kind of cultivated soil formed by the soil-forming process of hydroponics and maturation under the condition of long-term artificial flooding. It is the most widely distributed cultivated soil in Fujian Province, in which Nanping, Sanming, Longyan and Zhangzhou have the largest distribution areas, accounting for about 60.35% of the total paddy soil area in the province. The main soil types are black mud field, gypsum field, yellow mud field, yellow mud sand field and red soil field. According to the topographic position of paddy soil distribution, paddy fields can be divided into coastal plain fields, flat ocean fields, ridge fields and terraced fields. Flat ocean fields (mostly black mud fields and gypsum fields) distributed in alluvial plains and valley plains account for about 25%, terraced fields (mostly yellow mud fields and red soil fields) distributed in sloping fields account for about 35%, ridge fields (mostly green mud fields and cold rot fields) distributed in valleys account for about 30%, and sloping terraced fields in coastal plains (mostly coastal plains) have poor production conditions, low organic matter content and cultivated layers. Although the ridge field has a high content of organic matter, the groundwater is shallow, the soil drainage is not smooth, and there are obstacles such as cold, rot, acid, rust and poison, and the soil effective fertility is low and the yield is not high. Paddy soil is distributed in alluvial plain, valley plain and coastal plain, with deep plough layer, high soil fertility and good water source and irrigation conditions. After long-term transformation and utilization and directional fertilization, it has become a high-yield area of grain and cash crops in Fujian Province.

3. Other soil types

Besides red soil, lateritic red soil and paddy soil, there are purple soil, calcareous soil, newly accumulated soil, aeolian sand and fluvo-aquic soil closely related to agricultural production. The above-mentioned soils belong to the primary soil type, which was developed after being transported and piled up on various rock residues or parent materials. Due to the influence of erosion or accumulation or some characteristics of parent rock itself, soil is in the initial development stage. Purple soil is formed by the weathering of purple parent rock, which is mainly distributed in the hilly areas of northwest Fujian and east Fujian. Longyan, Sanming and Nanping have large distribution areas, accounting for 89.42% of the total purple soil area in the province. The soil properties of purple soil mainly inherit the characteristics of parent rock. Loose soil, shallow soil layer, weak corrosion resistance and serious soil erosion lead to the continuous renewal of soil layer, delay the development of soil and low fertility. Lime soil is the soil developed by limestone weathering, which is mainly distributed in limestone mountains, hilly slopes or eroded depressions in northwest Fujian and below 500 meters above sea level. Sanming City has the largest distribution area, accounting for 62.48% of the total calcareous soil area in the province. Lime soil is generally shallow and sticky, mostly neutral to slightly alkaline, with obvious biological enrichment, rich organic matter, high base saturation and rich mineral nutrients. Neogene soil series is developed from newly transported flowing water sediments, which are mainly distributed in rivers, low-lying areas along rivers and Xinzhou, among which Fuzhou and Zhangzhou have a large distribution area. The newly accumulated soil has a short soil-forming time, weak biological enrichment and not obvious profile development. Soil properties and fertility are dominated by the characteristics of parent materials, which generally show neutral to slightly acidic reactions. Aeolian sand is accumulated by wind transport, mostly occurring in the protruding part of the straight coast, mainly distributed in Fuzhou and Zhangzhou, accounting for about 76.49% of the total area of aeolian sand in the province. Aeolian sandy soil has weak development, sandy texture, low organic matter content, poor mineral nutrients and low soil fertility. The fluvo-aquic soil belongs to semi-fluvo-aquic soil, which is a dry soil on the alluvial plain of rivers. It is mainly distributed in the super floodplain and first-class terraces along the Minjiang River, Jinjiang River and Jiulong River and their larger tributaries, among which Fuzhou, Quanzhou, Zhangzhou and Nanping have a large distribution area, accounting for 82.96% of the total tidal soil area in the province. The groundwater level of this kind of soil is shallow, because of capillary action, the night tide phenomenon is obvious, the soil is often in a wet state, the alternation of wet and dry is obvious, the soil biological accumulation is less, the organic matter content is not high, the soil is mostly slightly acidic and the fertility is low.

(6) Vegetation condition

Fujian province is located in the humid forest area in the east of China, belonging to two vegetation zones: the south subtropical monsoon forest and the middle subtropical evergreen broad-leaved forest. Influenced by latitude, altitude and topography, there are obvious regional differences in China's climatic conditions, which lead to complex and diverse vegetation types and a wide variety of plants. Due to the long-term influence of human activities, most of the original vegetation has been destroyed. At present, the vegetation is mainly secondary vegetation, mainly including Pinus massoniana forest, Chinese fir forest, bamboo forest and shrub forest, and the basic characteristics of zonal vegetation can only be traced back in some areas.

1. Natural vegetation

The natural vegetation in Fujian Province includes monsoon forest in the south subtropical zone, evergreen broad-leaved forest in the middle subtropical zone, evergreen mixed forest, evergreen coniferous forest, shrubs, herbs and mountain meadows. The South Subtropical monsoon forest is distributed in the hilly platform along the southeast coast of Fujian. At present, only Nanjing County and Hexi have mature and well-preserved South Subtropical monsoon forest, and the original vegetation in other areas has been destroyed to varying degrees. The main tree species are Castanopsis fargesii, Castanopsis carlesii, Castanopsis carlesii, Quercus wulai and Machilus macrophylla. Subtropical evergreen broad-leaved forest is mainly distributed in southwest, middle, northeast and northwest Fujian. Due to the differences in water, heat and soil conditions, the vegetation structure and tree species composition in different places are different. The main tree species in northwest and middle Fujian are Cyclobalanopsis glauca, Castanopsis fargesii, Castanopsis fargesii and Castanopsis fargesii, and there are also some south subtropical tree species in southwest and northeast Fujian. Evergreen coniferous and broad-leaved mixed forests are scattered in hilly areas below1300m above sea level. The main tree species are Pinus massoniana, Taxus chinensis, Sabina vulgaris, Schima superba, Castanopsis eyrei, Cyclobalanopsis glauca, Liquidambar formosana and so on. The main tree species of evergreen coniferous forest are Pinus massoniana, Cunninghamia lanceolata, Cryptomeria fortunei, Sabina vulgaris, Tsuga Cephalotaxus, Taxus chinensis, Pinus taiwanensis and bamboo cypress, among which Pinus massoniana and Cunninghamia lanceolata are widely distributed in hilly areas below 1 100 meters above sea level, and most of the Cunninghamia lanceolata forests are artificial pure forests. Shrubs are mainly distributed in villages and hilly areas where human activities are frequent, and most of them belong to transitional secondary forests. Shrub species in coastal hilly areas are mostly xerophytes that like heat, such as myrtle, Che Sang Zi and other spiny vines. The shrub species in the hilly areas of Daiyun Mountain and Wuyishan Mountain are mainly cold-resistant positive plants, mainly including wood, Toona sinensis, black rice and azalea. In Zhongshan area, mostly deciduous shrubs, mainly white oak and mountain pepper. Herbaceous communities are widely distributed in hilly and low mountain areas, especially in the low mountain areas along the southeast coast of Fujian Province. They are all secondary vegetation after forest destruction, and are usually divided into tall grass plant communities (mainly five-awn grass) and middle-low grass plant communities (mainly Parthenocissus tricuspidata, Cyperaceae, Dictyophora dictyophylla, etc. ). Mountain meadow communities are mainly distributed in the gentle slope of Zhongshan Mountain at higher altitude, including Gramineae, Cyperaceae, Compositae, Gentianaceae, Umbelliferae, Hypericum and so on. The main grass species are Miscanthus, Wild Ancient Grass, Saxifraga, Chrysanthemum indicum, Hypericum japonicum and so on.

2. Agricultural vegetation

Fujian province is located in the subtropical climate zone, with abundant water and heat resources, which is very suitable for the growth of many crops, subtropical fruit trees and tea trees. There are mainly rice, sweet potato, barley, wheat, soybean and potato in the province, among which rice is widely distributed in the province, potatoes are mainly distributed in Nanping, Sanming, Longyan and Ningde in the north and northwest of Fujian, barley, wheat and sweet potato are mainly distributed in Ningde, Fuzhou, Putian, Quanzhou and Zhangzhou in the east of Fujian, and soybeans are mainly distributed in Sanming and Nanping in the inland and Fuzhou and Putian in the coastal areas. The cash crops mainly include peanuts, rape, kenaf, sugarcane, flue-cured tobacco, vegetables and watermelon, which are distributed in all counties (cities, districts) of the province. Among them, sweet potatoes, peanuts and sugarcane are mainly distributed in the southeast coastal areas of Fujian, and flue-cured tobacco is mainly distributed in Longyan, Sanming and Nanping in the southwest, northwest and north of Fujian. There are more than 3,000 kinds of fruit trees in the province, mainly including citrus, longan, litchi, loquat, banana, pineapple, olive, bayberry, mango, kiwi, peach, plum, nai, grape and plum. There are more than 400 kinds of tea trees in this province. Fruit trees and tea trees are distributed in the plains, terraces and hilly areas of the province, among which longan, litchi, loquat, banana, pineapple, olive, bayberry, mango, grape and kiwifruit are mainly distributed in the low hills, plains and terraces along the southeast coast of Fujian, while Naihe is mainly distributed in the hilly areas of central and northern Fujian.