Gamradt Seth C, Kats Lee B
Natural Science Division, Pepperdine University, Malibu, CA 90263, USA email:
Oecologia. 1997 May;110(4):546-549. doi: 10.1007/s004420050193.
We examined the effects of chaparral wildfire on stream-breeding California newts (Taricha torosa) in a 750-m stretch of a perennial Santa Monica Mountain stream (Los Angeles County). Detailed field surveys of 1992 and 1993 established the composition (run, riffle, pool) of this habitat and determined the oviposition sites of newts. We also quantified California newt egg mass density and estimated the density of newt adults. A chaparral wildfire burned the entire study site on 2 November 1993. Using the same methods, we collected field survey data in 1994 and 1996. Erosion following the 1993 wildfire produced major changes in stream morphology and composition. Pools and runs represented approximately 40-50% of pre-fire stream area. In the spring following the fire, the stream consisted of less than 20% run and pool. Pools that did remain were often smaller and shallower. The average density of adult California newts did not differ among years. The total number of newt egg masses observed in the spring after the fire was approximately one-third of egg mass counts from pre-fire surveys. Most California newt egg masses were laid in pools and runs; California newts prefer deeper slow-moving water. We conclude that fire-induced landslides and siltation have eliminated pools and runs, thus reducing the amount of habitat suitable for oviposition. Habitat alterations caused by fire likely account for the observed reduction of egg masses at the stream.
我们研究了灌木丛野火对加利福尼亚州圣莫尼卡山脉一条常年溪流（洛杉矶县）750米河段中在溪流繁殖的加州蝾螈（Taricha torosa）的影响。1992年和1993年进行的详细实地调查确定了该栖息地的组成（急流、浅滩、水潭），并确定了蝾螈的产卵地点。我们还对加州蝾螈卵块密度进行了量化，并估计了成年蝾螈的密度。1993年11月2日，一场灌木丛野火烧毁了整个研究地点。我们采用相同的方法，在1994年和1996年收集了实地调查数据。1993年野火后的侵蚀导致了溪流形态和组成的重大变化。水潭和急流约占火灾前溪流面积的40 - 50%。火灾后的春季，溪流中急流和水潭的面积不到20%。留存下来的水潭通常更小、更浅。成年加州蝾螈的平均密度在各年份间没有差异。火灾后春季观察到的蝾螈卵块总数约为火灾前调查中卵块数量的三分之一。大多数加州蝾螈卵块产在水潭和急流中；加州蝾螈更喜欢较深的缓流水域。我们得出结论，火灾引发的山体滑坡和淤积消除了水潭和急流，从而减少了适合产卵的栖息地数量。火灾导致的栖息地改变可能是溪流中观察到的卵块数量减少的原因。
