Geomorphology and Wetland Landscape

I. Types and distribution of landforms

According to the genesis and morphological characteristics of Huixian karst wetland and its surrounding areas, the landform types of Huixian karst wetland can be divided into normal middle and low mountains, hills and ridges, peaks and valleys, island peaks and valleys, karst slopes and valleys, peak forest (solitary peak) plains and karst wetlands (lakes and swamps). ) (Figure 2- 19).

1. Ordinary low hills

Normal middle and low mountains are mainly distributed in Jiaqiaoling Mountain range south of Huixian County, and are composed of clastic rocks of Devonian Xindu Formation. The mountain is tall and majestic. The elevation of the top of the mountain is mostly between 600 ~ 1200m, and the highest point is Liangsanwei, with an elevation of 1226m (also the highest peak in Huixian karst wetland area). Jiaqiaoling Mountains are distributed in the north-south direction, with high terrain in the south and low terrain in the north, and dense valleys, mostly in the east-west direction and north-south direction, with a relative cutting depth of 300-500 m. The surface water system in this area is developed, which is the main external water supply area in the south of Huixian karst wetland and the birthplace of major rivers in the south of the wetland, such as Liangfeng River, Huixian River and rivers near Luo Jin.

Figure 2- 19 Distribution Map of Geomorphic Types in the Core Area of Huixian Karst Wetland

In the northern Longquan Forest Farm-Livestock Farm-Zhang Cun-Baiyanjiao and other areas, there is a small area of low hills composed of sandstone of Xindu Formation of Middle Devonian, and the elevation of the top of the mountain is generally below 700m, which constitutes the northern surface watershed of Huixian karst wetland catchment. In addition, on the east and west sides of the wetland, especially on the west edge of the wetland west of Fenghuangling-jiepai-Sitang, low hills composed of Devonian and Carboniferous sandstone, siltstone, siliceous rock and mudstone are distributed in the north-south direction (Yangjiaoshan-Zhuliantang-Fenghuangling is the most typical, with a width of 1 ~ 3 km), with an altitude of 300 ~ 600 m and Maanshan-in the east. Low Carboniferous sandstone shale, marl, siliceous rocks and other soft rock formations mostly form hills and ridges that strike nearly north-south, with gentle fluctuation, with an altitude of 170 ~ 250 m, such as typical low hills and gentle slopes such as jiepai-Tuqiao in Sitang Township and Liangfeng Farm-Guilin Horticultural Field in Yanshan Region.

2. Karst peaks and valleys (valleys)

It is mainly distributed in the core of Huangcun-Mamian anticline and the northern oblique end of Jiaqiaoling anticline and its adjacent wing, namely, to the north of Xiguanzhuang (Jiutoushan)-Dulong-Mamian Xu line in Sitang Township, Lingui County, and to the south of Luo Jin-Ai Shan-Huixian Town-Shanwei-Liutang Town in Yongfu County.

To the north of the line from Xiguanzhuang (Jiutoushan) to Dulong-Mamianxu in Huixian Town, the peak cluster of Shishan Mountain is generally 250 ~ 500 m above sea level, with a steep peak, on which there are many layers of karst caves and karst underground rivers. The surface water system is undeveloped, and depressions and valleys of different sizes are distributed between peaks. There are many dissolution pools and underground river skylights at the bottom of large depressions or valleys, which accumulate more water in rainy season and form lakes or swamps.

The peaks and valleys south of Luo Jin-Ai Shan-Huixian Town-Shanwei-Liutang Town surround the normal middle and low mountains in the middle of Jiaqiaoling Mountains, forming an arc protruding northward. The arc-shaped peak-cluster depression (valley) is about 5 ~ 8 km wide. Controlled by the radial geological structures (faults and joints) at the north oblique end of Jiaqiaoling anticline, the surface water and groundwater in this area are mostly distributed in northwest, north and northeast directions. Especially near the contact zone between clastic rocks and carbonate rocks, influenced by the strong erosion and dissolution of external water, karst development is particularly strong, and surface water and groundwater frequently change, forming a typical karst landform with peaks and valleys as the mainstay and rivers alternating with light and dark. The elevation of the top of the stone peak is generally 200 ~ 600 m, which gradually decreases from the front of Jiaqiaoling Mountain to the periphery. During the rainy season, due to the narrow entrance of karst pipeline or surging undercurrent, the flood can not be effectively discharged, and the accumulated water appears in a large depression or inclined valley (such as Jiutu Cave in the southeast of Huixian Town).

3. Island peaks

It is composed of two or more connected stone peaks standing on the plain or water surface (lake, swamp). Most of them are distributed in the transition zone between peak-cluster depression (valley) and wetland (peak-forest plain), which belongs to the transition zone between groundwater and surface water in hydrogeology and the transition zone between surface karst wetland and underground karst wetland in ecological location (* * *). Due to frequent surface and groundwater activities, karst in the island peak cluster distribution area is strongly developed. Typical island-like peak cluster distribution areas, such as Jiutou Mountain near Xiguanzhuang in Sitang Township, Jiashan Mountain near Lingui County, and Lion Mountain near Feng Jia in Huixian Town, are mostly below 1.0km2, and the peak height of Shifeng Mountain is generally 200 ~ 350m, with a relative altitude of more than 50m; There are depressions or ponds between the stone peaks, and a large number of caves, karst springs or underground rivers (such as Jiutoushan Fushan Underground River and Shizishan Underground River, which have been detected for more than 900m) are exposed to the surface, becoming the main water supply source of Huixian karst wetland. Jiutoushan Fushan Underground River and Shizishan Underground River (the detection length is more than 900 meters) are typical representatives.

4. Hilly landform

It is distributed in the east and west sides of the study area, including the long and narrow mountainous areas below 400m above sea level intermittently distributed from Liutanggouhe Bridge-Maanshan-Yanshan-Yanshan Ertang in Lingui County, mostly in the north-south direction, with a width of 0.5 ~ 1 km, and the Luojinli-Sitang jiepai-Sitang Township-Tang Yang line in the west watershed, with a north-south distribution of about 20km. Hillsides and hilltops are gentle, mostly in the shape of steamed bread or strips.

The east and west hills are composed of Devonian-Carboniferous non-carbonate rocks or impure carbonate rocks, which not only constitute the east and west boundaries of Huixian karst closed water storage geological body, but also can effectively preserve (store) water. Many reservoirs built in Xishan provide good conditions for wetland water supply and agricultural irrigation.

5. Peak Forest Plain (Dissolved Plain)

Located in the center of Huixian karst wetland, it is a low-lying plain ground formed by long-term karst, on which there are isolated stone peaks of different numbers and sizes. Among them, Huixian, Mudong, Dulong, Mamian, Li Antang and other places are low and flat, and their plains are generally flat or slightly undulating, with an altitude of 146 ~ 150 m. The lowest point is located in the acacia valley in the western Dawan area, with an altitude of 145m. Isolated stone peaks, island peaks or low mounds or ridges are scattered on the plains. Isolated stone peaks are mostly composed of thick massive limestone, which is brittle and gentle (multi-level occurrence). When they are pulled up from the ground, the surrounding environment is steep and the scale is small (generally within 0.05km2), with the highest elevation of 180 ~ 300m and the relative height of 30 ~ 180~300m. The gentle hills or ridges are mostly composed of dolomite, argillaceous rocks or thin layers of impure limestone, with gentle slopes and gentle tops, and the elevation is mostly below 200m, and there are thick soil layers on them, which are the main dry land crops and planting forest areas in this area. On the other hand, lakes, ponds, aquatic plants and swamps are formed by long-term water accumulation in a large area of low-lying areas on the plain. Rivers and lakes are the main rice growing areas in this area and the core area of Huixian karst wetland.

Qingshui River Valley, Lanqiaobao Karst Valley, flat valley in the upper reaches of Huixian River and Liangfeng River, which are located in Guanzhuang, Dongquan, and Miancun, Sitang Township, Lingui County, are also called karst valley plains. The valley plain is long and narrow, with low and flat terrain on both sides. There are occasional solitary peaks and gentle hills in the valley, and the head or both sides (or one side, such as Qingshui River) of the valley source are peak-cluster depressions. Rivers are mainly supplied by karst underground rivers and karst springs (mostly small seepage karst springs). Due to the low terrain, the drainage of surface water and groundwater at the downstream outlet of the valley in rainy season is not smooth, which leads to flooding in the valley (typical representatives are Xiguanzhuang, Jiutoushan and Dawan in the downstream of Qingshui River).

6. Karst wetland

It is distributed in low-lying areas such as peak-cluster depressions, peak-cluster valleys, peak-forest plains, etc. It is a water area or water-like wet landscape area where the soil is flooded all year round or seasonally or the soil is saturated for a long time, and aquatic or wet plants are flourishing, including karst lakes, karst swamps, aquatic plants, karst reservoirs (ponds) and other types. Typical karst lake landscapes (landforms) in Huixian karst wetland include Mudong Lake, Dulong Lake, Baxian Lake, Miaohu Lake, Li Antang and Fenshui Pond, and typical karst swamps include karst river swamp, Jiutoushan swamp and aquatic plants, Shenlong swamp and Dulong swamp along Qingshui River.

Second, the typical karst wetland landscape

Landscape refers to the overall characteristics of a specific area on the earth's surface. Huixian karst wetland landscape is the crystallization of the integration of karst wetland ecological landscape and karst landform landscape.

Nature's uncanny workmanship has created the karst landform and wetland ecological landscape of Huixian Wetland, which is surrounded by mountains and rivers, with beautiful scenery and changeable patterns. Here, the lake is clear, there is water in the mountains, there are mountains in the water, the mountains are surrounded by water, the water is around the mountains, and the water and the sky are the same; In front of the mountain, the springs are gurgling, the water plants are green, and there are magical caves and underground rivers. It is a typical subtropical karst landscape in the south, with rich tourism resources.

Huixian karst wetland, as a typical and complete karst wetland ecosystem, has high landscape value. Its vast water surface, valleys and lakes in Jiuqu and Shibawan, diverse and rich wetland biological resources and the beautiful karst surface and underground landscape in and around the wetland reflect and blend with each other, forming a unique karst wetland landscape with integrated mountains and rivers. The "Acacia Bay" connecting Liujiang River and Lijiang River built after the Tang Dynasty has added rich historical and cultural connotations and landscape value to the wetland. Therefore, Huixian karst wetland has multiple values of water recreation, sightseeing, entertainment, popular science education and scientific research.

1.

Huixian karst wetland includes Mudong Lake, Dulong Lake, Baxian Lake, Miaohu Lake, Li Antang Lake, Damatang Lake and other major lakes, as well as the wide bends and banks of typical rivers such as Qingshui River.

There are more than 65,438+000 species of wet and aquatic wetland plants in Huixian karst wetland, which are composed of submerged, floating, emergent and wet plant communities, with diverse types, rich levels and obvious zoning (Figure 2-20). Different landscapes are distributed in rivers, lakes and coastal areas. Some characteristic ornamental plants and endangered precious plants increase the ornamental value and cultural connotation of wetlands. At present, wetland plant communities with large contiguous area and high ornamental value include lotus community in Mudong Lake (Figure 2-2 1), mosaic grass community in Mudong Lake and Fenshui Lake around the middle of Longshan (Figure 2-22), Typha longibracteata community in Lake and Mudong Lake between Dulong and Longshan (Figure 2-23), Mudong Lake and Qingshui. Especially in the annual lotus blossom season, it attracts many tourists to watch. At present, the villagers around Mudong Lake have partially developed wetland landscape leisure tourism, but it is still in the primary development stage, and eco-tourism still has important development potential.

Figure 2-20 Plant Coastal Zoning of Hu Si Lake Central Island

Figure 2-2 1 Mu Donglian

Figure 2-22 Crash, China

Figure 2-23 Typha

Figure 2-24 Reed at the intersection of Hu Si exit and Qingshui River

Figure 2-25 Landscape of Colorful Floating Plant Community

2. Karst landform and cave landscape

Including surface karst landscape and underground karst landscape.

The surface karst landscape includes typical peak-cluster depression landscape (Figure 2-26), karst peak forest plain (wetland) landscape (Figure 2-27), island peak cluster (Figure 2-28) and various forms of karst peak cluster (tower peak, cone peak, etc. ) and dissolution form (Figure 2-29).

Figure 2-26 Peak Cluster Decline

Figure 2-27 Geomorphology of Peak Forest Plain (I)

Figure 2-27 Geomorphology of Peak Forest Plain (II)

Figure 2-28 Island Peak Cluster

Underground karst landscape includes karst underground river, karst cave system, karst tiankeng and so on. There are many caves and underground rivers in Huixian wetland and surrounding karst hills. Various cave sedimentary landscapes, such as stalagmites, stalactites and stone pillars, formed by dissolution in underground river cave system are also important components of karst wetland landscape and important tourist landscape resources, which have high protection and development value. Among them, the Shizishan underground river (total length is about 1 100m, which has been measured about 800m) and its related cave systems such as karst tiankeng (underground river skylight), Bayin (immortal) rock, ancient fairy cave, etc. Fushan underground river in Xiguanzhuang, Sitang Township (about 200 meters long) and the upper cave; The Eddie Underground River in Sitang Township, the full tunnel underground river and its surrounding caves, the Mamian Underground River in Huixian County, and the Shendong Underground River Group in the south of Luojin in Yongfu County (Jinzhongshan Scenic Area has been developed) have good development prospects (Figure 2-30).

Figure 2-29 Karst landform landscape

Figure 2-30 Underground Karst Landscape

3. Comprehensive karst wetland landscape

Huixian karst wetland is different from ordinary rivers, lakes (reservoirs) or swamps, and it is also different from the general karst landscape widely distributed in China. The beauty of its landscape lies in the mutual integration and interaction of its mountains (karst landscape), water (wetland lakes, rivers and swamps), forest (wetland ecosystem) and pastoral (artificial landscape) (Figure 2-3 1). Can be divided into the following comprehensive landscape:

Figure 2-3 1 Panorama of Huixian Karst Wetland

(1) Lake forest, lake and swamp wetland landscape

It is distributed in the peak forest plain between Li Antang and Mushutou in Yanshan Mountains, and there are many swamps or ponds in the low-lying areas between lakes or gentle hills and valleys, where various wet and aquatic plants are growing. Trees and woodlands dominated by Pinus elliottii (Figure 2-32) grow on the lakeside or high swamp with gentle hills (slightly higher than the lowest water level), forming a wetland ecological landscape with a pleasant climate, which integrates karst buttes, waters, swamps and forests. Because of the low terrain, forests will be flooded by seasonal floods in rainy season.

Figure 2-32 Forests, Lakes, Marshes and Wetlands

(2) Comprehensive landscape of rivers and lakes

It is a comprehensive landscape with organic integration of rivers, lakes and karst landforms. According to the spatial distribution and landscape composition of rivers, lakes and karst landforms, it can be divided into many types, such as mountain ring, water ring and landscape reflection, forming a variety of landscapes or picturesque pastoral scenery with "water in the mountains, mountains in the water and landscape reflection".

Mountain-ring river and lake landscape: also known as "Stone Mountain Pearl", refers to the karst area around Huixian karst wetland, mainly composed of karst peaks and rocks. Because the underground water level is at a high level all the year round (generally 1 ~ 3m below the ground), large karst ponds with perennial water accumulation are formed in hills, lakes, ponds or swamps, and the bottom is sometimes poorly drained all the year round. In rainy season, many depressions or valleys (slopes and valleys) around Huixian karst wetland are flooded in a large area. These mountains, rivers, lakes, ponds or dissolved pools are like "pearls" embedded among mountains, which are reflected by the river winding through and connecting the "pearls" in series to form a beautiful landscape with mountains and water. Typical "Stone Mountain Pearl" around Huixian karst wetland includes Quandong Mountain Lake (waterlogged depression), Jiutu Cave Waterlogged Valley, Lion Lake and Baxian Lake (Figure 2-33 and Figure 2-34).

Figure 2-33 "Stone Mountain Pearl"-Lion Pond

Figure 2-34 "Stone Mountain Pearl"-Eight Immortals Lake surrounded by mountains

Watershed —— Landscape around rivers and lakes: Also known as "aquatic peak forest", it refers to a flat and low-lying peak forest plain with water areas (lakes, swamps and rivers) as the main body, with isolated stone peaks (mostly distributed in the center of peak forest plain and wetland ecological landscape) or conjoined stone peaks (island peaks, mostly distributed at the edge of peak forest plain and wetland ecological landscape), that is, the transitional zone between karst plain and mountainous area. The representative landscapes of "Shuifeng Forest" include Jiutou Mountain Flood Peak Forest Plain Landscape (rainy season), Longshan-Mudong Lake Landscape in Huixian County, Shuifeng Forest Landscape in Fenshui Reservoir, etc.

Some stone peaks in plain or lake waters, such as Phoenix Mountain, Lion Mountain, Elephant Trunk Mountain and Qilin Mountain, have unique shapes and single peak types, which further enhance the landscape appreciation of wetlands. In particular, the typical "water peak forest" landscape composed of island peaks such as Lion Mountain, Gufeng Stone Mountain, Baxian Lake and Fenshui Lake, combined with the ecological landscape of wetland plant community, is more vivid and more ornamental than the "Water Guilin" in Halong Bay, Vietnam.

River and lake landscape: refers to the reflection landscape formed by the mutual reflection of rivers, lakes and adjacent karst mountain landscapes and the reflection of mountains on clear water. Huixian karst wetland includes many landscape types, such as pastoral scenery, lakes and rivers.

There are lakes in Huixian karst wetland at present, with a total water area of about 5km2, and the average depth of main lakes is mostly below 2m. The lake is clear, leafy, shaded by willows on both sides, fragrant with rice and melon, and together with the river ditch connecting the lake, it constitutes a beautiful scenery of Jiangnan water town. They are integrated with the surrounding karst rocky mountains and various types of wetland plant communities, and the mountains are reflected in the clear lake water, forming a wetland natural landscape integrating lakes and mountains, natural ecology and pastoral scenery (Figure 2-36 to Figure 2-42).

Figure 2-35 Shuifeng Forest

Figure 2-36 Landscape and Pastoral Scenery of Peak Forest Plain in Huixian County (Wooden Cave)

Study on karst wetland ecosystem in Huixian county

Study on karst wetland ecosystem in Huixian county

Figure 2-37 Landscape of Mudong Lake in Huixian County-Qingshan Reflection

Figure 2-38 Landscape of Mudong Lake in Huixian County-lakes and mountains.

Figure 2-39 Landscape of Mudong Lake in Huixian County-Fairy Gathering

Figure 2-40 Lakes and Mountains (1)

Figure 2-4 1 lakes and mountains (2)

Figure 2-42 Green mountains, green waters, blue sky and white clouds

There are many rivers in Huixian karst wetland, and the riverside landscape is beautiful. Rivers with tourism development value include Qingshui River, Guguiliuqu, Mudong River and Liangfeng River. Among them, Qingshui River originates from the bottom of Miancun Village in Sitang Township, and meanders in lakes and swamps such as Hu Si Lake and Dong Quan Marsh, with clear water quality and beautiful scenery (Figure 2-43). Mudong River, like a ribbon, has successively passed through Dulongtang, Mudong Lake and other lakes and swamps and Jiutoushan floodplain wetland. The rivers are criss-crossing, winding and changeable, and the river is clear. There are all kinds of submerged plants, fish and shrimp, wetland aquatic vegetation communities such as reeds and cattails with beautiful pastoral scenery and well-maintained ecological environment on both sides of the river, and wide and flat floodplain swamps. The karst landforms of the mountains on both sides of the river are reflected in the clear river, creating a beautiful scenery of "boats walking in the mountains and people swimming in the water" (Figure 2-44). Acacia Belt is an artificial river with a long history, which runs through the whole Huixian karst wetland from east to west, connects Guangxi (Lijiang River) and Liujiang River system, and adds profound cultural heritage to the wetland landscape (Figure 2-45). The cool breeze river originated in Jiaqiaoling, and the typical karst river landscape on both sides of the middle and upper reaches makes people linger (Figure 2-46).

(3) karst swamp wetland landscape

Karst swamp is the largest wetland in Huixian karst wetland, and it is the main body of wetland. It is also the main living area of many national precious protected plants such as common wild rice and Chinese Isoetes, and the important habitat of some precious animals such as egrets (national protected birds).

Figure 2-43 Qingshui River Scenery

Figure 2-44 Wooden Cave River with Beautiful Scenery

Figure 2-45 East of Nansitangqiao Ancient Canal

Figure 2-46 Beautiful Liangfeng River (upstream section)

There are various types of karst wetlands in Huixian County, including beach swamps distributed in karst canyons or estuaries or inter-river plots, lakeside swamps distributed in low-lying areas of karst peak forest plains, and aquatic plants fields distributed in front of underground estuaries, karst springs or scattered karst Koizumi Group (Figure 2-47). The swamp accumulates water all the year round, and the soil is loose and fertile. During the rainy season, a large area is flooded, and most of the time the ground is muddy and difficult to pass. Plants are mainly wet plants, such as millet, willow and Alternanthera philoxeroides, which are suitable for scientific investigation, ecological leisure and exploration of field biodiversity and ecology, soil and sediments, hydrogeology and so on. It is suggested that it should be carried out in autumn and winter, and route crossing exploration is the best way.

Figure 2-47 Swamp