Proceedings: Shrubland Ecosystem Dynamics in a Changing Environment
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This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. Arroyo-Riparian Shrub Diversity Along a Transition Zone Between the Sacramento Mountains and Tularosa Basin, New Mexico Joneen S. Cockman Rex Pieper Dennis Clason Abstract-Four arroyos were examined in the Sacramento Moun The importance of arroyo-riparian or ephemeral drain tains of New Mexico to determine type differences and describe ages for birds has been well documented (Carothers and vegetation diversity of the main channel relative to the surrounding others 1974; Carothers and Johnson 1975; Finch 1989; watershed. Arroyos were selected to represent foothills and a Reichenbacker 1984). Floral structure variables such as submesa. Univariate analyses were conducted on shrub, half-shrub, patchiness, volume, and foliage height diversity were found grass, and forb functional groups. Each group responded to different to be not independent of one another (Anderson and Ohmart effects depending on the response variable (cover, density, diver 1980). Instead, variable complexes were identified as well as sity). However, nonsignificant interactions were masked by the fact ties between bird use and time of year. that response variables (especially diversity) were comprised of different species depending on the location of the arroyo in foothill Research Purpose _______ or submesa types. Obligate and exclusive species were identified. At this time, environmental regulations do not protect arroyo habitat. Data are needed to support management It has been suggested that arroyos in the southwestern decisions related to environmental quality. United States are of recent origin, and are a feature of Interest and concern for the protection of wetlands has accelerated erosion on once-uniform grasslands and cienegas increased since the inception ofthe National Environmental (Cooke and Reeves 1976; Bryan 1925). Antevs (1952) bor Policy Act (NEPA) of 1969. Four Federal agencies provide rowed the term "wadis" from Israeli and Egyptian literature regulating authority for wetlands. These are the U.S. Army to describe ephemeral drainages that are not features of Corps of Engineers (USACE), the Environmental Protection man-caused erosion. These drainages are limited to the Agency (EPA), the U.S. Fish and Wildlife Service (USFWS), headwaters of valleys, occur in moist areas, and are limited and the Natural Resources Conservation Service (NRCS). in size. The typical drainage described by Antevs is 3.6 Each agency provides a different definition of a wetland meters deep, 15 meters wide, and .8 km long. The drainages depending on the agency's function. However, all agencies of this study more closely resemble Antev's description of a include in their definition three basic elements: hydrology, "wadis." vegetation, and soil characteristics (Mackenthun and Classification ofriparian communities has been conducted Bregman 1992). by Pase and Layser 1977; Freeman and Dick-Peddie 1970; The USEPA and USACE have adopted the definition of Anderson and Ohmart 1980). Apache plume (Fallugia wetland from the Clean Water Act Section 404 (Mackenthun paradoxa) has been described as the most commonly found and Bregman 1992): riparian species in New Mexico, with more than 80% of the Those areas that are inundated or saturated by surface or arroyos in a southern New Mexico study containing this groundwater at a frequency and duration sufficient to support, shrub (Browning 1989). Littleleafsumac (Rhus microphylla) and that under normal circumstances do support, a prevalence and cutleafbricklebush (Brickellia laciniata) were listed as of vegetation typically adapted for life in saturated soil condi tions. Wetlands generally include swamps, marshes, bogs and close associates in areas of approximately 1,500 meters ele similar areas. vation. Burrobush (Hymenoclea monogyra) was listed as an associated species in washes at lower elevations (Browning It is important to note that this definition identifies 1989). The four arroyos described in this report resemble saturated soil conditions and a prevalence of vegetation closely the Apache plume series described by Browning suited to saturated soils. The presence of indicator species (1989) and also contain Burrobush at lower elevations. such as cattails that grow only in saturated conditions has been used to identify wetlands. Arroyos and wadis do not contain saturated soil conditions In: Barrow, Jerry R.; McArthur, E. Durant; Sosebee, Ronald E.; Tausch, Robin J., comps. 1996. Proceedings: shrubland ecosystem dynamics in a and do not qualify as a wetland by the USEPA definition. changing environment; 1995 May 23-25; Las Cruces, NM. Gen. Tech. Rep. However, they do support plant species that will grow on no INT-GTR-338. Ogden, UT: U.S. Department of Agriculture, Forest Service, other site. They also support a variety ofwildlife species and Intermountain Research Station. Joneen S. Cockman and Rex Pieper are Research Assistant and Professor appear to be critical habitat. of Range Science, Department of Animal and Range Sciences; Dennis Clason However, little research has been done to quantify plant or is Professor, Department of Experimental Statistics, New Mexico State animal species occurring in the arroyos. Studies are needed University, Las Cruces, NM 88003. 230 to test if the arroyo does support unique species or a higher The annual average rainfall for the area is about 30 cm. diversity compared to the adjacent watershed. However, there is a rain shadow between the submesa and The purpose of this research is to describe and quantify foothill. No rain gauge data are available to quantify the vegetation along ephemeral drainages in the Sacramento difference between sites. However, a difference in vegeta Mountains of southern New Mexico. The study will provide tion between the sites suggests that the foothill area receives baseline data to facilitate management decisions pertaining much greater rainfall. Also, many people who have worked to NEPA compliance. The focus of the study is to test for in the area and have observed the weather pattern agree vegetation differences between foothill and submesa ar that thunderstorms build up over the Sacramento Moun royos. It also examines the main channel relative to adjacent tains and flow south over the foothills. They have observed vegetation types, and adds to our knowledge of these impor torrential rainfall in the foothills while the submesa area tant habitats in the Southwest. receives little or no rainfall. This pattern appears to be a frequent occurrence. Soils of the area are dominated by rock outcrop and Study Area _________ limestone hills. Gravelly alluvium is prevalent on the lower slopes. Narrow bands of alluvial soil line the arroyos. Of The study area contains four arroyos particular to the particular interest is a major separation in soil classification research and one major drainage that connects the four between the foothill and submesa areas. The submesa is (fig. 1). The area occupies approximately 13,000 hectares mapped in southern desert soils while the foothill is mapped and is used jointly by the Bureau of Land Management as a in soils from the neighboring mesic region. This is a transi grazing allotment and a wilderness study area. It is also tion zone between the true desert soils and cooler plains designated military ground, identified as McGregor Range, soils. a portion of the Fort Bliss military establishment. Located at the southern tip of the Sacramento Mountains, the area is approximately 16 air km northeast from the Methods __________ village of Orogrande, NM, and 112 km northeast from EI Paso, TX. Elevation ranges from 1,200 meters to 1,600 Site Selection meters. Two of the arroyos (Indy and Carly) are located in a foothill area. The headwaters of these arroyos originate at Field reconnaissance using soil maps and aerial photos was approximately 1,800 meters, and the tailwaters drain into conducted prior to selecting study sites. Two similar arroyos Culp Canyon at approximately 1,670 meters. The other two (Indy and Carly) were selected in a foothill area (fig. 1). Two arroyos (Alien Temple and Four Bucks) are located on a more (Alien Temple and Four Bucks) were selected within a submesa. Their headwater originates at the j unction ofCulp submesa area. The submesa is positioned between an upper Canyon at approximately 1,500 meters, and they drain into mesa with sharp vertical boundary and the Tularosa Basin. the Tularosa Basin at approximately 1,370 meters. The land is hummocky and slopes gently between the mesa and basin. The foothill arroyos flow into a major drainage (Culp Canyon), and the submesa arroyos originate from Culp Canyon. The foothill arroyos are about 2.4 km in length. They range from 3-15 meters wide. The submesa arroyos are approximately 11 km long, and range from 2-30 meters wide. All arroyos range from 0.5-3 meters deep. Sample locations were selected along each arroyo at head water, midwater, and tailwater locations (upper, middle, and lower elevations) (fig. 2). An attempt was made to identify all vascular plant species in the study area. Plants too immature to identify were catalogued, and phenology was recorded. These plants were collected again when ma ture specimens were available. Vouchers were collected from as many species as possible to aid in accurate identifi cation. This paper provides results pertaining to two shrubby functional groups, half-shrubs and shrubs. The half-shrub group contains cacti because cacti were infrequent and low in number in the study area. This was done to follow their presence rather than delete them from analyses. Similarly, Figure 1-Location of arroyos in a 13,000 ha BLM the large shrub group includes trees because trees were grazing allotment. Indy and Carly arroyos are located in infrequent in the study area. a foothill area. The headwater portions of these arroyos originate at approximately 1,800 meters and drain into Culp Canyon at about 1,670 meters. The headwaters Response Variables of Four Bucks and Alien Temple arroyos originate in Culp Canyon at about 1,500 meters.