197'1 uS 011 ;1/5"-, 'I" r /,? 7/ If" . US /A.,ty,,;.. /!-." /;, Paper No. 11

MORPHOGENESIS AND MANAGEMENT OF ANNUAL RANGE PLANTS IN THE UNITED STATES

By Cyrus M. McKell 1

The annual mnge plant communit.y is n dy­nmllic f1 ggregntion of plnnt specics which finelll­lites yell!'!)' 1I1lt! s..:uSOJlully ill I'cspon9C to changing wcathet' conditions. Applicntion of variolls mun­agement practices such as grazing management., fertili7Altion. burning, seeding, and chemical spmJS can enhullce productivit:y, improve specics composition, lind change quality tremendously in annual rnll~oehmds. The lmnuai mnge is surpris­ingly more responsive than any other rangeland type.

The stnge of plnnt development is equally a5

important. 11$ the management practices employed. By careful attention to stages of morphogenesis, including germinntion, ,'egetati"e growth, stem elongation, flowering, and seed production, the application of nUUlagement practices can en­hance the. value of anllual rangelands in the United States.

Location Of Annual Rangelands

Annual I'allge pl:lllt .communities predominate in two IllI\jor types of' climates in tIm Unitild States. III Califol'llin. the Mediterranean-t)'pe cli­mate consists of moist. cool winters and dry hot summers (!e8) . The most fa"orable periods for plant growth, therefore, occur in the fall , after the onset of precipitation but before low tempera­tures limit plant growth and near the end of the moist senson in spring. as temperatures rise nfter the cool winter period. Plant species that ca n complete their growth cycle, produce seed, and then escape the long Slimmer drought, appear to be well adllpted to the i\[editel'l'Ilnellll-t'y{)e cli­mate. Considerably fewer perennial plant species can withstand extreme drought for up to 5 or 6 inonths. With range detedoration, the pcrcn-

• Director, En" lronment lind Mnn Program. Ulah S(ol(' Unlo;erslty, Logan Utah 84321.

Ilial species give wny to the invasion of intro­duced grasses and forbs from the 'Mediterranean rQgion.

Annual plant species also are important in the middle-latitude dQSCrt, clnssified as BSK by Kop­pen (£8). The northern Great Basin and Colum­bia Basin plains hn"c cold winters with precipi­tation oftlln occurring as snow. Spring growing conditions become favorable as temperatures in­crease and preci pitation remains adequate for a short period. Precipitation continues at It iow level through milch of the summer but is often undependable, lind long periods of drought pre­vail. Deterioration of lhe original vegQtative cover of this r!lgion allowed the invasion of annual species which were able to germinate, grow, and mature in a short period of time or to endure the periods of summer drought.

The southern e:'ttcnsion of middle-latitude des­erts in the United States, covering large expanses of the Southwest, also nave nn important com­ponent of the vegetation comprised of annual sPQci('s. Howfwer, in these desert areas the an­nual vegetation ocellrs as It minol' understory to the dominant shl'lIbb:\, vegetation and, therefore, is not considered of high importance from a man­agQm(mt or forage production standpoint. How­c\·cr. in an occasionally favorable year , the pro­fuse growth of desrrt ul\ lIual species is an inter­estill!! phenomenon and cannot 00 dismissed lightly (55). Such desert annual communities serve an important function in the ecosystem by recycling nutrients, by furnishing food and habi­tat to small nnimals, and by forming a protQctive plant and litter covel' over lhe soil surface under shrubs.

The allllUal range plant community in Califor­nia is It "ery dynamic aggregation of plant spe­ci(>5 that fluctuates. 1I0t only yearly but seasonal­ly, in response to the factors and interrelation-

111

112 MISCELLANEOUS PUBLICATION 1271, U.S. DEI)ARTltENT OF AGRIOULTURE

ships of the (!(!()System (48). Such predictions as "This is going to be n good clover," ufilnrect " or ugrass yenr" nrc commonly made in recognition of the dynamic nature of the nnnual fange plnnt community which may ha\'e a significllntly dif· ferent. specics composition each yenr. Tlllbot and others (50) reported such \'n rintiolls (table I ).

The dale of opening rains is an important factor in det.ermining the species composition. Brf)1n'U~ mollia L. and 1!.~r()<liU7n botrya (en",) TIel'tol. nrl} likely to be abundant with carly ef­fective mi llS, while the iuiLiuLiulI of I'tliu~ lutel' in the season appears to favor a greater r811Jrc of species, including the annual legumes. A drought period often follows the first min. Under such conditions, species which ure more drought resistant in the seedling stnge are likely t.o be the most. abundullt. Subsequent studies by many workers (J I, 18, 1U) on the Californin annual l'Ilnge type confirm that. yearly vnrintions in spe· cies com position are caused by wenther patterns thut follo,'I' the early period of germination.

Species composition chnngcs are also subject t.o allmlill ftuetuations in the upper Great Baain and Colu mbin Busin regions. ]n these regions, com· position docs not chnnge us much us the density of the stand docs in reSponse to favorable or lln­fn\'ornble weather condit.ions. Klemmedson nnd Smith (fO) reported thnt, at Arrow Rock, Idaho, one year's cheatgrass production was 361 pounds per acre, und in the following year, it wns 3,461 pOlLnds per acre- n tenfold increase, primorily in l"CSponsc to fnvomble precipitation.

TABU: 1.-r~ar to 'Y~ar t''Uct1lation.a between plant g1'QUpB. (From data. publi8Md by Talbot (l'Ild B;m,ll (50))

l'e rt"entnge IJ)" rent1l

I'hmt group 11135 1936 193; 11138 1939

Annual broadlea"l"ed plllnt, N .8 03.2 45.5 61 .7 62.6

AnnU1l1 grallSes 20.6 45.4 'M 34.1 '7.1 Annual grasslike plants 2.' ., .5 ' .6 'T

Total .... "'2 99.5 99.' 99.7

' T=trace.

Is the anlllmi range o( sufticient importance to maintain it as a type withont considering conver­sion t.o IXH'Cll niul grnss1 l\fnny of the eurly studies denlt with intensi t), of gm:l.illg, to determine the effect 011 stn lld <,lensity lind whether management could (u'·oI" the retul"Il of 1>C1'Clllliai grasses. Tal ­bot nnd Biswell (50) stated that, at the San .Jonquin Experimental Range in the. central vill­ley of Cn lifOl"lIia. the sparse pel'e.nnial grnsses showt!d no increase ill I'csponsc to mallngement dming II 5-y(,1I1' study period. Even ill completely protected places the stand of annual grasses and Forbs continued to pl'Cdominate. A. I-ePOrt o f Inter work (3) indicated nn Il\·erage of 4,4.00 pounds per aCI"C har'·£'sted fOJ·ag£, in swules us oompnred with 1,R:iO pounds of nil· dry forage 011 open roil ­ing slopes in good yeurs. During n 12-yen r study period, tllt~ estimated !n'c,·nge production of air dry hel"unge pCl" IICI"C wns 1,660 pounds. with the extrem£'s fluctunting from 1.200 pounds to nlmost 2,400 pounds pel· acre. During this ti me the aver­a!!c pl"Ccipitntion was about 20 inches.

Bentley and Talbot (3) concluded that restor­ing the original CO\·(,I" did 1101 appear possible, nor was it nec('ssariiy It log-ieni objective. Instead, they recommended rnnge mflnltgement that would prodll~ 1\ forage cover composed of the better species of introduced and native annuals and perennials. Also range mnnngement should be nimed at effective lise of the annual plant fornj!£' ill its Illost productive condition with adjustment s to incl·ellsc the valwlblc perenninl pl nnts where theJ' are import.ant in the stn nds. They hoped that it was possible to produce n forage crop superior to tim original co\'cr. These statements have pro\"('d to be true. especiall)' in "iew of more re­cent work in ,~hich improved mnnagement prac­tices, particularly ferti1il,ation, have produced forage ),ields as high as 4,400 pOllnds with t,he ad­dition of super-phosphate and introduced annual legumes (Ge) in the foothill s of the Sacramento Valley. Nitrogen fertilizers I\t rates of N up to 80 pounds have increased total yield more. thlln threefold (15, g1). A combination of 100 pounds of nitrogen and 88 pounds of phosphorus in the Sacrnllvmto Vnlley have l)1"oduced yields of over 4,000 pounds pel" acre (99).

Annual cheat grass range ill the northern Gt"Cnt Basin find parts of the Columbia Basin nre ex­tremely important to the livestock industries ill

l'C.ANT Mon p UOGENESIS Fon SOJENTIF IO AlANAGBMENT Ot' HANCE n.~SOURCES 113

those areas, H ull and Pochanek (17) stated lhat cheatgrass was proll1lbly the most impol'tullt for­age in soulhcnl Jetuho, A U,S, F orest Servico ro­POtt (51) stated that chentgrass pro\'ided the bulk of early spring grazing for all classes of stock on millions of ncres in the Intermountain West, Xot only is the foruge abundant in good yenrs but. it also has II. high nutritive vll.lue, In ~[ontllnn, HlLI'u (18) fonnd that the condition of horses grazed on cheatgrass pnsture compared \'cr)' fa\'ol'flbly with horses g razed on ndjnccnt percnninl g]'nss pnstm'e, I II ~ut.hcl'll T,lttho, the a\'crage grazing cnpncity of 5 to 8 acres pCI' nlli ­mnl unit month (AU1\[) is realistic for most of the chcnlgraal (£'6), ]-Io\\,('.\·er: the contrast in ~'ields bctwl'!!.'n poor und good forage years is ex­treme. In southern (daho under a mean annnal precipitation of 18 inches, the yield of cheatgrnss in 194-3 WIIS 361 pounds PCI' acre, while in the fol ­lowing year it WaS 3.461 pounds per ncre-o. ten ­fold incr('nse, 'I'I1I'se dnla illustrfl.te Piemeisel's obscJ'vat ion (.',0) th n!' fOl'age production of client· grnss fluctuates greatly from year to year in re­sponse to weather nnd is greater thlln tha I of perennial grasscs.

The qneslion mn~' be asked. "How did the lUI­nllnl rnn!-'l' plnnt oommunit)' comc into being where originally Ihe plnnt co\'er was I\. mixture of pert'uninl gnlS8eS nnd some annual spccies1·' ~lost range ecologists will concede thnt in every locntion wh(']'(' clH,'nlgl'llss th ,·i\,es its successful es­tablishnwnt cnn 00 nssocial.ed in some wny 01' other with n distlll'imnec or a dcteriorat ion of the ran~e ecos,\'stl'm. VariOllS factors arc respoll· sible for this. ineludill~ fire and abandonment of cropland, Dnubenmire (5) considered that, inas. much as cheatj!'mss does as well as the indigenous species of similnr life fonn. it is n thorou~hly nnturnlized nli(,1l in the Ag1YlPyrtrlll!lum.

In tl\e Cnlifornill nllllnni type. Biswell (4) concluded Ihnt the kind of plant co\'er existing OVCI' thc 1'eJ,!i01l before white man camc can ne\,l'r be detcrmincd prcc isely, since there is no enrl,\' lit('rntuN' thnt ntie(lllll tcly desc ribes it , and vir· tually no sanlples remnin of it. H owcver, many PCOlogists postulat(' that the original ve;!,etntioll in the present California anllual range type was II bllnch:rrnss. primnrily composed of Stipo sIX'­cies. plus numl'rous indig(,llons annual forbs and gwnsses of limited plant \'igor.

1\lallagemelll Practices Which 1\lay Condi. tion Or Alter Plant Development

In contrast with the opportunities available to the farme:r, the range manager hus fewer tools at his disposal to manipulnte nnd manage range­land vegetation, I-Iowc\'er. because of the mort' responsh'e nlilure und dynamic chllracteristic of unnual plants, mnnngl'fIIcnt may improve the pro­ductivity and qua lity of II lmual rangelnnds more than those of pe]'cnninl rangelands. Results of Illullngemellt pI'net iet'S n 1'(' often oblllined the samc )'ear in which I hey nI'l' apphed. Some of the mOI~

com mOl! manngcmen! IH'netiees that nre useful on annual rangcs include grazing management, fer­tilization. seeding'. bUl'Iling. and application of herbicides. In soml' situations 0. single manag<'­ment practice mil." sufficei whereas, in others a combination of two or more mn}' be necessary to accomplish thc d('sired ends, I n practically evcry casc whero n mnllnJ"rement practice is npplied, it pl'oduces nn impact on II pnl'tieulo.r stnge of plant development thnt Ilitel'S the course of subsequent growth: and of len the impact radiates to the rest of the plRnt community

Grazing management practices involve removal of plant tissue. Too early graz.ing of plant tissue reduces the photosynthetic area of tbe plant , and ClltS down the: production of photosynthate to feed the growin~ plant and to support reproduc­tion, Growing points lIlay be removed; this will th\\'fl. lt fUl'thf'I' dc\,t' lopment o f cer tain parts of the plant,

Rnnge impl'ol"l!lIlent by seeding involves many stages of developm(,llt, but. the most impol'tnnt ones al'(' J!('rminntion and establishment. St.nnds wi\l not bccolll(' ('stnbJished where the existinJ! plant comfllunit~, is 1I0t sufficientl)" open to allow introduction of 8('l'd('<i species. Seeding operations must also gh·1' 8On1(' compctiti\'e advnntagt., by seed placeme:l1t in 1\ fa\'orable position in thc soil or by earlicr plncement, to p ro\'ide a time nd\'lIut.­ngo agninst I' lI d.\' j.!cl'miunting seflds,

Runge fCl' ti\izntion is most efficient if npplied when environmcntnl cond itions 1lI'C most fnvor­nol(' fOI' plnnl dl'\'c loplIl('nt. In the fall, when scedliu~'5 nN' jusl de\'l!loping. root gro\vth lind lOp growth must proceed lit a rapid rate in ordcr 10 de\'elop nil nc\Nlllnte root system and sufficient lOp gro~\,th to withstand the cool winter ahead. In the sprin~, when predpitation and moisture

114 MISCELLANEOUS PUBLICATIOX 1271, U.S. DEPARTMENT OF AGRICULTURE

are agaill fa\'ornble and plants are in the rost!tte stagt!, f:H'orable nutrition will aid rapid develop­ment towards maturity.

Fire may be used as a Illanagement tool dl!ring seed development and at the mature plant stage. The mattu'e plant stage is not really a stage of gl"Owt.h but of existence in which the fire re­duces dry litter nnd concentrates the survi\·ing seed at the soil SUl·face. The d(!sired result is not 10 stim\llate plant gl'Owth but to mduce undC!sir­able species gl"Owth. Herbicides may be npplied to l"Cduce or eli minute 5(!t!d formation of undesirable species, to retaill plant.s in a given stage of de­\'(!lopment or to restrict other species from com­peting in the early seedling establishment phase.

Tn the following sections these management prnctices al"C deseribed as they work specifically on de\·elopmenta\ stages of annual range species.

Comparative Phenology

In dense populations of anmml forb and grass seedlings, rapid growth results ill n high demand for light, moist>lre, nutrients and other environ­mental factors (9). Plant survival under such cir­cumstanc(!s will be attained only by seedlings of high vigor, or by those with different rates of mOl'phogenesis which allows them to a\'oid the str~ss period by earlier or later development. In reporting the characteristic gl'owth curve for the :lnnual t.ype, Ratliff and Heady (47) repoI·ted that the period of most rapid growth extended from i\larch 28 to April 24. In 1060, growth of E"odiwn bOtTyS and tlfedicago hispida Gaertn. was earli~t"l followed by A·vena. bal'bata Brot., HI'ol/wl! "igid!/8 Roth, and Bl'o1nuS 1Itolli8, with Loliurn m.UUif101'UlI~ Lam. being latest. The pro­j!"l"essioll of phlllts towards maturity reached a static period of maximnm herbage wC!ight at the time of St.'Cd development. lIIedicogo Mspido. wns an exception, in that the maximum period ex­tended from the onset of flowering to the time of leuf shatter. After the penk of maturity, plnnts begall to lose weight as seeds were cast, but rye­grass lost its weight only half ns fast as the other speci(!s.

Species with delnyed maturit.y oft.en present, opportunities for applying management prnctices. Tal'weed (!Jemi2011ia. spp.), a summer-maturing, noxious plant, 'can be controlled simply by runge fertilization whieh stimulates the growth of

earlier maturing species and thus depletes the supply of soil moisture a\'lIilable for tarweed summer growth (6.5). Lotus pUI"ShianU8 (Benth.) Clements & Ckments :lnd Taeniathel'Um Qsperum (Sim.) Nevski also have late growth habit and depend Oil the soil moisture remaining after other range species huve matured (39,4(}).

B"OTIIU8 tecto/'tan J... is normally a winter an­nual, germinating in the fall when rain is suffi­cient lind growing rapidly nnt.i1 cold tempern­tur(!s set in, but it may act as II spring annual if there is too little fnll moisture available for ger­mination. Hulbert (16) noted striking varintion in the phenology of plants grown at Lewiston, Idaho, from sc(!ds obtained fl'Om several geo­graphic locations. There was a range of about 25 days in the time of emergence of the inflorescences, and ahout 20 days in the time when plants turn completely brown. These ranges in dat(!s of ma­turity are in striking contrast with t.he phenol­ogical development of t.he pefennial grasses with which cheatgrass is a competitor in the northern Great Bnsin.

The implications of differences in phenological de\'elopment for grazing management. systems are not eX:lctly c\enr. Much more knowledge is needed about the physiological status of plants in relation to morphogenesis before improved teeh­niqucs, such as hormone sprays and herbicides, can be used to condition plant development.

Germination

The seemingly simple process of 5(!ed germina­tion initint~s n. long series of morphogenetic changes that ultimately lead to a mature plant and reproduction of the species once again. The unnual habit allows a rapid turnover of the gene pool and . the annual exposure of all possible genetic combinations to environmental stresses, tlms eliminating the unfit individuals from the populat.ion. Perhaps this is why annual species are so highly adaptable and vigorous; it is simply n. matter of selection for such habitats.

Fnvornble temperature and moisture are es­sential fOI' successful development of the seedling during the first criticnl stages of growth. Numer­ous Ill!umgement practices CRn he used to stimu­late, retard, 01" eliminate plnnt growth during germination :lIld seedling establishment.

A high degree of priority exists for seedlings

I'J.AXT MORPHOGE:-"ESIS FOR SCJE:\Tlnc llANAO";l1EX'l' 01<' RA:-"GE RESOURCES 115

with n I'upid growth rate dUl'ing the endy stages. Varinbility in sl)('('d of germinntion exists among widely differing ~eographic collections of Tae1li­uthel'/l1II oapel'llIIl seeds in thl! United Stntes (41), Collections from :l.rens with It higher degree of uncer(ainty in the first. rainfall appeared to bJ"Crm· inate at a m.ol'o rnpid puce thall did seeds from 1I10l'e mes ic sites in the coastal region of Oregon,

'''hnUey and others (68) showed thnt increas­ing soil futility increased seed size and rate of germinat ion, Soil moisture stress duriug seed pro­duction reduced the number of seeds, but seed qunlity nppal'entiy was not materially affccted. Inasmuch ns seed size apparently is a cl-iticnl fuctor in promoting grenter seedling vigor (67), any Illunnbrement practice which would result in improving seed si)';e should hUV6 a corresponding­ly Ueneficial affect Oll seedling vigor und estnb­lishment.

Rapid Illobili)'.ntion of food reserves in the seed to soluble fonus hus been postulated ns a possible index to seedling \'igOI' (6) , Spccics known for low seedling \'igor upparently were slower in the

.. ••

, • ..

..

"

P TUlng" _d. 1~'!O""I.~ (TULI 5 .... 0$)

'\

--- .... <~ __ 16TH 'IIOU.

--_. o.WU'" ....... _.- _o"_acowu., "" ... w,,· __ nUL,", l UIT" ,

\ \ , \

""" no_ 'l ..... 011 I lOTTI .. (!IAn)

• 110 !..

i ,~ "

! , 10 ::

mobilization of food rcscrves than wus !l species known for its higher degl'eQ of seedling vigol' (fig, 1), Seed s ize in itself docs not appear to be a sole critel'ion of seedling vigor but is menning­ful ollly within n species or closely related group. Rapidity of carboh~'drnte mobilization varies nmong species. However, one of the most rapid mobilizatiOIlS report ed in the litel'utUl'e is that of Schilmlls ambicu.s (Nees.) (57). III this Il."\:treme­Iy small-seeded nnlHml grass, mobilization of stm'cd cal'boh'ydmte WllS almost complete within n 48-holl l" 1't!l'iuo.l.

Sccdcoat hardness or impermeability often re­tards gel'minntion. This pl'Oblem, howel'er, is less common Ilmong grasses thun nmong dicotyle­donous species, particularly the annual legumes. Tht' hard seedcoat mn.l' ha\'e an ecological ad· vnntnge. Willinms (61) demonstrated Lhn! hUI1:I seeds of T1·i.folium hit'llon All. provided sum­icicnt seed for surv ival of the species, when the seedlings which gel'lninnlcd first. weI'C eliminated by drought, rollowin~ the originally favorable conditions for germination, The remaining hard

• •

..

..

.. ~IO

"

- - - nu(~

- - TO"~ 'IIIU' _. __ . ~u •• ( ... '.tAU _.- .o. ·un ... , I\11U1

'\ , \ , \ /------------

\/ ! ,

,!IAn )

. .. , • • m"

i · .. ,

FIGUJlI: L-:llul.ollb.ullftl1 ftf ('ftrJ.,o,hyil rtlte reSC!r\·es In early ~ gerlllll1UIIo,n_ \ Wlmlle.'· !ll111 :llcti:eIJ. (S8).)

116 ),IISCELLANEOUS PUBLICA'.rJON 1271. U.S. DEPARTMENT OF AGRICULTUnE

s~eds in the litter provided u sutlicicnt reserve for a second wave of germination . Seed dormancies of from 50 to 80 percent wem regarded us It valuable mechilnism for SUITirui of the species.

In gcneml, germinution is reduced with in­creasing figC of seeds. Older seeds often produce malformed sc{'{llings. some wi thout the uppear­ance of ft root 01' radical. Removal of u portion of the seed awn of 1'. (lSpe1'U1n (45) appeared to increase germination of older seeds, however.

Williams (59) evaluated the emergence force cxcl't('d by small legumes. On the basis of dif­ferences in the force exer ted, he. concluded that the seedling size was not always n reliable index as to the force that the seedling was capable of exerting. I n ll('aY), soils. choosing the species with the abiJit.,· to emerge Hilder difficult conditions would 00 n wise management decision for seeding depleted unnual rangelands. Grass species difTer significantly in their abilit~y to cmCl'ge from dif­fClI'(mt plantinf! depths. Tlw data in table 2 show that T. flspe1'ltm has u limited ubility to emerge f l'om soil depths greuter tium 2 inches.

Emergence of seedlings is often takcn as un indication that establishment hus -{-ully occurred. This mar be a reasonable criteria for the germin­ation lubol"ntor.r or itl a humid (,llVironment. but under Ullllllfli range conditions, (>stablishment. is not secnre It! this point .. The number of plants early ill th(> growing senson has been reported (11) to vary from 20 to nearly 100 per square inch. Considerable reduction in this number tnkes place us the season pl"Ogresses. In a review of seedling: vigor. :'\rcKell (36) stated that establish­ment mn}' not. be fully assmcd until a grand rate of plant growth has been demonstrated (fig. 2).

F ertilizer may be applied in the area imnw-

TABU: 2.-Seedlhlg emergence /?'OlrL 1-. g-, 3-, and 4-inch l)lanting depths. Each figure is an (we,/,­age 0/ h; obsu'v(ltioll$

SpeciQ9 Num\.ler or seedllngs emerging

from depth ot

1 In.

Trifolium hirtufII ______ 160 I1r0Il11/3 mof/i3 _~______ 259

1'aenillthcrllll! a8/lcnllll_ 287

2 In.

01 42 32

8 In.

22 1 o

4 In.

1 o o

o

,­" . .: I

l ' ·f'1 " , .,

Period of Seedling

Time

E.tobl ishment _ : I ,

FIGURE 2.-Perlod ot seedling establiShment in relntlon to SUC(-ee(l!ng singes of Illan! growth. (After :'1C'Ke1I. 37.)

diatel.r adjucent to grass seedlings (53) . H owever, Lolimn lIwltiflm'll1Ih seedlings suppl ied with ex­tra nitrogen (1) failed to grow roots and t.ops as fast. as seedli ngs I'eceiying no additional nitro­gen. T he ability to utilize nitrogen efficientl.\· mllst deyelop latet .. because older Lolill1n seed­lings are known to 00 highly efficient users of fer­tilizer nitt·ogen.

ArtifiCial Seeding

The management of annual rangelands often requires thnl impro"ed species be intl"Oduced to the plant communit.y, The choice of adapted an­mml grasses and legumes is extremely impol't,ant and has recci"ed considemble sttidy over the past several years. Good management usually includes drill seeding, fertilizatioll, reduction of competi­tion b.,' grnzing Illunagement, proper depth of planting. und follow-up grazing management to assure favorable comlitiolls for seedling estnblish­ment.

I II B1'OlllllS tect01'/lln nreas, concern hus been ex­pressed thM sites formel"ly dominated by peren­ninl nlllge g rll sses arc nlmost impossible to l'C­

clnim to perennial grasses beennse of the intense competition offered by 8. tect01-um. Otherwise, grazing mUlIugement of the existing stand of antutiti grasses ap peal's to be t.he only solution a,'ailuble at the present time. Recent work by USDA's Agricultnral Research Service range­land scientists in :\evada and " rash ington appear to prodde some flnswCl'S Tor establishing pm'en­nifll grnsses in the areas dominated by B?'om118

PLAXT MORPIlOGE:\ESIS ~'OR SCIENTH' JC MANAGEM.E:\'l' 011' RANGE RESOURCES 117

tector!lm ('I). T hese studies show that the compe· tition for soil moislure by cheatgmss growing with Agropyron spp. is intense.

Herbicides hll \'C been used to manipulate plant <..'ompetition dlll'ing the seedling stage. K ay nnd )CcJ(e.\1 (24) IIscd pl'eemergence herbicides to con· trol eompetinl,! unnual range species, and favor the establishment of 1'1'ifoliwn hirtmn and Phal· (Jl'ilJ tubel'OlJ(I L. val'. 8tellopie1'a (Huck.) Hitch. Before weather conditions becnme favoruble fol' seedin:.r. nn expel'imentnl al'ca was bul't1ed to l'CIllOI'e old litter lind concentrate !lccds ut. the soil surface. SnbsCilllentl)·. pl'Cemer::,rence herbi· cides WCI1! npplied to the surface, Two months luter, after fn\'OI'uble moisture conditions oc· CUI'I1!d. the expcl'imentnl plots were seeded with the introduced species. Competition from an· nual weeds was sufficiently controlled to aHow successful stand establishment of the introduced species. Chemical tt'Catments which were most. effectil'e included atrnzine. simazine, and EPTe lit rates frOIl1 2 to 4 pounds per acre. Subsequent refinements of the originul techniques hn.ve re· suited in collsidel'llble success. Kay ~ applies 11 12· inch bund of paruquat, then seeds introduced species below it, The seeds lire protected by the soil from the effect of the chemical, which de· stroys the young annual grasses and forbs on the surface.

Root· Growth Rapid root gl'Owth is fundamental to estllblish·

ment and dcwciopmcnt in annual rangeland com· lI1unities, paiticulllrly when moisture stress is a cOllstunt lhrellt during the period of plant estnb· lisluncnt. Species may acquire a competitive ad· \'untage under s tress conditions by (a) Ii faster rnte of root growth. or (b) the ability to remnin acti" e in both root and top growth for a longer period. This extra growth is most impOltnnt at II lime when competing plants are inactive, 01' at the end of the gl'owing period, Hllrris lind 'Vii· SOil (10) reported thnt rapidly elonguting /J. lec­fOl'Um, and 1'. {1JI]Jel'll1Jl. roots penetrated the soil

.ahead of Agl'OPY1'OII spicatllm (Pursh) Scribn. & Smith. because they were able to continue root growth at low temperatures. Field studies indi· Cllted that B. leeloJ"tau roots grew well at temper·

' Personal communlcntlon. 1071,

atUl'es as low us 3" C, while A. IJpicat10n roots grew very slowly at temperatures below S" to 10", Therefore, B. leclOl'um seedlings are able to glllll a competiti"e advantage ovcr seedlings of A. spicatum by rapidly eJongnting tlleir roots during winter months and using moisture through a large poltion of the soil profile.

Any management practices which inRuence root growth are extremely important as' tools in mao nipulating the anllual plant forage resource, Fer· tilization has been shown to increase the overall ulmllll:lllcc of l'ooL:; in tbc lll'cas normally occu· pied by roots of tlnllual range spooies, although rooting depth was not changed much (39).

Grazing manllgement also has a significaftt ef· foot 011 root g rowth. Numerous studies (19, .eo) hav6 shown that intensc grazing decreases root growth. In gen61'al, plants which are grazcd e.". cessivelr will have II much shallmver root system than will plants which lire grazed conservatively 01' not at all (91). This favors greuter root de­"elopm~nt lind gl'cntel' seed production of less pllhttnble species. lind of lute-growing weedy spe· cics, such liS tllrweed Ilnd other noxious anllll!}\ forbs.

Grazing mnllngenl('lIt may also be uscd us a means of balancing competition during the es­tablishmeut phase of allllllaland pel'Cnnial seeded species. Love (se) recommends a moderate amount of grazing during the early spring period, whcli plant compet.ition is extreme. If eompeti· tion is not reduced, g l'owth of seeded species is l'Ctarded.

Top Growth In the de,'eloping annual seedling, expansion

of leaf blades proceeds at a rapid pace. With the de"elopment of tillers upon tillers, the in­('rease ill diameter of the g rass plaut ea.n be rap· id; t.his incrcnse may begin in the late fall and pl'Occed into the eurl)' spring period of growth, Under extl'Cmely crowded conditions, tillers do not form , and onl)' single stemmed grass plants l'Csult. Competition with othel' species is critical to the del'elopment lind survivul of annual range species at this point.. Wit.h sufficient space, most species begin to expand the diameter of the plaut. Under \,CI'y dense crowding, little if uny expansion takes place, and grasses continue to grow with a single upright rolled leaf sheath

118 :\ITSOELLA.N'EQUS PUBLICATION 1271, U.S. DEPARTMEN'£ m' AGRICULTURE

:Uld hlnde. Rroaclleavcd species, 511Ch as Et'odi1t1n lind the tlll!lllnl legumes, also show the effects of crowding in the carl)" seedling stuge. Knight and Hollowell (Z7) pointed out that ~tand density has u marked effect on the number of \'cgetntive stems, and later 011 the number of seed hends. produced by T1'ijolium, incar-nat'um L. E1'odiwn plnnts tend to spmud out Rnd form n mat when surface urea is IIvnilable. This mOl'ph­ologiell i characteristic mil}' or may not be nn udvantage III competition with the nnnulll g l'llR.<:;f'R .

With the onset of cool weather und lower light intensities dllring the winter months, many of the llnllual rnnge species will maintain them-5('\VCS in 11 rosette stnge. to continue through the less favorable growing conditions. Because of a temporary plnteau of the growth curve at this point: it might be appropriate to refer to the typical anllual range species as a winter bien­nial. HOII'el'er, because annuals do not continue their growth through the dry summer period they actually do complete their growth in the single senSOll typical of annual plants.

Low temperatures often stimulate the axillary buds all stems to produce additional new tillers. Dn vis nnd Laude (6) found that the main culm produced morc shoal s and more heads than did lat.er dereloping tillers. Reduced light intensity at the basal tissues of closely spaced shoots, and shndillg by screens, reduced tillering in the an­mml grass, Ih'o1n118 'f)wllis. This would cOrl'es­pond to the plant response seen .in the field, tmdCi' less fllvornble cnvironmental conditions of wint.er. Competition fOl' light nmong species of allnual dOl'ers was also found to be a critical matter in the mOl'phology of the seedlings. Wil­liams (GO) found thnt lenf arca and leaf po­sition in the foliage canopy of Trifoliutlt hif-­tum, T. i1/Carnat um, and T. 8ubterralieUtlt Linn. was related to t.he size of the cotyledonary leaves. This lldl'fLlItage was luter extended to larger uni­foliate leaves und in the higher elevation of unifoliate and first trifoliate leaves.

Some species seem to influence 01' interfere with the gl'Owth of otlll'r species. Lof.i.um, multi­jlorum (097) in a mixture of species always had a det r imental effect on the growth of these spe­cies, particularly during the seedling stage. The implications of these findings are clear for the

range manager who uses a seeding mixture con­taining the highly competitive L. muJ.tijlQ)'1t1n.

:MeCowan and Williams (35) found that £1'0-

dium b0i1'Y8, gl'Own with B 1'omu8 71wlli8, ac­quired a disproportionate sha re of available suI· fur, because of its mom mpid root extension. However, at high sulfur le\'els Bromu8 became increasingly competitive and, as its population density was increased, Er(Jdium was virtually eliminated. Many studies (2, 13, f]5?, f3, 63, 64) have shown that fertilizer stimulates plant growth, even dnring periods of cool tempera­tures. Fertilized plants appear to have an in­erease in cold tolenmce. The amount of litter left remaining 011 the ground from the previous season may be useful as an insulating layer (11).

Speeies of annual legumes appear to have dif­fering abilities to take up phosphorus from the soil. Apparently, introduced legumes have a higher potential for phosphorus uptake than some of the native speeies (4£). Additionally, there appears to be nn advantage in phosphorus uptake to offset the effects of low temperature. Other workers (8, 4:), 54) have shown that ap­plieation of fertilizers during the seedling stnge will accelerate growth and provide for earlier range readiness than plants which have not been fertilized.

Rapid Vegetative Development

Upon emerging f!'Om the cool winter periods, plant morphogenesis begins dramatic changes. The significant morphogenetic changes are leaf sheath and blade elongation in grasses and stem and leaf growth in forbs. Root and top growth of plllnts begin [I rapid rate of increase, and com petit jon for nutrients, light, water, and space again becomes extremely critical. Only those species whieh ha.ve boon able to develop a.n ade­quate leaf aren and root system will be capable of sUl'vival and development in this more ae­tive period of growth (3) .

Under some eonditions, an earlier rate of read+ iness can be obtained through fertilization (94). Fertilization, through its effect on differential species response, nlso has It significant impact on species composition. E vans (18) reported dif­ferences ill nitrogen uptake among three species of the ilUllllnl gl'llssland type. Combinat ions of grazing with fertilization hal'e a significant im-

PLAXT MORPIJOGE1I."ESIS !'OR SCIEXTIFIC l\[A.i .... AGElIEX1' O}' UAXGE RESOURCES 119

pa('t UpOll spl'<.'ies composition. Jones and Eyans (g1) reported thnt the percentage of B1'omU8 t/lOlli8 in a resident Rnntla! range was increased oy nitrogen fertilization for 2 or 3 Jcal'S, but in­creased 0111:". ill the first yCIH' 011 ulIgrnzcd plots. Walkei' and William (54) report.ed a nitrogen buildup in the soil by anuual legumes which had been fertilized wilh sulfur, The nitrogen buildup increased grass production, Most of these species composition changes occurred as a result of int(>l1;pecific competition, during seed­lillg estnblishment stnl{c and the initilll E;tag('s of rapid growth at the end of wint.er,

Remo\'111 of plant tissue tIt the beginning or soon after thc initiation of rapid plunt d{welop­mcnt, by either clipping or grazing, reduces plant. vigor and ellcout'agcs less palatable and cOlllpetitin~ species to predominate. However, if grnzing is not excessh'e in the early sta~res, an­lHlfIl \'egetatioll has n remarkable ability to sus­tain a hig-h intensit)· of grazing and yet. to con­tinue its growth and proceed towards maturity_ It is during this period of active growth that the annual I'IInge begins its period of highest producti\-it.y.

Stem Elongation

Under continued favorable environment, the meristemnlic regions :1.t the bnse of each inter­node ill the compact grass stem take on new ac­tivit)'. Formation of 1I0W cells and 0011 eJongn­tion urc 1'csponsible for the relatively rnpid growth of the culm in the grnss plant.

Competition for spllce is extremely intensive at this stage. Some plauts. by their greater \'igor or by I!. leaf display pattern, may have the edge iu competition with other species, Again, g raz­ing und fertiliza tion urc most important during the stem elongation stage. Grazing may 1'1'­

mo\-e the immature inflorescences, which grow in the proteetioll of the rolled shenth or ill the. boot. Some workers (30, 4.')) pointed out that not all species l'Cact the sume to herbage removal. B. 1IlQUis \\'IIS found to continue tillering and heading much longer thun Festucu megalu1'4 Nutt" when clipped il' a like manner, If grnz­ing were continued to the growth terminal stage of F. meglllul'(f, it would depress this species, yet would still pCl'mit t ilJering and abundllnt head­ing ill B. 1II_cllis,

High levels of fertilization on allllllal mnge spceies sti!lHllnte ;lcti\'e gl'Owth but also ncceler­lite the usc of soil moisture. In yenrs of inllde­<Junte rainfnll. fertilization ma:,>' canse the utili­zntion of lll'ailnble soil Illoisture before the plants malul"(, u full crop of seeds (38). H owever, nnde!' othel' condit iOllS. the. mOI'(l dlicient utilization of soil moisture will lenve none for slimmer grow­ing weeds (0';), Studies in the Sacrnmento Val­ley Oil fertilized rmlgll indicate a 300 percent in­cr('nse in ('fliC'icllt lise of soil moisture where plots wem fCI1iliz{·d with 100 Ib./a('rr of nitl'Ogen lind 8S lb./acro of phosphorus (39),

Clipping. ns opposed to grazing for clearing an aN'a. Illny niter species composition_ Murphy, .Jones, and Love (44) reported thnt clipping en­('ollrnges the. Sllll1l11el' g l'(:)\ving forbs. Clipping appenrs to inclocase the level of soil moisture re­maining for spcci('8 which develop late in the summer,

To pl'eSC'I'\'e the high content of protein) phos­phon!s, and carbohydrnte, Kay and Torell (e5) sug!.rcst using n chemical prc.sel·vative, such ns parnqunt (1.1' -dimethyl-4,4' ,bip:,>'ridinum dicillo­ride), to stop plant development and "cure" the standing fornge for usc by grazing animals. With grenter emphnsis on fortlge quality in the future, nnd where there is no need for the re­plenishmenl of seeds for stand l'eestablishment, the practice of ehemical curin~ ma:,>' offer ad­,'allta~'l'S to land managers,

Boo l Stage To Flowering

At this stage of morphogenesis, the inflores­cence is ready to emerge from the rolled led shenth. and to continue dC\'clopment towards nn­thesis and seed maturity_ I n annual grasses this is 1\ vulnerable stngc, beCIlUse plants are still pnlnb\ble fin d the immatutO seed hends mny be subj("cted to gl'llzing. I n annual forbs the prob­lem is !lot so critical. beeausc many of them do not have a determinant type of flowering, but produce flowers on Internl brnnehes, sometimes throughout Ihu spl'ing period, Erodium tl ml JlIedicago lIispi(/a are pnrticlilurly well adapted in this regnrd; flowers appcnr \'ery early and continue until very late. Some of the annual leguines, such liS T, illCm'1Ultllllt and T. hirtum, hnve a d('tel'minnnt flowering pnttern, and lire more vulnernblc to grazing during these latc

120 i\IISCEI,LANEQUS PUBLICATIQ;\, 1271. U.S. DEPAR'l'~IE~T 01" AGRICULTURE

stages. Only through the formation of lateI'll} f10WtW stems is this vulnerability rendered less criticnl. The high dt'-llsity of plants growing on annua l mnge vhtllnll}' assures adequate seed production in most years. if intense grllzing does not destroy the developing inflorescences. How­('vcr: the llumiJC!J' of plants which surv ive to the flowe-ring stage is drflstically rednced from the Ilumber of plants which germinated at the be­!!inning of the senson .

In curlier gl"Owth stnges, fertilizutiOll was nII­Hable in encourngill!! plant growth, but at flow­ering there is little Lcncfit from fertilization. I n fnet, it mny be> detl'imalltnl if it hns hnstcned maturity by depIcting the soil moisture supply,

Palatability often changes as flowering ap­proaches. 7', (lapel'rllll becomes much less palat­llble ut the boot sta~e (93) . Many fo rbs, par­ticulal'ly the ulllluul legumes, take 011 a degree of unpalatabili ty at this stage. Silica and fioor contents increase. uud many plants become much roll~h('r amI stifTer in character.

Seed Maturity

As seeds begin to develop, carbohydrates nre tl'nllslocated to the seed heads of grllsscs lind forbs. Concurrently, matumtion of other plant parts proceeds ntpidly. P hotosynthesis is ex ­ceeded by r~spimtion ill older plnnt parts, lind lowel' leaves begin to dil'. I n the IIllll\ml ra nge, soil moisture st] 'CSS is n common and prevalent environmentnl condition aud becomes an ovel'­riding effect in hnstening plant maturity and seed ripening:, i\[anllgement of annual range­Innds at this stage may concentrate on se\'el'al practices designed to manipulate the plllnl co\'e]' 0]' to make contin ued use of the forag:e resource.

Runge fertilization incrcases plant palatabil­ity, which pro\'idC's excellcnt opportunities fol' continued grazing of the dry herbage, Less pal­!ltuble spec ies, when fcrtilized, ha\'c been ob­served to be consumed readil,y by livestock (4$), The forage produced b,y fertilization is high ill protein and other nutrients for the grazing ani­mal (5e).

Seed matlll'ity of Illldesirnble species can be prevent.ed with he]'bicides dming' the period of seed maturation (9) , Aminotriazol has effecth'c­ly prevented the de\'elopment of seeds of T , 08-

perum, a late-matming species, Late-maturing,

weedy species hn\'e been cont rolled by fire, which desho.rs their immature seeds after the desirable fomge species hu\"e matured (14)., DUl'ing n critical period of 1 01' 2 weeks, the cady-matur­ing. !lnllllnl fOI':l1!C' spC'cies are dry enough to ful'­nish fuel to support !I fire which will desll'oy the maturing crop of medusahead seeds (41) . Burn­ing after the maturity of medllsahead seeds is cOllsidembl," less efl'ective, beclluse the hard seeds lIa\'e heen cnst from the heads and lost into the litter, where tlwy are pl'Otected by the volume of plant matcrinl lind a]'e unnffccted by the pass­ing of a fire ov(>]' t he nrea. I n addition, mature seeds arc less suscC'ptiblc to the effects of high tempel'atlll'e (f20) ,

Seed Dissemination

Disseminntion of seeds from annual range spe­cies occurs at yal'ious ti mes following maturity. depend inl! 011 w('ather conditions and the struc­t.ure of particular species, Seeds may be cast in­dividually. ns in B1'Om1l8 tect.ol'!t'm, Bromu8 ?lwl­/i8) Taeltiatlle1'to/1 (t8pel'!On. A vena barbata. and n'ifoli1l111 81tbtu'1wneum; 0]' by dehiscence of en­tire seed heads of Aegilop8 e,'ittncialis L.

Seeds of annual species oft.en have Imdesir­able cil!lractcristies, stich ItS spines, stont barbed awns. 01' coiled seC'(\ stalks, which catch ill the fleece of sheep and reduce its \'nlne. These stl'llC­tUI'(>S for attachment mny provide nn effecti\'(' m('llns of disseminfition find evell n means of , tmnsport and ilwasion to new range Ilrcns,

:\ Iallngement practices that may affect seed dissemination incllld(> l'emO\'al of g]'flzin~ ani­mnls (g1'odin7l~ areas) before seed dissemination, l'cstri('tion of liH!stock to weed-free areas, :1lld b11l'ning. Some arC' ineffective; bU1'lling mny ac­tnally scll l' ify seeds, l'educe litter corel' and jm­pmve conditions for seedling establishment. Re­moval of livestock may not be realistic unless al­tC'r llftte feed SOUI'Cl'S are available.

Summary

l\lanllgement of annual rangelands has grad­I1nll.\' de\'eloped on 1\ foundation of estublished uio\og:icul principles, Fo]' ex ample, we utilize in­formution on l\\Ih'itionn\ requirements and phen­ology of plants as a bnsis for mAnagement, deci­SIOns.

PI.ANT MORPHOGEI'\'ESIS FOR SCIENTIFIC MANAGEhlE~'l' Ot.' UAl\'GE RESOURCES 121

)Iuch remains to be done to utilize existing knowledge in impro\'ing management prnctices. Because of their diversity, biological plasticity, and aggressive growth hnbits, annual species of­fcr interesting oppol·tunities fOr forage produc­tion, :More information is needed on responses 10 manipulation by grazing and fertilization and on ways 10 mnnipnlate competition during seed­ling establishment.

AnnulIl fomge plants lUl\'e not always reo ceh'cd the credit due them bccnllse of precon­cciH.:d iucns ('mbodied in runge mnnngemcnt prnctiees that are bllsed on climax concepts. An· IIuals lire gencl'ull,r regarded as invaders (in· deed most are) and they are listed as prime in­dicatol's of depleted or poor range conditions (which \'el'y well can be true in many cases), However, in some areas, annuals represent a tre­mendous gl'flzing resource where they nre rela­tively stable 6'om year to yenr. Annuals often kel'p the community closed and make the most of the potential of fayo l'o,ble weather conditions.

Lite rature Cited

(1) An:KF., C. A .. and C. M . i\l CKELI~ If"';!). t:.\IILY S.:r~III\'G GIIOWTII or ITALI.\:'1 RYEGII,\SS

,j,ND SMILO A8 AITECTED 8T :'1U'n.lTIOS. J. Range Mangt. 22: 2U·82.

(2) BElI'TLEY, J. It. snd L. n. GIIUN'.

If).-.... lSTUI\:UTIOll' Of' SATin: AlI':'1VAL CLO\'DU!

TIIIIOUGII AI'PLlCATION or aULTUll ox CALIFOR­

NIA FOOTIIILL RANOY.. .T. Range :'lIIngt, 7: 25·30,

(8) --- nml :'1. W. TAUIOT.

1{)51. f:FFICl £ST USE or A!'O:'1UAL rLANTS ON CATTI.r.

IIANGE8 IN THE CALlFOIINIA f'OOTIIIL1.8. U.l't. Del)t. A&r. Clr, 870.

(4) BISWJ:LL, R.1I , 1056. r'(''OLOGY OF CA I,lrOIiNIA OIiASSLASI) . .T . Rnnge

Mangt. {): 19·24.

Hi) DAuBJ:lI'MtJtt:, R. F , 1040. PLANT SUCCE8SIOlf IIUI: TO OVJ:IIGII ... ZINO IN '1'11£

AGIIOPYIION BUNcnORASS l'RAllltE OF 8OUTIt·

F .... STElllI' \\'ASRINOTON. Ecol. 21: ~64,

(6) DAVIS, r., A., nnd H. 1I. LAUDY..

1H{I-I. TilE l)t:\'ELOI'~IE:ST 0 .' TILU: IIS 1:-; 1I110llUS lIOL'

LIS L. Crop Scl. ,,: 477-'180.

(7) ECKJ:IIT, R. E. JII .. and n. A. EVAN8.

1007. A ClfJ::UICAL FA I.LOW TECUSIQUF. FOil eOSTIIOL

OF DOWNY 8110:1.11: ASP r..8TABLISJlllE.."IT OF PER­

E:SNIAL OIlASSES os RAlI'OELANP$. J . Range

:'lnngt. 2(): 85-11,

(8) I-~V"'N8, R. A.

1060. OU'FEIIE:-;TIAL IIF.8I'()NSE OF TUIIEE SPECIt:b OF

TilE AN:-;\!AI. (lILMi"l .... lI'U TY I'~: TO I'LAII'T COll­

N;TJTIO:-; ,\NU :I.IINr.RAI. SUTIIJTIOS. 1~1. -11: 305·310,

(0) --- 8. I.. K,\y, lind C.;\1. :'l cKELI~

1963. HEllIIIClOY.8 TO PREVl':NT SEEn 8ET 011 OERMl:'U­

'1'10:1' or :I.IEDUlJA,ur .... n. Weeds ll: 27S·2i{l.

(10 ) 8.1.111118. G. A .. nnd A. :.t. W1L80S,

1070, COllI'F.TITIOll' .'OR lfOIS'I'U1U: '\).IONG s r.JI:IIL1NOS

or ,\S:-;UAL A!'OII PERJ;.. .. $IAL IlRAIjSES AS INnu·

"NCEIl BY kOOT ELONOATIO$ AT lOW TE:I.II'F.lt ... -

TUII£. 1')('(\1. 1)1: r.sO·OS4.

(11) HEADT, 1'1, ~'.

(12)

l!JOO. CUANGElI 1$ ,\ CALlFOR$IA A:-;:"'UAL 1·1 .... .:-;'1'

COlUWNITY INDUOJ:D IIY M,\NU'ULATIOll' OF

I'IATli liAL )'!ULCII. F.c<II. 37: 7{)8·S12.

1915S. VEOETATIONAL CRANOES 1:-; TilE CALTFORlI'lA AN'

NUAl 'I'YI'E. Ecr>1. 89: 402416,

(lS) --- I). W . COO"':R •• 1. W . RlIlI.£. amI J . E , I1ooFf:JI. 1003. (''O MI'AIIATIVF. FOIIAOE VALU.:S OF CAI.lrOIlNIA

OATOU89 AII'D 80FT CUESS, J . Runge lInngt ,

16: 51-6-\,

(14) HEIIV£T, D. ~'.

1049, RI:AcrlOll' OY A CALIFOR:-;IA ANi'I'UAL TTl'!: C011-)IUNITl' '1'0 PIRE. J . Range Mllngt .. 2: lUH21.

(Ui) HOOLUN D. O. K" H. W. MILLER, and A, 1" HAI'ES­

IUCIlTF ...

1052. API'LICATIO!'O or rER'I'II.IZEII8 TO Am Q)!fSF.R\·A·

TIOll' OF ASN UAL .·OIlAOE IIA$Gt:. J . Range

Mnngt, 5: 51).61.

(1{1) II ULBEIIT. L. C ,

11)55. ECOLOGICAl, STUDU:S OF 8RO)1 US TF.CTORUll A~"

0'1'111:11 A$lI'UAL IIROllE GRASS.:S. }~COI. :-' I ono~.

25: 181·213.

(1.) IIUL~ A. C .. and J . PECtlANEK.

19.17. CliEATGRA8S _ A CUAI.LENOE TO IIANGI': IIF.­

SEAIICU .• 1. ForeSlr), 45: .>56·004. (18) HUllTI', L. C.

1930. 1lQ\\'NY II"O)IE (ClIr:ATOIIASS) IIANOE l'OR 1I0IlS.:S. U.S. ~'ore~t Service, Nor thern R OCky

:.It. I-'orefrt ftnd Hange Expt. Stn. AI!I!!. }o'or eflur Note ro.

( 19) JA.\U:SON, D. A, 1063. IIESI'OlI'SI: 0.' IlI'UI\'IUUAL PLANTS TO tlARVr.8T­

INO. 801. Uevlew 20: 532-594. (20) JAN'I'I, A., II n(II'. J, KII"'~IF.R.

1036. R.:.o80\\,'I'1i OF PASTUIlYJI IN 1Ir.I..\,TIO~ TO SOli.

)IOISTUIIE ASII IIEFOLIATlON. l' roc. VB Inter. naU, Grll$.lli. Congr .• New Zco.lnnd. Pit 334-1.

(21) JOSES. :'1. IL nnd R. A. EVANS.

1960. BOTA:-;ICAL CO)[I'()' ITIOS CllANOE8 IS ANlI'U"'L

GJlAS8f .... $1I AS ArFl:CTl!D BY FF.IITn.I7 .... TI0)( AII'll

ORAZING, Agron. J. G2: 450-'161.

122 lIiSCELLAl'\EOVS PUBLICATION 1271, U.S. DEP"ARTl1E:-IT OF AGRICULTURE

12"..!) nnd S. S. WIl'I'J.N8. 1007, 8UlITf.JtHANJ'..A;'\' CI.ol't:R VElISUB NrntOOY.S' n:J!.

Tl1.l7.EII ANNUAL QRA8SLA;"II)S: BOTANICAL COli­

POS I'l'IO:'1 ANU l'IIOTt:ll~ CONTE;';T. J . Rnnge

:\I,lngt. 20: 8·12.

(23) --- W. K :\1.\1I1"Il'!. I,. J . B~IIR\". Olltl V. OSTRELI.

1001. GROUX!) COVUl ",;'1'11 PLANTS PBESE.:"T O!'l' ORAZP.II

,\;,\,XUAL U:I"tlt: A8 "Fn:arm BT :OTIIOOf.l' PEA'

TII.lZloTlON. J. Rnnge Mnngt. 14: HB-l48.

(211 - - - nnd C. )1. llcK..-.I.I ... 11)(1.1 1'ln:t:.I,t:HGl::'Il(' !': IIHIUItLUEB A8 AN AlII IN BEEt)·

INO AN~UAI. III\NOr.' .... N1I8. Weeds 11: 260-20.1.

12;;. - - - uwJ I), T. TOilE!./...

1070. CUJlINO STA:o!UI;'I'G RANGY. FORAGE WITI[ nt:x· IIICltlt:fl. J. Runge Ynngt. 23: 34-41.

(26) 1~u:loult:IJSON. J. 0 •• and J. G. SUITB. 1004. CIIt:.ATGRASlI (IIROlolUIJ TF.c'rORU"! 1..). Sor.

Rov. 80: 220·2t}2.

(27 ) I\NIOHT, W. E. , nnd E. A. HOLLOWEl'.l ..

lQ:'iO. 1'111: KFI'ECT 01' STAlHI 111:;-16111' ON I'IfT"IOl.O(l­

ICAL AND lfORI'Il0Ul0IOAL CBARACTr;R18TIC8 Of'

CR1.\ISO:'l' CUl\'I'.R. Agron. J. 51: 73-m.

(28) Kopp!:!!. W.

1023. 011'; KLiMATI: IIEX r.RH£, de Grnyler. Bcrlln.

(29) --- Bnd B. A. CDAUOI./L.E.

l~r~~. EFFT.('1" OF STAGt: or 6f..!'.JILI:"i0 Dt:"'£I.()P)Ir.ST

UPON nr.AT TOI.Y.IIASCr.8 IN BRO~Ili: DBA68. J. nunge ~Inngt. 6: 820·824.

(30 ) _ A. K"'''If!It. Gnd n.. :'1. Lon:.

1!lm. UIFTDW..lI"TIA.I. unx:T OF n~BAOE RJ:JoIO"'AL ON

RANGE Sn.;CU:S .• 1. R IUljte Mangt. 10; 116-120.

(81 ) 1..,.Wlll:. H. :..I. 1007. OROWTII or TIll': ANSUAL 0llAS8 PLANT 111' 11';'

SI'ON8E TO III'..IIOAOE RE'yOVAl~ J. Rang(! :' Iangl.

10: 3i-39.

(32 ) L(l ... r~ H. M .• nntl W. A. WIUIAlI8.

11'1:->6. II",Nnl:UNU U£\"10P)II:":" BY liANIPUJ.ATIOlf

O"F TUE BOIL·PUlfT·ANIWAL CQMPL£X HI" Tllr.

1II1"IC,·tT L.",'IItO:O.n:NT8 OF A YEDITI'!RIlAN·

&AN-TYPE CLU'AT£. I'roc. VU Internlltl. GrillS'

111ntl Congr .• lIP. :;0(1·518. New 7.ealand.

(38) LU6K. W. C .. )1. B . . 10NM. 1'. T . TORI-:LL. nnd C. M.

:'loKr.I.L.

1001. lfEDU6AlIF.AIl l'ALAT,I.!IlLtTT. J. Rangt Mangl.

14: 2-18-251 .

(34) :'IARTI:I", W. E., nnd 1 .. J. BDIIY.

jU.o. EFFECTS Ol' NIT_"_"I"OU8 P"EaTD.I".I.F:&8 ON CALI­

FORNIA .IANOE All lfl'.A8UK£Il BY \,'EIOJJ'f OAIN8

OF OR.\ZlNO CAtTl.& Callt. Agr. Expt. Stft.

Bull. 846. 24 Ilil.

{ffii} ll(:COWN. n. t., lind W . A. WILt.L\).f6.

1968. COUI't."T ITION POll NUTHII';NTS AND 1.I011T liE'

TW I:t:N Till: Al(lH' AL OIlA6SU~U IIPtc lES BIIO­

MUS ~Otl.lS ANII l!.'IIODlUloI BOTIIT6. Ecology 49:

081-900.

(30) 11cKsu.., C. :\1.

1971. SI:t:t'Lll'IO 1'10011 AND 8E£11LI~O I:8TABLlIIIlWE~T.

fx The Biology and UUlI:w.tlon ot Grnases.

lIP. 74-80, V. n. YOUIIJ;.'f !Hld C. ;\1. :'lcKell. ed8. Acaucmlc: l'reslf, ~c\\" York, ~. Y. (In

prc88).

(3n --- C. DUNCAN. Rnd C. II. MuLLElI. JOO!). COloll'r:rITIVt: IU:l.ATIOl'lSIIlPl 01' A.."iNUAL IlYE·

OIASS (LOLIUM lIULTIPLORU).f 1..\101.). Ecol. 60: 6M-857.

(38) --- C. GRAUAlI. nnd A . WILIIOlt.

1960. BI-:NI-:P[T6 OF FERTILIZINo Al'INUAL IIA NOI'; IN" A

DRY Y£A6. U.S. !>'nr .. ~t Rf'rvll'e. PIlf'lflf" ROllI.h· wesl Forest and Range Expt. S!a. Re1I. Note 1.2, !l 1111.

(39) --- J. )1A.1oK. ami E. R. PDlIll1

ll)oo. ANNUAL MNO(f; FT.IlTIUZATION IN II.r:u..TION TO

SOIL MOISTURE UI;:J'L£TION. J. RSD,;e MBngt. J2:

189·193.

(40 ) --- .T. P. ROHISON. ull(l J. lIAJOIl.

1002. f.COTYI'IC '· ... II[,\TIOS6 IN In:UUSAIU:.\U ,l.NI) IS '

TIIODUCI:Il ANNUAL OIlASBEK. Ecol. 48: 686-6fI8. ( 41) --- A . ;\1. WILSON. and ~. L. KAT.

1962. O"FECrtvl: BUll.NINO OP .... NG~l'fDS INPUTEIl

WITH l'EDUSAlIEAJI. Weedll 10: 125-181.

( 42) - __ A. :\1. WIl.SO~. Hnll W . A . WnLIAMs

1062. f.I'FT.cT OF TEMI'DIATUR£ ON I'HOSrnOllUS

UTILIZATION BY NATIVt: AND INTItODUOEI.I LE·

GU)!~:S. Agron. J . M: 100·113.

(43) --- ,'. W . BROWN, R. 11. AIlOLI'Il, and O. OUI'l·

OAN .

(44 )

(415)

(46)

(47)

1970. t'Y..ITILIUTIO!l' or ASI'IUAL MNOE:L.U'l"D WITH

MANURE. J . Range :'olllnll1. 23: 336-340.

:'oIUHPIIT, A. U .. )1. B .• 101'1£8, and R. If. Lon;. 1970. En"£CT OF CLIl'I'IN O ISTl!.'II"'AL 011' BOTANICAL

COli POSITION or 8t1J1TImRANI-:AN CI.()Vf.'II. J. Range Mangt. 2S: 160·11)(1.

NlWJOl'I, J . R. Rnd A. WILSO~.

1069. I:rFLm:~CI: OF AO£ AN D ",W!'I" .lElfO ...... L ON

no.YANCT OF MEDUSAHP.AD 8£ED9. J. Rsnge

:'oranxt . 22; ~200.

1'1£101£18&1., R. L. 19:11. C,l.U8E6 AFFECTING CHANOE AND UTE OP

CIIANOE IX ,I. ... roETATION or ... l'INUAL8 IS

IDAlia. Eccl. 32: f"J3. 72.

RATLlY£, n . D .• nnd H. F. HEADT.

1962. 8EA80l'IA.L CUANGEtI IN DI'!RB,l.OI: WElGDT 11'1" ,1.1'1"

ANNUAL 0llA8B C01UIUl'IlT1". J. Range !Ul\ngt.

115: 146-149.

(4S) R068ITE1l, R.. C.

1906. ECOLOOT or Tnr. MEDITEKRANE,l.N ANNUAL­

TTPE I'ASTUIIE. A(h'ances In Agron. 18: 1 · 1S6.

(49 ) STECIUfAN. J. V .• nnd It. M. Y"",UVE.

1002. REPRODUCTIVE POTf:NTlAL OP FOUR ANNUAL

&..I.1'I0E GKA8SM .0108 Il'fFLUI:HOEO 8T SEA80NfII OF

CLll'l'I NG OR ClJIAZUiO. J . Range Mangt. lIS;

98-103.

PLANT MORPHOGENESIS Fon SOIENTIFI C MANAGE!I1E!I;1' O~· HANC E RESOURCES 123

(00) TAI.BOT, M. W .. and H. H. BI811'I':I.I~

1942. TOE lI"OIlAOr. ClIOI' ANII ITS MANAOEMENT IN Tin ;

IAN JO,\QUI:oI llANO£. Vnlv. or Calif. Agtte. Erpt. SIn. Butl. 663. 1"11. 13-43.

(51) U.S. Fo.r.8T S£IIVUlJ:. 1931. .A:'fOr. l'U.IfT IUNOBOOK. U.S. Coyl_ 1>rlnl.

Otlke, Wash. D.C.

(52) VA!'! DTIfE, G. :'01., and H . F. HF..AIlT. 1961:i. UIETA.T ClIl':)lICA L CO)ll'OSIT IOlf or CATTI.Y.

.. Nil II I1Er.!' GRA7.ING I N CO)llION ON ,\ IlRT AN'

lWAL RANot. J. Rnnge Mangt. 18: 18-86.

(53) WAL"F.R. C. lo'., n",1 B. L. KAY.

1955. ORA8IH..£GU)If. IlANIl 8££1>11'10. Cnllf. Agr. 0(11) : 15-16.

(M) --- and W. A. WILLlAloI.8.

1963. '£8I'ON81: or ANNUAL TYI'f. IlANOI': VE(lr:r.ATIOl'

TO 8UU'UI f"Y.RTI LTZATION. J. Range llnngl. 16: ...... (55) W ENT F . W .

1940. J:COLOOT OF U&SUT 1'l..ANTB. II . TilE 1':n"EC"l' Ot

UIN .ANII TUI",:RATURE ON Q!:BMIl'{ATlo)!'I ANP

Q801l"TIi . t-:l"l'l. 311: 1·13.

(OOj WIIALLEY, n . O . B., nnd C. M. :'oICf(EI.1.

1007. TNTEiUIl:LATION OF C.AR80IIYURATE 1II\"1'A801.18)1,

alllWLINO I.IltvtLOI'ldeNT, ANO al':tllL1:<:o OaoWTII

RATE OF a!n'£IIAL 8pr.cn;s or I'IlAI .... '"8. Agrnn. J. C!oO: 228-226.

(~1) -- C. ll. lI c KI:LL.. and I~ R . GRUlI".

1966. al'.J:lILINQ V'GQII. ANII EAIILT l'IOll"·l'llOT06Y!'l·

TUETIC 8TAOl: OF olt.Aur..ll. Croll Sel. 6:1047·150.

(58) --- Co :'ot. ~h Kt:l.I~ nlllJ I,. R. G8~:.:l'.

1!"1G6. EFFECT 01' £NI'IAONlIl:ST.\I. COl'Ull'IOl'1I UlJlIll'1l

Tin: P.\Rf.N T OI: NI:RATION (I;o;" 6~I>I.INO I'!QOR OF

8UaSl:QUENT S I;wu~lGa 01" OHYZOP8111 ).111.1.1-

ACf:A (L) BroXTII. "l'0 llooK. Croll Sel. 6: ul0·u12.

(59) WlI..LI").I8. W. A.

( 00)

1356. 1:V"lU"TIO!'l" OF TilE EMtROJ:.'fCE FORM:: I;X ­

I:RTI"JI BY Sr.r.III.IXOIl 0,. alULL IiEEQlm LF.O IJ).IFA

UlH!'ifl rlWIIIT .\ l' .II.YSI!< . . \grun .• f. 4S: 273·274.

19G3. l'Olll'r.TITlON YQII L!QIIT HETWEI:l< ANNUAl.

III'I:CI.:11 III' TRlrOLlI,J)1 UtiRINO TII£ l'I:Ilr.rATI I'.;

f'1I M11'~ l-:Cnlo.l:J' 44: 41;'-485. (Ul) --- lUlU J. It . 1::1.1.10"l-r.

1000. EOOLOOI(,AL 8 IG lI' IFI<':A!'iCE OF 81!:£1I COAT Ilol­

PEJI).l" .... OII.lTY TO ).IOIIITUIlE TN CIU).IIIOX. 0;011'

T&RIIA!'IFAS "XII ROSr. CLOI'ER!I IN A ).Irlll­

T£IIIANK.\S·TYf'I: CI.IJ.lATF~ Ec:ol. 41: 783·742. 1(2) --- n . ~1. 1 ,(i\'I~ 'Illd J _ 1'. COl'UI).

1950. IAl'Qr. I).IPROI·[).Ir.NT Il' CAI.IFQRNIA BY IIr.F.V­

IX O " NXUAL CLOVI:II, I'I:lITTLI7.ATIOl'l Al'1I

GJAZIN G ~1":<:"Q ':31f.NT. J. Rllnge )lrlngl. fl· 28·33.

/U3) --- C . ~1. ~td'EI.L.. UIHI .J. ~ . RICI'Pl:RT.

100-1. 8ULrllR n ' lIl'lI. IZATIOX 01' AN .Al'NU"I. IIAl'G';

aQlI. IfUlUNO "£o\R8 OF nr.I.oW-l'OfiMAt. lIoIIS ­

F.ALL .1. Hungo 1I1ln~!. 17: H'.

(641 WII.SON. A. ~I., G. A. !IARKI!. rind D. n . GATEI!.

HII36. F£IITII.IU,l' IQl' OF ).IUI:U CHFATGRAaS-111.I1I'

OUNCII WIlY.ATORA!la STAlWS. J. Hnngl' :'01011(:1. 19: 134· 1R7.

(65) WI.!I'MI;;;. !:to K. lind C. :'oj. llc K r.LL..

11lG3. TAR\\·t:t~I. A XtTI8.I XCF. PLAXT 0:': CAl.Il'"OAlI'l"

8.l..NGI:.II. Calif. Agr. Ii : n·13.