烏石坑地區森林與溪流環境兩棲類群聚受地震影響之研究

Study of Earthquake Effects on the Forest and Stream Amphibian Communities in Wushykeng Area

本研究分析1997至2008年春、秋季烏石坑地區無尾目兩棲類固定穿越線監測調查資料。調查路線包含屬於森林與溪流棲地環境各2條穿越線；依921地震發生及調查路線調整等因素分為4個時期。共記錄13種兩棲類動物，其中2種為地震後的新紀錄種。森林環境地震後一期種數明顯減少可能因植被破壞之故；而地震後二期、三期兩棲類種類數回升，且數量上明顯夏季多而秋季少。溪流環境地震前和地震後一期兩棲類數量同森林棲地般無明顯季節變化，地震後的種數增加則可能是森林性兩棲類另覓生殖場所的結果；且地震後二期、三期因秋季梭德氏赤蛙大量出現，在數量上有明顯的季節性變化，但為夏季少、秋季多的狀況。地震後二、三期秋季溪流環境之各項指數明顯較低，主要因為梭德氏赤蛙單一種數量大增。烏石坑地區斯文豪氏赤蛙族群在地震後一期便已回復到地震前水準，和關刀溪地區的研究結果相符；其族群波動雖然甚不穩定，但大致有森林與溪流棲地環境彼此消長現象，推測個體會在不同棲地間移動交流。至於梭德氏赤蛙直至地震後二、三期才發生的秋季生殖高峰現象，初步推測可能是溪流環境改變合適梭德氏赤蛙繁殖，加上附近植群回復之結果。

Summer and autumn anuran line-transect survey of two forest and two stream transects at Wushykeng area before and after the 921 earthquake (1997 to 2008) was analyzed in this research. We found 13 amphibian species with two new species records after the earthquake. No distinct seasonal variation was found in the number of frogs between pre-quake and the first post-quake periods in forest habitats, but the number of species reduced in the post-quake periods. It might be a result of the destruction of forest vegetation due to the quake. In the second and the third post -quake periods, amphibian abundance recovered but showed seasonal fluctuation with high in the summer and low in the autumn. There was no seasonal population variation in stream habitats in pre-quake and early-post-quake periods. Increase of species numbers might be a result of frogs seeking new breeding sites after forest habitats destruction. The total frog abundance fluctuated conspicuously from low in the summer to high in the autumn due to the explosive increase of Rana sauteri individuals in the autumns in the latter post-quake periods. Biodiversity indexes were lower in stream habitats in the latter post-quake periods, resulting from the increase of Rana sauteri abundance. The Odorrana swinhoana population in Wushykeng recovered in the first post-quake period, probably as a result of the frogs moving between forest and stream habitats. In addition, the autumn Rana sauteri population bursts in the latter post-quake periods were presumably due to the stream habitats becoming appropriate for breeding and the recovery of nearby vegetations.