|
<br />1:';\.LLoFQ,:!\1 i !lrAf.T~; ~1l ;:r,. :~.;rAtJ;.-,,!..L:!~'.1~:~I^'fI,t}.l~._""lli_1HE.2~.!'LJtAN MOUNTAINS OF COLORADO
<br />C:HAJ:'TER 1 ~!i.!.RpI>UCJ ((IN
<br />
<br />r" fI 1"':14, ,I, }~" SI:,"'IIf'.\', II, ....'. Stctnhnff. ,,"r1 W. W, Howell
<br />
<br />Thill docUlnent tfi the flnnl l'I'pI'rt 111' tIL... Sail Juan
<br />Ecology Project (S.Jf.P) \oIhJdl hl1s been supported by till'
<br />UnitEld ~tRte6 BureAlI of ReeJ.lmlltiOIl unrter C('ntract
<br />No. 14-06-1l-705:? (rom 1970 tn 197,. All 1~lIrl1er study.
<br />that was prepRred n9 ;J prl1hlem l1nalysis, _has been re-
<br />ported previnUJ'lly (S.lEI'. Phfls(' I FIIIIII It(")lnrt: TC'lJer
<br />et R 1. 1970). 'I'll(' 111"NI~'1I1 r~pl1rt <PhI'tAf' II) llnl'ft nnt
<br />include ony or th(' fOnr)y. I'r"pnrnl.lrv rnntr.rlnl.
<br />
<br />SUMMARY OJ.' t:.F.Y f:(INCLl!S IONS
<br />
<br />This Summar condenses the evaluat iOIl of ecologic
<br />imD8ct8 due to v8rvin~ snoyPac in tie an uan oun-'
<br />taina. It is based on a study of the influence of a
<br />snowfall whlch Is quite vsriable in both space and
<br />time. O1rect observation of the effects of snowpack
<br />fugmentation were not possible during the 5-year life
<br />of the San Juan Ecolo y Project. but the relationships
<br />tlsta . e etween ecoaystem components an .now
<br />conditions allow the eatinmtion of pOfll'llble cUr-cta of
<br />long-term successful cloud Ap.cdlug.
<br />
<br />The ststementA which fnllow trent thE' mOlln r.r.osyatem
<br />components in urdt'r, Thr 111I1I(I(:t IIf ~llO""l'nrk HllH,ln('n-
<br />tation on each ecosystem ,"umlt(lllenl IN nl'rnrlR('11 IIC~'lIrtl-
<br />ing to the nLltun' tlf lllf' t"nvlr-onmcntnl ch^Il~p. which
<br />produced the effect. The hAsic environmental changE'S
<br />are the addition of more snow and more silver. Such
<br />changes could 1nltjnt\~ n chain of effr.l:ts thnt would
<br />radiate throughout tlw {'coaystem. The firat links in
<br />the chain which havt! .'1 slR"ificant impact on ecosystem
<br />components are: (I) Illwer Roil tempr.rAtllre In the
<br />spring. (2) more moisture In the 8prin~. (3) deeper
<br />snowpack. and (I.) more ~Jlver"
<br />
<br />This summary includes only statements verifiable from
<br />the data. with causal connections and conclusions
<br />that would be acceDtcd by scientific peers in envlron-
<br />, ment41 disciplines. Speculntiun about causal links in
<br />the chain, or extension of impliCAtions beyond effects
<br />which were studied in the chain, and where the extension
<br />involves appU,cnt!on of Rene-rAl eC(llo(!,lc llndQr8J:..!!ndln~,
<br />tire avoided in this summary. Such appropriate ec1en-
<br />titie conjecture can be tound in Chapters II and lIT
<br />and in seaments of individual reports that are spec-
<br />ulative by implication t.hrollRh the use of terms such
<br />88 "may be" or"pt"ubahly", nr whidl Art'; IlJbelled 1'1.8
<br />lib road sign1f1cnnce" Ill" "Implications."
<br />
<br />Many other findings, which are not dlreC"tly related to
<br />the effects of snoWf'ad augmentation on the, indicated
<br />ecosystem components Bre a natural rart of such studies.
<br />For a Bummary of theRe find1nR9 reference is made to
<br />the abstracts of in(livJdIIU\ report~ Of to the detailR
<br />of the individual fp.ports themse]vt's III ChApter IV.
<br />
<br />~
<br />
<br />Onl twu (!nv:J rU,lllll'HI 111 ChilllWS ~'hl('h ml'ht he Jnduced
<br />by increasel.l f1IHlW nil ha\'l.l Iwen !mllld Cf' r(.Jllte slgnif-
<br />icantl to .Jantl:!.111 tilt" SOln ,1111111 N.llml1dnsi llllo'er
<br />aoil temperatures lln nl(lrc so mu sture.
<br />
<br />_ Lower SoiJ 'fempcrAtUTl'R
<br />
<br />itlatlon of shoot cloll ,,,tinll .....,S d",'1.,yp.d for pl:mtA
<br />oth in the tmlllrn ami fllrc9lH nl" 1\ rt>::IllJ t 'J l(l~'(.'r
<br />"801 tem eral"llreS 8f1S01" nte w t 1;1 C!~pcr 9nOWl'lIC fur
<br />',the species 8tudiC!d. Thefle il\.: II el .ng ernann spruc:"
<br />Clli.!! .cnr.e!..m..!D.!l!-.!.J. (l'l<!,kil.t! 111''''':11 <l'E.!'.u_U'-s, ~'.I_tl?J!;I.~.~).
<br />Thurber rttsr:ue (,,)..~_t:..UY.;1 1-'~\I.rE.('r',). 1\11.1 IlIlm.'rUlI!'I
<br />
<br />19
<br />
<br />hcrhl1c:eoUR species in both the tundra and fOrf':fit meA-
<br />dows. e dela vas most apparent in apecies~ith
<br />Rrowth p,ointa n t e mate a e zone 0 ower-
<br />tern eratures st the round level. This includes pri-
<br />marily tie er aceous spec ell. e growth regions of
<br />tref'!B, in the cambium and terminal bud8. WElre affp.ctl'i
<br />morl' tndirectly, pn..sibly throuah 80il temperllturf!
<br />e(fe-I:tA on root function. From this A les8 clt'Br re-
<br />lntionehip between growth inception snd snowpack VB!:.
<br />AnticJpAted although there "was a general correlation
<br />uf bud buret dstes for both spruce and aspen with thl:!
<br />snow clear dates. HQisture stre88 in spruce was un-
<br />usually hiah durin a the period of snowmelt and decrees
<br />dramatically at about the .now clear date. This did
<br />not affect the annual total radial growth of spruce,
<br />which initiated 2 to 4 weeks .earlier than bud burst,
<br />apparently independent of snowpack. Resultant annual
<br />biomass Rrowth of .pruee w...remarkablY constant ~
<br />year to year, unrelated to anowfall. Aspen was more
<br />variRble in annual biomass product10n. Aspen growth
<br />inrept ion wall dl!'layed by ,. later anow c!(OAr dllt~. bllt
<br />we did not determine whether or not this waR directly
<br />ltnked to variations in biomass production.
<br />
<br />The delay in bednnltfR of growth persisted throuRh
<br />thE' other stagea of the life cycle of mo~t plants,
<br />'hut with less magnitude. There seemed universally a
<br />compensatIon tactor Whlch rerm1~~ed every 8pecIes
<br />to complete its annual eye . of development each
<br />.summer. regsrd~e.. at anowpack depth. Except tor
<br />spruce, there was no Slml~ar compensatory mechanism
<br />for biomsRs production. In moat herbaceou9 species
<br />of the tundra, biomass production was inversely
<br />related to depth of snowpack.
<br />
<br />No effect was found on either initiation of developmen
<br />or biomass production of oak (Quercus Kambellii), pre-
<br />sumAbly because even in a deep snow year the snow had
<br />always disappeared from oak plata before the enrliest
<br />date of growth initiation.
<br />
<br />- tlnr.. Moisture
<br />
<br />Ph)'tosociological 8tudies in both forests and tundra
<br />showed that plant communities ware arranged along
<br />8now clear date gradients. In the lore.ts ask give.
<br />WR)' to aepen, then to .ubalplne fir (Ables lasiocarpa),
<br />and finally to Englemann spruce a. the snow clear date
<br />extends later into the year. The change was less
<br />obvious in the drier communitles. t.e. ln oak. ,The
<br />tundra changed from xeric (drier) to more mesic or
<br />even hydric communities. This could be expected to
<br />result in an increase in frequency of the rarer species
<br />
<br />A dendrochronologie survey of pondeross pine (Pinus
<br />ponderosa) immediately outside the target area-shOWed
<br />it~ growth on dry sltes to be a.soctated with December
<br />preripitation. The relationahip is a direct one and
<br />Ine would reaurnabl ahow an increa.e in ro'Wth if
<br />cloud seeding were to a to m -w nter snow 8 L 0
<br />'Buch relationship WIlS found for Engellllann spruce, the
<br />(lull' other species on which dendrochronologlc work
<br />has I>l!'!en conducted in thls study.
<br />
<br />~nlf1l~"
<br />
<br />Only the lo....er soil temperature and greater aDo\,,' depth.
<br />which ~lRht be expected to follow an increase in snow-
<br />fall. have been found influential on an1mal sctivity,
<br />
<br />A-13-2
<br />
|