Brigham Young University BYU ScholarsArchive
Theses and Dissertations
1971-05-01
An ecological life history of tall bluebell in Utah
Verl B. Matthews Brigham Young University - Provo
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BYU ScholarsArchive Citation Matthews, Verl B., "An ecological life history of tall bluebell in Utah" (1971). Theses and Dissertations. 8087. https://scholarsarchive.byu.edu/etd/8087
This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. AN EXX>LOGIC.ALLIFE HISTORYOF T.ALLBLUEBELL IN UTAH
V
A Thesis
Presented to the
Department of Botany
Brigh-. Young University
In P-artial Fulfillment
·of the Requirements for the Degree
Master of Science
by
Verl B. Matthews
Au~st~ 1965 ACKNOWLEDGEMENTS
Appreciation is e:xpres-sed to personnel of the Intermountain Forest and R.ange Experiment Station, United States Forest Service, Ogden, Utah, who mggested, supported, and financed the field research of this study during- the summers of 196:3 and 1964. Without such assistance~ this study would not have been possible. The author especially- gives thanks to - ' Dr. William A. Laycock and Paul w. Conrad, project personnel, for their
interest and encouragement- throughout all phases- of this study. Acknowledgement is also given to Dr. Earl M. Christensen and Dr.
Joseph R. Murphy for their interest in the problem and for reviewing the manuscript, Dr. Kent H. McKnight for confirming the identity of the powdery mildew found on tall bluebell, and Dr. -Stanley s. Welsh for confirming the identification- of -all plant species collected as associates. - Above all, --appreci11tion is e:xpressed to my-wife, Elaine.
Without her interest, encouragement, and willingness to forego personal pleasure, this thesis could not have been completed.
iii LIBr OF TABLES
Table Page
1. Vegetative and physical characteristics 0£ 5 study sites on the Mud Creek Sl.eep Allotment ••••••••••••••••••••••• 12
2. Physical characteristics .of .the soil layers .at each .of the .. .5 stuct, si.tes ••••••••••• •-••...... 15 3. Moisture equivalents and penqanent 'Wilting percentages .tor the top foot of soil at each stuct, si.te•••••••••••••••••••••• 17 4. Number of mounds and pocket gophers.(Thomom;ys ta;tpoides). per acre at each study si.te•••••••••••••••••••••••••••••••••••••• 22 5. Number and length of transects~ and points taken .to sample foliar cover of grasses~ forbs! and shrubs••••••••••••••••••• 26 6. Percent ground cover of grasses; forbs~ shru.bs~ and trees ••• •... 28 7. Percent composition of grasses, forbs~ and shru.bs••••••••••••••• 29 8. Bluebell seedling and stem densities per .square foot! The. nnmber of transects and quadrats used are also shown••-•••••• J2
9. Bluel:>ell stem and seedling densities outside of exclosures..... 33
10. Average maximum stem height attained by bluebell ••• •••••••••••• :36 ll. Number of weeks from snow melt to first flower~ ma:xi:mnm fl.oweringi and completion of the flowering period... • • • • • • • • 'J'/ 12. Average fiowering potential pe~ bluebell st9r1~ shown as the _-sumof opened ..nowers,. remaining buds,-. .and .destroyed .. buds••••••••••••••••••••••••••••••~••••••••••••••••••••••••• 40 13. Comparison of ..open pollinated! plastic..wrapped! .. and paper ... bagged bluebell stems ••• •••• ••••• •••.- ••••••• ••.••.• •• ••••••• 42 14. Comparison.of fruit production per stem. 196J••••••••••••••••• 4J 15. Dates of 'Wilting. and .deying ...of bluebell ..as.related .to ..soil ... moisture•••••••••••••••••••••••••••••••••••••••••••••••••••• 45
iv Table Page 16. Dates of initial and maxi.mumrates of mildew infection, ••••••••• 47 17. .Average weekly temperatures at time of initial mildew infection and maxi.mummildew infection rates••••••••••••••••• 49
18. &lrvival of bluebell seedlings by month••••••••••••••••••••••••• 64 19. Root lengths ..of' bluebell-seedlings. ...and.-SOllle .asso.ciated .... annuals •••••• •• ••• • ••••••••••••••••••••••••. • •••••••••••••• ,., 6.5
20. Seasonal use of ..bluebell._by ..sh.eep-on.tb.e ..Mud._Creek.Sheep ...... Allc,tm.ent...... 7.5 21. Root data from bluebell plants grown in the ~eenhouse...... • • • • 77
22. Seed germination, conditions and results•••••••••••••••••••••••• 80
V OONTENTS
Page ACOOWLEOOEMENTS••••••••••••••••••••••••••••••••••••••••••••••••••••• iii usr. OF TABLES.••• O • • • • • •• • • • • • • • • • O O O • •-• • • • • • • • • 0 • • • • • 0 • •• 0 • 0 •• 0 • 0 • • iv CHAPTER
I. I~~CTION••••••••••••••••••••••••••••••••••••••••••••••••••• 1 P~bi~- •• • •·•• •• • •. •-••. •. •·•·•. • •. • •. •·•·•••.• ,•• • • • • •••• • • • • • • • • •.... l General Literature •••.•.•••••••••••••• " •••••••••••••••••••• •-•• • • • 2 Ta:xononzy-••••••••••••••••••••••••••••••••••••••••••••••••••••••• 4
Literature••••••••••••••••••••••••••••••••••••••••••••• 4 Descript.i.Qn•••••••••••••••••••••••••••••••••••••••••••• 5 Distribution. •• ••••••• -•••••••••••••••••••• •-•-•• • • • • • • • • • • • • • • • 6 Description of study .Area•••••••••••••••••••••••••••••••••••••• 8
Vegetation••••~•••••••••••••••••••••••••••••••••••••••• 8 A.spenCutting •••• •-.... • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 9 History••••••••••••••••••••••••••••••••••~••••••••••••• 10 Description of Study Sites••••••••••••••••••••••••••••••••••••• 11 II. MEl'HODSAND RESJLTS•••••••••••••••••••••••••••••••••••••••••••• 12
Sc?i~-~0 O O O O O O O O O O o O O O O O O O O O O O O O O O O O O O O •••-• O •-• 0 0 0 O O O O O .• O O O ...... O •·• 12 Soi:L Moisture •• •-••••••••••••••••••••••••••••••••••••••••••••••• 16 Climate ••• _•••• _._._••••••••••••••••••••••••••••••••••••••••••••••• 18 Gopher Population•••••••••••••••••••••••••••••••••••••••••••••• 21 Vegetational .Analysts ••••••••••• ••• •••• •• •• • •••••••• • •••••••••• _ 25
Cover and ..Compo..si. ti.on •• •·•·•• •••• •-••••••••••••••••••••••• 27 Densi -cy•••••••••••••• ·•••••••••••••••••••••••••••••••••• 31 Phenolog:,_••••••••••••••••••••••••••••••••••••••.•••••••••••••••• 33
Tall Bluebell.• •• ,.•.•.-~•••.•••• •• •. • •. • •. • • • • • • • • •. o o-o • 33 Rate of Stem.Growth.,•••• :.••••••••••••••••••• .. • Flowering•••••~••••••••••••••••••••••••••••••••
vi Page Pollination ••••••••••••••• •·•·••-• •• • ••••••••••••••• 41 Other Observations••••••••••••••••••••••••••••••• 44 Associated Species •• _••••••••••••••••••••••••••••• •• •••• 49 Rate of Stem.--Growth.•••••••••••••••••••••••••••••• Flowering•••••••••••••••••••••••••••••••••••••••• S~edlings •• •. • • •-•-••••••••••••••••••••• -•••••••••••••••••••• "'•• Root_Systems •.•••••• •-•·••·• ••••.••••• ·•••••••••••••• -'-••:•.·••·• •••••• •- Palatability •••••••••••••• •-•••••••••••••••••• •·•·••·••••-•...... Lal:>era~ry-•••• •••••••••••••••••••••••••••••••••• • •••••• •. •-•·. Gree~use Observations •••••••••••••••••••••••••••••••• 76 Seed Germination and Emergenee••••••••••••••••••••••••• 79 stJ!O!AR.Y• • • • • • • • • • • • • • • • • •·•• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 84 LITERATURECITED•••••••••••••••••••••••••••••••~••••••••••••••••••• 87
AJ»I£NDI'XES• ••.•• 01• ••••••••••••••••••••• • •••••••• • •• ••• • • • • • • • • • • • • • • 90 ABBrRACT
vii CH.APTERI
INTRODUCTION
The Problem Tall blu-ebell, Mertensia arizoniea Gr-eene var. leonardi (Rydb-:)
Johnston (!1.leonardi Rydb.), is the most common of the large bluebells
in the aspen zone of C-entr-al Utah, occurring at elevations from 6,000 to 11~000 feet (Range Pl-ant Handbook~ u. S. Forest Service~ 1937): There
-are two major problems associated wiJth -its management -as ,a. f-ora.ge-pla.nt of aspen rangeland. First, in certain areas only. a smal.l portion of the
total herbage is utilized because- mature stems become infected-with. mildew
and collapse onte the ground. As a reSQl.t, the-foliage rapidly becomes
dry about early to mid-July. Grazing prior to July 1 on -aspen ·ranges in
Central Utah is-generally not advisable; the-ref&re, much-of
forage is not utilized. -Second, under certain- grazing- conditions. blue-
bell becomes the dominant forb, appearing to crowd out other desirable
and later maturing species.
This investigation was- conducted during the Slllllllers of 1963 and
1964 in Central Utah~ Specific objectives were to study the. phenology,
palatability,. root system, seed germination, seedling development and
describe the physical site-fao.tc,rs where tall bluebell occcurred. both in
-pure -stands and in association •with other speoie,a. The studies followed
· outlines suggested by Stevens and Rock (1952)( and Pelton (1953) for
1 2
~co.logical life history studi-es. Determination of the correct ta.JCDn.and distribution of this species were also a part of this study. Knowledge gained in this study has provided -a better understanding of this tall bluebell and associated species and will be valu,able in developing better management systems for aspen ranges.
General Literature
.Available literature on the ecology of Mertensia arizonica var! leonardi _is fragmen:tary and widely scattered. "An Investigatio?) of the \ . Ecology of Mertensia ciliata in Coloradotf by Pelton (1961) represents tile oiµy direct ecological stuey _found for the genus in western North America. _Nearly all literature citations are based upon vegetative studies in which Mertensi.a w.as included. as one of the perennial forbs •
. . In Central Utah, M. arizonica var~ leonardi is one- of the major_ forbs in the subalpine zone (Ellison, 1960). Ellison (19.54) listed !1~
arizonica var. leonardi as one of 16 relict. bro-adleaved. species on over-_ grazed cattle range. He further indicated that blueb&ll constituted from l to ,50 percent of the original upland herb association. His data were based upon cover composi.tion estimates obtained at- _si.x relict natural areas on the I • Wasatch Plateau. Houston (19,54) listed the species as one of the major 1-"orbs of aspen·· r.anges in good :toexcellent condition in the :rn-termountain Region~ .According to the· Range Plant Handbook (U! s. _Forest Service, 1937), .. !1• arizonica · var! lec,nardi prodl-1-ees an abmdanc-e o-f succulent forage classi.fied r-rom good to very· good in pal.atabili ty- for sheep 8.!ld goats and fairly good for cattle~ Heady, Richard, and Lommasson (1947) listed the genus Mertensi.a under a proper use rating of 70 or 80 percent utilization by weight in the Bridger- Mountains- of Montana. They also
called Mertensia, -a ch0ic~-torb on sheep range in th-e--above area.
Ellison (19,54) cited evidence to- show that gr-a,zing-by-. sheep resu:J,.ted in an increase of -grasses and a d-eerea-se of £orbs including H~-arizonica var. leonardi. This he attributed to the--grazing habits of sheep.- He pl-aced bluebell i-n ·two pref-erence class-es showing a combined range of 20 .. to 100 percent utilization by sheep c,m a dry-weight basis. - Ellison's
{19.54). data furth-er showed a mark-ad ciecrease in percent.age sf cover com.., po st.ti0n of bluebell -on --ar-eas having h&a'YYcattle. use when contr-asted to n<:mgrazed areas in the same vicinity. This is' of interest because total percent cover composition of forbs increased under cattle u-se while bl~ bell decreased-~ Ellison (1954) indicated that M. arizonica var~ leonardi
-was-an easily distinguimed invad.er of open areas when protected from overu-se by grazing.
Utilization of bluebell by deer is slight~ Captive mule de,r were fed freshly obtained forage by Smith (1953) at Logan, Utah. Of the 62 different species of forbs included in the experiment, H• arizonica var. leonardi was consumed in quantity amounting to only 4 percent of the
average daily -consumption~
Snall animals are also involved in bluebell ecology. Marston ~d
Julander (1961) studied plan_t cover reduction by the pocket gopher .. Thomom;ystalpoides in Parish Canyon, Davis Coun-cy-, Utah. Their study
showed a threefold increase of percent ground cover by .H.•arizonica v~. leonardi. over_ a 10-year period after aspen removal. They further inaj_ ..
cated that aspen removal resulted in an increase of gopher activity in which 75 percent of all bluebell plants investigated showed injury to 4
the outer roots. The role of pocket gophers in decreasing or increasing
ground cover of bluebell.was not established. Bluebell has also been
found. in the "haystacks" of the Uinta Pika Ochotona princips (Hayward,
1945).
Literature
Great difficulty has been encountered in attempting to ..segregate
the genus Mertensia into distinct species taxa. Mertensia arizonica was
first described by Greene (1897). A closely related entity-was also des-
cribed and named as a new species by Rydberg (1909); This he called
Mertensia leonardi. Johnston (1932) recognized a r.alationship between -- the two entities and placed M• leonardi Rydb. with )1• . arizonica. Greene uncier the new• combination, M• arizonica Greene.var~ leonardi Rydb-; Lat.er; Williams (1937) did a detailed and thor-ough tamnomic treatment of the -- -- genus in which he r~cog:nized Johnston• s combination. H• arizonica var~ leonardi has been retained as the correct designation in this present
study because it was recognized in the latest authoritative treatment of -- the genus~_
Little work has been done to show phylogenetic relationships of
the different species within the genus. Popov (1953) made a limited
study of the phylogeny of the genus Mertensia in 'Which 45 speci'es are
recognized world-wide. Of these, 15 are located in Siberia, Mongolia~
and Central Asia, 6 are in the Himalayas and Tibet, and the remaining 24
- species occur in North America~ The North American species were based
upon the earlier work o, Williams (1937) Limited cytological studies .5
by Britton (19.51) on .5 different. species of the genus indicates a somatic
chromosome-number of 24~ These counts were made on root-tip material,
and did not include Mertenm.a arizonicao
As yet, the number of different species and varietal forms occurring in Utah has not been investigated thoroughly!
Description
The species Mertensi.a arizonica and its variety leonardi are des-.
cribed as followsg
Mertensia arizonica Greene, Pi ttonia '.31197. _1897o
Erect or ascending, 3-8 dm. or more tall, stems 1-several from each
rootstalk; basal leaf (only one seen) narrowly ovate, -acute, 1.5 cm~·long,
6 cm~ bro_ad, slightly de-current on the petiole, petiole as long as· the
blade, glabrous but slightly papillate, margin ciliate; lower cauline
leaves from spatulate to elliptical, usu.ally petiolate, the petiole winged,
upper cauline leaves usu.ally sessile, elliptical to narrowly -ovate~ acute,
3-12 cm! long, 1-.5 cm. broad, glabrous or papillate, ciliate on the margins,
not becoming abruptly smaller upward; pedicels 2-~ mm~long, glabrous,
papillose or sometimes the papillae developing short hairs; inflorescence
usu.ally branched. the peduncles bearing a several-flowered elongated
scorpioid cyme; calyx 4,.,8 mmo long. campanulate, glabrous on the back,
hairy within, the lobes one-half or less the entire length of the calyx,
a definite ring of hairs at the base within; corolla-limb 7-11 mmolong. always longer than the tube, moderately e:xpanded; anthers 2~.5-:3-~.5mm-! long,-
as long as or shorter and narrower than the filaments, filaments 3-4 mmo
long; fornices conspicuous, pubescent; style 10 .. 1.5 mm! long, usu.ally 6 shorter than the corolla; nutlets rugo se, shorter than the calyx~
Description Williams.
Mertensi~ arizonica var~ Leonardi (Rydb.) Johnston in Contr~ Arn.old Arb. No. Jg 83. 19J2. .. !!• Leonardi Rydb. in Bull. Torr. Bot. Club J6: 680! 1909• .. H~ Sampsonii Tidestrom in Proc, . Biol~ Soc. Wash. 261 122. 1913. H• arizonica var. umbratalis Macbr., ace~ to Macbride in Contr .• Gray ijerb~ Nos. No~ 481 9. 1916, as to synonyms !:!~..Leonardi and H• Sampsonii, and specimens cited from Utah except Pamme11 & Blackwood 3820. Very similar to the species; calyx 4-8 mm~long, divided almost to the. base, the lobes ,-.7 nnn~ (rarely 2 nnn~) long, lanceolate, acute, cili- ate; anthers and filaments averaging slighily shorter than in the species.
Synonomy and description fide Williams.
Distribution
Mertensia arizonica occurs in central to routhwestern Utah and
Arizona (Williams, 1937). The variety leonardi occurs throughout the mountain range extending the length of central Utah and into southwestern
Wyoming and southeastern Idaho. The occurrence of tall bluebell in Utah
(by county), is shown on the map in Fig~ 1. The varietal form is distinct throughout its range, but it may intergrade with the species and J:!~fran- ciscana Heller where these populations overlap!
All specimens of Mertensia from Utah in the herbaria. of Brigham
Young University and University of Utah, were examined and compared with original descriptions. A list of citations was prepared and can be found in the APPENmXoIn general, the citations are lacking in ha.bi tat and colllllJUnity type information, but do show an al ti tudinal range of 4,600 to 7
Mertensia arizonica •••••••••••••••••• A Mertensia arizonica var. leonardi •••• L
\
I L I ' I \:---",,,. I , - 1, ) '\, ,~- ....~( .... ., I I ,, ------••-•---- I I \ I ,. I,_, • , L .. -- i' t L ' ; , ,---I ---- !--'', , , ! :-- -...--': L -- , ' : ~\ : L I I 'I L\ \ I J,~ \ I I ---- - ______...\ : ,'~ . "''; . L / ,, L,_ ,,',,-,--·-·------., I I • ' ------,II fJ . I ,,.'' \ , ______·;·'1 • I I L .,.•--I ___I, , I L __f L : ',' I ------·:.."----~', __ i ______' _ A \ I L ; AL :
-- - - - ·-- - - - _#:.I ---- -'·------I I A / I ____ r•: --.__.,J_J __ - A
FIG. 1 •. Map of Utah showing the occurrence of bluebell by county. 8
10,000 feet w::i.thmost showing an intermediate altitude~ The-~uthor• s
observations indicate that M-.-arizonica var! leonardi has strong associa-
tion w.i th aspen or spruce-fir vegetation types, and it may be restricted
tQ deep soilsi
Description of Study Area1
This study was conducted_ on the Mud Creek Sheep Allotment of the Uinta National Forest in Wasatch-County, Utah! It is located in/fownship 1
J -l!_West Range .'.3South, Uinta Special Meridian~ The allotment contains
··----·· . approximately----- 4,160 acres anci lies between 7~500 and 9,1)0 feet elevation! Drainage- runs to the east and enters the Strawberry Reservoir~ The west-
ern half -of the allotment is rolling terrain with north and -south facing
slopes~ On th.a lower or eastern portion the slopes .are steeper, up to
50 percent!
Soils on most of the area are deep and consist of loams with reddish
, or yelle>w.i.sh hues. A few outcrops of sandstone occur on the upper portion
of the area and on some of the steep, rocky south_ facing ridges on the
lower areas to the east.
Veg-etation
The upper two-thirds of the area is covered with open aspen stands~
The- openings- were badly depleted by grazing before and during the ear1y
period of National Forest admim.stration (1898 - 1918)~ Many of these
areas still have only sparse ground cover of annual weeds although per-
ennial. .grasses-and ..!orbs are .slowly becoming established~ .. A few .of the -
1unpublished file data~ Intermountain Forest and Range Experiment Station~ .Provo~ U'tah~ 9
openings have-dense blueb&ll•and· e-lderberry stends --and some have a f.air
eover of gras&~ forba,- -and browse~"
The main plant species in the area--are:. blu-ebell (Mertensia
ari,zonica var~ leonarai), elderberry ( Sambueus racemc>•saH •niggerhead.
(Rudbeckia occidentali s) snowberry (Symphor.tea.rpo;s oreophilu-s) •
lfhea:tgrass• (Agropmn traehycaulum), .bearded wheatgr:ass· (Agro:emn
. sw:i.s.curiaum),tarweed (Madia· glomerata)~ "'White pol,emonium-(Pol-emonium foliosi ssi.Jnum) _starwort (Stellar:ta j ame-si-ana)·~· •.Imo tweed (P&l;ygcmum~p! ) . ~eedlegra,ss ( Stipa lettermani) • cSedge (Carex •hoodii), penst,emon (Pen..
ft:emon spp~), yarrow (Achillea millefoli\llll)
Big• sagebrush and chokecherry are found iri some· openings;. Some of
the north-facing slopes- are •covered w.Lth· conifers and:·aspen •. In S0111e
areas the coni.fers, consisting of subalpine fir ( Ab.tes- lasioearpa) and
Engel.ma.ml spruce (Picea engelmanni) are fairly dense with 1i ttle under.:.
story.
Aspen Cutting
Approximately 320 acres of aspen were logged on the- lower eentr.al
portion of the ar·ea during-1956..1959~ · Cutting,was done on a selective
ba.sis and restricted to the larger tr.ees~ Slash was lopped and left on
the greund! In some places ..so much debris was left that it created a
H:wind£all" ,which. prevented• 1110,vementof sheep~
. Dllring the logging. period sheep, were kept off the .ar~. and after
the logging. was- completed~ bru.sh .was .too, d~ on macy-.areas. to ..permit
free movement of the sheep! Aspen sprouts ,are abundant on much of the
cutover area~ especially on the heavily .cut areasi 10
History
Preston Nutter acquired a .5-year• lease on Strawberry V4lley (part of the-Indi-an Reservation•lands) in 189·3! He gr~z,eq, 8-10,00Q head of cattle in this valley up to 1898. The Heber• Land arid Livestock Company acquired grazing rights at this• time· and permitted,150-200~000 sheep to. gr•ze.-the valley, along.with· additicmal: cattle and he>rses up to-190.5 wti,n. the• U~ ted • States forest S&l'Vice acquired· rights- to the land! . At this time~ much of the area had been overgrazed and partly denuded of vegetation!
In 1915, 3,202 sheep grazed on the Mud Creek Allotmentl The first cattle (56 head) were p&:rmitted on l&we:r Mild Creek in 1917~ In 1918, 205 cattle -:were-permitted -to graze ·on Mud and Clyde Creeks~
:Cn 19:33, the number. of sheep-allowed to graze the- Mlld Creek Allot- ment-wa-s reduced -to 2~635 because of past overuseo At that time, 160 head of cattle were allowed: to graze en the Mud Creek and adjoining Clyde
Creek drainages~ In 1950! the number or sheep •Was reduced to. 2:463 and the sheep, and cattle use was segregated~·- the sheep taking the-upper part of th~ allotment (currently known as the Mud Creek a>.eep Allotment) and the cattle the lower~ In 1951, the number of sheep was- further reduced to 800 a 67 percent reduction~- From 19 52 to 19 58, the grazing use r~ mained at 800. sheep with the grazing period or July 1 to September
In 1960~ the start of grazing was advanced to June 15 to try to make better use of the early growth or bluebell~
Response of the Mud Creek Sheep Allotment to the 67 percent reduc- tion in grazing has been rapid and impr.ovement in range conditicm is. readily visible. Dp'Sirable forage grasses are replacing tarweed and other 11
apnuals- on bidly depleted open .areas in the aspen! __Many areas heaVily
. Brazed- in the past ar& now producing contuderabl:e amounts of C~x~ Poa~
Agropyron, ·.and other desirable plantsr
In 1957~ this allotment was designated as a demonstration allot- • C -- . ment •. In 1959~ plans were made for experimental studies on range rehabi- -- litation and sheep management! At this ti.me the allotment was divided into 5 fenced grazing uni ts (Figr 2f! Si.nee 1959, each of these uni ts .
has received use during .a different season or combination of seasons~
Description of StudyI . Sites
Five study sites, representing diff-erent vege-tati.on types at two • ~levation's, were , selected in the early summer of 1963 (Fig.,, 2) One of these study sites (upper open forb) was-inside an exclosure established
in 1959 as part of the grazing study! Exclosures were established at the other 4 sites in 1963 to protect- selected plants from grazingl The
vegetative and physical characteristics of each site are shown in Table 1.
TABLEl! Vegetative and physical characteristics of 5 ~udy sites on the Mud Creek S:leep Allotment!
Exclosure Slope
Date. · Site Elev. Size (ft~) Estab~ 'Ii Azimuth Upper ?Pen forb 9000 66 X 66t 1959 11 60
Upper ~spen r orb 8965 34 X :341 1963 10 171
Lower open f orb 84~ 136 X 1441 1963 10 101
Low.er aspen forb -. 8350 28 X 40t 1963 12 146
HPu.re" bluebell 8~0 120 X 1401 1963 10 126 12
N ) C
Road ------,0 .o Upper One Mile Aspen Forb
0 Lower Open Forb
' ' • •\ I \ I ' \ \ 11Pure" '.• .., ', Bluebell o \ O •, • ', I
L~wer I Aspen For I , , I , I - , ,
, , '
FIG. 2 • Map of the Mud Creek Sheep Allotment showing the _location of each of the 5 study si tea in relationship to the grazing units and boundary fence. CHAPTERII
METHODSAND RESULTS
Observations on growth, phenology, root systems, and reproduction of tall bluebell were made ,a,t the 5 study sites in 1963 and 1964i In .a.ddition, soil characteri sties, climate, and vegetal com.position of each site were studied~ ---
A soil pit was dug w.l.thin or adjactnt to the exclo sure at each site t,o study root systems~ and to obtain sou·.profile descriptions! On Oct- 9ber 7 and 8~ 1963~ Devon Nelson, Soil Scientist~ W~satch National Forest, described th~ texture, structure, depth and color of each horizo?\l Several hundred gr.ams of soil from each horizon were collected for laboratory ana1y sis!
Percent organic matter and J>H~,rt9 de~ermined from, procedures ouilined by Russel (19.58). This consisted of using a chromic acid o~dative method for organic matter and a glass electrode pH meter for pH~
Total so:1,.uble salts was determined from saturated sail paste samples with a wheat.stone electrical conductivity bridge! Mechanical analyses were made using the hydrometer method (Bouyoucos, 1951H
Soils at each study site were derived from alluvial sandstone and to a lesser extent! from limestone parent material~ Profiles from all
sites, except the lower open forb, show a bi sequal pattern wherein well
]J 14 developed soil horizons have had. additional parent material superimposed on them~ giving rise to similar well dev-eloped horizons at the soil sur- face. This supe-rimposed layer of parent material constitutes a highly fragmented. layer of decomposing sandstone located about 2 feet. beneath the surf ace. This layer restricts the effective soil depth for many species of grasses. and forbs, but not bluebell which has roots penetrating into the deep, well developed underlying soil. Laboratory analyses of all exposed soil horizons show very close agreement with profile descriptions. Because all horizons within the same soil layer are similar, only the layers for each study site have been shown in Table 2. Descriptions of the soil profiles and soil anal- yses are in the APPENDIX.
Soil data from the 5 soil pits show a textural range of clay to loam in the A layer, or zone of leaching. Further, all sites.have soils. of clay or clay loam at depths of about 4 feet and greater {Table 2). The "pure" bluebell site had the highest pH readings of all sites for the A, B, and II B layers. Here, a range in pH of 7.3 to 8.9 was obtained. The two lowest pH readings of 5.4 and 5. 5 were obtained ..at the upper open forb and upper aspen forb sites respectively. A pH range of 6.5 to 7.7 was observed for surface horizons. The percent organic matter was highest at the two aspen forb sites. In general~ organic matter decreases with depth. The2 adjacent horizons within the Band II B layers at the "pure" blu.abell ~ite have an unusually high organic matter content. These 2 horizons may, 'therefore, constitute a buried II A Layer and snoUld not be assigned to the Band II B Layers as presentLy designated. 15
TABLE2. Physical characteristics of the soil layers at each of the 5 study sites.
-- Study Site Layer Textural Class Depth '1,O.M, pH (inches) - Upper open £orb A Loam 0-50 .48-3.96 6.4-7.0 B Clay Loam .50-60 • .50 .5• .5 II B Clay 60-74 .67 6.5
11Pure11 bluebell 'A Loam to clay loam 0-18 J.,52-4.70 7.3-7.7 B Clay loam 18-27 6.65 7.5 II B Clay loam to clay 27-.58 1.0,5-5.J0 8.0-8.9
- Lower open £orb A Clay to silty clay loam 0-4J 2.83-5.24 5.9-6.8 B Clay 43-60 2.68 6.9
Lower aspen £orb A Loam 0-21 J.67-7.44 7.;') II A Clay loam 21-J.5 2.21 6.9 II B Sandy Clay 35-42 2.52 6.8
Upper aspen £orb A Loam 0-.57 2.18-5.28 6.3-7.4 II B Clay 57-64 2.26 ,5.4 C Clay 64-76 1.70 7.7
Total soluble salts constituted less than 500 parts per million at all sites and in all horizons. Soil structure ranged from granular to blocky to mas-sive. Alls-oil pits were dugduri:ng August and September of 1963, yet at least one clay horizon near the bottom of each soil pit was found containing 16 sufficient moisture to be hand molded. All such horizons were within reach of mature bluebell roots, and may constitute the most important soil fac- tor allowing for survival o.f this species. This seems especially signi- ficant, because· very few. roots of other species were fo-und extending to these moist soil horizons. All other horizons were very dry and hard at the time of excavation.
Soil Moisture
To determine variations in soil moisture throughout the-summers of
1963 and 1964~ soil samples were collected at two depths from each site at weekly intervals from mid-July through September (11 and 12 weeks) using a 3/4-inch LaMotte soil sampling tube. On each sampling. date.,
5 soil cores, 1 from each corner and 1 from t~e center of.the exclos~e. were obtained at each site. Successive sample. cores were obtained in the same vicinity but not closer than 6 inches to any previous sampl.e. Two -· sections, each 2 inches long, representing. soil depths of 5 to 7 and.11 to lJ inches. were cut from each core. Sections from each of the 5 cores at -ea-0h site were combined as a composite sample- and placed in a 500-gr-am soil can. Samples were then weighed to the nearest one-tenth of a gra,m on a triple beam balance. Later~ the samples-were oven dried. at 105° C for 48 hours. Percent moisture was computed on oven-dry weights approxi- mately 6 hours after the soil samples were removed from the oven.
Pennanent wilting percentages and moisture equivalent determinations were obtained for each site by subjecting water saturated soil samples to pressures of 15 and 1/J a_'tmospheres, respectively. An Irrigation Engineer- ing Corporation pres.sure membrane extractor was used inthel5 atmosphere determination, while an Irrigation Engineering Corporation porus plate 17 apparatus was us-ed for the 1/3 atmosphere~ Percent moisture wa-s ,determined
~· as described above. Sample&, consisting of soil cores tak-en. from each site throughout th-e-summer of 1964, were used as a composite -sample for that site. Each composite sample represented the top foot of soil.
The moisture equivalents and penn.anent wilting perc-entag-es are -shown in Tabl.e J.
TABLE3. Moisture equivalents and permanent wilting percentages for the top foot of soil at each study sit,.
Moisture- Permanent Site ; F.quivalent Wilting (Percentage) (Percentage) Upper open forb 17.20 5.35 "Pure"bluebell 21.20 ll •.27 Lower- open forb 26.15 14.-80 Lower aspen forb 17.22 8.28 Upper---aspen--forb - - 14.07 ----"-·------4.92·-·
The.moisture in the top foot of soil at all sites" except-the upper ... aspen forb site, showed a level approximating the permanent wilting per- centage by late July each year. In early June, the soils ar-e completely saturated from theinelting of snow. Soil moisture gradually decreases through evapo-transpiration loss until the permanent wilting p.erc-entage is reached. This condition of the low moisture then exists for about 4 weeks. The precise rela~onship existing between total available water and pQOent moisture was not established. In 1963, a total of 2.84, 1.25, and 2.25 inches of precipitation were recorded at the- "pure" blue-bell site during the months of June, July, and August r~s~tively. Rainfall in the corresponding months of 1964
W&6 somewhat less. Summerprecipitation, while significant in prolonging 18
the green-vegetative &tate of bluebell and other species, is not suf'.ficient
to offset evapo-transpiration losses and.prevent the occurrence of perm.&nf9nt wilting conditions in the top foot of soil.
Climate Temperature, humidity, and precipitation data were obtained during the summers of 1963 and 1964.. Continuous records o.f temperature were ob- tained at all sites, while humidity and precipitation were obtained only at some of the- sites. (see- APPENDIX). AlJ. instruments, except rain gauges, were housed in shelters located 5 fee.t above the soil surf ace.. A standa~ Weather Bureau shelter wa,s used at the "pure" bluebell site while small portable instrument shelters (Hungerford, 1957) were u&ed at all other &ites. All temperature. readings are in Fahrenheit degrees. Accuracy was-determined from mmnmm..minilllWll thermometePs-while humidity recordings were periodically checked :with a sling psychrometer.
A part of each summer's climatic data is found. in Fig. 3 for ellch
study site. Maximumand minimumtemperatures are shown as. weekly averages. The highest and lowest temperature reco;rdings for each week are also plotted to show variation from the weekly means. Permanent snow.cover melted in the latter part of May in 1963 and 1964 at the three lower sites and about the first part of June for the
two upper sites. Snow melt was followed by cool temperatures ranging up
to the mid 6o1s during the daytime and down to the JO's during the night throughout the month of June. July temperatµres ranged from the mid JO' s
&11 the way up· to 83°. In August, low temperatures· ranged in the mid 40 1 s with sustained high temperatures in the 70 1s occurring until the latter 19 1963 Upper "Pure" Lower Lower Upper Open Forb Bluebell Open Forb Aspen Forb Aspen Forb 80 ,. ·-· 70 - Cl)~ 6 H •rl 0 ::s- (I) ~ii 50 f..i (I) r ...... ~i Lo \ . . . ~e 30 .'l \ . 20 -1-i- l
"C r:: tiO
(\1 -~ 100 [ 0 0 l;~
196L 80 .,_. ... .,,•-· . • 70 (I)~ a-·s 60 ~-§ • Q.l r_ f..i ,o (I) S-t J:·-Ir • 0.,§ Lo . • a3 . . p- e-.- 30 ,.,., . ... .1/ J"· r- 20
'g bO (\1 r:: 'M 10
~· i~ 0 [ . . rS~ % I I I I I I I I I I I I I I I I -I· I I I I I I I I I I I I I I I I I I I I I I I Extreme High and Low Temp. Max. and Min. Temp•. (Weekly Ave.) ·-·-· Inches of Growth per Stem (Weekly Ave.) Numberof Flowers Opening per Stem (Weekly Ave.) Fig. 3. Relationship of weekly growth and flowering rates ·-·-· of bluebell with temperature over an 8-week period. The first week ends on June 11 in 1963 and June 9 in 1964. 20
part of the month, when temperatures:; dropped with arrival of late, summer
thunderstorms. Rising temperatures- occurred again during the latter part of September and early part of October. In general, the three lower sites experienced slightly higher daytime temperatures than,did. the two upper sites, while the two aspen sites experienced slightly lower daytime temper- atures than the ne-arest open sites. The daily maximumwas reached between the hours of noon and 3 P.M. and the minimum during thehours,of 4 to 6 A.M. The length of the frost·free period varied among the different study
I sites. For those sites where data is available, the pure bluebell site
and upper open forb site had a frost-free period of about 110 days be-
tween the- weeks of June 25 and October 15 in 1963. In 1964, the "pure'' bluebell site had a frost-free period of about 75 days, (June 23-Sept. 8) while all other sites had a frost-free period of about 62 days (June. 2.3- Aug. 25)~ The shortness of the frost free period may. not be too signifi- cant because injury to bluebell stems, leaves, and flowers.did not occur
until te~ratures dropped to the mid 20 1 s. Such temperatures occurred after mature seed had been shed except for two occurrences in which the temperature dropped to 27° and 26° during the period of flowering and active stem growth at the lower open forb site. This latter event.failed to cause visible injury. The lack of low freezing temperatures could re-
. sult in an overall 11growil)g period" of 145 days in the aspen zone as indicated by Costello (1939). Total precipitation recorded at the upper open forb site approximated
that of the 11pure 11 bluebell site in quantity and frequency during both summers. In 1963, a total of 10.47 inches of precipitation, mo~tly rain,
fell at the 11pure" bluebell site between the weeks of June 11 and.October 21
1,5. This was lllllCh greater than for 1964_in which a total of 3.95 inches was reco~ded for the_ same_period. A breakdown of this period by month
~owed 2.84, 1.25, 2~25, and 3.68 inches in 1963 for June, July, August and September respectively~ and_ 3-!38~ 0~12, 0.70, and 0.33 inches in 1964~ Thts is in_general agreement with the data of Lull and Ellison (1950).
Theyfound that mon1:hly precipitation was low~st in September followed by
July and then August in the aspen zone in the Wasatch Plateau. The w-eekly averages of percent relative humidity showed strong
I correlation with the occurrence of precipi t-.tion. The relative humidity was higher_ during periods of frequent shower activity. The average maxi- lllllm humidity showed a sharp drop at the end of June . and then rtarted in- creasing about mid-July at the "pure" bluebell and upper aspen forb sites, and early August at the- upper, open forb site during both 1963 and 1964. These sites reached a period of maximum humi.di ty about mid-August which lasted about 4 to 6 weeks. During this period, the -weekly aver.ages of maxilllUlllrelative humi.di ty ranged from 80 to 99 percent. These weekly averages were generally lower during August and September of 1964 than in 1963 due to the less frequent occurrence of storm activity in 1964.
Gopher Popu?-ation
Relative gopher _population of the 5 sites was determined by counting the current year• s mounds within each site exclosure and comparing with the gopher population index established by Richens (1964). Count~ Wf3re made <>n September 9, in 196, and on September 14, in 1964. Exclo sures at the two aspen forb sites were smaller than those at the other three sites so 5 plots, each 23~6 feet in diameter (1/100 acre), were sampled 22 outside but adjacent to these" exclosures to make the sam1>ling ar.ea mpre comparable. The mound counting was-conducted"under the supervision of Dr. -· Odell Julander, Range Conservationist, Intermountain Forest and Range Experiment Station. Mound~ounts were converted to number of gophers per acre (Table 4) according 'to the population index established by Richens (1964) from studies on the Cache National Fores~, Utah.
TABLE4. Number of mounds and pocket gophers (Thomomystalpoides) per acre at each ~tudy site.
September 9, 1963 Se.pt1;1mber14, 1964 Site Mounds Population Mounds Population
Upper open forb 4,140 5o+ 1,450 5o+ "Pure" bluebell 377 Ca.24 247 Ca,22 Lower open forb 2 Ca.o J6 Ca.12 Lower aspen forb 1~600 5o+ 828 Ca.41 Upper aspen f'orb 2,266 50+ 2,063 5o+
A downward trend in gopher population or general burrowing activity occurred at all sites in 1964 from that in 1963 except for the lower open .. f'orb site where a slight increase may have occurred. Fewer mounds in 1964 may be due to reduced activity rather than reduced populations (Laycock, 1957). Soil moisture was lower during the months of August and September in 1964than in 1963 and may have resulted in less soil being brought to the surface to create mounds. On several occasions, pocket gophers were observed reaching f'or 23
bluebell stems from- inside the entrance- of open burrows. All stems. taken
wer.e-green and succulent, and were cut with the teeth at a height of 1/2 '
to 1 inch above the ground. The- front feet- -wel"e-used to support th-e stem
d.uring the cutting act. Afterwards, the entire shoot was- pulled down out
of s~ght into the gopher burrow. The taking of st--ems one at a time occurred
repeatedly until as maey as 7 stems had-been removed from one plant.
0ccas-ional bluebell plants, in areas of extensive burrowing activity, had
up to 0ne- half -of -their stems removed by gophers. Such plants had back-
filled burrow openings.within a few inche-s--from where the stems had. b•en removed, oce-asionally in the center of the plant crown. Stems of -Pole- 1110nium.foliosissimum were also taken in the same way as-bluebell st-.u.
The above-ground feeding areas-of pocket gophers appear greatly
restricted to the areas of recent burrowing activity. However, they may
. actively- forage for food--at dis-tance-s of 15 to 20 meters from the. ne~st
.. mound (Hayward, 194-5). At the upper open forb site (area- of greatest
-gopher activity) numerous tunnels- about 4- inches-- in diameter~ extending
from a few- inches below the soil surface to- a depth of 36 inches, were.
found in the- face of the soil pit. In one tunnel, an enlarged-round cavern
. measuring 10 x 1.0 inches- was- found. This- cave-rn contained dried. and. fresh
plant. material consisting of leaves and culms of A,grop:yron trach..ycaulum
and Stipa.
Fresh Collomia linearis, PolYgonum douglasii, and bluebell.stem
tips containing,.--seed were also found, along with numerous leaves of- blue-
. bell and Rudbeckia occidentalis. All material had been cut into lengths
m~asuring 1 to 2 inches and was- underla-in with fresh scat. The occurrence
of such caches has been observed by others (Aldous, 1945). -24
Injury to bluebell roots- was most extensi v-e at the upper open forb
site-whe:re-15 tunnel cross sections -wel'& ?"&Vealed on the west-facing wall
of the soil pit. Many of the main roots up to 1/2 inch in diameter had
been severed by. such burrowing activity. Some..of these- inju:red roots had
healed· over, while others had died back .to the "caudex. 11 Some of. the
11 . caudexes-" supported a pro-fuse m.a-ss-of new- root&• extending to a depth of
about 24- inches. This is -whe:re most of the injury occurred. The lack of
. tall stem height and vigor of deep-rooted bluebell at thi-s- upper open
forb site may be the result of root damage at. the 2 to ,3-foot depth •
.· Gopher tunnels- are also- eJEtens-ive near the soil surf ace. These tunnels
,-f3as-ily collapse under foot if one walks- through the exclosure:• Such
tunneling activities- did appear to cause-, --exc-essive injury to fine.- roots
and may be beneficial. This was--evidenced by numerous-• fine. bluebell
. roots- aetually traversing old tunnell3 and in some- :instances completely
tilling them. At this--s-ite, gopher activity is great.throughout both
-winter. and summer. Winter. activity results in hardened- -winter. casts,• ..,rid
is. followed,with mollnds--during summer, f:resh- mound& being observed -as ..
early. as. J.une- 13 and continuing ·well into- September •.
Pocket g.o.phers have been as-sociated with changes in. plant. covc- .
. composition. It has been found that some species of. gr.asses.. increase with
. the. presence. of gopher activity (Ellison, 1946, and Ellison and. Aldous,
. 1952) while-others- may decrease (Julander, Low, and Morris, 1959.). Tap-
. rooted species may:.-dee-l"&ase-with gopher activity because- of. preferential
• feedi~ (Ellison: 1946-, and Ellison and- Aldous, 1952). Aldous (1951)
. indi-c-ated- that the above•ground use of plant material may not be prefer-
ential while studies of Ward and Keith (1962) showed that the diet of pook-et gophers- consisted of 93 percent forbs and 6 -percent. -grasses- in- .
. habitats con&is-ting of .42. percent forbs- and 50 perc-ent grasses-- by -weight,
. re-s-pectiv-ely. This latter &tudy furth&r showed that pock.-t gopher diet.s
consis-ted ot 74-percent stems and 26 percent root material' ..
It is certain that pocket gophers- can and do. aft-ect thegrowth,and
. compositiori of bluebell in areas-where it cons-titute& the.- dominant forb •
. The specific effects of feeding and burrowing on plant develo~nt-and
changes-in composition are in need of inv-estigation, however •
. Other small anilllal.s known- to inhabit the study area •re the Mountain
. Vole (Microtus montanus) Dee-r Moua& ( Perom.yscu& maniculatus) Western
. Jumping Mouse (Zapus prinoeps), Leas-t Chipnu:nk- (Eutamias.. minimus), and
. the Sn0web&e Hare- (Lepus- americanus-). All of thee& animals are lmown
. to include plant m&terials in their di-et. The -effect of these animals
on bluebell was not studied.
Vegetational Analysis-
The foliar cover of grasses, forb&, and shrubs was mea-sured at,, -.ch
. site with a line-point method (Cain and Castro.,.1959)., Sampling.was done
between July 11 and 16 in 1963 and betwNn July 2 and 14 in 1964when
bluebell and mos-t other s-pee-ies-had reached their maximum-growth. . An-.
attempt- was- made to keep the total number of points per site relative to
. the ~a, but no precise formula was-used. The number and length of
. transects- and the number of points used to sample ea.oh site are listed
in Table ,5-.
A J-footwideborder around the edge but inside of.eachexclof\lure
-was excluded from the sample. Transects were located on a restricted :randa basi-s- --so that- -adi}-a-oenttransects could not -ee cl-o~r than 2 -f~t.
TABLE5. Number and length of transects, and points taken to sample foliar cover of grasses, forbs, and shrubs.
Transect
Sita Year No. Length (feet) No. a.f Points
Upper open forb 19(j3 2 40 160 1964- 4- 6o 476 "Pure" bluebell 1963 3 100 6oo 1964- 3 110 663 Lower open forb 1963 3 100 600 1964 3 100 6o5 Lower aspen forb 1963 2 20 ao 1964 6 24 280 Upper aspen forb 1963 2 20 80 1964 6 _33 390
A 190-foot metallic fiber tape stretched above the vegetation was. used to mark the- trans-eets. At each 6-inch mark (beginning 6 inche,s from the starting- point) a 9-gauge blunt-ended wire pin- was loweiHQ toward. the- ground and a record was-made-of the first and successive species hit. When a pin- failed to touch a plant, the basal hit was recorded as bare -soil, rock, orlitter.
From these data, percent cover composition and the percent of ground covered by veg-etation were calculated for each species sampled. at each
site as follows-:
Total.number of' hits Percent cover eompo~ition = for each s.peci!s . .x. ,100 of each species Total number of hits for all species .27
Percent of ground covered = composition x '1,of' ground by each species of each species covered by vegetation
Since shrubs- we-Pe•rare-ly enc-ountered., hits on shrub f-oli,age -were
recorded. in the, same. manner as for hi ts on grasses and forbs .•
The foliar cover of aspen at the- two aspen forb sit&s, was measur.ed
on August 5;.1964- using a line-intercept method.. Four 500-foot transects
,:were- spaced 150 feet apart, to include the study site- at each area .sampl.ed •
. Cover :measurements were-. obtained by recording the total intercept of
leaf foliage-at-each site.
Intercept was- dete-rmined by holding a• 4-foo.t. long sight.ing stick at
arms-length and strikimg twe-arcswlterever a break in cover occurred-.s
. described by Andre-sen and McCormick (1962). Foliage openings measuring less than 6 inches across were ign9req.
Cover and Composition Understory and overstory.plant cover are- shown-in Tables 6 and.7 •
.. for a. oompl-ete treatment by species., consult the. APPENDIX.- Results. of.1963
and 1964-are generally in very close agreement, and were sUJIDllaru.e.dinto
six classe-s- -as- indicat.ed.. Bluebell was included with the class perennials
and also listed:ieparately.
The percent of ground. covered by bluebell ranged from 11.5 for the
lower aspen forb site up to 37.1 percent for the lower open forb site in
.1964.; A:lowe-r percent 0£ ground covered figure was obtained.for. bluebell
in 1964. at the lower aspen forb site than in 1963. This may be the result
. of an increased sample size-. . Pe!'Ceftt composition of blu-ebe-11,-was--lew-M--in
1964 than that of 1963 at the- upper open forb and lower aspen forb sites. 28
------. TABLE6. Percent ground cover of grasses, forbs, shrubs, and trees.
1963 ·
·- ·' ., .. -· ...... Site G• Se A p· B•• s T*•• Total Upper open forb 26.7 0.4 24.0 35.7 25.0 2.4 89.2 11Pure" bluebell 9.9 .o 19.9 56.9 25.7 o.o 86.7 Lower open forb 22.2 0.5 0.5 p8.0 39.0 1.7 92.9 Low.er aspen forb Jl.2 .o 19.6 .37.5 17.4 5.6 -- 9.3.9 Upper .aspen ..fa.rb - 27._6 _.• o. _ l4.6 .. .5.5.9- i6.4 . 1.9 -··· ..-- J.OQ.. O
1964
- - - Site G* Se A p B*• s T*** Total
Uppe-ropen forb 29.9 1.0 17• .3 39• .3 21.5 .3.9 91.8 "Pure" bluebell 17.4 .o 18.6 56.9 2.3.9 .o 92.9 Lower ~pen forb 29.4 1.8 2.6 60.8 .37.1 0.7 95.8 Lower a&penforb -44.6 .o 1.3.2 .30• .3 11.5 .3.0 59.0 92.4 Upper_asp.en. .forb _25.8 .0 ...5 .16• .3 _.,5.5.1. . 17.6 .0.4 46.. ,5. 98.;i.
•G = Grasses **Bluebell also included with pe.rennials Se = Sedges A= Annuals ***Tree cover not included in totals P = Perennials B = ID.uebe-11 S = Shrubs T = Trees (Aspen) 29
.. -- TABLE7. Percent composition of grasse~, forbs, and shrubs.
Site· G* Se A p B** s Total
Upper open forb 30.0 o.4 27.0 40.0 28.1 2.7 100.1 11Pure 11 bluebell 11.4 .o 22.8 65.1 29.5 .o 99.3 Lower open forb 23.7 0.5 0.5 72.4 41.6 1.8 98.9 ' Lower aspen forb 33.3 .o 20.8 40.0 18,6 6.o 100.1
Upper aspen forb - 27.6 .o 14.6 55.9 16.4 1._9 1.00.0 ., -·
.. Site G* Se A p B** s Total
Upper openforb 32,8 1.2 18,8 42.8 23.5 4.J 100.3 "~re" bl.uebell 18.6 .o 19.8 60.5 25.5 .o 98.9 Lower open forb 30.9 1.9 2.7 63.7 38.9 0.7 100.3 Lower aspen forb 48.1 .o 14.1 32.6 12.4 3.2 99.4
Upper_.aspen !orb_ 26.2 0.5 16... 6 - 56.. 0 17.9 0.4 .. 99.7
*G = Grasses **Bluebell also included with perennials Se = Sedges A= Annuals P = Perennials B = Bluebell S - Shrubs This may-be attributed to a sm.a.11sample size at the lower aspen f'orb site and to the variable distribution pattern of' bluebell at the upper open f'orb site! These same two sites ala:, show a reduction in percent
ground cover for annuals while all other sites show little changel This
ala:, may-be attributed to the variable distribution pattern of' bluebell because maey annual species appeared to occur 1110reabundantly in areas not overshadowed by bluebell foliage.
An effort was ala:, _made to relate the abundance and distribution of
bluebell with site factors on the Mud Creek ::beep Allotment and adjacent
Clyde Creek Cattle Allotment. This was _accomplished by comparing the
amount of ground covered ( shaded) by bluebell with: (1) the amount of
ground covered by each of 10 asmciated sp49Cies; (2) the amount of aspen
shade; ( 3) percent slope; ( 4) direction of slope; and (5) mil depth. Percent ground cover was ocularly estimated to the nearest cover class
consisting or 1 to 5, 6 to 10, 11 to 20, 21 to "JJ, '.3]. to 40, and 41 to 50 percent! Aspen shade was designated as dense~ moderately open, or openl
Percent slope was determined with an Abney level, direction with a compass,
and mil depth with a l¼ inch mil auger!
Compari mns were accomplished by ranking all sites for each factor
separately in a decreasing order. Ranking of bluebell with Agropyron
subsecundum,_ Agropyron trachycaulum, Bromus polyanthus, Carex hood.ii,
Lathyrus J.e.•, Polemonium foliosiss!!mm, Rudbeckia occidentalis, Salllbucus racemosa, §Ymphoricarpos oreophilus, Vicia J.e.•• and annuals failed to show correlation of percent ground cover. Ranking of bluebell abundance with aspen shade, slope, direction or slope, and mil depth ala:, failed to
show correlation. '.31 The results are quite unusual because direction of slope included
.. north, east, and south-facing slopes with steepness ranging from 5 to 45 per~ent, the highest being found on the south-facing slopes. This repre-
sents a wide range of exposures found in the study area for bluebell. The
soil depth was in excess of 4 feet at all 25 sites and may account for the
range of exposures possible for this specie11 especially on south-facing slopes.
Pol.ygonum douglassi is the most abundant annual species on the basis
of ground cover at the upper open forb site while this distinction is
shared with Madia glomerata -at the"pure"bluebell site. At the, two aspen
forb sites, Nemophila _brevifiora, Gali.um bifolium, and Colloma lineari s
were the most abundant annuals. Mertensia is the most abundant perennial _!'orb ~t aµ sites except the upper aspen_ forb site, where Lathyrus leucanthus is about equal with Mertensia.
Density
The density of mature bluebell and Polemonium stems and bluebell
seedlings was determi.ned at each site between July 2 and July -19 in 196:3,
and between July 1 and 15 in 1964. This was accomplished by counting the
number of stems and seedlings occuring within quadrats measuring 2 feet
on each side. These quadrats were placed at random along randomly located
transects. The number of transects and quadrats used to sample density at
each site are sho_wnin Table 8.
Except for the upper open forb site, data from both years reveal a positive relationship of bluebell stems to seedlings. The greater
the density of stems the greater the density of seedlings. The upper
open forb site had the lowest number of seedlings per bluebell stem
for both 196:3 and 1964. This site also had the next lowest seed yield per stem in 196:3 ( see Table 28) which may account for the low 32
TABLE8. Bluebell seedling and stem densities per square foot. The number of transects and quadrats used' are also shown.
Site. Year Transects Quadrats Seedlings Stems
Upper open f'orb 1963 3 24 0,1 6.8 1964 4 40 0.1 9.0
-- 'fPure" bluebell 1963 8 94 l_.4 9.5 1964 6 104 2.1 9.4
Lower open f'orb 6 88 2,3 13.0 - J..963 1964 6 88 2~5 17~2 -
Lower aspen f'or? 1963 2 10 1.3 4~0 1964 6 JO 0.8 2.6
Upper aspen f'orb :i,963 2 14 o~.5 3~1
1964 6 32 0.7 2.9 number of seedlings per stem in 1964. A ranking of' all study sites fof 1 both SUJlllllerson the basis of' decreasing seedling density, bluebell stem density, and total ground cover of grasses, annuals, perennials, and bluebell separately reyeals the f'ollow:ings
1. Seedlingdensity is greater with greater stem densities.
2. Stem density is greater with greater ground cover by tall
bluebell.
3~ A direct relationship between seedling density and the percent
ground cover of grasses, annuals, and perennial f'orbs, separ-
ately, was not found. 33
Bluebell seedling; reproductive potentials are greatest in dense bluebell stands and may :ac·t, to resist change in cover and composition of the vegetative structure. In general, seedling density outside of the site exclosures was less than inside (Table 9).
TABLE9. Bluebell stem and seedling densities outside of exclosures.
Aspen Total Plots Seedlings* Blu~bell Stems Cover 1963 1964 1963 1964 1963 1964-- None 10 40 0.2 .o 9.9 5.2 None 10 40 0~5 .o 16.3 10.1 None 40 1.3 6.1 None 22 0.1 6.1 Present 10 40 o.6 0.1 6.3 4.4 Present 40 0~6 2~1 Present. 40 0.2 2.1
*Data were obtained between July 19 and A~gust 2 in 1963 and Figures are based upon square-foot density~
Lower seedling densities outside of the study site exclosures may be caused by the reduction of seed yield due to grazing. This occurs when grazing animals consume the flower inflorescences along with the terminal portion of bluebell stems (Plate V). Trampling and removal of shade. cover may also occur. Field observations show that utilization amounting to about. 'JJ percent, and more, virtually eliminated .all current year's seed production and seedlings.
Phenology
_-Tall Bluebell
Phenological development of Mertensia arizonica var. leonardi, was observed throughout the summer of 1963 and again in 1964 on 4 plants 34
selected at each site. Stem growth and stage of flowering were observed and recorded at weekly intervals beginrrl.ng about June 5 and continuing
~til the end of September. ill plants selected were similar iff'.:en~ C
and stage of growth. Each plant was marked wi. th a wooden tent peg driven
into the ground 1 foot from the outer edge· of the. plant crown~ The 5 long"6-&t stems• on each marked plant were then• tagged, and me.a-sured-weekly
to determine growth rate~ Measurements were obtained weekly until cessa- tion. of growth• occurred.
Rate or Stem Growth
The rate of weekly stem growth is plotted r or all of the study si te.s
in Fig. 3~ In 1964~ the "pure'' bluebell, lower aspen forb~ and lower ol>en
•forb sites all showed• a period or decreased growth rate in Jun~ that
occurred wi. th a corresponding decrease in temperature. Afterwards, the.
previous high weekly growth rate wa-s ne.v,er-again• attained. -This condition
occurred even though the average temperature was higher following. the
growth slump than before. The growth rate did increase slightly, however,
r ollowed by a leveling off wi. th continually rising average temperatur-e.
In 1964~ the upper open forb and upper aspen forb sites both showed
an increasing rate of stem growth corresponding with increasing temperature until J weeks after- snow melt. (month of June). At this time, a sudden ~d .. rapid- decrease. in gr<:>wthrate occurred with eontinually. rising temperatures~
This high point of growth rate was reached two weeks earlier at the three , lower sites, and is related to the date when the winter snow cover melted
off, occurring about May 26 at the three lower sites and about June 9 at the two upper• sites in 1964~ The condition of late snow melt created a
time lag of about two weeks for the two upper sites~ Maxi.mumr.ate or growth 35
occurred iib:>ut three weeks after snow--melt-or l!Ei.d.wey,·b&tween-the date--of
stem emergenee--and c&ssation of growth •. The entire- growth-period, then,
requir-ed about 6 weeks for completion from. the time· of• snow melt~ T-emperature appears to constitute a limiting. fact.Gr prior to the
point of optimum growth while·• genetic• and soil factors (other than soil
moisture) :may-constitute limiting factors after the growth peak has been
reached~ · ·In 1964. the-· optiJllUJilg-rc,wing point was reached -at an average
temperature· ·r-ange of -47'! to 48°F for the three ·lower ·sit-es and. 56° to
5i'F for the two upper si. tes~ This indicates that the average optimum temperature for growth may not be critical or that growth rate is .r._ stricted by other factors prior to and after the 1118.Xi.llllllllgrowth rate has
been attained. -- Data of 1963 are in very close agreement with_ that or 1964. I~
1963, sno-w went off the lower sites about May 21 and the upper sites about
June 4 and 11. This allowed stems to start growth --one week earlier at the
-lower sLte-s. Ces-sation of growth also occurred ·one :week •-&arli-er in 1963
than for 19641 At all sites, growth extended- over a period of. 6 to 7
weeks from the time of snow melt with a high point in growth r.ate being .. reached-mid-way in the growing period. This occurred at -an average te1Qp-
erature of 59° for th~ upper open forb s:i.te -and 48° to 54° for the three
·- lower si. tes~
It is of. interest that the amount of growth, or maxi.mm stem height,
is· not proportional to the length of the frost-free period which was
similar at all sites in 1963~ This indicates. that stem height is deter-
mined by• the availability of moisture and nutrients during a restricted
time period. The average maxi.mm height attained at each s:i.te for both swam~rs is shown in Table 10.
TABLE10: Av,erag,e maxi.mum stem height attained by bluebell;.
Site 1963 1964
Upper open forb 23.0 inches 19.5 inches
"Pure"·. bluebell. 26.5 inches 25~0 inches
Loweropenforb 25.5 inches 24.0 inches .. Lower- a-spen-.,forb 28~5 inehes 2.5.• 0 inches- Upper aspen ..f'orb ___ :,O!0 inches .. 31.i,oinchas ..
Maximum-stem-height-was slightl;y less-in 1964-than-in 1963~ This ma,y be attributed. to the greater quantity ef prec-ipitati0n- that tell- duri~g the-latte?"- part of the· 6-- 7 week· grewi:ng pel"iod--in 196)i Addi- tiGmal-precipi tation- -r-eeeiv-ed af-ter cessation of growth occurred and prior to wilting-failed to induce the further growth of stems~ The con- tinuous -watering of -bluebell plants inside- the ~eenhou~,,al-so- -f'aileQ.
-to-induce growth beyond that developing during a limited growth period~
FloW'81'ing
Weekly obseryations were made on the-phenolog:1.cal dev:elo.pment of bl.11ebell!-. -Dates -of fi-r.st flowering -and •seed"di ~nation- were r.ecorded-
. at each site~ The longest stems- on each marked bluebell-pl.ant .wae . .also 5 • I
•ohse~ ..weekzy- for th,e number of a:xillar;y infio.r.e«>ences .and. the. number
•of ~£low.era. ,which were -open or had -o~ed- previ,ou.sly.; The n,pber of dead
. or ..se-vere-1.y • injur~ bads ,-was-recorded -at• or near the ..end of th.a. i'lo:wering_ pe!'j_od~ At or near the time- of ·seed-dissemination~ the- number of flow.ers that had produced fruit, the number of nutlets produced ( still attached to 37
th-e.--stem <>•ralready•· shed)• and the number or "normal" unopen-ed buds r.e-
~aining wer-e ·recorded~
One additional bluebell-plant at the ttpure" bluebell site was s~lected for detailed observations or flowering in 1963 only~ Five,, stems
. or this plant were ob-served dai+Y· (.~xcept· week-ends). from- July 6 until August 7. For each stem the- date or occurrence- and the number, where applicable-~ were recorded. for the following: (1) buds initiated; . ( 2) buds which were de-stroyed or injured and failed to develop; (3) flowers
which opened; • (4) pollen shed; (5) corolla shed; ( 6) flowers which pro-
duced fruit; (7) nutlets per fruiting flower; and (8) seed di6J)ersal. On
each stem. individual buds and fl.owe-rs ·we!'e identified by a•numbering
system· so that dev&lopment• o·f each-individual bud cou-ld be followed •
. The characteristics of fiow-ering among all of the study sites are
shown in Tabl-e ll~
TABLEll~. Number or weeks from snow melt to first fio~r, maxi.JllUlll fiowering, and completion or the fiowering peri-od.
1963 1964
Snow First M~ End of Snow First End of __ Site off Flower Flower! Flower! off Flower Flower~ Flower.
Upper open forb June ll 4 6 4 3 June 9 ...5 6 "Purett ., " bluebell May21 4 6 8 May 26 3 5 6 Lower open forb May 21 4 6 7 May 26 3 6 7 Lower aspen ' forb May21 4 6 8 May26 5 6 7 Upper aspen £orb June 4 4 5 8 June 9 J 5 8 Snow cov-er melted off the- "purett bluebell si. te one week later- in
1964; however, flowering started th-e. same-week· bci>thyears~ Maximum.-
flowering occurred and finished abc;,-ut the. same time in 1963 as-it, did in
1964- {Fig~ 3)"~ Snow also melted off the lower aspen f{)rb si.te one -week
later in 1964.~ HoW&"M:P,··flowering started two weeks- lat&r-, p&aked-one
. I week---later, and finished flowering- -at the same time· as in 196-3, • Snow
left the--lower•e-'f)8llforb si.te-on&-·week-•lat&r-in•-1964,- -y.et fio.weri-ng
stet.eel-the- same-time,. reaeh-ed maximwn one week- later ·than in-1963~ · and
finished flowering one-week• late-~ &low lef.t-the--upper open forb site
abci>ut the same-time during both years, yet flowering• started, -reached
maxtmwn., and~ finish~•one week-later-in 1963~ Flowering ,started, at the
upper aspen forb site one --weeklater in 1964 and finish-ed about the same
time each• year •. ReSlllts Ehow that first flowering occurred J to 5 weeks after snow
melt with 4 weeks- being most .frequent in-196J and J-week:s in 1964!
Ellism (1954 ) - .found that-M. I arizonica var. i leonardi started,
flowering about 20 days after. anew melt on the Wasatch -Plateau, .and that
floweri11g continued for an additional 25 days~ Pelton (1961) mgge~ed
that time of sna-w melt and soil temperatures may be si._gnificant in the date of first,. flowering in H~ ciliata, a closely related species~
First flo-werj.ng is related to stem growth~ occurring about. one we,k after the maxi.mumpoint in growth r.ate has been reaehed. The shorter time between- anew melt and first flowering in 1964,indicates, that stem
growth and fao-wering were supressed until a period of higher. or more
. uniform temperat\ll"e occurr~ to cause a rate of development in excess of
that in 1963~ This-~· to catch up on early developmental stages is suppo~ted by the studies of Saq,~n (1918) and Costello (1939)~ Where data.is adequate, the rate of flowering was shown to incr-ease with :1.n-. . 0reas:b1g temperature until a maximumpoint in fiowering rate was reached!
• Afterwards, a gene-r-al decre~e in growth rate was experienced. The p~ak: in rate of flowering occurred 4 to 6 weeks• after snow-melt in 1963 and 5 to 6 weeks- after snow-melt in 1964~ The flowering period required from 6 to 8 weeks, for completion while the maturation of.fruit required- an addi- tional 18 to 28 days! In general, the- two upper sites reached a flo~ering peak in a.bout l to 2 weeks less time from the date of snow melt than did the three- lower sites~
Daily observations, between the hours of 8 and 10 A.H., were made on the flowering of one mature bluebell plant_ from July 6 to 26, and once each on .August l and 7! The observed plant, was located at the ... "pure" bluebell site. From these data, it was found that anthesi.s oc- curred within 2-4 hours from the time of nower opening but not before; that corollas are generally shed 2 to 5 days after-fi0wer opening~ but may persist until fruit is fully formed; and a period of 18 to 25 days was required from the. time f.l.owers open until mature seed was shed nat- urally from the plant!
The total number of flower buds produced p&l' stem appears to consist of a relatively fixed number as shown by !'potential flowers" in Table 12.
for all si. tes! •A few new buds were ini ti.ated later in the flowering period; this_ indicates that potenti.a.L indeterminant growth may exist! All
flowering plants -in the greenhouse failed to develop new buds when main-.
tained under conditions of optimum soil moisture. This indicates that
factors other than adequate soil moisture are necessary if new cycles of buds are to be initiated. The infi-0re-sc-enc-e-of -each stem was-observed, to consist of 5 or 6 , axillary peduncl--es, occurring at the terminal. portion of each steml The ~rder,of' maturation -among-peduncles was-variable. Flowers usually opened fir.st. on peduncles mo·st proximal to the• stem terminus and last on peduncles
mG>stdistally -located from the stem terminus-£. A def-ini te order of matura- tion within axillary peduncles -was observed, however! It was found that
buds located lowermo-st on- the pee.uncle mature-into flowers• first and those
higher up mature last, th some indicatien of -potential indeterminant growth being present! Each peduncle constitutes a cyme showing strong
I• scorpioid deyelGpment from alternately developed buds.
A summary of flowering potential measured at all si. tes is shown in Table 12!
TABLE12! Average flowering potential per bluebell stem, shown as the sum of opened flowers, remaining buds, and destroyed buds!
Opened Remaining Destroyed Potential Nutlets Site Year Flowers Buds Buds Flowers Produced
-- ~pper open forb i96.3 14i7 i5 8! .3 23.5 11i20 1964 7~9 !.3 8!5 16~7 8~90 .. "Pure" bluebell 196.3 20~.o is 1,7 22_;,.5 41!20 - i964 25.1 ~o 1!7 26.8 !49!45
Lower.·. open r orb 1963 16.~5 ~7 5t7 22,9 15165 J.964 _8.5 .1 9.9 18!5 5~95 .- ·- Lower aspen forb i963 15~1 ...,3 9~9 25... 3 1er10 1964 6.7 ~o 1.3!5 20!2 ~65 -- Upper aspen forb 1963 21~1 ~-P 13 2414 52105 -· 1964_ 21.0 .3io 3J..,- 33~.3- 1.7!65
I 41
The •pure" bluebell and upper aspen forb sites showed t'lfl> consecutive ye-ars,of' good seed yield while the three remaining sites showed great variability~ particularly the lower aspen f'orb si. te! This indicates that seed yield cannot be e:xpected to remain consistent from year to year even thc>ugh potential production may be. The difference• between fruiting potential and actual yield is due primarily to insect infestations re- sulting in the eating of buds or injury to the delicate, ficral structures making 119-rmal flower development and subsequent opening impossible. R~ sults further show that moderate shade does not reduce fruiting potential, indicating that bluebell has no particular adaptation for moderately
shaded or open ·areas!
Pollination
Five bluebell plants were selected at the"purEf' bluebell site for the purpose of investigating self-pollination1 On June 27~ 1963~ 5 stems w~re selected from each plant~ All open flowers~ flowers with shed coro~ las, and injured buds were removed so that only uninjured and unopened flowers remained! The inflorescence of each stem was than wrapped w.i.th a plastic• sheet~ The bottom and top of each wrap was tied SEl)QUrelywith a string to prevent entry of insects and. wind born pollen!
After 2 weeks, the wraps were· removed and the outer half of the style on each flower that had shed its corolla (during the 2 week period) was clipped off with a small pair of sci ssorsI Removal of the stigma was neces$ary to prevent subsequent occurrence of pollination and fertiliza- tion after ~emoval of the wraps! The 2-week period should have been
. sufficient to pernrl.t pollen tubes to reach the ovules of all flowers opening shortly after the wraps were affixed~ Clipping off the style may 42 also have some effect on seed developmentl Each treated flower was marked with a piece of thread ( tied around the pedicel) and checked 3 weeks later for presence of normal fruit. Nearly all treated flowers failed to develop fruit~ Because wat"8r accumulated in the plastic wraps,
.. the above procedure was repeated using paper bags~ The results of, b(,th plastic~wrapped and paper.bagged stems are shown in Table 13! The open- pollinated flower data were obtained from one additional stem on each of the 5 plants studied!-
'!'ABLE13l Compar::i.son..of open pollinated, plastic.wrapped, and paper- bagged bluebell stems!
Flower Condition Open- Plastic- Paper- Pollinated Wrapped Bagged ·--- D~ad ovaries - 11' 22.8 98~6 98!9 .,_ ... .. Deyeloping fruit - 77~2 1~4 1~1 Total -flowers ... 2~3.0 223!0 275~0
The low number of flowers developing fruit when wrapped with plastic or paper-bagged indicates that Mertensia arizonica var! leonardi is self-incompatible or that pollination was not effected~ Some pollina- tion may have occurred because a few seeds did form within the i.solat.ed infiorescencesf A study of pollinator vectors was not made but insects are-likely involved because of flower color and structure! Bagging the inflorescences -would thus reduce seed yield by excluding the agents of pollinatton.
Fifteen flowers from different plants_ in the greenhouse were self pollinated by hand. All of these nowers failed to develop fruit even 43
though they were well formed and appeared to have receptive stigmas. Pollen, obtained later from other greenhouse plants of the same lot, were all found to be full and of normal size when treated with cot ton blue
. stain. Pollen samples collected from the study area during early August of 1964 and stored until October 5 of the same year appeared normal when si-milarly examined. This stored pollen was not tested to determine its germination capacity, however. Pollen grains may remain viable for some time after anther dehiscence, whereas the stigma does not remain receptive after 2 to 4 days from the time of flower opening. The latter event is characterized by discoloration of the stigma, followed by a shriveling of the style. As shown in Table 14, there is rather low seed set among plants in nature. This may be due to a lack or pollination or incompat- ability after pollination has been effected.
TABLE14. Comparison of fruit production per stem - 1963.
.. Total* Fruit rl, Total Flowers Nutlets/Fruit Site Flowers Flowers Developing Fruit Flower
Upper open forb 14.6 6.4 43.? 2.? ttPurett blu~bell" 20.0 17.0 85.0 2.4
·- Lower open forb 16.4 6.4 38.? 2o5
Lower aspen rorb 15.0 ?.6 51.0 2.4
Upper aspen rorb .. 21.1 l?.O ao.5 3.1
*"Normal" flowers
Tall bluebell appears to propagate itself almost entirely through the enlargement and fragmentation of root ttcaudexes" (Plate llI) Frag- 44
11entation occurs when the tissue in older portions of the "caudex" dies and undergoes decomposition. Each fragment subsequently enlarges through iateral growth and in turn becomes fragmented. This process may consti- tute a mechanism whereby the species can retain its ecological fitness.
Genetic flexi.bili ty may be retained within the species population through sexual reproduction involving seed formation. The compromise between fitness and flexibility may lean toward fitness because: (1) root systems are p-erennial giving longevity; (2) many flowers fail to develop fruit (Table 14); (3) few seedlings survive the first sumer (Table 18); and ( 4) seedlings in their second season of growth could not be found.
Other Observations
Other observations consisted of noting the date ~nd presence of:
(1) mildew on plant; (2) stem necrosis; ( 3) yellowing of leaves; (4) wilting; (.5) lodging; and (6) drying. The number of leaves infected with mildew, and the relative percent of the upper leaf surfaces covered by fungal growth were also reco-rded for the 5 tagged stems on each marked bluebell plant. The dates when conditions related to maturity and soil moisture occur are shown in Table 15.
In all instances, the first severe wilting cf marked bluebell plants occurred when the percent soil moisture in the upper 1-foot of soil dropped to a range of 7 to 1.5 percent. These low moisture levels approx.. imated thf:3 permanent wilting percentages. During both years this event was preceded by several weeks of uniform weekly temperature averages at all sites. This indicates that wilting occurred as a result of soil 45 moisture e:xhaustion and not because of sudden increase of temperature-re- lated transpiration loss. The percent soil moisture was slightly higher at the three lower s1tes in 1964 than in 1963 at the ti.me wilting occurredo This difference may be related to the greater quantity and frequency or precipitation that r ell during the latter part of July and fore part of
August in 1963. A.s a result, condi ti.ons of higher humi.di ty were e:xper ... ienced during this period. This condition of higher humi.dity in 1963 over that of 1964 could result in lower evaPo-transpirati.on rates and allow wilting to occur at the lower moisture percentages. Precipitation falling during this period did not significantly affect the low moisture percentages in 1963 or in 1964.
TABLE15. Dates of wilting and drying of bluebell as related to soil moisture.
,<- Soil First Severe Moisture All 4 Plants All 4 Plants Site Year Wilting Top 1-ft. Necrotic Dried up
Upper open forb 1963 Aug. 13 7 Aug. 6 Septo 10 1964 Aug. 4 7 Aug. 4 Sept. 1 ttPurett bluebell 1963 July 'JJ 11 July 'JJ Sept~ 13 1964 July 21 12 Aug. 4 Aug. 18
Lower open forb 1963 July 'JJ 13 July 'JJ Sept. 10 1964 Aug. 4 15 Aug. 4 Sept. 15
Lower aspen forb 1963 Aug. 13 10 Aug. 13 Sept. 10 July 21 15 Aug. 4 Sept. 15 Upper aspen forb 1963 Aug. 13 10 Aug. 6 Sept. 24• . -1964 .Aug. 11 9 Aug• 4 Sept. 15,*II!_..
*One plant dried up. ••Twoplants dried up. 46
Wilti,-,;g and steni necrosis occur about the same time. Necrosis firErt.
beCGmes,vis1.ble as dark brown to black colored specks at the base or each
stem. These- -specks become-confluent in time and eventually involve the
entire stem•unless checked, by rapid drying of th-e• foliage. This necrosis
appears ·re-stricted to the- cortical region. and may develop from the water
stre&a th-at cau-se&,wilting. This latter view-is mpport.ed from observa-
tions med&C!tf•inclividuel- stems with resu.lts sho~ng that-wilting may
•preoed:e- n-eoro sl s or, vice versa~ · •.Also, stems grazed• by anima1s may r-emain
in a gre,en and-Mn-wilted condition well into September -while remaining
complet&ly :necrotic.
Th-e-natural lodging of stems (F.Lg~ a. Plate IV) appears related. to • the height and severity of w.i.lting conditions! Lodging-wa,a-observed to
. occur at ,,any time between the first severe wilting, and drying up of stems.
Heavy rainfall, charaeteri stic of late swnmer·-storms, can also -beat dewn
wilted or turgid stems and thus hasten lodging. The time at which drying
first starts- and duration of the drying perled are related to the. avail-
. abi.li ty of• sail moisture. The drying• period of plants was m&re-prolonged in 1963 than in 1964. This m~ be--attributed to the grea:ter quantity or
precipitation that was reeeived throughout the late summ.er-of 1963 over
.. that ef 1964. Wat.ering of grffl'\hou81!t plants also caused foll-age to remain
green· into la:te -September•_ in 1964.
Powdery mildew (Er,ysiphe-- cichoraoerarum) • does· no,t appear ta cause
the• initial drying or lodging of bluebell· stems~ Field observations show
that many non.:.inteeted stems lodge- and dry up at th& same time as infected
stems. Powdery mildew may hast.en the drying of foliage, once drying has
started because drying and JQ:ildewinfection often occur at same time. 'l'.abl• 16 characteriZ:es the occurr-ence of mildew by si.te.
_, TABLE16~ Dates of' ini tie.1 and maxi.mumrates of mildew infi9ction.
·- 1963 1964 Site Started Maximwn Started Maxi.mum
Upper open !orb .A.ug. 6 Aug!.20 Aug~ 11 Aug~ 18 .. "Pure11 bluebell July 16 July 'JO July 14 Aug~ 4 Lower ?pen forb Aug~ 6 Aug~ 20 Aug~ 4 Aug! 18
Lower ~spen f'orb Aug! 6 Aug! lJ Aug~ 4 Aug! 18 Upper _asp.en .£orb .A.ug~.27 Sept! ..l Aug~ .18 Aug. 2.5.
The above table shows that the upper open forb, lower open forb~ and the lower aspen forb si. tes all had mildew infection occurring ini tally ' . . about the same time and reaching maxi.mumat the same time f'or both years~
Mildew appeared latest at• the• upper aspen forb site during both years, but peaked later in 1963 than it did in 1964! This may be due to the reduc-
tion in the quantity of secondary - innoculum caused by excessi. ve- precipi- tation f'alling~between Augast 27 and September 24, 1963! This period of' high precipi ta ti.on did not occur until after the mildew had peaked at the other .four si. tes! The date of initial infection and severity of total infection may be· related to "pocketstt of overwintering innoculum because the lfpure" bluebell te showed ini tia:1 infection 3 weeks earlier than any other si. te for both summers. This early development of infection cannot be
attributed to dense bluebell foliage because-thi-s site did not have the -- greatest stem density, percent cover composition, or percent ground cover.
Mildew wa.s plotted weekly as rate of' change in total infection! This 48
£:igure was obtained through summation of the number of infected leaves,
multiplied by the percent of upper leaf surface covered by mycelial
growth, and divided by the twenty tagged stems at each site. The maximum
rate of mildew infection represents a point beyond which the drying of
foliage renders an evaluation of leaf surface covered by mildew impossible.
Data :from most of the study sites, with the exception of the "pure"
bluebell, sh.ow a trend of increasing rate of mildew infection with in-
creasing average maxi.mumrelative humidity. Decreasing temperature and
increased frequency of summer precipitation are both associated with .. rising maximum humidity. Data of the "pure" bluebell site failed to show
decreasing temperature corresponding with an,increasing rate of mildew
infection during 1963 and 1964. Data :from this site further showed that
a period of ~ecreased average maximum relative-- humidity prevailed during
the development of infection. This-perio_d of lowereµ. humidity existed
both summers during the time infection developed.
Yarwood (1957) stated that relative humidity has little affect on
the development of powdery mildew. This may. account. for the different
trends in relative humidity observed at the time of mildew inf'e~tion!.
-Yarwood (1957) also stated that high temperatures may reduce the tolerance
of mildew to low humidity. This may e:xplain how the general development
.of mildew infecti-on is pNvented a.t most of the study sites until after
the first part 9f August. Studies have shown (Yarwood, .!i al., 1954) that Erysiphe cichora- cearum has an average minimum, optimum, and maximum temperature for germ
tube development! These temperatures are 48.?°F., 71.6°F~, and 93;2°F~ respectively. The optimum temperature range for germ tube development and subsequent infection by this species is 51!8°Ft to 82~4°F~ (Yarwood, 1957f; Average weekly temperatures prevailing at each study site during the weeks of initial infection and maxi.mumi:n,f'ection rate are show in Table 17.
TABLE17. Average weekly temperatures at time of initial mildew infec- tion and maxi.mummildew infection rates.
Initial Infection - Maxil111lllfInfection Rate··
Min. Max. Min! M~
Site 1963 1964 1963 1964 1963 1964 1963 1964
Upper open forb 48 50 71 73 43 46 64 69 o,.,,__ .. ,.w-,,,,, .. "Purett bluebell 43 40 71 74 44 47 75' 75 •·· Lower op~ forb 47 46 75 74 47 44 76 71 Lower aspen forb 52 51 78 76 49 48 78 74 Upper . aspen _forb _ 41 46 62. 67 42 ':1) 61 61.
.All of the above temperatures show a range falling in the lower one- half of the optimum range given by Yarwood (1957h Factors other than temperature and humidity may be importanti Yarwood (1957) stated that~
"powdery-mildews are generally favored by relatively dry atmospheric and soil conditions, moderate- temperatures, reduced light, r ertile soil and succul-ent plant growth." All of these c0nditions may be found in a varying degre-e, and may account for the sporadic occurrence of infection observed in the study area! Associated ~ecies . Rate of stem growth_ Weekly measurements of growth were obtained on some of the major 50 species associated with tall bluebell at the two open for~ sites. The number of plants used for each species is listed below. Upper open forb Lower open forb
Caro: hoodii 2 4
Delphiniwn occidentale 0 4 Gera:niWll_parm 0 4
Polemonium. folio si.asillWll 4 4
Potentilla glandulosa 2 0 Rudbeckia occidentali s 4 4
Sambucus racemosa 2 0
Stipa letterma:ni 2 0
Height of associated species was measured at the same time and in the SIJlle manner as for bluebell plants. The 5 tallest stems of Polemon- plants were measured whereas an average height was obtained to represent the other species. Observations made during 1964 were obtained in the same way and from the same plants used in 1963 except that different
Sambucus plants were used at the lower open forb and upper open forb sites. ~so·; 4 additional plants (Geranium parrrt) were included at the lower open forb site. Results are shown in Fig. 4. The time at which the maxi.- mumrate of stem growth occurs is variable among the different species observed. The variation in growth rates of Sambucus racemosa is clue to an inadequate sample size, This beclJlle apparent when individual stem groups showed great differences of stem vigor.
Temperature appears to be the 1110st important factor of stem elonga. / I
Lower Open Forb Uppe:rOpen Forb 1963 10 Bluebell 1963 Bluebell Polemonium ••••• Polemonium ••• • • •····· _.,.,,.\ Delphinium •... I Stipa ,-};.•-• 5 >:~- .. ·-·-· ', . ·\. - \ ,. ~\~-, .:::i· 0 ...... , .... 10 .Carex Carex· Sambucus ••••• ' Sambucus ••••• Rudbeckia Rudbeckia 5 , ...... Potentilla ·-·~· ·--·-· .' ' . ... l ..:,:•-,', t'.. ·-· ·,.:-----. '~.... ,, 0 e 1961.i 1961.i ' 0 10 Carex 'i!l ft-I Carex - 0 Sambucus ••••• (I) . Sambucus ••••• Rudbeckia (1) ,...... /\ ·-•·-• 5 , .... Rudbeckia Potentilla g ·•,:\ :,, ..... ·-·--· ·-· H ... ,.- ., 0 ·,.