“Beaver in the Sierra Nevada”的意思、由来-开放百科全书

The North American beaver (Castor canadensis) had a historic range that overlapped the Sierra Nevada in California. Before the European colonization of the Americas, beaver were distributed from the arctic tundra to the deserts of northern Mexico.^[1] The California Golden beaver subspecies (Castor canadensis subauratus) was prevalent in the Sacramento and San Joaquin River watersheds, including their tributaries in the Sierra Nevada. Recent evidence indicates that beaver were native to the High Sierra until their extirpation in the nineteenth century.

Until recently, beavers were considered non-native pests. Beavers and their dams are still being removed by wildlife managers in the Sierra Nevada despite evidence of being native mammals and of their beneficial effects on biodiversity for fish and other species in mountain wetland ecosystems.

Historical range and distribution

In 1916, Harold Bryant wrote in California Fish and Game, "The beaver of our mountain districts has been entirely exterminated and there are but a few hundred survivors to be found along the Sacramento, Colorado and San Joaquin Rivers."^[2] Earlier, in 1906, Frank Stephens wrote in "California Mammals" that Castor canadensis' historic range was from the "Pacific slope from Alaska to central California east to and including the Sierra Nevada and Cascade Mountains" and adds "In most parts of California the presence of beavers is only made known by the stumps of the trees and saplings that they have cut."^[3] McIntyre hypothesized that beaver were trapped out of the Sierra early in the nineteenth century by trappers before records could be kept.^[4] Other early twentieth century naturalists (Grinnell, Tappe, etc.) questioned whether the California Golden beaver dwelt above {{convert|1000|ft|m|-2}} of elevation in the Sierra.^[4]^[5] Recently novel physical evidence has demonstrated that beaver were native to the Sierra until at least the mid-nineteenth century, via radiocarbon dating of buried beaver dam wood uncovered by deep channel incision in two locations in Red Clover Creek in the Feather River watershed.^[6] That report was supported by a summary of indirect evidence of beaver including reliable observer accounts of beaver in multiple watersheds from the northern to the southern Sierra Nevada, including its eastern slope.^[7]

Reintroduction to the Sierra

California Golden beaver taken from Snelling, California (elevation {{convert|256|ft|m|0|disp=or|abbr=on}} and Waterford, California (elevation {{convert|51|ft|m|0|disp=or|abbr=on}}) were stocked in 1940 at Mather Station (elevation {{convert|4522|ft|m|0|disp=or|abbr=on}}) west of Yosemite National Park and in 1944 at Fish Camp (elevation {{convert|5062|ft|m|0|disp=or|abbr=on}}) by the California Department of Fish and Game (CDFG). These native "Central Valley" beaver have been building dams and rearing young successfully for 70 years in and near Yosemite at elevations higher than {{convert|5000|ft|m|-2}}.^[8] A second reference confirms that the CDFG re-introductions of beaver into Mariposa County in the Merced River watershed were all C. C. subauratus (Golden beaver) taken from near sea level elevations.^[9] These lowland beaver adapted to the high Sierra without difficulty.

Ecology

Effects on aspen, cottonwood and willow

In 1987, Beier reported that beaver had caused local extinction of Quaking aspen (Populus tremuloides) and Black cottonwood (Populus trichocarpa) on 4-5% of stream reaches on the lower Truckee River, however Willow (Salix spp.) showed good vigor despite heavy use in most reaches. He further speculated that without control of beaver populations that aspen and cottonwood could go extinct on the Truckee River.^[11] However, not only have aspen and cottonwood survived ongoing beaver colonization but a recent study of ten Tahoe streams utilizing aerial multispectral videography has shown that deciduous, thick herbaceous, and thin herbaceous vegetation are more highly concentrated near beaver dams, whereas coniferous trees are decreased.^[13] These findings are consistent with those of Pollock, who reported that in Bridge Creek, a stream in semi-arid eastern Oregon, the width of riparian vegetation on stream banks was increased several-fold as beaver dams watered previously dry terraces adjacent to the stream.^[12]

Effects on salmonids

Until recently, beaver were considered pests who caused flooding and impaired the passage of spawning trout and salmon. However, it has been shown that trout and salmon move freely across beaver dams.^[13] The presence of beaver dams has also been shown to either increase the number of fish, their size, or both, in a study of brook, rainbow and brown trout in Sagehen Creek, which flows into the Little Truckee River at an altitude of {{convert|5800|ft|m|-2}}.^[14]

Current control methods

Recently beaver have been documented in the upper and lower Truckee River, Ward Creek, Cold Creek, Taylor Creek, Meeks Creek, Blackwood Creek, and King's Beach, so the descendants of the original nine beavers have apparently migrated around most of Lake Tahoe.^[15]^[16]^[19]

All of the beaver dams in Taylor Creek, which flows from Fallen Leaf Lake to Lake Tahoe, are destroyed annually each fall by the U. S. Forest Service in order for Kokanee salmon (Oncorhynchus nerka) to spawn. A recent study of Taylor Creek showed that the beaver dam removal decreased wetland habitat, increased stream flow, and increased total phosphorus pollutants entering Lake Tahoe - all factors which negatively impact the clarity of the lake's water.^[17] In addition, beaver dams located in Ward Creek, located on the west shore of Lake Tahoe, were also shown to decrease nutrients and sediments traveling downstream.^[17]

The California Department of Fish and Game are using beaver control methods instead of flow devices in the Tahoe area. In 2006 the town of Truckee worked with the CDFG and the Lahontan Regional Water Quality Control Board to remove beaver dams from Trout Creek because of rising creek levels by de-watering and dredging a 500-foot section near Donner Pass Road.^[18] In November 2009, a beaver family was caught in snares underwater and drowned in Griff Creek in King's Beach, California, when Placer County Department of Public Works ordered their removal for fear that the beaver would cause flooding.^[19] When another beaver family of four recolonized Griff Creek in 2010, officials had them shot by snipers.^[20]

See also

References

1. ^{{cite journal|title=Alteration of North American Streams by Beaver |journal=BioScience |date=Dec 1988 |pages=753–762 |url=http://www.landscouncil.org/documents/Beaver_Project/Articles/Naiman_et_al_1988_alter_n_american_streams_by_beaver.pdf |accessdate=Feb 28, 2010 |first1=Robert J. |last1=Naiman |first2=Carol A. |last2=Johnston |first3=James C. |last3=Kelley |doi=10.2307/1310784 |volume=38 |deadurl=yes |archiveurl=https://web.archive.org/web/20120304035814/http://www.landscouncil.org/documents/Beaver_Project/Articles/Naiman_et_al_1988_alter_n_american_streams_by_beaver.pdf |archivedate=2012-03-04 |df= }}
2. ^{{cite book |title=California's fur-bearing mammals |last=Bryant|first=H.C. |year=1915 |publisher=State of California, Resources Agency, Dept. of Fish and Game |location=San Francisco, California |page=96 |url=https://books.google.com/?id=Uu3UAAAAMAAJ&pg=PA99 |accessdate=Mar 17, 2010 }}
3. ^{{cite book |title=California Mammals in West Coast Nature Series |first=Frank|last=Stephens |year=1906 |publisher=The West Coast Publishing Company |location=San Diego, California |page=97 |url=https://books.google.com/?id=oRqdMVhdtOYC |accessdate=2010-06-19}}
4. ^{{cite book |title=Fur-Bearing Mammals of California: Their Natural History, Systematic Status and Relations to Man |publisher=University of California Press |location=Berkeley, California |page=636 |year=1937 |isbn=978-0-7812-5041-2 |first1=Joseph|last1=Grinnell|first2=Joseph S.|last2=Dixon|first3=Jean M.|last3=Linsdale }}
5. ^{{cite journal |title=The Status of Beavers in California |last=Tappe|first=Donald T. |year=1942 |journal=Game Bulletin No. 3 |publisher=California Department of Fish & Game |url=http://www.martinezbeavers.org/wordpress/wp-content/docs/The%20Status%20of%20Beavers%20in%20California%20Tappe%20DT%20Game%20Bullletin%20_3%20California%20DFG%201942.pdf |accessdate=Apr 11, 2010}}
6. ^{{cite journal |title=Novel physical evidence that beaver historically were native to the Sierra Nevada |last1=James|first1=C.D.|last2=Lanman|first2=R.B.|journal=California Fish and Game |date=Spring 2012 |volume=98 |number=2 |pages=129–132 }}
7. ^{{cite journal |title=The historical range of beaver in the Sierra Nevada: a review of the evidence |first1=RB|last1=Lanman|first2=H|last2=Perryman|first3=B|last3=Dolman|first4=CD|last4=James |journal=California Fish and Game |date=Spring 2012 |volume=98 |number=2 |pages=65–80 }}
8. ^¹{{cite journal |title=A New Park Resident |first1=Robert N.|last1=McIntyre |journal=Yosemite Nature Notes |date=April 1948 |url=http://www.yosemite.ca.us/library/yosemite_nature_notes/27/27-4.pdf |accessdate=Jan 23, 2010 }}
9. ^{{cite journal |title=A Progress Report on Beaver Management in California |first=Arthur L.|last=Hensley |journal=California Fish and Game|volume=32|issue=2 |pages=87–99 |year=1946 |url=https://archive.org/details/californiafishga32_2cali |accessdate=Mar 26, 2010 }}
10. ^{{cite journal |title=Beaver Distribution in the Truckee River Basin, California |last1=Beier |first1=Paul |last2=Barrett |first2=Reginald H |journal=California Fish and Game |year=1989 |url=http://oak.ucc.nau.edu/pb1/vitae/Beier-Barrett.1987.CDFG_Beaver.pdf |accessdate=Jan 17, 2010 |deadurl=yes |archiveurl=https://web.archive.org/web/20110720012004/http://oak.ucc.nau.edu/pb1/vitae/Beier-Barrett.1987.CDFG_Beaver.pdf |archivedate=2011-07-20 |df= }}
11. ^{{cite journal |title=Beaver Habitat Use and Impact in Truckee River Basin, California|journal=Journal of Wildlife Management |date=October 1987 |pages=794–799 |jstor=3801743 |first1=Paul|last1=Beier|first2=Reginald H.|last2=Barrett |volume=51 |issue=4 |doi=10.2307/3801743}}
12. ^{{cite journal |title=Geomorphic changes upstream of beaver dams in Bridge Creek, an incised stream channel in the interior Columbia River basin, eastern Oregon |journal=Earth Surface Processes and Landforms |year=2007 |doi=10.1002/esp.1553 |first1=Michael M.|last1=Pollock|first2=Timothy J.|last2=Beechie|first3=Chris E.|last3=Jordan |volume=32 |issue=8 |pages=1174–1185|bibcode=2007ESPL...32.1174P }}
13. ^{{cite journal |title=Hydrologic and geomorphic effects of beaver dams and their influence on fishes |first1=Michael M. |last1=Pollock |first2=Morgan |last2=Heim |first3=Danielle |last3=Werner |journal=American Fisheries Society Symposium |volume=37 |year=2003 |pages=213-233 |url=http://www.albergstein.com/cao/Best%20Available%20Science/Fish/Beaver%20dam%20effects%20paper%20final.pdf |accessdate=Jan 17, 2010 |deadurl=yes |archiveurl=https://web.archive.org/web/20110707103342/http://www.albergstein.com/cao/Best%20Available%20Science/Fish/Beaver%20dam%20effects%20paper%20final.pdf |archivedate=2011-07-07 |df= }}
14. ^{{cite journal |title=Effects of beaver on trout in Sagehen Creek, California |last=Gard|first=R |year=1961 |journal= Journal of Wildlife Management |pages=221–242 |jstor=3797848 |volume=25 |issue=3 |doi=10.2307/3797848}}
15. ^¹{{cite thesis |title=Aerial Multispectral Videography for Vegetation Mapping and Assessment of Beaver Distribution within Selected Riparian Areas of the Lake Tahoe Basin |first=Michael Benson|last=Ayers |date=October 1997 |pages=71 |publisher=University of Nevada at Reno |url=http://www.tahoe.unr.edu/pubs/dissCat.aspx?p_catID=3 |accessdate=2010-08-26 }}
16. ^{{cite web |title=The Beavers of the Truckee River |publisher=Tahoe Arts and Mountain Culture |url=http://www.tahoeculture.com/green-tahoe/eco-tips/the-beavers-of-the-truckee-river-going-to-town/ |date=July 20, 2009 |accessdate=Jan 19, 2010 |archive-url=https://web.archive.org/web/20110609011329/http://www.tahoeculture.com/green-tahoe/eco-tips/the-beavers-of-the-truckee-river-going-to-town/ |archive-date=2011-06-09 |dead-url=yes |df= }}
17. ^¹{{cite thesis |title=The Effect of Beaver (Castor canadensis) Dam Removal on Total Phosphorus Concentration in Taylor Creek and Wetland, South Lake Tahoe, California |first=Sarah|last=Muskopf |publisher=Humboldt State University, Natural Resources |date=October 2007 |url=http://hdl.handle.net/2148/264 |accessdate=2012-09-30 }}
18. ^{{cite news|title=Trout Creek beaver dams removed for flood prevention |first=Sierra |last=Countis |newspaper=Sierra Sun |date=November 21, 2006 |url=http://www.sierrasun.com/article/20061121/NEWS/61120005/-1/rss02 |accessdate=Mar 8, 2010 |deadurl=yes |archiveurl=https://web.archive.org/web/20110727042119/http://www.sierrasun.com/article/20061121/NEWS/61120005/-1/rss02 |archivedate=2011-07-27 |df= }}
19. ^¹{{cite news |title=This is Wildlife Management in the 21st Century? |first=Keaven |last=Van Lom |publisher=Moonshine Ink |date=Jan 16, 2010 |url=http://moonshineink.com/articles.php/70/1618 |archiveurl=https://www.webcitation.org/64PkDcLH4?url=http://moonshineink.com/articles.php/70/1618 |archivedate=2012-01-03 |accessdate=Jan 17, 2010 |deadurl=yes |df= }}
20. ^{{cite news |title=North Tahoe officials: Human beings, beavers can peacefully co-exist |first=Mathew |last=Renda |newspaper=Sierra Sun |date=2010-11-08 |url=http://www.sierrasun.com/article/20101108/NEWS/101109895 |accessdate=2010-11-13 |deadurl=yes |archiveurl=https://web.archive.org/web/20101119152617/http://www.sierrasun.com/article/20101108/NEWS/101109895 |archivedate=2010-11-19 |df= }}