Laserfiche WebLink
<br />Appendix to Question No. 13 <br /> <br />1. Report No. <br />CSU FNR-7052-1 <br />4. Title <br /> <br />2. <br /> <br />3. Recipient' s Accession Np. <br /> <br />Ecological Impacts of Snawpack Augmentation in the San Juan <br />Mountains of Colorado <br /> <br />5. Report Date <br /> March 1976 <br />6. <br />8. PerformioR Organtz8t ion Report No. <br />O. Work Unit No. <br />~l. Contract or Grant No. <br /> 14-06-0-7052 <br />J. Type of Report <br /> Final Report <br />4. <br /> <br />7. Author(s) <br />Harold W. Steinhoff and Jack D. Ives (Eds) <br />9. Performing Organization Name and Address <br /> <br />College of Forestry and Natural Resources <br />Colorado State University <br />Fort Collins, Colorado 80523 <br /> <br />2. Sponsoring Agency Name and Address <br /> <br />Bureau of Reclamation <br />Building 67, Denver Federal Center <br />Denver, Colorado 802~5 <br /> <br />5. Supplementary Notes <br /> <br />This document represents a cooperative research effort between Colorado State University, the University of <br />Colorado, and Fort Lewis College. This report supersedes the previous Interim Progress Reports of 1971, <br />1973, and 1975. Also, this report has been designated as a contribution to the United Nations Man and the <br />Biosphere (HAB-6) Program. <br /> <br />6. Abstract <br /> <br />The following conclusions summarize the work of 33 scientists fr~ Colorado State University, the University <br />of Colorado, and Fort Lewis College who studied the effects of varying snowpack on the ecosY6tems of the San <br />Juan Mountains in Colorado from 1970 to 1975. Initiation of shoot elongation was delayed for plants In the <br />tundra and forests as a resdlt of lower temperatures associated with deeper snowpack. The delay was most 4p~ <br />parent for herbaceous species, such a8 Thurber fescue (Festuca thurber1). whose growth points lay tn the <br />immediate zone of lower temperature at ground level. The effect on trees such as Engelmann spruce (Picea <br />enR;elmanii) and quaking aspen (Populus tremuloldes) was less. The result was a decrease In hJmJlass productIon <br />of herbaceous species, but not of tt'ees.or of Gambel oak (Quercus Rambelli!), willch was found in a zone that <br />became snow clear very early. The delay in beginning of growth persisted through the other stages of the <br />annual cycles of most plants but with less magnitude. There seemed universally a comoenR~tinn f~rrnr uh1ch <br />permitted each species to compress its annual cycle In.years with a shorter growing-season caused by greater <br />depth ~ack. Phytoso"ciological studies In both forests and tundra sho\.1ed that plant communlt'Ies.-were <br />arranged along a snow clear date gradient. In the forest, Cambel oak gives way to quaking aspen, then to sub- <br />alpine fir (Abies lasiocarpa)~ and finally ta Engelmann spruce, 8S the snow clear date extends later Into <br />the year. A noticeable decline in forest populations of deer mice (Peromyscus maniculatus) and~ ta a lesser <br />extent,chipmunks (Eutam1as spp.) and Microtus spp., followed winters of heavy snowfall. the basic reason <br />was a dp.lav in breedin2 and in availability of essential foods. No similar effect was found for the pncket <br />gopher (Thomomys talpoides) or mountain toad (Bufa boreas). Elk (~ canadensis) were almost excluded <br />from re~ions with more than 10 cm of penetrable snow deoth. and their ~r8vel was noticeably restricted at <br />dePths over 40 em. Movement of elk to higher elevations in sprinx coincided with the initiation of growth ..f <br />?erbaceous plants rather. than directly with the receding snow line, and adeQuate calvin~ areas were always <br />present. Plant litter 1n the tundra decreased in areas dt deeper snowpack. ~cal chan~eA in the rate of I <br />soil erosion may increase by a factor of 10 as a result of the greater area of bare soil left bY' tilt" d~l"re~H.' <br />in vegetative cover around snowbanks. The area involved 1s small and thus the total impact is very sma <br />re~ionally. The long term climatic trend since 1930 has been toward higher temperatures and leBA prpc1pitat~n,~ <br />....ith short term fluctuations. of a few years, from relatively dry to wet modes. No siRnificant increases in <br />silver concentration ....ere detected, because of the small amounts added 1n cloud seedin~ and the hl~h back- <br />ground levels of silver in the target area. No deleterious effects of silver iodide have been found at con~ ( <br />cent rations ....hich could be expected due to cloud seeding. ~ <br /> <br />17. Key Words <br /> <br />18. DIstribution Statement <br />Available From: <br />National Technical Information Service <br />Springfield, Virginia 22151 <br /> <br />alpine tundra, aspen. climate, cloud seeding, Co10rado, <br />ecolo~. ecosystems, elk, environmental impact, fescue, <br />forests, geomorphology, oak. phenology~ phytosociology, <br />productivity, 53n Juan Mountains, stlver iodide, small <br />n~mm3ls, sno..... spruce, weather modifica~ion. <br /> <br />19. Secuicty Classif. of this report 20. Security Classif. of this page 21. <br />Unc1assifted Unclassified <br /> <br />No. of pages <br />489 <br /> <br />22. Price <br /> <br />, <br /> <br />oc <br />