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<br />Appendix to Question No. 13 <br /> <br />1. R~p(1rt No. <br /> <br />2. <br /> <br />3. Recipienc's Accession Nt'. <br /> <br />CSU-fNR-7052-1 <br />4. Title. <br /> <br />Ecological Impacts of Snowpack Augmentation in the S~n Juan <br />Mountains of Colorado <br /> <br />5. Report DatE: <br />March 1976 <br /> <br />6. <br /> <br />7. Author(s} <br />Harold W. Steinhoff and Jack D. ryeS (Eds) <br />9. Performing Organization Name and Address <br /> <br />8. PerforminK Organization Report No. <br /> <br />O. Work Unit No. <br /> <br />College of Forestry and Natural Resources <br />Colorado State University <br />Fort Collins. Colorado 80523 <br /> <br />2. Sponsoring Agency Name aod Address <br /> <br /> . <br /> l. Contract or Crant No. <br />. 14-o6-D-7052 <br /> 0 .' o' <br /> 3. Type of Report. 0 . <br />- 0 <br />0 .. <br /> . <br />- Final Report <br />.. . <br /> 4. , <br /> , <br /> <br />Bureau of Rec13m3tlon <br />Building 67, Denver Federal Center <br />Denver, Colorado 80225 <br /> <br />~5. Supplementary Notes <br /> <br />.. <br />This document represents a cooperatfv~ research "effort between Colorad~'State University. the ,University of <br />Colorado, and Fort Levie College. Thla report supersedes the previous Interim Progress Reports of 1971, <br />1973. and 1975. Also, this report has been des,lgnated as a contribution ~o the United Nations Man and the. <br />Biosphere (MAB-6) Program. n._ .__ <br /> <br />. . <br /> <br />6~ Abstrac.t <br /> <br />The following conc.lusions summarize the wor~ of'33 scientists from Colorado State University, the University <br />of Colorado, and Fort Lewis Coll-ege vho studied the effects of varyinR snovpack on the ecosystems. uf the, San <br />Juan Mountains in Colorado from 1970 to 1975. Initiation of shoot elonp;atlon was delayed for plant-s In the <br />tundra and forests as a result of lower temperatures associated wIth deeper snowpack. The delay wa~ most ap- <br />parent for herbaceous species, such as Thurber fescue (Festuca thurber1), whose growth points 1ay.in the <br />immediate zone of lower temperature at ground level. The effect on trees such as EDgel~nn spruce (Picea <br />enRelmanii) and quak.ing aspen (Populus tremuloides) was less. The result 'Was a decrease In hJomrtS6 productIon <br />of herbaceous species, but not of trees.or of ~mbel oak (Quercus gambel11i), wh1cn was found in a.zone that <br />became sno~ 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 comoen~3tion f~rtnr ~h1ch <br />permitted each species to compress its annual cycle in.years with a shorter grOWing-season caused by greater <br />depth~ack. Phytoscrciological studies in both forests and tundra shoQed that plant communI~Le:S~ <br />arranged along a snow clear date gradient. In the forest, Gambel oak gives way to quaking aspen. then to sub- <br />alpine fir (Abies lasiocarpa), and finally to Engelmann spruce, as the snow clear date extends later into <br />the year. A noticeable decline in forest populations of deer mice (PeromysCUS maniculatus) and~ to a lesser <br />extent, chipmunks (Eutamias spp.) and Microtus spp., followed winters of heavy snowfall. The basic~ reason <br />was ~ rlpl~v in b~p-edin2 and in availability of essential foods. No similar effect was found for the ppcket <br />gopher (Thomomys talpoides) or mountain toad (Bufo boreas). Elk (Cervus canadensis) were almost excluded <br />from reKions with more than. 70 cm of penetrable-&now depth. an~the1r travel was noticeably restricted at <br />depths over 40 CID. Movement: of elk to higher elevations 1n spriD& coincided with the initiation of growth ..f <br />herbaceous plants rather. than directly-with the receding snow line. and adequate calvln2 areas were always <br />present. Plant litter in the tundra decreased in areas df deeper snowpack. Local chanRes in the rate of <br />solI erosion may increase by a factor of 10 as a result of the greater area of bare soU lefr by tht> rlc\-'re::l!'l'- <br />in vegetative cover around snowbanks. The area involved is small and thus the total impact is very small <br />re21onallv. The long term climatic trend since 1930 has been toward higher temperatures and le9~ pr~clritat~n,~ <br />with short term fluctuations, of a few years, from relatively dry to' wet modes. No siRnificant increase~ in <br />silver concentration were detected. because of the small amounts added in cloud seedlnK and the hiRh back- <br />ground levels of silver in the target sr. ea. No deleterious effects of silver iodide have been found at con: ( <br />cent rations which could be expected due to cloud seeding. ~ <br /> <br />17. Key Words <br /> <br />alpin~ tundra. aspen, climate. cloud seeding, Colorado, <br />ecolo.';r. ecosystem9-._ elk,. env1ronlllental~ impact,. fescue, <br />forests. geomorphology, oak, phenology,' phytosociology. <br />productivity. 53n Juan Mountains, silver iodide, small <br />n~Inm319. snow. spruce, weacher modification. <br /> <br />19. Secuirty Classif. of this report 20. Security Class!f. of this page 21. No. of pages <br /> <br />18. <br /> <br />Distribution SCatement <br />Available From: <br />National Technical Information Service <br />Springfield, Virginia 22151 <br /> <br />22. Price <br /> <br />Unclassified <br /> <br />Unclassified <br /> <br />489 <br />