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2 8 2 5 2 8 2 5 :~ 11111 . 11111 . 1.0 :; 11111 . 11111 . ~~ ~p.2 2.2 I~ !P2 2.2 ~ II w ... I~ ... I~ &:.:: I.i.: I:l :r I~ ~ m~ "" ~ ... " 1.1 1i.I~ .... 1.1 10.1 .. 1.0 "11/2·~ --- 11111 1.8 .""'1.2~ "'" 1.4 ""'1.6 ""'1.25 "'" 1.4 ""'1.6 MICROCOPY RESOLUTION TEST CHART MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS-1963-A NATIONAL BUREAU OF STANDARDS-1963-A , "" ,; . • " Seasonal Development and Yield of NATiVE PLANTS on the upper SNAKE RIVER plains and • their relation to certain CLIMATIC FACTORS By J{/mes P. Blaisdell, Forest Service • 'l"echnical Bullctin No. 1190 Novcmhcl" 1958 UNITED STATES DEPARTMENT OF AGRICULTURE \Vashington, D. C. • ACKNOWLEDGMENTS The author acknowledgei\ his indebtedness to many members of the U. S. Forest Service who have made invaluable contributions to this study. He is particularly grateful to Joseph F. Pechanec, who initiated many of the studies and made the early observations; to the late Lincoln Ellison, who reviewed several drafts of the manuscript and made many valuable suggestions; and to Walter F. Mueggler, who assisted both in field observations and in compiling and checking the data. He is also grec'ltly indebted to Donald B. Lawrence of the University of Minnesota for his constructive )'eviews of the manuscript. Blaisdell, .lames Pel'shing, I!HR- • ~1)aSOllal dt'n'loplllPlit alld yipld of Ilati\'(' pIallts Oil thl' lIPIWl" Snakl' Hin',' Plains and tlll'i,' r(·fatioll to ('('r-tai" <"Iimat it" fae-to,';';, "rnshingtoll IF. ,so nO\'!". P"inL 011'., lDJK iii. os Jl, illll!;, 2;) ('Ill. (['. S. I '''pt. of A;,!I'it'ult:1II'p. TpI'lIllic'nl h1l11Nili 110. 'll!lO) TSS1lNI also il1l1lic'roflllll (0..111, ns tllpsis, l'lIin'r"ity 01' )litlll('I'Dlu, lllHIt'l'litll': ~l'nsollnl IIp\'l'loPIIWlIt :\11(1 yiplll 01' 11:11 h'p plnll!s 011 111(' lI11P.... SlIn kt' ~ti n'.. l'lnills of Idalll) :111(1 [hpi!' n'iatinll til ('ljlllnl;1' [a('tOl':". p:;pro!'ialiy Pl'Pl'ipitatioll alld tPIII11(' ..atllrf', "U\('I'atlll'l' <'itl'(r': p. (j·t-liS. 1. H',tall,\'-,Idaho, [l. Hllakl' Iti\'('.I' l'laills. Idaho-nolan,\', :!. Uotany. ,. 1';('0 I o,;:-y. I:!' ('lilll:lt(' a lid \'Pgr'l:l (jOIlJ ::. I 'h('II()I().~,\.. .1. l Sua k(· Itil't'l' 1.'111 iu;<, Idnhn-l'lilllnlPj (~('I'i(':iJ S~I.~\'T2 110. lIf)/) ,')SI.I:}.JJ.-d .\:!\' JH-:!!l(j I'. K Ilppt. uf AgT. LillI', l.\g-,'i... ITt' 110. 11!1() (01' Lihl':I1'Y o( t'OIl.!!'l'(''':'' I • CONTENTS l Puge Page Introduction___ _____ ___ ___ _ _____ 1 Climatic factors____________ ----- 29 The Upper Spake River Plains__ 1 Methods of study____________ _ 29 Topography and soils________ 1 Results_____________________ _ 30 Climate_ ______ _____ _ _ _ __ _ __ 3 Precipitation______ - _______ _ 30 Vegetation and its relation to Temperature_______________ _ 30 certain environmental fac- Wind_____________________ _ 30 tor;;_______________ . _ . _ _ _ _ 3 Cloudiness_____ -- -- --------- 33 Seasonal development and yield of Comparison of factors _________ _ 34 native plants _____________ _ 6 Development and yield in relation 36 Methods of study___ ..._____ _ 6 to climatic factors__ --------- Method of study_____________ _ 39 Seasonal development_.------- 7 Seasonal developmenL _______ _ 4.0 Annual yield _______ • _______ _ Phases____________________ _ S 40 Results____________________ _ Growth ___________________ _ 9 '12 Seasonal development_______ _ 9 Discussion_________________ _ 4.2 Phases__________________ _ Annual yield. ________________ _ 45 Height growth __________ _ Weight____________________ _ 45 12 Area______________________ _ Weight growth___________ _ 4.9 15 Height____________________ _ Annual yield _______________ _ 16 51 .Flower stalk numbers_______ _ 51 Weight__________________ _ 16 Area ____________________ _ Discussion_________________ _ 52 17 HeighL_________________ . 23 Prar.tical considerations -------- -- 5£i Summary and conclusions ______ _ 59 Flower stalk numbers_____ _ 2·1 CommOn and scientific names of Discussion____________________ 2(i species mentioned _______ . 63 Literature cited_______________ __ 6·1 • III • Seasonal Development and Yield of Native Plants on the Upper Snake River Plains and Their Relation to Certain Climatic Factors· JAMES P. BLAISDELL, Division oj Range Management Research, Forest Service INTRODUCTION THE UPPER SNAKE RIVER PLAINS As described by Russell (72) ,:! the Snake River Plains consist of a roughly crescent-shaped belt along the Snake River extending entirely across southern Idaho. This belt is about 350 miles long and from 50 to 75 miles wide. The general appearance of this area is that of a vast, stream-eroded valley; however, it is actually a plateau formed principally of lava sheets, and does not owe its • major surface features to erosion. The eastern part of the Snake River Plains (about one-fifth of the total) is mostly above 5,000 feet elevation and is commonly ;) known as the Upper Snake River Plains. This area is roughly cir­ cular and has a dia.meter of approximately 60 miles; its center is in- the vicinity of 112° west longitude and 44° north latitude. It is bordered on the east by the Teton Range, on the north by the Centennial Mountains, and on the west by the Lemhi and Lost River Ranges. All of these are fairly high mountains, and many peaks are higher than 10,000 feet. Topography and Soils The lava of the Upper Snake River Plains is approximately 4,000 feet in depth and occurs in generally horizontal sheets from 10 to 200 feet thick (72, 21). 'fhe surface layers that overlie the Pliocene acid lavas are mostly Pleistocene basalt. Since basaltic lavas were very fluid, individual flows sometimes extended for miles, and formed a fairly level surface broken only by ridges forced upwards by pressures at the time of cooling. Low basaltic mounds that mark points of extrusion and a few well-formed • craters provide the major relief. , Formerly runge conservationisl, Inlet·mountain POI·est and Rang'c Experi­ ment Station, Forest Service. • 2 ftalic numbers inpul·cnthescs rcfcr to Litcraturc Citcd, p. 64. , ..~ 2 TECHNICAL BULLETIN 11 no, u. S. DEPT. OF AGRICULTURE Although total relief in the areas where flows originated may be several hundred feet, variations in the general surface of the • Upper Snake River Plains are slight (fig. 1). The Snake River and its main branches have not cut deep channels in this area, but flow on the plateau surface. Farther downstream, however, the river has cut a gorge that eventually reaches a depth of more than a thousand feet. Even though there are numerous lava outcrops on which no .soil has deve10ped (fig. 1), most of the Upper Snake River Plains is covered by a soil mantle varying in depth from a few inches to several feet. Much of the soil is residual from the underlying basalt, but aeolian materials from alluvial deposits, ancient lacustrine beds, and cinder cones are· also important components in certain areas. The texture is normally sandy loam at the surface and sandy clay loam beneath. These soils are relatively low in nitrogen and organic matter. but as a result of the low precipitation, they have undergone little leaching and are consequently rich in mineral fertility, par­ ticularly calcium (51). Near the mountain borders and along the streams is a local covering of alluvium. Often this is coarse or gravelly, but along the Snake River and some of its larger tributaries, the alluvial soils are deep and fertile, and provide the bulk of the arable land. • • FfGURE l.-A typical part of the Upper Snake River Plains ncar head­ quarters of the U. S. Sheep Experiment Station. The Centennial Moun­ tains are in the background. ... ,.,. SEASONAL DEVELOPMENT A.!.~D YIELD OF NATIVE PLAi~TS 3 Climate The continental climate of the Upper Snake River Plains is • characterized by scanty precipitation, cold winters, and hot summers. This is typical of regions that have mild relief, are re­ mote from tempering influences of the ocean, and are deprived of their full share of precipitation by the presence of high mountains in the path of the prevailing winds. Precipitation averages about 10 inches annually and except for a slight concentration during May and June is rather evenly dis­ tributed throughout the year. Snow usually covers the ground from about mid-December to the end of March and attains a depth of from 1 to 3 feet. Snowmelt usually occurs gradually and most of the water sinks directly into the ground, providing abundant moisture at the beginning of the growing season. Summer pre­ cipitation comes largely as showers, usually of short duration, and provides little effective moisture. Soil moisture of the surface 18 inches usually falls below the wilting coefficient during late June or early July. Humidity is generally low, particularly during the summer and early fall. Temperatures may reach a maximum of about 100 0 F. in snmmer and a minimum of -300 in winter. Despite low winter temperatures, the blanket of snow ordinarily prevents soil freezing below the depth of a few inches. The frost-free period is about 4 months long; the last spring frost occurs in Mayor .June, and • the first fall frost in September or October. In the Slimmer, nights are cool and days are warm. Rapid temperature changes are characteristic. "Winds are common during all seasons, in the summertime usually blowing from the northeast at night and the southwest in daytime. High winds in winter, particularly from the north, cause considerable drifting and therefore a somewhat unequal distribution of the snow blanket. Summer winds combine with high temperatures to cause high water loss from both soil and \-egetation. Vegetation and Its Relation to Certain Environmental Factors The native vegetation of the Upper Snake River Plains is pre­ dominantly shrubs with an understory of perennial grasses and forbs (nongrasslike herbaceous plants); howeyer, vegetal cover is not continuous, and numerous patches of bare ground are exposed (fig.

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