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~i._r :-.;rt FHD10Lt):-;IC;.L L:,':':f!...O."~E~;I (ir HI:~_bAC:::u;S f'IJ\-.t..;j':-; i.. ;.;.:::..;..:IO~ TO S~O'''''XEi.:! DAT&-l/ ',. "_. ',).;l'~' ABSTRACT In an atte~pt to det~rmine th~ eff~ct of an in~rca~eJ -sn~pack on the develor~ent ct CCrt21r. her~ac~o~s plant species, six sites ~erc chosen, one each on north and south aspects at three clevat1ons. LYUG m. 3140 ro, and )~/U m. lwenty-t1ve speC1€S of plants were observed for the van.cus phE:.nOphaSes ""1.th 1) spec- imens of each spec1es measured at each site. Over a per10d at tour grow~ng seasons, aODut )U,UOG observa- cions were recorded. The'follo~ing charactE:.ristiCS were observed: leaf growth, shoot growth. inflores- cence height, total plant height, inflorescence devel- opment by percentage of flowers In bud. open. or in various Gtates of fruit development and se~d dispersal. Correlation coefficients were determined between the year day of various phenophases and year day of 100 percent snow di'~ppearance in the plots. An analysis of var!ance was done betwe~n'ihurber fescue (Festuca thurberi Vasey) y~ar day of maximum growth and year day of snow disappearance in 1971. 1972. and 197). The data produced the following generalizations: 1. In general for every 10 percent increase in snow above the lon~ term average, the earlier pheno- 'phases are delayed up to ~ days, depending on otner varlaoles sucn as a1r temperature. IhiS delay is not linear tor all phenophases ot a species. Lenerally. the earlier phenopnases are delayed more than the later phenophases, for a given sp~cies. 2. Plants of the same species on south aspects reached maximum growth. tlower11.t0. trultln~. and maturity up to ~ weeks ahead of ~~]nts occurring on equivale~t nOTLh aspects. 3. Plants of the same species at hi&~ler elevations on equivalent aspects reached vegetat1ve and re- productive ~turity up to 6 weeKS later than plants at lower elevat1ons. 4. The north aspect and higher elevation plants matured. tlowered. and tru1ted at a smaller size than the same species on south aspects ~nd at lower elevations. 5. There was greatest correlation between the various phenophases and sno~ free date in the excessive snow year and on south aspects. 6. The late blooming species' phenophas~s (probably long day plants) were least 1ntluenced by sno~' depth. 7. Certsin plant species showed an ability to "catch- up" in theft development despHe a late ~ti:.i:-Tti--. the spnng. 8. The difference in dates of phenophases between norch and south aspects decreased as tne altirude increased. The data support ~ill result in a and maturation. i:lOoth . the thesis that an increase in snov delay io1herbaceous plant ~evelopoer.t This delay could be as long as 1 See +w, '.5 DM,.ffed . CONCLUSIONS An increase in snow fall in the. forest ecosystem will cause the snOw tree date to occur later 1n the spr1ng. In turn, initiation of growth of herbaceous plants ,will be later which will "set back" "most. it not all. phenophases. This ""ill cause "spring" to come later 'ln the year on the average. As far as affecting the ,herbaceous plant populations. an increase 1n snow fall lis unlikely to have any direct effee~. The eene Dools [Of these plants allow a high variation 1n date of Igrowth inltiatio~~:nd still obtain maturation before I the end af the g-r~~-ins. season. The study needs to be carried on for seve~al more years for a ~ore definitive conclusion. l/tn ~ceinhoff. H.W., and J~D. Ives (Eds). 19i(.. Ecol~gical impacts of sno~~ack augroentation in th~ 5an Jua~ ~ountain~, Colorado. San JUMn Ecolo~Y Pro:~(t. Fin~l Report. Colorado State Univ. Pobl.. Fot~ Colli~$. l..!present address: Dept. of Bin] og:.-. Fct"t Lc.'.:i s ;" lj q;e. Durango. Colorado. 81301. n 323