美工圖片   Investigation of Current Status in Lan-yang River System (Water Resources Planning Institute, WRA, MOEA. April, 2004)

The purposes of this two-year study are to compile ecological information and current status on the Lanyang River System in order to provide a basis of for ecological engineering planning and an establishment of ecological resource database. Our first year focused on the main river and the second year on the connected streams within the watershed. In addition to the compilation of abiotic factors (river physical information, water pollution index, human construction and recreation usage), we conducted seasonal biological surveys in aquatic ecosystem on algae, aquatic insect, shrimp, crab and freshwater fish, and in terrestrial ecosystem on riparian vegetation, mammal, bird, reptile, amphibian, and butterfly.

A ground survey with the aid from remote sensing imagery indicated that the riparian areas were highly disturbed by human. The up-stream areas were developed as the high-mountain vegetable agriculture, while in the down-stream regions, urbanization was evident. The water pollution condition is low to medium, based on the standard by the Environmental Protection Administration. There are many recreation spots within the watershed.

Lanyang River Basin
 

A total of 462 species of plant was found. Of these, 30 species are endemic. There are only four rare species (Albizia julibrissin, Entada pursaetha, Juglans cathayensis, and Vanilla albida) in the study area. Overall, vegetation community in this watershed is influenced by the vegetation height and topography. Current vegetation types include forest community, tall grass community, short grass community and aquatic plant community. We identified plant species that are suitable for landscape and ecological planning in this region.

In the aquatic ecosystem, we collected 36 species of fish, 12 species of shrimp and crab, 33 species of algae, and 36 genera of aquatic insect. Overall, the species show gradient changes from the up-stream to down-stream. Some species (i.e., shrimp and crab) showed a seasonal abundance pattern due to the migration, while most of the species maintained a fairly constant population size. There are 8 endemic freshwater fish species. There are also 6 exotic fish species.

In the terrestrial ecosystem, there are 28 species of mammal, 124 species of bird, 20 species of reptile, 16 species of amphibian, and 117 species of butterfly. In general, most of the species are typical animals that represent the ecological status in this region. There are 22 endemic species and 32 conservation species along the Lanyang River and its tributes. Some of them, especially bird and butterfly, can be used as indicators for future resource monitoring.

 

Itea parviflora Hemsl.

Cunninghamia konishii Hayata

Tetrastigma umbellatum (Hemsl.) Nakai

 

A resource database based on GIS technology was compiled. In the database, various layers of abiotic and biotic factors were digitized. These maps include administration, topography, river, human development, water survey, pollution index and biological resources. A web-based query system was also established and installed. Users can access these pages from remote computers.

Oriolus traillii

The current ecological status in the Lanyang River System indicated strong human disturbance. To better protect the biodiversity in this region, we provided various recommendations on how to design and manage the river resources. Especially, we proposed an ecological monitoring scheme for the potential sand/rock extraction operation.

Our work on the current status in the Lanyang River System is only a beginning for effective management of the natural resources in this region. We expect similar work can be conducted in other rivers of Taiwan in the near future, and these data can be compiled in a well-designed database. These status reviews should provide a starting point for our river management work and, thus, a better environment for future generations.

Paguma larvataManis pentadactylaRhacophorus moltrechtiTakydromus formosanus