WSP00036

• File Number: 8200.750
• Description: San Juan River General
• State: CO
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 3/1/1975
• Author: BOR
• Title: San Juan Ecology Project - Interim Progress Report - March 1975
• Water Supply Pro - Doc Type: Report/Study

succession to spruce-fir. In the spruce-fir forest,
spr~ce survival might be favored where the snow lies
late. The likelihood of any tree seedling establish-
ment where the snow lies very late would be decreased.

Thus, the weather modification program in the San Juan
Mountains will likely alter the species composition of
the subalpine forests in those mountains. The degree
and nature of this response will depend upon the
nature of the alteration.

LITERATURE CITED

Aulitzky, H. 1958.
der Waldgrenze.
18-33.

Walkbaulich-Bkologische Fragen an
Centralbl. f.d. ges. Forstw. 75:

Billings, W. D. 1969. Vegetational pattern near
alpine timberline as affected by fire-snowdrift
interactions. Vegetatio 19:192-207.

Brink, V. C. 1959. A directional change in the sub-
alpine forest-heath ecotone in Garibaldi Park,
British Co1umbis. Ecology 40:10-16.

Franklin, J. F., W. H. Moir, G. W. Douglas, and
C. Wiberg. 1971. Invasion of subalpine meadows by
trees in the Cascade_Range, Washington and Oregon.
Arctic and Alpine Research 1:215-224.

Friedel, H. 1952. Gesetze der Neiderschlagsverteil-
ung im Hochgebirge. Wetter u'. Lebein i: 73-86.

Geiger, R. 1971. The climate near the ground
(Revised edition). Harvard University Press.
Cambridge, Massachusetts. 611 pp.

Gittens, R. 1969. The application of ordination
techniques. ~: Ecological Aspects of the
Mineral Nutrition of Plants. Ed. I. H. Rorison.
Blackwell Scientific Publications. Oxford and
Edinburgh. pp. 37-66.

Harrington, H. D. 1954.
Colorado. Sage Books.

Manual of the Plants of
Denver. .666 pp.

Helmers, H., M. K. Genthe, and F.
Temperature affects growth and
Englemann spruce. Forest Sci.

Ronco. 1970.
development of
16:447-452.

Kreeb, K. 1954. Die Schneeschme1ze als phUnogischer
Faktor. Met. Rundscbau L:48-49.

Larsen, E. S., and W. Cross. 1956.
petrology of the San Juan Region,
Colorado. USGS Prof. Paper 258.

Geology and
southwestern

Noble, D. L. 1973. Englemann spruce seedling roots
reach depth of 3 to 4 inches their first season.
USDA Forest Service Research Note RM-241. 3 pp.

Orloci, L. 1966. Geometric models in ecology. I.
The theory and application of some ordination
methods. J. Eca!. 54:193-215.

Patten, D. T. 1963. Vegetational pattern in
relation to environments in the Madison Range,
Montana. Ecol. Monogr. 11:375-406.

Ronco, F. 1970. Influence of high light intensity
on survival of planted Englemann spruce. Forest
5ci. 16:331-339.

Seal, H. L.
Analysis
London.

1964. Multivariate Statistical
for Biologists. Methuen and Co. Ltd.
209 pp.

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Waldmann, G. 1959.
Standortsfaktoren
C. 1!:98-108.

Schnee-und Bodenfrost ale
am Groben Falkenstein. Forstw.

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Walker, B. H., and C. F. Wehrhahn.
ships between derived vegetation
measured environmental variables
wetlands. Ecology 52:85-95.

1971. Relation-
gradients and
in Saskatchewan

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Wardle, P. 1968. Englemann spruce (Pices
ena1emannii Engel.) at its upper limits on the
Front Range, Colorado. Ecology 49:483-495.

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Stearns, F. W., and C. A. Carlson. 1960. Correla-
tions between 801l-moisture depletion, solar
radiation, and other environmental factors.
J. of Geophysical Research. 65t3727-3732.

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Acknowledmnents

We gratefully acknowledge the volunteered assistance
of Jeanie Barney in the collection of field data. We
are indebted to Ordell Steen for his early work on
tllis/project and his assistance in data collection
and -analysis. Our thanks are also extended to Steve
Whipple for his advice and, criticism and the use of
his computer programs.

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