期刊
ECOHYDROLOGY
卷 3, 期 3, 页码 325-338出版社
WILEY
DOI: 10.1002/eco.113
关键词
beaver dam; Castor canadensis; ecohydrology; habitat conversion; lotic-lentic ratio; managed flood; riverine ecosystem; Sonoran Desert
资金
- US Geological Survey
- US Fish & Wildlife Service (Region 2)
- US Army Corps of Engineers (Los Angeles District)
Beaver convert lotic stream habitat to lentic through darn construction, and the process is reversed when a flood or other event causes darn failure. We investigated both processes on a regulated Sonoran Desert stream, using the criterion that average current velocity is <0.2 m s(-1) in a lentic reach. We estimated temporal change in the lotic : lentic stream length ratio by relating beaver pond length (determined by the upstream lentic-lotic boundary position) to dam size, and coupling that to the dam-size frequency distribution and repeated censuses of dams along the 58-km river. The ratio fell from 19: 1 when no beaver dams were present to <3 : 1 after 7 years of flows favourable for beaver. We investigated the dam failure-flood intensity relationship in three independent trials (experimental floods) featuring peak discharge ranging from 37 to 65 m(3) s(-1). Major damage (breach >= 3-m wide) occurred at >= 20% of monitored dams (n = 7-86) and a similar or higher proportion was moderately damaged. We detected neither a relationship between dam size and damage level nor a flood discharge threshold for initiating major damage. Dam constituent materials appeared to control the probability of major damage at low (attenuated) flood magnitude. We conclude that environmental flows prescribed to sustain desert riparian forest will also reduce beaver-created lentic habitat in a non-linear manner determined by both beaver dam and flood attributes. Consideration of both desirable and undesirable consequences of ecological engineering by beaver is important when optimizing environmental flows to meet ecological and socioeconomic goals. Published in 2010 by John Wiley & Sons, Ltd.
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