本研究利用農林航測所1983、1989、1991、2002年的五千分之一航照圖及2007年的Google地圖,分析台南市北門區急水溪口與嘉義縣東石鄉朴子溪口紅樹林分布的消長,探討地層下陷對於河口紅樹林生態系之影響與衝擊。研究結果如下:(1)北門急水溪口的海茄苳紅樹林於1983、1989、2002及2007年的覆蓋面積分別是48.53、25.26、34.35及17.49 ha;平均高度從河口往上游五王大橋依序遞減,分別為302.9、278.3及236.8 cm (N1~N3= 15);樹齡約23.4± 3.6年,直徑每年增加約4.2± 0.4 mm (N= 10);鄰近的頭港大排的樹齡約22.3± 7.5年,直徑每年增加約5.0± 0.9 mm (N= 10),北門區內急水溪口與頭港大排2組紅樹林的成長速率無顯著差異。(2)朴子溪口的海茄苳與水筆仔紅樹林面積於1983、1991、2002及2007年的覆蓋面積分別是8.29、2.78、10.0及13.4 ha;朴子溪東石南橋附近至河口的海茄苳,因浸泡海水,導致枯死,形成裸露的泥灘地。兩個河口的海茄苳,都因地層下陷,呼吸根長時間浸泡海水,導致紅樹林從河口往上游方向逐漸死亡,亟需謀求保育對策。
This study assessed the influences and impacts on mangrove development due to land subsidence both in Jishui estuary and the lowreach of Pujsu river. By means of four aerial images of 1983, 1989, 1991, and 2002 years and one Google map of 2007 year, the mangrove areas were evaluated among different years. The results shows that the mangrove areas changed with 48.53, 25.26, 34.35, and 17.49 ha related to 1983, 1989, 2002, and 2007 years respectively around the Jishui estuary. The average heights of mangrove varied with 302.9, 278.3, and 236.8 cm (N1- N 3= 15) from Jishui estuary to the upreach of Wuwang Bridge. Besides, the tree age was evaluated to 23.4± 3.6 years old and tree diameter increased 4.2± 0.4 mm per year (N= 10) in Jishui estuary. At the same time, the tree age was estimated 22.3± 7.5 years old and tree diameter increased 5± 0.9 mm per year (N= 10) in Toukang drainage. Two habitats given above are identified without significant difference in growth rate. The mangrove areas were calculated 8.29, 2.78, 10.00 and 13.44 ha for 1983, 1991, 2002, and 2007 years respectively in the lowreach of Pujsu river. The mangrove was long submerged by seawater and could not survive at the lowreach of Toushunan Bridge in Pujsu river, and it showed mud habitate without vegetable. Both of two habitate conditions for mangrove around Jishui and Pujsu estuary degraded due to land subsidence and restoration project must be proposed.