WMOD00258

• Applicant: Western Weather Consultants
• Project Name: Vail & Beaver Creek
• Date: 11/1/1987
• Weather Modification - Doc Type: Application

Appendix to Question N~'

1. Report No. 2. 3. Reel t's Acces.s'1.on N.'.
~ CSU-FNR-7052-1
4. T1t1e S. Report Date
Ecological Impacts of Snowpack Augmentation 1n the San Juan MATCh 197.
Mountains of Colorado 6,
7. Author(s) 8, PerforminR Organization Report No.
Harold W. Steinhoff and Jack D. Ives (Eds)
9. Performing Organization Name and Address O. Work Unit No.
College of Forestry and Natural Resources
Colorado State University 1. Contract or Crant No.
Fort Collins, Colorado 80523 14-06-0- 7052
2. Sponsoring Agency Name and Address 3. Type of Report
Bureau of Rec13matlon Final Report
8ulld1ng 67. Denver Federal Center 4.
Denver, Colorado 80225
5, Supplementary Notes
This document represents a cooperative research effort between Colorado State University, the University' of
Colorado, aDd Fot't Lewis College. This report supersedes the previous Interim Progress Reports of 1971.
1973, and 1975. Also, this report has been designated as a contribution to the United Nations Han and the
Biosphere (MAB-6) Program.
6. Abstract
The following conclusions summarize the work of 33 scientists from Colorado State University. the University
of Colorado. and Fort Lewis College who studied the effects of varyinx snovpack on tbe ecosystems of the San
Juan Mountains in Colorado from 1970 to 1975. Initiation of shoot elonKatlon was delayed for pl.-lilts tn the
tundra and forests as a result of lower temperatures associated with deeper snowpack. The delay was most ~p-
parent for herbaceous species, such as Thurber fescue (fescues thurberi), whose growth points lay fn the
immediate zone of lower temperature at ground level. The effect on trees such as Engelmsnn spruce (Picea
engelmani1) and quak1ng aspen (Populus tremuloides) was less. The result vas a decrease In hlo~ss production
of herbaceous species, but not of trees. or of Gambel oak (Quercus gambelli1). whTch was found in a zone that
became snow clear very early. The delay in beginning of growth persisted through the other stages of the
annual cycles of most plants but with less magnitude. There seemed universally a comDen~atinn f~rtnr whjch
permitted each species to compress its annual cycle in.years vith a shorter graving-season caused by greater
depth ~wpack. Phytosociological studies 1n both forests and tundra showed that plant communiiTe'$-were .
arranged along a snow clear date gradient. In the forest, Gambel oak gives way to quaking aspen. then to suh-
alpine fir (Abies laslocarpa), and finally to Engelmann spruce, as the snow clear date extends later tnto
the year. A noticeable decline in forest populations of deer mice (Peromyscus maniculatus) and. to a lesl'ier
extent. chipmunks (Eutamias spp.) and Microtus spp.. followed winters of heavy snovfall. The basic reason
was a del~v in breedln2 and in availability of essential foods. No similar effect was found for the p~cket
gopher (Thomomys calpoides) or mountain toad (Bufo boreas). Elk. (Cervus canadensis) were almost excluded
from reRions with more than 10 cm of penetrable sno~ depth. and their travel was noticeably restricted at
depths over 40 cm. Movement of elk to higher elevations in spring coincided with the in i tlation of growth ..f
?erbaceous olants rather-than directly with the receding Snow line. and adeQuate calvlnR areAS were always I
present. Plant litter in the tundra decreased 1n areas dt deeper snovpack. Local .chanKeA in the rate of
8011 erosion may increase by a factor of 10 as a result of the s:reater area of bare 8011 left by tllf~ rlccrerli<~'"
in vegetative cover around snowbanks. The area involved is smalJ and t us t e tota impact is very 6ma II
rell;ionally. The long term climatic trend since 1930 has been toward ~igher temperatures and lesA preclpitrliti.n,a.
with short term fluctuations. of a few years, from relatively dry to wet modes. No ai~nificant Increase~ in
silver concentration were detected. because of the ~all amounts added in cloud 8eedln~ and the hl~h back-
ground levels of silver In the target area. No deleterious effects of silver iodide have been found at con~
cent rations which could be expected due to cloud seeding.
17. Key Words 18, Distribution Statement
alpine; tundra, aspen, climate, cloud seeding, Colorado, Available From:
National Technical Information Service
ecoloR)' , ecosystems. elk. environmental impact. fesc ue. Springfield. Virginia 22151
forests. geomorphology. oak. phenology. phytosociology.
productivity, S3n Juan Mountains. silver iodide, small
m.am.m.3.1s. snow. spruce. weather modification.
19. Secuicty Classif. of this report 20. Security Class if. of this page 21. No, of pages 22, Price
t;nclasslf~ed Unclassified 489
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