WMOD00258

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

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rI-!E:,'OLl1'~le,:.J_ E':i:~()i'~:E.'\'j r.F :~:,~,h.';C::'u'~ l-'LJ..~:<': '.' "';_:....~.1l\):\ TO 5!'0'.:}'..Ei..T DAT-JI

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ABSTRACT

In a~ att~~pt to cet~r~in~ th~ ~ff~ct cf an incrc~~cJ
sno~pack on the develor~~nt ct ccrt~ln h€r~ac~ous
plant sp~cies. six sites ~erc chosen, one each on
north and south ilspecrs at three Cl€V~tlons, 2YUo-m.
3140 m. and 32JU m. T~entY-!1Ve species of plar.ts
",'ere observed for the:. yarlOUS pht:.n0pl1fl&€S wlth 1:> spec-
imens of each specles measured at each site. Over a
perlod or tour bro~lng sccsons, ~oout jU~nOO observa-
tions were record~d. The'follo~ing characteristics
~ere observed: leaf gro~th. shoot gruwth, inflores-
cence height, total plant height. inflorescence devel-
o~ment by percentage of flowers in bud, open, or in
various stages of fruit development and seed dispersal.
Correlation coefficients ~ere determined between the
year day of various phenophases and year day of 100
percent snow disappearance in the plots. An analysis
of variance was done betwe~n Thurber fescue (Festuca
thurberi Vasey) year day of maximum growth and year
day of snow disappearance in 1971. 1972. and 1973.
The data produced the follo~ing generalizations:

1. In general for every 10 percent increase in snow
above the long term average, the earlier pheno-
.phases are delayed up to ~ days, dependIng on
-otner varIaOles sucn a5 aIr te~perature. IhlS
delay is not linear tor all phenophases ot a
species. Generally. tne earller pnenopnases
-are delayed more than the later phenophases.
for a given species.

2. plants of the same species on south aspects
reached maximum growth, 110werIng, trultlng. and
maturity up to 4 weeks ahead of plants occurring
on equivalent north aspects.

3. Plants of the same species at higher elevations
on equivalent aspects reacned vegetatIve and re-
productive maturity up co 0 ~eeks later than
piants at lower elevations.

4. The north aspect and higher elevation plants
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than the same species on south aspects and at
lower elevations.

5. There was greatest ccrrelation between the various
phenophases and sno~ free date in the excessive
sno~ year and on south aspects.

6. The late blooming species' phenophas€s (PFobably
long day plants) were least lntluenced by ~n6~^
depth.

7. Cereain plant species sholo.'~d an ability to "catch-
up" in their development despIte a lat~ st..r-~- 1"n---
the spring.

8. The difference in dates of phenophases bet~een
north and south aspects decreased as Lhe altltuae
increased.

l/Jn ~teinhoff, H.W., and
":oentain.<;, Coloraco.
l/i'resenc address: Dept.

J ..D. Ives (Eds).
S~n Juno Ecolo~v
of BinJot:.Y ;.-C;:l.

197(. Ecol~gical impacts of sno~pack aug~entatlon
Pro].;-! ~, Fi~-'ll Kepon. Color3clo State Univ. Pub!.,
Le,',:i s Cd 1 "'8€. LlurangC'. C01orado. 81301.

in the Sfor. JU.1:'
Fort Collir.;;.

Th~ data support
~ill r~~ult in a
.End ma.tL:r,nicn.
l:lDnth .

the thesis that an increase in snow
delay in herbaceous plant development
This delay could be as long as 1

See ~n5

DM,ifed -

CONCLUSIONS

An increase in snow fall in the forest ecosystem will
cause the snow tree date to occur later ~n the spr~nR.
.I~ turn, initiation of growth of herbaceous plants
w~ll be later which wiU "set back" most, it not all.
-phenophases. This will cause "spring" to come later:
. ~n the year on the average. As far 35 affecting the
,herbaceous plant po ulations an increase in snow fall
~is unl e y to have any direct effect. The ~ene oo~
iof these plants allow a high variation in date of
'growth initiation and still obtain maturation before
the end of the growing season. The study needs to be
carried on tor several more years for a more
definitive conclusion.

30'
d

A-8d-3