Investigations and Prediction of Vegetation changes and Corresponding Sediment transport Characteristics in Guandu Nature Reserve

The aerial photographs from 1986 to 2002 were used to analyze and predicted the
temporal and spatial variations of the vegetation changes in Guandu Nature Reserve.
The results revealed that the marsh habitat, dominated by Cyperus malaccensis Lam.
and Phragmites communis (L.) Trin, has changed into a swamp habitat, dominated by
Kandelia candel (L.). The coverage area of Kandelia candel (L.) has increased from 7.2
hectares in 1986 to 23.8 hectares in 2002. It causes significant impacts upon the
ecosystem and flood control operations. GIS-based technique has been used to
determine the vegetation changes in this area. TABS-2, a horizontal two dimensional
sediment transport simulation model, can be utilized to evaluate the sediment
transport characteristics of this estuarine wetland.
The Shannon’s diversity index decreased from 0.98 in 1986 to 0.77 in 2002.
Additionally, the Shannon’s evenness index also decrease form 0.77 in 1986 to 0.5 in
2002. We have concluded that the habitat diversity became lower and lower and will
be unbenefited to water birds.
Significant sediment deposition occurs due to the extensive root network of Kandelia
candel (L.) Druce. The average deposition is about 33 mm during a 200 years return period
flood event. Removal of Kandelia candel (L.) Druce is able to reduce the sediment deposition
rate. When the removal ratio reaches 20%, the reduction in sediment deposition is about 5
mm. It is also found that mangrove remove will improve the ecological restoration of Uca
(Thalassuca) Formosensis Rathbun which is an endemic species of the fiddler crab in Taiwan.