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.'___r~.' , " ii. 1 t".ft I fHENOLll'.;LCAL i)r:':!:!...or~:[.:-n (t!" HL!JiACUJ'I~ I'LA!,n'; I,' i\,ELATlO~ TO SNOWHtLT DAT&-l/ 11.:1~1'=. ABSTRACT In an atteQPt to determine the ~ffecl of an incren~eJ so~p&ck 00 the development ot ccrta1n hernac~ou~ plant species, six sites were chost!n. one each on north and south aspects at tnree elevations, 2~UU m. 3140 m, and JZIU m. Twenty-live species of plants were observed for the various phE:nOpllllses with 1~ spec- imens of each species measured at each site. Over a - per10a ot tour &row~ng seasons, aoout ~O~ observa- tions were. recorded. The'follo~ing characteristics were observed: leaf growth, shoot growth, inflol:es- cence height. total plant height. inflorescence devel- opment by percentage of flowers in bud, open, or in various stages of fruit development and seed dispersal. Correlation coefficients were 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 (Festues thurberi Vasey) year day of ~ximum growth and year day of snow disappearance in 1971, 1972. and 1973. The data produced the following generalizations: 1. tn general for every 10 percent increase in snow above the .10ng term average, the earlier pheno- 'phases.are delayed up to ij days, dependlng on other var18D~ea sucn 8S a~r temperature. Ihls delay is not linear tor all phenophases ot a spec~e8. ~eneTa~lY. tne e8r~~er pnenopnases are delayed more than the later phenophases, for a given species. 2. Plants of the same species on south aspects reached maximum growth. tlower1nR. truiting. and maturity up to 4 weeks ahead of plants occurr1n~ on equivalent north aspects. 3. Plants of cbe same species at higher elevations on equivalent aspects reached vegetative ana re- productive maturity up to b ~eeks later than plants at lo~er elevations. ---4. The north aspect and higher elevation plants matured. flowered. and trulted at a smaller size than the same species on south aspects and at lo~er elevations. 5. There was greatest correlation between the various phenophases-snd sno~ free date in the excessive snow year and on south aspects. 6. The late blooming species' phenophases (p,obably long day plants) were least intluenced by snow' depth. 7. Cert.ain plant species showed an ability to "catch- up" in t.heir development desrl.t.e a late start~'in--' the spring. 8. The difference in dates of phenophtlse" bet\.leen north and south aspects decrea:'leo as ttle alttfude increased. ThL d<'_ta support ..,ill re~ull in a and maturation. month . the thesis that an increase in snow delay in herbaceous plllnt development: This delay could be as long as 1 See ~..s DM ..+fed - : CONCLUS IONS An increase in sno\.l fall in the forest ecosystem ~!ll .cause the snow tree date to occur Aater in the spring. ;In turn, initiation of growth of herbaceous plants :""111 be later ",hie-h will "set back" most, 11 not alI. ;phenophases. This \1111 cause IIspring" to come later~ 1n the year On the average. As far as affecting the iherbaceous lant 0 ulations an increase in snow fall is un y to sve any direct effect. The Rene DO~ of these plants allow a high variation in date of . growth initiation and still obtain maturation before the end af the growin& season. The study needs to be ,carried on lor several more years for a =ore definitive .conclusion. . l/ln Cjteinhoff. H.W., and JoID, Ives (Eds). 197(.. EcolC'.Q:ical impac.t:" of snow-Pllck augmentation in the ~Il.n .Ill;"!!' '1ounlain~, Colorado. ~an JUAn E<.:ologv 'i'ro'~'\~. lin.fll Repotl. C:010tado State Univ. Publ.. fort Col11nl'l. .~./Present address: Dept. of B!olof!,y, ~'un !.t'\o.'is (<-11iege. Durange>. CCllorado. 81301. 32)