Guangxi Zhuang Autonomous Region is located in the southeast edge of the Yunnan-Guizhou Plateau in the second step of the national terrain, located in the western part of the two hilly areas. The entire terrain from northwest to southeast tilt, rolling hills, huge mountains, mountain valleys, surrounded by mountains, plateaus, basin-shaped, known as the "Guangxi Basin". In this special geographic environment and the role of atmospheric circulation, the formation of abundant heat, abundant precipitation, wet and dry, moderate sunshine, long summer and short winter, the four seasons of farming, but frequent disasters, droughts and floods highlight the characteristics of the climate. The total land area of the autonomous region is 237,600 square kilometers, accounting for 2.47% of the country's total land area. The maximum east-west span is about 771 kilometers, and the maximum north-south span (south to Shiyang Island) is about 634 kilometers.
(I) Geology and Geomorphology
1. Geology The Guangxi Zhuang Autonomous Region is located in the combination of the Pacific Ocean tectonic belt and the ancient Mediterranean-Himalayan tectonic belt, and is in the middle and western part of the Nanling tectonic belt. In the long geological era, through the vicissitudes of change, the formation of sedimentary strata complete, frequent magmatic activity, complex geological structure, mineral resources are relatively rich in geological features. The history of regional geological development of Guangxi Zhuang Autonomous Region can be traced back to the Middle Proterozoic era, which is 1.67 billion years ago, and has passed through the Late Proterozoic era, Early Paleozoic era, Late Paleozoic era, Mesozoic era, Cenozoic era and even the modern era.
The rocks exposed in the Guangxi Zhuang Autonomous Region include sedimentary rocks, magmatic rocks and metamorphic rocks. Sedimentary rocks have the widest distribution throughout the counties (cities and districts) of the autonomous region, with carbonate rocks as the main ones, mainly distributed in Guizhong, Guixi and Northwest Gui, constituting one of the typical karst areas in the country and even in the world, with an area accounting for 88.00% of the whole autonomous region. Sedimentary rocks often form various kinds of sedimentary minerals under specific sedimentary conditions, and some pure sedimentary rocks are non-metallic minerals themselves. Magmatic rocks are also widely distributed, mainly located in Gui Southeast, Gui Northeast and Gui North, covering an area of 9.03% of the whole Autonomous Region; the formation of a number of eras, including the Himalayan Period, Yanshan Period, Huarixi-Indochinese Period, the Gali East Period, the Sibao - Xuefeng Period, and a complete range of rock types. Magmatic activities are favorable to mineralization and mineral enrichment. Metamorphic rocks are only found in the northern part of Gui and southeastern part of Gui, with simple rock types and low degree of metamorphism, forming fewer minerals and accounting for 2.97% of the total area of the autonomous region.
Under the action of geological forces within the earth, the earth's crust and its rocks undergo various tectonic deformations mainly in the form of folds and fractures, forming three types of tectonic patterns: uplifts, depressions and inland basins. Folds and ruptures are very well developed, with 21 major ruptures or rupture zones***, and the north-east, north-east and north-west ruptures constitute the basic framework of the regional tectonics of the Guangxi Zhuang Autonomous Region. There have been 19 tectonic movements*** in the Guangxi Zhuang Autonomous Region since ancient times, the main ones being the Sibao Movement, Guangxi Movement, Dongwu Movement, Indo-Chinese Movement and Yanshan Movement, which are land-forming movements or fold movements.
The time distribution of seismic activity shows cyclical ups and downs, alternating between relative calm and significant activity. A cycle of seismic activity lasts 360 to 400 years, of which the quiet period lasts 160 to 200 years and the active period about 200 years. From the earthquake data since the 1950s, earthquakes of magnitude 4.75 or higher occurred once every five years on average, but the distribution of time is very uneven, sometimes once every few decades, and sometimes year after year.
In the current cycle of seismicity, there are two major regions of medium- to strong-magnitude earthquakes in the Guangxi Zhuang Autonomous Region and its neighboring provinces, namely Pingguo-Leye-Funing in Yunnan Province and Lingshan-Rongxian-Lianjiang in Guangdong Province, in which about 69% of earthquakes of magnitude 5 or higher and all earthquakes of magnitude 6 or higher occur. About 69% of earthquakes of magnitude 5 and above and all earthquakes of magnitude 6 and above occurred in these two regions, and most of the micro-earthquakes recorded by modern instruments are also in these two regions.
The distribution of earthquakes in the Guangxi Zhuang Autonomous Region is determined by its special geological structure, and is especially intrinsically linked to the distribution of active ruptures. There are six groups of active ruptures in the autonomous region: north-east, north-west, north-north-east, north-north-west, near-south-north and near-west, with north-east and north-west being the main ones, constituting the "X"-shaped framework of active ruptures in the Guangxi Zhuang Autonomous Region. The north-east oriented fractures are mainly located in the southeast of Gui, and the north-west oriented fractures are located in the northwest of Gui, and the activities of these two groups of fractures have led to a series of earthquakes of medium-strength and above in the Guangxi Zhuang Autonomous Region. In recent times, earthquakes of medium-strength or greater intensity have occurred mainly in the southeast and northwest regions of Guangxi Zhuang Autonomous Region. Another feature of the seismic activity in the Guangxi Zhuang Autonomous Region is the high frequency of small earthquakes, fewer earthquakes of medium-strength or above, and shallower depth of the earthquake source, so the intensity of surface damage is relatively high, and this small-magnitude, high-intensity seismic phenomenon is more typical of Hechi City.
2. Geomorphology
Guangxi Zhuang Autonomous Region generally shows a hilly mountainous basin geomorphology with a lot of mountains and few plains, in the shape of a basin, which is characterized by the following features:
(1) Basins of mixed sizes. West and north of the edge of the Yunnan-Guizhou Plateau, northeast of the South Ridge mountains, Cat Mountain, Yue Cheng Ling, Ocean Mountain, Du Pang Ridge, Mengzhu Ridge, the elevation is generally 1500 ~ 1800 meters, 2000 meters up and down the peaks are also quite a lot. Southeast and south of the Yunkai Dashan, 60,000 Dashan, 100,000 Dashan, west of the West Guanxi karst plateau, the elevation of about 1,000 meters, the plateau above the six Shaoshan. In the northwest are Jinzhong Mountain, Cenwanglaoshan, Qinglong Mountain and Dongfengling, forming the southern edge of the Yunnan-Guizhou Plateau, with an altitude of 1000 to 1500 meters. In the north are the Fenghuang Mountains, the Jiwan Mountains, the Da Miao Mountains, the Da Nanshan Mountains and the Tianping Mountains, with an altitude of about 1,500 meters. The central part of the Guangxi Zhuang Autonomous Region is mostly plains and basins with an elevation of less than 200 meters. Because of the central arc of the mountain range (driving bridge ridge, Dayao Mountain, Lianhua Mountain - Duyang Mountain, Daming Mountain, Lianhua Mountain) separation, the formation of Liuzhou as the center of the Guizhong Basin, along the arc of the Guangxi mountain range in front of the depression for the right river area, Wuming County, Nanning City, Yulin City, Lipu County, and so many small and medium-sized basins, the formation of large and small basins mixed with the structure of the geomorphology.
(2) The mountain system is mostly in the shape of an arc, layer by layer. From north to south, it can be roughly divided into 4 columns, the first column is Da Miao Mountain - Jiwan Da Shan, the second column is Da Nanshan Mountain - Tianping Mountain - Fenghuang Mountain, the third column is Gaoqiaoling - Dayaoshan - Lianhua Mountain - Zhen Longshan-Damingshan-Duyangshan (this column is also called Guangxi Arc), and the fourth column is Yunkai Dashan-60,000 Dashan-100,000 Dashan-Daqingshan. The direction of the mountain system clearly shows signs of extrusion by the Pacific Plate in the east and the Indian Ocean Plate in the west. The mountainous area is dominated by the middle mountains with an elevation of more than 800 meters, accounting for 23.50% of the total area of the Guangxi Zhuang Autonomous Region; the low mountains with an elevation of 400 to 800 meters come second, accounting for 15.90% of the total area. The main peak of Cat'er Mountain in northeast Guangxi is 2,141 meters above sea level, which is the highest peak in Guangxi Zhuang Autonomous Region and also the highest peak in Nanling. The Xianggui Corridor between Yuechengling-Cat'er Mountain and Ocean Mountain is one of the three major corridors in China.
(3) Hills (200 to 400 meters above sea level). Hills account for 10.30% of the total area of the Guangxi Zhuang Autonomous Region, with high hills predominating, concentrated in the southeast, south and southwest of Gui.
(4) The plains are scattered and small in scale. The plains with an altitude of 200 meters or less (including valleys, river valley plains, pre-mountain plains, deltas and low platform mountains) account for 26.90% of the total area of the Guangxi Zhuang Autonomous Region. The plains of the Guangxi Zhuang Autonomous Region are mainly of two types: river alluvial plains and erosion plains. River alluvial plains are mainly distributed along major and medium-sized rivers, and the larger plains include Xunjiang Plain, Yujiang Plain, Binyang Plain, Nanliujiang Delta, etc. Among them, Xunjiang Plain is the largest. Among them, the Xunjiang River Plain is the largest, with an area of 63,000 hectares.
(5) Karst landforms are widely spread and of many types. Guangxi Zhuang Autonomous Region has the most typical karst landforms, accounting for 37.80% of the total area of the autonomous region, centralized and contiguous, and the development of its many types is rare in the world. Its karst landforms include peaked depressions, peaked valleys and peaked plains, with peaked depressions mainly located in northwest Gui, peaked valleys mainly located in northeast Gui and southwest Gui, and peaked plains mainly located in central Gui and southeast Gui.
(ii) climate
Guangxi Zhuang Autonomous Region is located in low latitude, surrounded by mountains, the territory is dominated by hills and mountains, south of the tropical sea, is a subtropical monsoon climate zone. The average annual temperature of 16.50 ℃ ~ 23.10 ℃, isothermal basically latitudinal distribution, the temperature increases from north to south, from the valley plains to the hills and mountains decreasing. Extreme annual maximum temperature of 33.70 ℃ ~ 42.20 ℃, the annual minimum temperature of -8.40 ℃ ~ 2.90 ℃. Average daily temperature ≥ 10 ℃ cumulative temperature of 5000 ℃ ~ 8000 ℃, the number of days 240 ~ 330 days, is one of the provinces with the highest cumulative temperature. Frost-free period of up to 280 ~ 360 days, some places in the south of the frost-free all year round. According to the average temperature & lt; 10 ℃ for the winter, & gt; 22 ℃ for the summer, 10 ℃ ~ 22 ℃ for the spring standard division, Wuzhou City, Wuxuan County, Laibin City, Bama Yao Autonomous County, Baise City, most of the areas north of a line, the winter is long 1 ~ 3 months, south of the line, the winter is long less than 1 month, the rich heat resources for the development of multi-maturing production of goods to provide favorable conditions. The rich heat resources provide favorable conditions for the development of multi-maturing product production according to local conditions.
Guangxi Zhuang Autonomous Region is one of the richest regions in the country in terms of precipitation. The annual precipitation is above 1080 millimeters in all areas, and most of the areas are 1200-2000 millimeters, which is more than double of the national average of 630 millimeters, and the highest precipitation in Dongxing City can reach 2840 millimeters, and the lowest precipitation in Tianyang County also has 1086 millimeters. The spatial and temporal distribution of precipitation is uneven, with more in the north, south and east, and less in the center and west; more in the hilly and mountainous areas, and less in the plains of river valleys; and more on the windward slopes, and less on the leeward slopes. In the seasonal distribution due to the alternating influence of winter and summer winds, the seasonal distribution is uneven, dry and wet seasons, rain and heat in the same season, is a humid and semi-humid climate. 4 ~ September for the rainy season, the precipitation accounted for 70% to 85% of the annual precipitation, floods are prone to flooding; October to March for the dry season, the precipitation only accounted for 15% to 30% of the annual precipitation, drought, less rain, easy to cause forest fires. The average annual sunshine hours of 1200 ~ 2200 hours, its geographical distribution is characterized by more in the south, less in the north, more in the valley plains, less in the hilly mountainous areas; seasonal changes in the number of hours of sunshine to the most in the summer, the least in the winter, in addition to the Baise City, the southern and northern mountainous areas of the spring is more than the fall, the rest of the region is more in the fall than in the spring. In summer, the number of hours of sunshine is 355 to 698 hours, accounting for 30% to 40% of the annual sunshine hours; winter is 185 to 380 hours, accounting for only 14% to 20% of the annual sunshine hours.
Guangxi Zhuang Autonomous Region meteorological disasters are frequent, often subject to drought, flooding, low-temperature cold, wind, hail, tropical cyclones and lightning hazards, of which drought and flooding is the most prominent. According to the seasons in which droughts occur, there are spring droughts, summer droughts, fall droughts and winter droughts, but mainly spring and fall droughts. The geographical difference of spring droughts is very obvious, and the frequency of occurrence gradually increases from the northeast of Gui to the southwest of Gui. The geographical difference of fall drought is also obvious, and the frequency of occurrence gradually increases from southwestern Gui to northeastern Gui. Flooding is caused by a variety of factors, the emergence of long duration and intensity of heavy rainfall is often the main cause of flooding (Figure 1-2 ~ Figure 1-6).
Figure 1-2 Distribution of annual average temperature of the Guangxi Zhuang Autonomous Region
Figure 1-3 Distribution of annual precipitation of the Guangxi Zhuang Autonomous Region
Figure 1-4 Distribution of annual sunshine hours of the Guangxi Zhuang Autonomous Region
Figure 1-5 Distribution of annual evaporation of the Guangxi Zhuang Autonomous Region
Figure 1-6 Distribution of annual frost-free period of the Guangxi Zhuang Autonomous Region
Figure 1-6 Distribution of annual frost-free period of the Guangxi Zhuang Autonomous Region
(C) Soil
Guangxi Zhuang Autonomous Region soil of the soil formation of the parent material mainly sandstone, shale, conglomerate, limestone, granite, purple rock and other weathering material and a small amount of quaternary red soil, alluvial deposits, sediments and so on. Among them, weathered materials of sandstone and shale (including sand, conglomerate and shale) accounted for 56.15%, which were distributed all over the world; weathered materials of limestone accounted for 13.23%, which were mainly distributed in the karst areas of southwestern Gui, northwestern Gui, central Gui and northeastern Gui; weathered materials of granite accounted for 11.77%, which were mainly distributed in the southeast of Gui, northeastern Gui, and the area around Kunlun Pass in the northern part of Nanning Basin; weathered materials of purple rock accounted for 5.31%; and weathered materials of red soil of Quaternary period accounted for 5.28%. 5.31% of the weathered material is purple rock; 5.28% of the material is laterite; the rest is alluvial material, sediment, and weathered material of siliceous rock.
Guangxi Zhuang Autonomous Region has a complex topography and rich soil types. The valley, plain area is mostly alluvial soil and quaternary red soil development of rice soil, the main soil types are tide sand mud field, yellow mud field, etc.; mountain valley alluvial field, low-lying Pangdong field is mostly various cold dip field; hilly area of the mountain slopes are mostly developed by the zonal soil into a variety of terraces, dry fields and dry slopes, the main soil types are loamy soil field, mud field, purple mud field, red loam soil, etc.; coastal areas for the seaside sandy soil field (land) and salty acid field; The karst and rocky mountainous areas are brown lime soil, black lime soil, brown mud soil, lime mud field, black mud field and duck shit field. Among these soils, loamy soil fields, mud and flesh fields, and tidal sand and mud fields have better production performance, are richer in organic matter, generally up to 2% to 3%, and have fertile soil and higher yields; various cold flooded fields, with low water temperatures and cold, acidic soils; various calcareous soils in the karst areas of northeastern Gui, central Gui, and most of the southwestern part of Gui, with clayey soil textures and poor permeability, bad arable properties, low organic matter content, and a lack of effective phosphorus, potassium nutrients, and susceptible to drought and flooding; salty and acidic soils. The soil is prone to drought and flooding; the salty and acidic fields contain many sulfate acidogenic substances, and the soil is highly acidic with many toxic substances. Most of the karst areas, alpine mountainous areas and coastal areas in northwest, central and southwest Gui have poor soil quality, and farming is also more extensive, with lower crop yields. Gui Dong and Gui Nan as well as the plains of the Right River Valley have good soil quality, high levels of agricultural production and higher crop yields.
Because of the Guangxi Zhuang Autonomous Region's vast area, diverse climate and complex geomorphology, soil formation is affected by topography, biology, climatic factors and soil-forming matrices, with obvious differences in zonation, and therefore its soils can be classified into two major categories of zonal soils (apparent domain soils) and non-zonal soils (hidden domain soils). The zonal soils are red soil, reddish soil and brick red soil, while the non-zonal soils are mainly carboniferous soil, purple soil and rice soil. The distribution laws are as follows:
(1) Latitudinal zonal distribution: in horizontal distribution, about 23°30′ north latitude as the boundary, north of the area is roughly red soil distribution belt, mainly in the subtropical evergreen forests red soil; south to the coastal areas of the distribution belt for the crimson soil, mainly subtropical monsoon forests crimson soil and brick red soil; in the south of the coastal areas there are a small amount of brick red soil distribution. The red soil is affected by the process of iron-rich aluminized soil formation, acidic, less nutrient content, but the soil layer is thicker, the organic quality varies according to the degree of vegetation cover, the organic content of the high cover can reach 3% to 5%, on the contrary, it can be less than 1%; crimson soil and brick red soil is affected by the process of iron-rich aluminized soil formation is greater, the degree of weathering is more thorough than the red soil, the nutrient content is less, the soil viscous barren and thin.
(2) Vertical distribution: in vertical distribution, from low to high, brick red soil, reddish red soil, red soil, mountain red and yellow soil, mountain meadow soil or mountain short forest meadow soil. The vegetation of mountain red loam is mainly middle subtropical evergreen broad-leaved forest and mixed evergreen broad-leaved and deciduous broad-leaved forest, the degree of weathering is lower than that of reddish red loam and brick red loam, and the soil has more nutrients, but the soil layer is shallow and thin.
Yellow soil is the vertical band spectrum soil of Guangxi Zhuang Autonomous Region, mostly distributed above 700 meters above sea level. Different base zones have different vertical zone spectra of soil, with the northern region mainly composed of red soil - yellow red soil - yellow soil - mountain yellow-brown soil - mountain meadow soil, and the southern region mainly composed of red red soil - red soil - yellow soil - mountain meadow soil. -Yellow Loam-Mountain Meadow Soil, and Coarse Bone Soil constitute the vertical zone spectrum in the southern region. The climate in western Gui is relatively dry, with obvious wet and dry seasons, and the vertical distribution of soils is generally higher than that in the east, for example, the base zone soil in the west is red soil, with a distribution height of up to 1300 meters above sea level, and the lower limit of the distribution of its montane yellow loam has also risen from 1400 meters above sea level in the east to 1850 meters above sea level, and the mountainous yellow-brown loam is generally not present.
(3) Distribution of non-territorial soils (crypto-territorial soils): the non-territorial soils in Guangxi Zhuang Autonomous Region mainly include limestone soils, purple soils and rice soils. Among them, rice soil has the largest area and is widely distributed in alluvial plains, coastal paddies, mountainous hills and broad valleys, mountainous basins and piedmont fields, and terraces on hilly slopes and narrow valleys and alluvial fields, etc. Among them, there are more in the southeast of Gui than in the northwest of Gui, e.g., rice soil accounts for a larger proportion of the cultivated land in Yulin City, Wuzhou City, Nanning City, and Guilin City, all of them are about 75%, whereas the proportion of rice soil accounts for a smaller proportion of the cultivated land in Baise City, and Hechi City, respectively, is 42% and 46%. The proportion of rice soil in Baise City and Hechi City is smaller, 42% and 46% respectively. Limestone soils are mainly distributed in karst areas and developed in carbonate rock weathered materials, which differ from place to place due to different climates and time of soil formation, and the main types are black limestone soils, brown limestone soils, red limestone soils, etc. Purple soils are developed in purple sandstone soils. Purple soil is developed on purple sandstone and purple sand shale, the distribution of sporadic, small area.
(4) Natural Resources
1. Water Resources
Guangxi Zhuang Autonomous Region is located in the low latitude region, rainfall is relatively abundant, the development of rivers, rich in water resources, most of the rivers along the topography of the sloping surface, flowing from the northwest to the southeast, forming the Hongshui River - Xijiang River as the main trunk across the middle of Guangxi Zhuang Autonomous Region as well as tributaries of the river. There is a dendritic water system distributed on both sides of the river, among which there are 986 rivers with rainfall catchment area of more than 50 square kilometers, total length of about 34,000 kilometers, and river network density of 0.14 kilometers/square kilometer, which belongs to the four major water systems of the Pearl River, the Yangtze River, the Guinan Coastal Solitary Stream into the Sea, and the Baidu River. Pearl River system is the largest water system in Guangxi Zhuang Autonomous Region, the basin area in Guangxi Zhuang Autonomous Region is 202424 square kilometers, accounting for 85.20% of the total land area of the autonomous region, accounting for 44.40% of the total area of the Pearl River Basin, of which, the rainfall area of 50 square kilometers or more of the river has 833, the main Nanpanjiang - Hongshui River -Qianjiang-Xunjiang-Xijiang River crosses the whole country from northwest to east, originating from Mashong Mountain in Qujing City, Yunnan Province, initially known as the Nanpanjiang River, through the Hongshui River section, Qianjiang River section, Xunjiang River section and Xijiang River section, exiting Wuzhou City into the South China Sea through Guangdong Province, with a total length of 1,239 kilometers. Among them, the Hongshui River section of 658 km, the river has a large specific drop, many beaches and water, rich in hydroelectric resources, known as China's hydropower resources, "rich mine"; and the main tributaries of the Xijiang River in Guangxi are the Yujiang River, the Liujiang River and the Guijiang River, of which the Yujiang River is the largest tributary. The Yangtze River system is distributed in the northeast of Guangxi, with a basin area of 3.50% of the total area of the Guangxi Zhuang Autonomous Region, and 30 rivers with a rainfall catchment area of 50 square kilometers or more. The main rivers in the Guangxi Zhuang Autonomous Region are the Xiangjiang River and the Zijiang River, which are the upper reaches of the Dongting Lake system, and merge into the Yangtze River through Hunan Province, among which the Xiangjiang River communicates with the two major water systems of the Yangtze River and the Pearl River through the Spirit Nullah, which was dug by the Qin Dynasty, in the vicinity of Xing'an County. The main rivers of Guinan Coastal Solitary River into the sea system are Nanliujiang River, Qinjiang River, Fangcheng River, Maoling River, Beilun River, etc., with a watershed area of 22900 square kilometers, accounting for 9.70% of the total land area of the whole autonomous region, among which the largest river is Nanliujiang River, Nanliujiang River, Qinjiang River, Beilun River and so on, which are all injected into the Gulf of Beibu. The mainstream of the rivers along the western coast of Guangdong, the Kyushu River originates in Luchuan County, flows into Guangdong Province through the Wendi, with a basin area of 2,300 square kilometers in the Guangxi Zhuang Autonomous Region, accounting for 0.97% of the total land area of the Autonomous Region, and the rivers are characterized by a short flow and a steep gradient. The Baedu River in Napo County belongs to the water system of the Red River of Vietnam, which is injected into the Gulf of Tonkin through the Red River of Vietnam, and its basin area in the Guangxi Zhuang Autonomous Region accounts for 0.60% of the total land area of the whole autonomous region. In the Guangxi Zhuang Autonomous Region, there are 433 underground karst rivers, of which 248 are more than 10 kilometers in length, and the Poxin River and the Disu River have formed their own underground river systems. in 2007, the annual runoff flow of the whole region was 122.120 billion cubic meters, and the reserves of water energy resources amounted to 21.33 million kilowatts.
The mainland coastline starts from the mouth of the Saimi River in Hepu County in the east, bordering with Yingluo Harbor in Guangdong Province, and ends at the mouth of the Beilun River at the border between China and Vietnam in the west, with a continental coastline of about 1,500 kilometers and an island coastline of 461 kilometers. The coastline is winding and diverse. The mouths of the Nanliu River and the Qinjiang River are delta-type coasts, the mouths of the Tieshangang River, the Dafeng River, the Maoling River and the Fangchenggang River are drowning-valley type coasts, the coasts of the cities of Qinzhou and Fangchenggang are mountain-type coasts, and the coasts of the Beihai and the Hepu are terrace-type coasts. In the Guangxi Zhuang Autonomous Region, the offshore shoals are vast, covering an area of 1,005 square kilometers, and the shallow sea between 0 and 20 meters is vast, covering an area of 6,488 square kilometers. The entire Beibu Gulf covers an area of about 129,300 square kilometers, starting from Leizhou Peninsula and Qiongzhou Strait in the east, Hainan Island in the southeast, Guangxi Zhuang Autonomous Region in the north, and Vietnam's socialist **** and country in the west. The seabed of the bay is flat and gradually slopes from northeast to southwest, with an inclination of less than 2°, and the depth of water is generally 20 to 50 meters, with the deepest not exceeding 90 meters. There are 697 islands off the coast of the Guangxi Zhuang Autonomous Region, with a total area of about 66.90 square kilometers, of which the largest, Weizhou Island, has an area of about 24.70 square kilometers.
The topography of the Guangxi Zhuang Autonomous Region is roughly characterized by a high northwest and low southeast, surrounded by mountainous basins, which, together with abundant precipitation, creates rich surface water resources and good groundwater storage conditions. The total amount of groundwater resources in the region is about 39.160 billion cubic meters, with an exploitable amount of 24.870 billion cubic meters, of which carbonate karst water accounts for 61.50% of the total amount of groundwater resources, bedrock fissure water accounts for 36.40%, and pore water of loose rock types accounts for 1.40%.
2. Biological resources
1) Plant resources
Guangxi Zhuang Autonomous Region is one of the richest provinces in China in terms of biological resources, and it is the region with the most concentrated distribution of various plants and terrestrial animals. There are three vegetation zones distributed from north to south, i.e., the mid-subtropical evergreen broad-leaved forest zone, the south-subtropical evergreen monsoon rainforest zone, and the north-tropical seasonal forest zone, which are dominated by the tropical and tropical-subtropical components, with a large number of endemic species, and there are differences between north and south and between east and west in the distribution. The latitudinal zonation of vegetation changes from south to north in the order of monsoon rain forest - monsoon evergreen broad-leaved forest - typical evergreen broad-leaved forest. The longitudinal and latitudinal zonal change of vegetation is influenced by the east-west change of rainfall, with moist evergreen broadleaf forest in the east and semi-moist evergreen broadleaf forest in the west; in warm coniferous forests there also exists the eastern moist area of horsetail pine forests, while the western semi-moist area is replaced with fine-leaved Yunnan pines. The vertical zonation of vegetation varies from low to high, from monsoon forest - montane evergreen broad-leaved forest - hilltop dwarf forest in the southern mountains, to monsoon evergreen broad-leaved forest - montane evergreen broad-leaved forest - montane mixed evergreen broad-leaved and coniferous forest in the mountains of Gui Zhongshan -mountain top dwarf forests, and in the mountains of northern Gui for typical evergreen broadleaf forests-mountain evergreen deciduous broadleaf mixed forests and mixed coniferous and broadleaf forests-mountain top dwarf forests.
The main characteristic of vegetation in Guangxi Zhuang Autonomous Region is the secondary nature of vegetation, most places no longer exist primary vegetation, secondary vegetation mainly includes scrub, scrub, vine scrub, deciduous broadleaf forest, evergreen deciduous broadleaf mixed forest and so on. According to statistics, there are 5 vegetation type groups (broad-leaved forests, coniferous forests, bamboo forests, scrubs and grasses), 14 vegetation types and 301 clusters of natural vegetation. 14 vegetation types are warm coniferous forests, hot coniferous forests, warm deciduous broad-leaved forests, evergreen deciduous broad-leaved mixed forests, evergreen broad-leaved forests, monsoon rainforests, secondary monsoon rainforests, mangrove forests, warm bamboo forests, hot bamboo forests, warm scrubs, hot scrubs, and gramineae-grass scrubs, Fern Grassland. Warm coniferous forests evolved from the destruction of broad-leaved evergreen forests, and are now the larger forest type in the Guangxi Zhuang Autonomous Region.
According to the statistics of annual inventory of forest resources in Guangxi Zhuang Autonomous Region at the end of 2000, the existing forest area of the whole autonomous region is 9,819,100 hectares, with a forest coverage rate of 41.49%, and there are 59 nature reserves for various animals and plants (among which there are 10 state-level nature reserves), with a total area of 1,646,400 hectares and 752,000 hectares of forested area, which account for 7.7% of the total area of the autonomous region respectively. They accounted for 7.00% and 3.20% of the total area of the autonomous region respectively. By the end of 1992, there were 288 families, 1,717 genera and 8,354 species of vascular plants, second only to Yunnan and Sichuan Provinces, and ranked first in China. Among all kinds of plants, according to their uses, there are more than 120 kinds of wild fruits with development value, 2,426 kinds of wild medicinal plants, 109 kinds of wild starch plants, 210 kinds of wild chemical raw materials plants, more than 400 kinds of wild fiber plants, 156 kinds of wild aromatic plants, and about 700 kinds of cultivated fruit trees. There are 37 species of plants under national key protection and 61 species of plants under secondary key protection, which are mainly distributed in three places, namely, southwestern Gui, centered on Langgang Nature Reserve and 100,000 mountains, central Gui, centered on Dayaoshan Nature Reserve, and northern and northeastern Gui, centered on Huaping Nature Reserve. Known as the "living fossil", the silver fir is a precious tree species with great scientific research value, and it only exists in the Huaping Forest Area, the Dayao Mountain Forest Area and the Jinfo Mountain of Chongqing in the Guangxi Zhuang Autonomous Region.
2) Animal Resources
Guangxi Zhuang Autonomous Region is rich in wild vertebrate resources, with a large number of animal species, *** found 929 species (including subspecies) of wild terrestrial vertebrates, which account for 43.30% of the national total, and more than 700 kinds of marine and freshwater fish, which account for more than 30.00% of the national total. Among these animals, there are 150 rare species under national key protection, accounting for about 44.50% of the national key protected animals. Among them, there are 26 species under national-level protection, accounting for 26.80% of the country, and 124 species under second-level protection, accounting for 51.70% of the country. In addition, there are 82 species of animals under the key protection of the Guangxi Zhuang Autonomous Region, of which 18 species are endemic to the region. Among the animals, there are 10 species under national level protection and 16 species under second level protection (among them, 6 species of primates are under national level protection and 3 species are under second level protection); the number of species of bird resources accounts for about 45.00% of the national total, of which there are 9 species under national level protection and 78 species under second level protection; 4 species of reptiles and amphibians are under national level protection and 14 species under second level protection; wild fishes are under national level protection and 14 species under second level protection; and wild fishes are under national level protection. Four species of reptiles and amphibians are protected at the national level and 14 species at the secondary level; three species of wild fish are protected at the national level and 16 species at the secondary level. In addition, a large number of plankton, intertidal organisms and benthic organisms grow in the wide mudflats and shallow waters of the Guangxi Zhuang Autonomous Region.
3. Aquatic resources of Beibu Gulf
Beibu Gulf is a high-biomass sea, one of the famous fishing grounds in China, with more than 500 kinds of fishes, 200 kinds of shrimps, 50 kinds of cephalopods, 20 kinds of crabs, and a great variety of shellfishes, other marine animals and algae. The coastal area of the Guangxi Zhuang Autonomous Region is an important fishing area in the Beibu Gulf, with a vast area of shallow sea, fertile water quality and rich marine biological resources. Bounded by the mouth of the Dafeng River, the shallow sea bottom is flat in the east, mostly sandy and sandy mud seabed, except for scattered rock reefs between Weizhou Island and Beihai; in the west, it is mostly muddy and sandy mud. Good bottom conditions, coupled with suitable water temperature and the sea rivers carry a large amount of organic matter and nutrient salts, which provide sufficient nutrients for the reproduction of plankton, which is the main bait for fish and shrimp. There are more than 50 kinds of economic fish in the shallow sea, with a resource of about 6,900 tons; more than 10 kinds of economic shrimps, with a resource of about 8,000 tons; the main economic shellfish, such as pearl oysters, sun and moon shells, oysters, clams, arkshells, pectinated mother-of-pearl and so on, with a resource of about 38,000 tons; the main economic crabs, such as green crabs, pike crabs, and so on; and the main algae, such as Gracilaria, Sargassum, etc. The coastal pearl is dominated by the horse pearl, which is the most important species. Pearls along the coast are dominated by Ma's pearls, and the famous south pearls are distributed in the Yingpan sea area of Beihai, and the areas around Pearl Harbor in Fangcheng and Sanniang Bay in Qinzhou. Abalone is produced in the waters around Weizhou Island and Shiyang Island.
National-level nature reserves include the Shankou Mangrove Nature Reserve, the Hepu Yingpan Harbor-Yingluo Harbor Dugong Nature Reserve, the Beilun Estuary Nature Reserve, and the autonomous-level Weizhou Island Bird Nature Reserve. The coral reefs of Weizhou Island are the only coral reef resources in Guangxi Zhuang Autonomous Region and the northern boundary of coral growth along the Beibu Gulf coast, with 21 genera and 45 species of corals, which are valuable resources.
4. Tourism resources
Guangxi Zhuang Autonomous Region is rich in tourism resources, high grade, wide distribution, many caves and beautiful landscape, known as "no mountain is not a hole, no hole is not strange"; the region's peaks and forests are perfectly developed, which is a typical representative of the tropical karst landforms. According to statistics, there are about 100,000 caves, and in these magnificent and colorful caves, stone milk, stalagmites, stone mantles, stone pillars, stone flowers, stone lotuses, stone forests and so on are full of beauty; and limestone peak forests can be seen everywhere in the northeast of Gui, the middle of Gui, the southeast of Gui, the west of Gui and so on; dozens of peaks higher than 1,500 meters above sea level, with majestic mountain landscapes, majestic mountains, lush forests, beautiful scenery, and abundant resources of animals and plants, which are suitable for scientific research and study. Rich in flora and fauna resources, suitable for scientific research, hiking and climbing; is located in the border between China and Vietnam in the Quichun River upstream of the Detian Waterfall is famous, its waterfall surface is more than 100 meters wide, about 80 meters high, in a three-stacked cascade, the sound of the water roaring, the momentum of the galloping horse, very spectacular. Other famous waterfalls are Bao Ding Waterfalls in Resources County, Lengshui Waterfalls in Longlin Autonomous County, Sanjialing Waterfalls in Jingxi County, Ringshui Waterfalls in Longzhou County, Yingtianfu Waterfalls in Shangsi County, and so on. On the land of Bagui, there are many springs, widely distributed, cold, hot, warm and boiling springs; the coastline is 1,595 kilometers long, there are many islands, the sea water is clear, the sandy beach is clean and gentle, the coastal scenery is very attractive, and the construction of the supporting infrastructure for tourism in the coastal cities is becoming more and more perfect. The main coastal tourist attractions include the national 4A level Beihai Silver Beach Tourism Resort, Beihai Underwater World, Shankou Mangrove Ecological Tourism Area, "72 Jing" Scenic Tourism Area, Maran Island Marine Ecological Tourism Resort, Jintan Jing Ethnicity Tourism Resort, Jiangshan Peninsula Tourism Resort, Hepu South Xingdao Lake Tourism Resort, Lianzhou City Historical, Cultural and Monumental Tourism Zone as well as Weizhou Island and Xiayang Island Tourism Zone.
Guangxi Zhuang Autonomous Region has a long history, with many ancient human beings, ancient buildings, ancient cultural sites, ancient water conservancy projects, stone carvings, tombs and other ancient cultural relics and memorial sites of revolutionary struggles; at the same time, it is also an autonomous region of ethnic minorities where many ethnic minorities live together, and colorful ethnic customs have become a major feature of the autonomous region's tourism industry. Especially in recent years, focusing on the natural scenery represented by Guilin landscape and Baise Dashiwei sinkhole group and other karst landscapes, the coastal charm represented by Beihai Silver Beach, Qinzhou Sanniang Bay and Fangchenggang Golden Beach, the Sino-Vietnamese border excursions represented by Daxin Detian Transnational Waterfall and Pingxiang Friendship Pass, the folk customs represented by Zhuang, Yao, Miao, Dong and other ethnic minorities, as well as Xing'an Spiritual Nullah, Ningming The development of the six kinds of Guangxi Zhuang Autonomous Region characteristic tourism, represented by the mural paintings of Huashan and Liu Sanjie culture, and red tourism, will give full play to the advantages of tourism resources of the Guangxi Zhuang Autonomous Region and accelerate the pace of development of the tourism industry.