云南洱海水生植被

AQUATIC VEGETATION IN LAKE ERHAI, YUNNAN

洱海是云贵高原上第二大湖泊。其周长117公里,平均深度10.5米,最深 20.5米。湖内共有40种植物,其中18种为沉水植物。植物区系以眼子菜科植物为主(计8种),是洱海多数群落的优势种;云贵高原湖泊植物区系的特征成分海菜花在洱海占有重要地位。洱海植被由12个群落组成,其中1个挺水植物群落,1个浮叶植物群落,10个沉水植物群落。

Erhai is Yunnan-Guizhou Plateau's second largest lake,lies at the east hillside of the Dian-cang Mountain extending from 100°05' to 100°17'E,and 25°35' to 25°58'N.The Lake, 1974m in elevation,measures 250km2 at the surface. The water volume amounts to 282×107ma. The depth averages 10. 5m,the deepest measurement being 20. 5m. Since 1970s being in a state of imbalance between income and expenditure the water level descended 2. 73m. thus ecosystem in Erhai has changed clearly.Analysis of water samples indicated that Erhai's waters are still clean. In 1983 the water average transparency is in 4.0m, the pH value 8. 10-9. 05, the dissolved oxygen content 5. 31-9. 33mg/l.The aquatic flora of Erhai consist of 40 plant species (table) among which dominated submerged plants amounting 18 species and sharing 45% of total number such as Hydrilla verticillata. Ottllia acuminata,Vallisnuria gigantea ,Potamogeton maiackurnus and so on.The principal vegetation types of Erhai are grouped into the following communities.. L Com munity Zizania caduciflora,2. Comm. Trupu + Myriophyllum spcatum.3. Comm. Potumogeton erispus. 4. Comm. P. nialmnus, 5. Comm. P. lucens 6. Comm. P. perfoliatus, 7. Comm. Ottelia ucuminata, 8. Comm. Myriophyllum spicatum,9. Comm. P. maackianus,, 10. Comm. Hydrilla rerticillata, 11. Comm. Ceratophyllum demersum,12 Comm. Vallisaneria gigantea. The basal characteristics of these communities, for example .the dominant species.stratification .frequency .coverage.are described .and the distribution of communities is shown in figure.Since 1970s the changes of Erhai's vegetation are very clear; the coverage of vegetation is increased,the density of some communities is growing with each year.some dements of aquatic flora in Erhai are destroyed,the community Ottelia ncumaiata is failing, while the growth depth of other species.e. g. Vallisneria gigantea,in Erhai has gone up to 7. 0m.