Geographical Environment of Baiji Dolphin National Nature Reserve in Swan Island, Hubei Province

The geographic coordinates of Hubei Yangtze River Swan Island Baiji Dolphin National Nature Reserve are11213'-12 48', and 29 30'-29 37' north latitude. Swan Island is the old path of the Yangtze River, located on the north bank of the Yangtze River about 20 kilometers downstream of Shishou City. The total length of the old road is 20.9 kilometers, and the water surface area is 18 ~ 20 square kilometers, which is connected with the Yangtze River in flood season. Hubei Yangtze River Swan Island Baiji Dolphin National Nature Reserve is located in the southern edge of Jianghan Plain. Due to the low terrain, the swing and erosion of the water, the Yangtze River has formed a unique landscape of Jingjiang River, which has left many old roads (oxbow lakes) after natural or artificial bending and straightening. The old road of Swan Island was formed by natural bending and straightening at 1972. The old road is crescent-shaped around Swan Island, oval-shaped, and the southeast side is connected with xiaohe town in dry season, which is peninsula-shaped; It was completely surrounded by the old road during the flood season.

Tianezhou wetland has the lowest water surface of the old road, and the shoal of the old road gradually increases to the river bank. The average altitude is generally about 35 meters, with the highest point of 38.44 meters and the lowest point of 32.9 1 meter, and the relative height difference is not large. The annual river flood, coupled with the top support of Dongting Lake, reduces the velocity and silts up, forming a large reed swamp wetland. The repeated oscillation of the Yangtze River channel has formed an old channel of "nine bends and ileum" here, leaving a precious wetland ecosystem based on a large reed swamp. The reserve covers an area of 23,000 mu. According to experts' investigation, there are 100 kinds of plants in the nature reserve that can be used as food for elk. The annual biomass of these plants is more than 6000 tons, which is enough for 1000 elk. There are more than 400,000 mu of swamp wetlands around the reserve. Hubei Yangtze River Swan Island Baiji Dolphin National Nature Reserve belongs to subtropical monsoon climate. The total annual solar radiation in the nature reserve reaches 106 kcal/cm2, which can fully meet the needs of plant photosynthesis. The total sunshine hours in the whole year are 65,438+0,844 hours. There are many sunshine hours in summer and early autumn. In 7 months (April-65,438+0.00), the monthly average sunshine hours reached 265,438+0.5 hours, and the annual average sunshine hours were more than 5 hours per day. The most "monthly sunshine" is in July, which is 3 18.8 hours, and the least "monthly sunshine" is in June, which is 25.7 hours, with an average annual sunshine percentage of 42%.

The annual average temperature in Hubei Yangtze River Swan Island Baiji Dolphin National Nature Reserve is about 65438 06.5℃, the average temperature in the hottest month of July is about 28.5℃, and the extreme maximum temperature is about 38.6℃. 1 1 month, the average temperature in Leng Yue is about 3.5℃, the extreme minimum temperature is-14.9℃, and the active accumulated temperature above 0℃ reaches 6000℃. The annual frost-free period is 26 1 day, exceeding the average of 258 days in Shishou city. Winter is controlled and influenced by strong Mongolian cold high pressure, with northerly winds and cold and dry weather; Summer is influenced and controlled by the Pacific subtropical high and the Indian Ocean thermal low, with southerly winds and hot weather. In spring, early summer and late autumn, cold and warm air from the north and south often meet in the middle and lower reaches of the Yangtze River, resulting in more precipitation, and spring rain, plum rain and autumn rain often appear.

The annual precipitation in Hubei Yangtze River Swan Island Baiji Dolphin National Nature Reserve is above 1, 200mm, with the highest in June, reaching about 1, 9 1mm, and the lowest in June, reaching only about 30 mm. The annual average absolute humidity 17.4 mbar, and the annual average relative humidity is about 80%. Over the years, the average rainfall from March to August 100 mm or more, and the total rainfall from April to June was as high as 859.7 mm, accounting for 74.5% of the total annual rainfall.

Shishou City, where the reserve is located, has 13 kinds of disaster weather: rain and shower, cold wave, low temperature, strong wind, snowfall, blizzard, hail, lightning, fog, frost, frost and so on. Among them, drought, waterlogging, wind and freezing are four kinds that deserve enough attention in the reserve. phytoplankton

1997 Hubei Fisheries Research Institute set up five sampling points according to the horseshoe shape of Swan Island, and monitored the phytoplankton in the waters of the nature reserve for three times in May, August,165438+1October. Seven phyla of phytoplankton were detected from the collected water samples, and the detected species were as follows. Dominant species in each month: green algae and diatom in May; August is chlorophyta and cyanophyta; 165438+ October is diatom. From the microscopic examination results, the species proportion of Chlorophyta and Cyanophyta is the highest, and the species proportion of dinoflagellate is the lowest. If the algae in each phylum are arranged from less to more, the order is dinoflagellate.

Wetland vascular plants

1997 to 1998 investigated the aquatic and wet plant resources and vegetation in the Baiji Dolphin Nature Reserve in Swan Island, the old channel of the Yangtze River. The investigation scope mainly covers the seasonal submerged wetlands in the waters and shores. Collect plant specimens, classify and identify them, consult relevant documents and materials, and sort out the list of plants in nature reserves. There are 69 species of higher plants belonging to 59 genera and 30 families, including bryophytes 1 family 1 genus 1 species and ferns 1 family 1 species. Angiosperms belong to 28 families, 57 genera and 67 species.

According to the number of species in each family, there are 1 3 families with seed plants1species, accounting for 46% of all seed plants,1species with 2-4 species, accounting for 29.3% of all seed plants, and 4 families with more than 5 species, accounting for1species of all seed plants. The largest family is Compositae with 8 species, followed by Gramineae with 7 species, accounting for 2 1.7% of all species. According to the subordinate statistics, there are 53 genera 1 species, accounting for 9 1.2% of the total genera. Ranunculus has the most species, followed by POTAMOGETON, with 3 species, which are the dominant genera of wet plants and aquatic plants, accounting for11.99 of the total genera.

(1) Metasequoia glyptostroboides plantation, existing in Guti, mainly distributed on the bank of Swan Village, with a large area of water, zonal distribution, and a preference for wet habitats, interlaced with Taxodium ascendens plantation.

(2) Populus euphratica artificial cultivation forest is the main berm forest in the reserve, and it is on the right bank from the upper mouth to the middle (reserve management).

(3) The artificial willow forest is planted near the water's edge, continuously distributed in the dam of the village section of Mushanghekou, with a length of 4km, and has strong flood resistance. (4) The artificially cultivated Taxodium ascendens forest is strip-shaped, intermittently distributed on both banks near the water's edge, and embedded with Taxodium ascendens forest, which is small in area and also resistant to waterlogging.

submerged plant

(1) POTAMOGETON bambusae community is the absolute dominant species of aquatic vegetation in this area. It is distributed continuously in a strip shape at about 5- 10 m off the coast of Heding, with a bandwidth of 5- 10 m. It is distributed in a large area in Hekou Village Shoal of Shangkou Port, covering the whole water surface in dry season. The composition of the community is relatively simple, with mixed spike fish and black algae. The absolute dominant species of POTAMOGETON bambusa in difficult cost areas is related to the clear water quality, poor nutrition and hard sediment in the old course of the Yangtze River in Swan Island. (2) The Myriophyllum community zone is distributed in the Potamogeton bambusae zone, with a bandwidth of 15-20m. Plant roots are deep, about 3-4m, but mainly occupy the upper water body, which is occupied by Sophora alopecuroides and Ceratophyllum. (3) The community of Kuroshio+Potamogeton crispus distributed in a strip shape in POTAMOGETON bambusae, and the water depth was shallow, about 1-2m. Many spirogyra are often distributed in the community in the form of smoke, which affects the photosynthesis of plants and is very harmful in water. Appropriate measures should be taken to control it. (4) The rush community is widely distributed in the shoal of Hekou Village, Shangkou, with a water depth of about 1m, and it stands out from the water in the dry season, accompanied by rush and rice fields of broken rice. The unique geographical and climatic conditions of Hubei Yangtze River Swan Island Baiji Dolphin National Nature Reserve provide a good habitat for all kinds of terrestrial, aquatic and amphibious animals. According to statistics, there are 23 1 species of terrestrial vertebrates in this area. Among them, birds 14 order, 33 families, 20 1 species, mammals 13 species and amphibians, 3 families 12 species. 50 species of fish, belonging to 7 orders 1 1 family; 26 species of benthos; There are 54 species of zooplankton.

Swan Island old stadium is rich in bait, with superior hydrological conditions, water quality close to the Yangtze River, and basically no pollution. Because the old road used to be the distribution area of the national first-class protected wild animal Baiji dolphin, the nature reserve can be an important base for protecting and restoring the semi-natural Baiji dolphin population. The reserve is protecting the baiji ex situ, and successfully captured a baiji from the Yangtze River and put it into the old waterway of Swan Island. But he died after hitting the net in the flood.

197 A total of 54 species of zooplankton were detected by Hubei Fisheries Research Institute * * *, of which 22 species were protozoa, 5 species were rotifers 18, 5 species were copepods and 9 species were cladocera, accounting for 40%, 33.3%, 9.3% and1respectively. Protozoa are mainly Carniptera, rotifers are mainly Brachionus and Brachionus, and Cladocera are mainly Lepidoptera, Cyclops, Daphnia and Daphnia.

After collecting benthos for three times, * * * collected a total of 26 species of benthos, including 8 species of oligochaeta, 4 species of aquatic insects, 0/2 species of molluscs and 0/species of other animals.

Fish 1997 According to the investigation and statistics, the catch of Baiji Dolphin National Nature Reserve in Swan Island, Hubei Province from June 5438 to October-September was 87.4kg, belonging to 50 species of 7 orders 1 1 family, including 30 species of CYPRINIDAE, including 3 species of loach, 4 species of perch, whitebait and fish.

There are 3 families and 5 species of amphibians 1 order in Tianezhou Gudao Wetland Nature Reserve. The five amphibians found in the nature reserve can be divided into two ecological groups, among which Rana chensinensis, Rana nigromaculata and Rana Luzer belong to the type of still water habitat, and the latter two are more abundant. In the shallow water covered with wormwood in the nature reserve (not the old road), their calls and the sound of jumping into the water on the shore can be heard constantly; The second ecological group is the giant salamander, the frog in Luze and the decorative frog. In a slightly higher place covered with reeds, many Ruze frogs can be found. On the land covered with wormwood around shallow water and residential areas, a giant salamander can be found in almost a few steps, and the density is very high.

There are 3 orders, 6 families 12 species of reptiles in the wetland reserve of Swan Wet Ancient Road. Three orders are: tortoise, lizard and snake; These six families are freshwater turtles (turtles) and soft-shelled turtles (soft-shelled turtles) of Tortoise, Eupolyphaga sinensis (Eupolyphaga sinensis) and Gecko (Gecko verrucosa) of Lizaraceae, Ophiopogonidae (red snake, king snake, black-browed snake, tiger-spotted snake, squirrel snake and Zaocys) and Agkistrodon.

There are 0/3 species of mammals/kloc-belonging to 6 orders and 8 families in Swan Island Wetland Elk Nature Reserve. Baiji dolphin and elk are national first-class protected animals, and Yangtze finless porpoise is second-class protected animals.

There are birds 14 orders, 33 families and 20 1 species in Tianezhou Wetland Elk Nature Reserve, including 6 species under national first-class protection and 7 species under second-class protection.