Semlitsch Raymond D, Conner Christopher A, Hocking Daniel J, Rittenhouse Tracy A G, Harper Elizabeth B
Division of Biological Sciences, 105 Tucker Hall, University of Missouri, Columbia, Missouri 65211-7400, USA.
Ecol Appl. 2008 Mar;18(2):283-9. doi: 10.1890/07-0853.1.
Numerous studies have documented the decline of amphibians following timber harvest. However, direct evidence concerning the mechanisms of population decline is lacking and hinders attempts to develop conservation or recovery plans and solutions for forest species. We summarized the mechanisms by which abundance of amphibians may initially decline following timber harvest into three testable hypotheses: (1) mortality, (2) retreat, and (3) evacuation. Here, we tested the evacuation hypothesis within a large-scale, replicated experiment. We used drift fences with pitfall traps to capture pond-breeding amphibians moving out of experimental clearcut quadrants and into control quadrants at four replicate arrays located within the Daniel Boone Conservation Area on the upper Ozark Plateau in Warren County, Missouri, USA. During the preharvest year of 2004, only 51.6% of the 312 individuals captured were moving out of pre-clearcut quadrants, and movement did not differ from random. In contrast, during both postharvest years of 2005 and 2006, the number of captures along the quadrant edge increased, and a higher proportion of individuals (59.9% and 56.6%, respectively, by year) were moving out of clearcut quadrants than entering. Salamanders moved out of clearcuts in large percentages (Ambystoma annulatum, 78.2% in 2005, 78.2% in 2006; A. maculatum, 64.0% in 2005, 57.1% in 2006). Frogs and toads also moved out of clearcut quadrants, but in lower percentages (Bufo americanus, 59.6% in 2005, 53.3% in 2006; Rana clamitans, 52.7% in 2006). Salamanders moved out of clearcuts with low-wood treatments more than out of clearcuts with high-wood treatments. Movement of salamanders out of clearcuts was independent of sex. Estimated movement out of clearcuts represented between 8.7% and 35.0% of the total breeding adults captured for two species of salamanders. Although we recognize that some portion of the amphibian population may retreat underground for short periods and others may not survive the effects of timber harvest, these data are the first direct evidence showing that individuals are capable of leaving clearcuts and shifting habitat use.
众多研究记录了木材采伐后两栖动物数量的下降。然而，关于数量下降机制的直接证据却很缺乏，这阻碍了为森林物种制定保护或恢复计划及解决方案的尝试。我们总结了木材采伐后两栖动物数量最初下降的机制，归纳为三个可验证的假设：（1）死亡，（2）撤退，（3）撤离。在此，我们在一个大规模的重复实验中对撤离假设进行了测试。在美国密苏里州沃伦县上奥扎克高原的丹尼尔·布恩保护区内的四个重复区域，我们使用带有陷阱的漂移围栏来捕获从实验性皆伐区域迁出并进入对照区域的池塘繁殖两栖动物。在2004年采伐前的年份，捕获的312只个体中只有51.6%从采伐前的区域迁出，且迁出情况与随机情况无异。相比之下，在2005年和2006年这两个采伐后的年份，沿区域边缘的捕获数量增加，且迁出皆伐区域的个体比例更高（每年分别为59.9%和56.6%），进入皆伐区域的个体比例更低。蝾螈大量迁出皆伐区域（环纹钝口螈，2005年为78.2%，2006年为78.2%；黄斑钝口螈，2005年为64.0%，2006年为57.1%）。青蛙和蟾蜍也从皆伐区域迁出，但比例较低（美洲蟾蜍，2005年为59.6%，2006年为53.3%；绿蛙，2006年为52.7%）。低木材处理的皆伐区域中蝾螈的迁出量多于高木材处理的皆伐区域。蝾螈从皆伐区域的迁出与性别无关。估计从皆伐区域迁出的个体占两种蝾螈捕获的繁殖成年个体总数的8.7%至35.0%。尽管我们认识到两栖动物种群的一部分可能会在短时间内退居地下，还有一部分可能无法在木材采伐的影响下存活，但这些数据是首次直接表明个体能够离开皆伐区域并改变栖息地利用的证据。
