Wetland Flora In Taijiang National Park
A typhoon in 1823 brought heavy rains for 20 consecutive days. Zengwen River, flowing down from Alishan Mountain, carried a large amount of soil and rock into the Taijiang Inland Sea, which rapidly changed the landform of the Taijiang Inland Sea. The explosive flood caused Zengwen River to divert its course, and a large amount of siltation made the floating soils of the inland sea submerge. The land cover quickly emerged. Tainan, the seat of Taiwan Prefecture, which was originally located by the sea, was extended by forty miles. Therefore, the landform we see in many places today has existed for less than 200 years. The coastal area where Taijiang National Park is currently located was formed at a later period. Sicao as an example did not appear on the map a hundred years ago. The plants here are mainly seaside plants. In the dramatic process of land forming, the mangroves and their associated plants that first appear after silting provide food and habitat for all kinds of wetland creatures. Through the process of aquafarming and salt production, large amounts of salt marsh plants such as reeds, Suaeda nudiflora, Indian Pluchea (Indian Camphorweed) started growing. The beaches along the coast of the Taijiang River have always contained large amounts of beach morning-glory, spinifex, coastal jack-bean, shoreline purslane, and seashore paspalum. It is also home to plants such as beach cabbage and Taiwanese puncture vine. In the ostensibly simple coastline flora, each plant has evolved into a unique way to survive and thrive in this evolving and fickle sea.
In this national park and surrounding areas mostly featuring wetland ecosystems, the results of the plant survey were 507 species of vascular plants, 6 species of endemic plants, and 227 species of native plants, of which naturalized plants and cultivated plants accounted for half. This indicates that during 200 years of settlement in the area, it has always been an ideal place for fishermen to reclaim land for economic development and utilization, such as agricultural cultivation and drying of salt.
Like the ancestral inhabitants of this island, many plants in Taijiang drifted here with the sea. As the Kuroshio (black current) flows across the oceans, they settle down and take root on the new floating land of the inland sea of Taijiang, opening up a new world. These sea drifting plants that drift to this land by natural forces are classified as native species, such as sea hibiscus, white mangroves, black mangroves, nicker nut caealpinia, wood gossip caesalpinia, common derris, sea cabbage, Asiatic colubrina, beach morning-glory, coastal jack-bean, vigna marina, Ipomoea imperati, Taiwanese puncture vine, beach moonflower, etc. Among them, the black mangroves can travel long distances in the sea for a long time to find a suitable habitat to sprout.
Take the Chengxili area on the northside of Luermen River as an example. Since the Japanese era, windbreak forests have been widely planted as seawalls. At present, the main species in the forest is Taiwan scouring rush and Casuarina equisetifolia (beefwood). The fruits of the black mangrove tree drift along the canals and ditches and start to grow in rows. Many rare plants in the windbreak forest grow in the sunlight in the gaps under the forest, including the swamp shield-fern, beach moonflower, nicker nut caealpinia, wood gossip caesalpinia, and Asiatic colubrina, etc.
The Asiatic colubrina was previously only distributed in the Hengchun Peninsula and on Orchid Island. The Taijiang National Park Management Office conducted a field survey in 2019 and found this plant species growing among the windbreak forests of Chengxili, creeping up a beefwood tree to the height of 20 meters. The thriving plant was an extraordinary sight, considering it is a rare plant species.
Other rare drifting plants that are thriving in Taijiang National Park include the Ipomoea imperati, commonly known as the beach morning-glory. This plant is hard to find along the sandy coastlines of Taiwan. However, this elegant and slender plant has been found to be thriving under the sandy embankments of Chengxili. The seeds of the beach morning-glory are light and the surface is densely covered with long hairs, which can float on the water; the leaf shape comes in many varieties and has a waxy surface, which can prevent water evaporation, making the plant impervious to the hot sun and cold winds. Therefore one can often see this plant bravely growing along the coastlines of the beach alongside the seahore vine morning-glory.
These plants that grow after drifting here have unparalleled vitality and can survive all kinds of adversity, shaping the rich plant diversity in the Taijiang area, which is worth admiring and savoring.