| Summary: | 碩士 === 國立中興大學 === 植物學系 === 86 === Tachiashi is one of the principal rivers in center Taiwan.
It originates in Hsueshan and Nanhutashan of Central
Mountains of Taiwan, and it flows into Taiwan Strait passing
over 124 km. The plants of riparian vegetation
are growing on the sides of both riversides and
riverbed. Their growth are influenced by the periodic flood.
Those sites are eroded by river water in the rainy season and
are arid in the droughty season.Therefore, the diversity of
those plants are dependent upon their environmental
conditions. The riparian plants are tolerant toward wateriness
and drought. The composition of riparian vegetation and the
distribution of riversideplants in the middle and downstream
areas of Tachiashi were investigated by employing the line-
transect sampling method at the fifteen plotted sites. The
vegetation distribution may be divided into two types : (1)
downstream- area vegetation and (2) middle-area vegetation. The
former is characterized by its higher richness in plant
diversity and having some dominant species : Saccharum
spontaneum , Pennisetum purpureum , Rhynchelytrum repens ,
Bidens pliosa and Brachiaria mutica ; the latter lower
richness and having various vegetation composition in the
different plots. According to the
growing locations , riparian vegetation can be categorized
into three types of distribution patterns. (1)
Watercourse-tolerant distribution pattern , e.g. Saccharum
spontaneum which is a perennial herbaceous plant growing
near the river and propagating by its subterranean stems.
(2) Widespread distribution pattern, e.g. Bidens pilosa
,propagating by its seeds and widely distributing in riparian
area by means of the highly germinating rate of seeds
dispersed by animals or wind . (3) Specialized
distribution pattern , e.g. Arundo donax var. coleotricha
and Miscanthus floridulus , appearing in the special sites
where probably have a proper disseminating environment.
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