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南澳神秘湖自然保留區湖沼演替隻脈衝穩定性理論探討
Study on the Pulse Stability of the Succession of the Lacustrine Ecosystem in the Sheng-Mi Lake, Nau-An, North Taiwan
摘要
脈衝（Pulse）是指「產品逐漸累積的轉變與極端消耗的一段很短的時間，這將物質回收提供為另一個循環的生產與消耗」。Odum（1969）提出脈衝穩定性（Pulse Stability）理論，指出脈衝現象使得生態系發展維持在年輕與成熟狀態間擺盪，形成一種特殊之動態的穩定狀態。南澳神秘湖自然保留區，集水區林相完整，無人為開發行為，適合瞭解自然湖泊演替發展。如以植群初級演替的推論，則神秘湖應朝向演替後期前進，未來湖將逐漸長滿挺水植物之東亞黑三稜及水毛花，最終必全面淤積而達湖泊之死亡期，同時未來的40年或以上，會發育為水社柳－赤楊型，並終至湖泊消失。然而，以Odum之脈衝穩定理論觀點，神秘湖可能因為暴雨洪水，維持動態的脈衝穩定狀態。本研究應用1980年起迄今的各類的遙測資料，進行水生植物區域範圍的判讀，瞭解其歷年的變化情形，以探討神秘湖演替的方向。結果顯示開闊水域、與各類植物類型面積呈現約20年週期之循環消長情形，並以餘弦函數回歸分析得到開闊水域面積的逐年消長變遷之推估函數，其推估誤差在3%內。因此，本研究初步推論神秘湖在近數十年之演替應較符合脈衝穩定理論，並台灣地區暴雨與颱風頻仍，脈衝穩定現象應為湖沼之普遍現象，建議湖沼生態系保育上，應考慮脈衝機制對於生態系演替之影響。
並列摘要
”Pulse” means ”alternation of the gradual build-up of production and a short period of frenzied consumption that recycles materials for another cycle of production and consumption”. Odum (1969) proposed the ”Pulse Stability” theory, that pulses maintain an ecosystem at some intermediate point in the developmental sequence, resulting in a compromise between youth and maturity. The Sheng-Mi Lake is located in Nan-Au Natural Reserve, North Taiwan, surrounded with a well-developed virgin forest. According to the vegetation succession theory, the Sheng-Mi Lake was gradually silting up, would success to the Willow-Alder vegetation type in 40 years, and eventually would become a forest system. However, according to the ”pulse stability” theory, the lake may maintain its current status due to the pulses caused by frequent storms and typhoons, the typical weather types in Taiwan. The possible succession of the Sheng-Mi lake ecosystem was studied using the recent remotely sensed data from 1980 to realize the temporal changes of the areas of the open water and different vegetation types in the lake. The results showed a near 20-year cycle of the area changes of the open water and vegetation types. The relation between the open water area verse time could be regressed as a cosin function within 3% estimated errors. Therefore, the ”pulse stability” can be considered as appropriated in a time scale of decades in the Sheng-Mi lake. Frequent storms and typhoons is the typical weather pattern in Taiwan, so the influence of pulses caused by them should be normal to the wetlands in Taiwan. The conservation and restoration of the Taiwan wetlands should well consider the mechanism of pulses.