AN ABSTRACT OF THE THESIS OF Milton Lee Dean for the LS. inBotany (Namej (Degree) (Major) Date thesis is presented i7 i1, jJ5 Title A Taxonomic and Eeoloic Stud of the Vascular Plants of a Section of the Owyhee River Canjon in Oregon Abstract approvedSignature redacted for privacy (Najo professor) A taxonomic and ecologic study was made ofthe vascular plantsof asection of the Owyhee River Canyon of Malheur County, Oregon,Theparticular study area is known as Three Forks, and is located at the junction of the North Fork of the Owyhee River, East Fork of the Owyhee River, and LittleOwyheeRiver. The Three Forks canyon is a relatively broad portion of a river canyon which cuts through the high plateau country ofsoutheastern Oregon. The plateau has been built up of sedimentary material from the Tertiaryperiod, and then covered by layers of lavapouredout in Pliocene times or later, Thethree streams flowing into Three Forks arisefrom various points in southwestern Idaho, northern Nevada, and southeastern Oregon. The first white inhabitants of Three Forks arrived in 1863, although Indians had probably occupied thearea for centuries previously. Since that time, farming has been the primary occupation of many settlers, The closest ranch today is about six miles fromThree Forks. Little evidence of grazing can be seen. No fires have been re- corded for the area. The climate of Three Forks isone of hot dry smnuers and cold winters, Most ofthe approximately 13 inches of precipitation falls in the winter and spring. The years of l96 and 19S7 had above average moisture conditions, Collections were made periodicallythroughout the growing season of1957and part of 1958. An attempt was made to collect specimensof every species of vascular plant. When collectionswere made, ecological noteswere taken, These notes were correlatedinto a of vegetation, description with anattempt to define plantassociations. Three horizontal beltsof vegetation were distinguished, encompassing13 plant associations. The main body of thethesis deals with the taxonomic treatment, and consistsof keys constructed toclasses, families, genera,and species, with descriptionsof gen. era and species, The study area yieldeda total of 211 species, classified into lL..8genera andLi.5families. Of special interestwas the discovery of a new, undescribed species of Artemisja, A TAXONONIC AND ECOLOGIC STUDY OF THE VASCULAR PlANTS OF A SECTION OF THE OWtBEE RIVER CANYON IN OREGON by MILTON LEE DEAN A THESIS submitted to OREGON STATE COLLEGE in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE June 1960 APPROVED:. Signature redacted for privacy. Albert N. Steward Professor of Botany In Charge of Major Signature redacted for privacy. Chairman of Dei inen Both? Signature redacted for privacy. Chairman of School Graduate Committee Signature redacted for privacy. ..- Dean of Graduate School Date thesis is presented Typed by Gwen Flnkbeiner ACKNOWLDGENENT S The writer wishes to express sincere appreciationto several people who have contributed to thecompletion of this thesis. Special acknowledgment is due the late Dr. Albert N. Steward, major professor and advisor,who was most helpful and generous with his time and suggestions. Thanks go to Dr. Frank H. Smith for assuming advisory duties following the untimely death of Dr.Steward. Several men gave valuable assistance with identi- fication of species in particularly difficult genera Dr. Arthur Cronquist, Aster and Artemisia; Dr.David Keck, !thnulus; Dr. I. N. Johnston, Hackelia; Dr. Narion Ownbey, Astragalus; and Dr. S. Conrade Head, Penstemon. Finally, appreciation and thanks go to my wife, Shirley, for her encouragement during this project. TABLE OF CONTENTS Page Introduction . 1 Physical Description and Geology 2 History 7 Climate 9 Description of Vegetation 12 Sedge/Rush Association l Salix/Ribes/Rosa Association 16 Elyrnus Association . 20 Arternisia/Ohrysotharnnus Association 21 Artemisia/Prunus Association 26 Festuca/Chrysothamnus Association 26 Artemisia/Sarcobatus Association 27 Agropyron/Poa Association . .... 29 Juniperus/Festuca. Association 32 Gravia/Sarcobatus Association 3. Artemisia/Sitanion Association 3 Hackelia/Ivesia Association 39 Taxonornic Treatment . 141 Keys to Classes and Families . L12 Class I. Filicineae . 51 Class II. Equisetineae 51 Class III. Gymnospermae . 52 Class IV. Angiospermae 52 Page Subclass I. Nonocotyledoneae . 52 Subclass II. Dicotyledoneae . 70 Sun]mary lL3 Bibliography lL6 ILLUSTRATIONS Page . Fig. 1The Study Area of Three Forks, Oregon . 3 Plate 1South-facing slope of Three Forks Canyon . 5 Plate 2North Fork Canyon. ..... 5 Plate3 Sedge/Rush Association . 18 Plate L Salix/Ribes/Rosa Association 18 Plate5Elymus Association . 23 Plate 6Artemisia/ChTysotha1nus Association . 23 Plate7 Arternisia/Sarcobatus Association 31 Plate 8Agropyron/Poa Association . 3]. Plate 9Juniperus/Festuca Association . 3L Plate 10 Juniperus/Festuca Association , , 3. Plato 11 Artemisia/Sitanion Association , 37 A TAXONOMIC AND ECOLOGIC STtJDY OF THE VASCULAR PLANTS OF A SECTION OF THE OWYHEE RIVER CANYON IN OREGON INTRODUCTION Although a finetreatment of the vascular flora of Oregon hasbeen in print for 18years (10, p. l.'866),it is felt that some of themoreremote areas of the state are incompletely known. One such area is the Owyhee River Canyon of Naiheur County, southeastern Oregon. That portion of theOwyheeCanyon which comprisesthis study is known as Three Forks, and is located at the junction of the North Fork of the Owyhee River, East Fork at the Owyhee River, and Little OwyheeRivers. These streams converge to formthe main Owyhee River. The area is accessible to passenger cars only by an unimproved (dirt) road from the town of Jordan Valley, Oregon,3 miles to the north. The Idaho state line is seven miles to the east,and the Nevada state line is about LO miles to the south. The primary purpose of the study was to cover the areathoroughly andobtain ascomplete a plant list as possible. Collecting trips were made, weather permitting, every third or fourth week throughout the growing season 2 of 1957 and the first half of 1958. The main body of the thesis consists of keys to and descriptions of the plants collected. Wherever collections wore made, ecological notes were taken, andthese latercorrelated in an effort to define and describe the plant communities. Nearly all of the study and collecting was done in the Three Forks canyon and on the plateau surrounding the canyon. Some sampling was also done in the adjoining canyons. PHYSICAL DESCRIPTION AND GEOLOGY The study area is part of the great plateau region which is characteristicof most of southeastern Oregon. This plateaugenerally varieá from tOOO to 5000 feet above sea level, The elevation at Jordan Valley is L4OOfeet with a gradual rise to the rim aboveThree Forks at L800 feet. This breaks away sharply some 900 feet to theriver. All of the various river forks flowthroughan alternating succession of sheer, rock-walledgorges, and broader, open-sloped canyons, The sheer rock portions are formed of resistant igneous rock, while theopen slopes are composed of a softer, sedimentarymaterial. The canyon rims are made ofa dark, very hard basalt rook, and are called the rimrock, Figure 1.The Study Area of Three Forks, Oregon. Legend: 1 inch =.mile )v,nuirrYRimrock Road x Bridge b Cabin Plate 1 Thesouth-facing slope of the ThreeForks canyon. Note thenarrow gorge at the canyonbottom to the right (part ofNorth Fork canyon), flaring slopesand upper rlmrook. The road can be seen in the lowerleft corner. Plate 2 The North Fork canyon, typical of the various canyons leading into the ThreeForks canyon. 6 It is thought that much of the sedimentary rock was laid down under large lakes in early Tertiary times. Then in the Fliocene Age, much volcanism occurred, pour- ing out layers and layers of lava from fractures in the earth's surface. This lava, or"ColumbiaRiver basalt," is one of the main components of the high plateau country of central and eastern Oregon. Within the canyons, the rimrocks arethemost obvious evidence of the old lava flows. The Three Forks canyon proper is one of the broad, open portions of the OwyheeCanyon.It lies in an east- west direction and is roughly a square, being approx- imately one and one-half miles in length, and In width. As here defined, Three Forks Includes a portion of each of the contributing stream canyons. The entire study area (Fig. 1) is three miles square. The North Fork arisesin the South Mountain area of southwestern Idaho and comes into Three Forks from the east. About one-half mile past its entrance intoThree Forks, the North Fork is joined by the East Fork.This stream has its beginnings far to the east in the Independ- ence Mountains of northeentral Nevada. It flows across the southwestern corner of Idaho and enters Three Forks 7 from the southeast. The Little Owyhee originates in extreme northernNevada andsouthern Oregonand flows slightly to the northeast to reach Three Forks. About seven milessouth of Three Forks, theLittleOwyhee is joined bythe South Fork.Thisfork arises inthe Tuscarora Mountains or northoentral Nevada (west of Independence Mtns.), and also flows across the south- western corner of Idaho into Oregon. With such widespread origins, and thevariety of habitats through which they flow, the streams,withtheir potential f or carrying seed, have undoubtedly had con siderable effect on the flora of theThree Forksarea. HI STORY Most of the historical information was obtained from long-time residents of the area. Especiallyhelpfulwere Mr. and Mrs. Ernest Fenwick ofthe Circle Bar Ranch, six miles eastof ThreeForks. Theremainder ofthe data was taken from a book by Jacob Greggabout the early history ofMaiheur County(7, p. 2O37). The known history of Three Forks dates back to about 1863 when a fort wasestablishedthere.When gold was discovered to the east in Idaho, a road was built from the mines to the town of Winnemuca, Nevada. The road 8 went throughThreeForks. However, Indian raids on the travelers became so frequent that a fort was built, with soldiersassigned toprotect the road.