WMOD00211

• Applicant: Western Weather Consultants
• Project Name: Vail & Beaver Creek
• Date: 11/1/1984
• Weather Modification - Doc Type: Application

;.:.~ r:-,:. ~

nH':SOW-:;IC;..!.. ......c::...(;?~:Si (.[ !i:::':-.~';C::{):~.:i t'r..i\!;i'~ :: ~~:::...:..;10:; TC' 5.s-0'.....":I1..: DArJ!

,.}..-t:;~'

ABST[LA..CT

In an ac[e~pt to de[~rmine th~ eff~ct cf ~n i~cr~a~~J
-snOJ.'pack on the devt:lornenc 1..:1 ccr~.1tr: ne[":).;.c",O'lS
plant sp~cies, six sites ~~rc chos~n, one-each-on
north and south aspects at thr~e ~levatlOns. l~~.
3140 m, and JLJU m. l~entY-[1Ve species of pla~ts
vere observed for the varlOUS p"t:.noJphases \.Iltn 1) spec-
imens ot each specles measured at eac" site. Over a --
perlod ot tour grol.lln~ seasons, about ~u,UOG observa-
tions l.Iere recorded. The' follo'....ing characte:ristics
~ere observed: leaf gro\olth, shoot grovth. infloreS-
cence height, total plant height, inflorescence devel-
oPQent by percentage of flovers In hud, open, or io
various stages of fruit develoPQenc and seed dispersal.
Correlation coefficients were determined between the
year day of various phenophases and year d.:lY of 100
percent sno~ dis3P?earance i~ the plots. An analysis
of variance ~as done betye~n Thurber fescue (Festuca
thurberi Vasey) Y~3r day of maxi~um &ro~th and year
day of snov d1s3??earance in 1971. 1972. and 1973.
The data produced the follo~1ng generalitations:

1. In general fa" every 10 percent increase in sno~
above the lon~ term average, the earlier oheno-
.phases are ce~ayed up to H aays, aepend1n& on
other var1ables such as alr te~perature. In15
delay is no~ linear tor all phenopnases ot a
spec~es. Gene"allY, the ear11er phenophases
are delayed core than the later phenophases,
for a g1v~~ s?ec1es.

2. Plants of the saoe species on south aSpects
reached QaX~~~ gro~cn. tlo~erl~~: :ru~tlng. ane
maturity up to ~ ~eeks ahead of ,~tS occurring
on equivalent norrh aspects_

J. Plants of the same species at hi3~'''':'' ele"a~ions
on equivalent aspectS reached vegecat1ve and re
productive maturity up co 6 ~eeks lacer tnan
plants at lo~er elevat10ns.

4. The north aspect and higher elevation plants
matured, tlo\.lered, and tru~ted dt a smaller size
than the sa~e species on soutn aspects a~d at
louer elevations.

5. There was ~reatest ~orrelation bet~een the various
phenophases and snOW free date in the excessive
snow year and on south aspects.

6. The late blooming species' phenophas~5 (probably
lon~ day plants) ~ere least lnrluencec 0: ino~'
depth.

7. Certain plant species show~d an abili~y to "catch-
up 1n their development despite a J.a.::e .",C.-f:-Tn---
the s pnng.

8. The difference in dates of phenophases ~etuee~
north and south aspects decreAsec 3S :::ne ci.u::fuce
increased.

Th~ data s~pport
~ill res'llt in 3
an"; fr.aturaticn.

the thesis that an increase in Sl1010
delay in herba~eous plan::: deveIop~nt
This del~y could be as long as 1

;:-,o;1t11 .

See. ~ns

DM..7fed
I

CONCLUSIONS

An increase in sno\.l fall in the. forest ecosystem will
cause the 500\.1 tree cate to occur later ln tne sprlng.
In turn, initiation of gro~th of herbaceous plants
\li11 be later which \.liB "set back" ::lost, i;; not all,
phenophases. This will cause "spring" to come later
1n the year on tne average. As far as affecting the
herbaceous plant populations. an increase in 5nO\ol fall
iis unlikely to have any direct effec:::. ThQ 2ene 00015
:of these plants a~low a high variation in date of
!growtb. initiatlo~. ;;;:d still obealn c:taturat1on before
,the ~nd af the g:'~~.Ln& season. The seudy needs to be
carr~ed on for sev~(al mQre y~ars for a ~e~e
definitive conclusion.

IIIn ~te1nhoff, H.W., and JJD. Ives rEds), 197(., EcolG~ical impacts of sno~~ack aug~encat10n in the San Jua~
'10untain.", Colorado. Siln JUiln :':":0 lop' P["Q":<';:~, Fi;;:tl !tepo::-t. Coloc.ldo State Univ. Pub!.. Fot:,t Collir.s_
l.lPresent address: Dept. of Bi0]O;~:; !-'u::t :,/',.-is ::. :'j l.:bO< , QUTiWgC. Colorado, 81301.

-9-

)2J

A-8d-3