Riparian Ecosystems and Their Management: Reconciling

This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. Xeroriparian Systems Used by Desert Mule Deer in Texas And Arizona1 Paul R. Krausman2 , Kurt R. Rautenstrauch3 and Bruce D. Leopold4 Abstract.--We examined desert mule deer (Odocoileus hemionus crooki) occurrance in xeroriparian systems in Arizona and Texas. Most deer in Arizona were located in washes. Most deer in Texas were located between washes. Xeroriparian areas are important habitat components for desert mule deer when they provide forage, thermal cover and travel lanes. INTRODUCTION STUDY AREAS Desert mule deer inhabit the Sonoran and Desert mule deer use of xeroriparian systems Chihuahuan Deserts of North America. Their range was evaluated on the northeastern edge of their extends from southwest Texas to western Arizona range in Big Bend National Park (BBNP), southwest and south into central Mexico (Wallmo 1981). Texas; in the westcentral part of their range in the Belmont Mountains, central Arizona; and on the Desert mule deer are a popular and important northwestern edge of their range in King Valley, game animal, but have received limited attention southwest Arizona. by the scientific community. Clark (1953) examined desert mule deer behavior and movement BBNP, Brewster Co., is representative of the patterns, Truett (1972) studied their general rugged Chihuahuan Desert and is included in the ecology, Krausman (1978) and Leopold (1984) Chisos biotic district (Dice 1943). Elevations evaluated their forage preferences, and Krausman extend from 573 m along the Rio Grande to 2384 m (1984) and Rautenstrauch and Krausman (unpublished at Mt. Emory in the Chisos Mountains. data) have studied desert mule deer home range size and movements. Descriptions of desert mule BBNP is characterized by hot summers, mild deer habitat are general (Phillips 1974, Anthony winters and low rainfall. Temperatures exceed 38 and Smith 1977, Dickinson and Garner 1979, Koerth C in the desert regions in summer and rarely 1981, Leopold and Krausman (1983) and there is freeze in winter. Precipitation occurs from May little published information on desert mule deer through October, ranging from 28-41 cm. habitat use. Leopold and Krausman (1983) identified 10 We began studying desert mule deer in Texas vegetative associations in BBNP. The associations in 1972 (Krausman and Ables 1981, Leopold 1984), were differentiated into three categories based on and in Arizona in 1979 (Krausman 1984, dominant plant cover: creosotebush (Larrea Rautenstrauch and Krausman, unpublished data). tridentata) dominated, non-creosotebush dominated, During these studies it became apparent that and associations not dominated by shrubs. xeroriparian washes and their associated vegetation were an important component of desert The Belmont Mountains, Maricopa Co., are 80 mule deer habitat. Our objective in this study km west of Phoenix, cover 360 km2 , and are was to document desert mule deer use of representative of the upper Sonoran Desert. xeroriparian systems (Johnson et ale 1981) across Elevations range from 426 m to 914 m. the northern boundary of their range and to describe the vegetation of washes used by deer. The average annual precipitation is 20 cm. Most rain falls from January through March. Temperatures above 45 C in summer are common. 1Paper presented at the first North American Krausman (1984) identified 9 vegetative Riparian Conference. [University of Arizona, associations in the Belmont Mountains. Most Tucson. April 16-18, 1985]. associations are dominated by triangleleaf bursage 2Paul R. Krausman is Associate Professor of (Ambrosia deltoidea), brittlebush (Encelia Wildlife, University of Arizona, Tucson, Az. farinosa) and creosotebush. The areas between the 3Kurt R. Rautenstrauch is Graduate Research mountains and foothills having major washes are Assi~tant, University of Arizona, Tucson, Az. classified as the Triangleleaf Bursage-Transition Bruce D. Leopold is Wildlife Research Association. Vegetation in this association is Assistant, University of Arizona, Tucson, Az. dominated by the same three plants, but the washes 144 contain the larger trees, ironwood (~ tesota) Arizona and paloverde (Cercidium sPP.). Belmont Mountains.--The density of perennial vegetation was measured in 50-100 0.004-ha Over 60% of the Belmont Mountain area is in randomly located Circular plots in each of nine the Creosote Flats Association. Dominant plants associations identified. In major washes that include creosotebush and triangleleaf bursage. bisected associations, line intercept transects The species composition of the major washes is (Canfield 1941) were established to estimate similar to the transition association. the vegetational composition in xeroriparian components of the association. King Valley, Yuma Co., is 45 to 60 km northeast of Yuma and 110 kID southwest of the King Valley.--Washes in King Valley were Belmont Mountains. Elevations range from 85 m at divided into 4 classes depending on the number of the Gila River to 450 m at the base of the drainages and the width of the associated surrounding mountains. The average annual vegetation. Simple washes have only one drainage precipitation at the lower end of the valley is 12 (a water fluve greater than 1 m wide). Complex cm. washes (washes with more than 1 fluve) were divjded into 3 classes based on the width of the The slopes of the mountain ranges surrounding vegetation: less than 50 m wide (C1), between 50 King Valley are sparsely vegetated and dominated and 150 m wide (C2) and greater than 150 m wide by creosotebush, brittlebush, white bursage (C3). (Ambrosia dumosa), and ocotillo (Fouquieria splendens). The canyon bottoms have xeroriparian The percent cover of perennial vegetation in washes dominated by ironwood and paloverde. washes was measured using the line-intercept method (Canfield 1941). Ten transects, spaced ten Most plant life in King Valley is restricted m apart and running perpendicular to the flow of to the xeroriparian drainages. The areas between water, were measured in each wash. drainages are usually covered with wind eroded desert pavement, and have no vegetation or very The density of perennial vegetation between sparse stands of creosotebush, brittlebush and washes was measured in six to 10 .0314 ha white bursage. circular plots next to each wash measured. The plots were either 100 m away from the edge of the The dominant overstory species in the washes wash vegetation or half-way between the measured are little-leaf paloverde (~ microphyllum), blue wash and the adjacent wash if the washes were less paloverde (~ floridum) and ironwood. The width than 200 m apart. of the vegetation in the largest washes in King Valley is over 300 m wide. Contrasting Washes and Adjacent Habitat Because deer were rarely located in the Shannon-Weaver Diversity indices were mountains and foothills surrounding King Valley, computed to contrast plant species diversity in this study deals only with the xeroriparian washes and adjacent habitats in Texas and between Paloverde-Ironwood Association found in the bottom areas in Arizona. Morisita coefficients of of King Valley. overlap (Morisita 1959) were computed to determine degree of similarity of perennial vegetation within washes and adjacent vegetatiave associations in Texas. The equivilence of percent METHODS forage species occurring in the washes and the adjacent vegetatiave associat!ons was determined Vegetation Sampling using the binomial test for proportions (Zar 1984:395-400). Texas Deer Occurrence in Washes Twenty five to 50 point-quarter plots (Dix 1961) were sampled in each of ten vegetative Texas associations identified in BBNP (Leopold and Krausman 1983) to determine the density of Deer use of washes was determined from 750 vegetation between washes. independent observations of deer in three classes: initially observed in wash, within 30 m of a wash, A transect line was established along the or greater than 30 m from a wash. All center of each sampled wash running parallel to observations were made from January 1980 through the flow of water. The initial plot was randomly 1981. Habitats were sampled for deer in determined and subsequent points were 15 m apart. proportion to their availability in the study At each point, width of wash, and all perennial area. plant species to the left and right of the point were recorded. We also noted which plants were Arizona deer forage. Desirable deer forage plant species was based on diets determined by fecal analysis Deer use of washes was determined from 1180 (Leopold 1984). independent locations of 12 radio-collared deer (4 145 Table 1.--Summary and comparison of vegetative characteristics of plant associations and adjacent wash systems in Big Bend National Park, Texas. Plant association vlash systems Diversity Vegetative Total Pltnt Deer Deer vlash Adjacent Coefficient association density forage2 forage2 width3 habitat wash of overlap I. Creosote bush dominated Creo-Iech-grass 3.01 43.4*6 29.3 18.6 2.25 2.81 0.09 Creo-Iech-candel 0.74 28.3 41.3**7 23.5 2.31 2.38 0.40 Creo-Iech-Opuntia 0.65 27.8 31 .1 19.6 1.59 2.58 0.27 Creo-tarbush 2.30 40.1* 26.4 5.4 2.69 2.25 0.50 Creo Flats (Loc 1)4 0.64 5.9 8.2 13.3 1.55 1.80 0.66 Creo Flats (Loc 2)5 0.04 0.0 55.8** 25.0 1.09 2.37 0.30 Creo-Iech 0.24 33.6 55.3** NA 1.95 1.59 0.32 II. Non-creosotebush dominated Vig-Iech-grass 2.46 44.3 62.4** 5.5 2.58 2.40 0.76 Yucca-Sotol 4.34 46.8* 23.7 9.7 2.74 2.70 0.37 Sotol-Iech-grass 4.05 53.0 60.2 6.3 1.87 2.87 0.25 III. Non-shrub dominated Lech-grass (Loc 1) 1.72 68.6* 53.1 3.8 2.73 3.01 0.35 Lech-grass (Loc 2) 1.04 59.1 57.7 5.2 2.35 2.69 0.60 'expressed as stems/m2 2expressed as percentage 3expressed as average of all points sampled 4Creosotebush Flats of upper elevations ~Creosotebush Flats of lower elevations *=deer forage in vegetation association significantly greater (alpha = 0.05) than in washes within association 7**=deer forage in washes significantly greater (alpha = 0.05) than adjacent association.

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