Juniper Woodlands Research Articles

The distribution and status of the montane juniper woodlands of Oman

Abstract. The distribution, condition and reproductive status of Juniperus excelsa M. ‐Bieb. subsp. polycarpos (K.Koch) Takhtajan were determined and assessed in the Hajar mountains of northern Oman, Arabia. Juniper is restricted to the highest areas, viz the central massif of Jebel Akhdar and the outlying mountains of Jebel Qubal and Jebel Kawr, where it generally forms open woodlands.On exposed slopes juniper is distributed from an altitude of 2100 m to the highest summit at 3009 m, with no upper tree line, while on well‐shaded north‐facing slopes juniper trees grow as low as 1375 m. Above 2300 m, juniper is the dominant woody species, while below this altitude it is often co‐dominant with Olea europea L. The woodlands are generally in poor condition on exposed slopes below 2400 m, with high proportions of dead or dying trees and low proportions of reproductively active trees. Above 2400 m and in shaded sites, woodland condition is better, with markedly higher proportions of reproductively active trees on exposed slopes at these altitudes. A predictive model of woodland condition based on topographic variables is presented. Altitude, shade and habitat account for 30.8% of the variation in a tree condition index, with slope being unimportant.The absence of juniper from lower and more outlying mountains is likely to have resulted from the alternation of pluvial and arid periods over the last 40,000 years. We speculate that the current dieback of juniper at lower altitudes is due to continuing climatic change. Anthropogenic factors do not appear to be seriously affecting the juniper woodlands at present.

Breeding Habitat of the Mexican Spotted Owl in the Tularosa Mountains, New Mexico

We studied nest and roost habitat characteristics of Mexican Spotted Owls (Strix occidentalis lucida) in the Tularosa Mountains, New Mexico. Owls selected both nesting and roosting sites in mixed-conifer forests that contained an oak (Quercus sp.) component more frequently than expected by chance. With the exception of one cliff site, no owls were observed using piñon pine (Pinus edulis)/alligator juniper (Juniperus deppeana) woodlands for nesting or roosting. Owls selected nest and roost sites in forests characterized by mature (dbh > 45.5 cm) trees with high variation in tree heights and canopy closure >75%. Because we found little difference between nest microsites and their surrounding forest patches, the presence of a suitable nest structure may have determined nest-site selection within nest stands. Characteristics that best described nest sites in the Tularosa Mountains were also applicable to Mexican Spotted Owl nest sites in surrounding mountains. Seventy-five percent (n = 28) of nests were in Douglas-fir (Pseudotsuga menziesii), and 61% (n = 28) of nest structures were on clumps of limbs caused by dwarf mistletoe (Arceuthobium sp.) infections. Nest trees averaged 163.7 years of age (SD = 44.8) and 60.6 cm in diameter (SD = 22.4).

Combining Remote Sensing and Climatic Data to Estimate Net Primary Production Across Oregon

A range in productivity and climate exists along an east—west transect in Oregon. Remote sensing and climatic data for several of the Oregon Transect Ecosystem Research Project (OTTER) forested sites and neighboring shrub sites were combined to determined whether percentage intercepted photosynthetically active radiation (%IPAR) can be estimated from remotely sensed observations and to evaluate climatic constraints on the ability of vegetation to utilize intercepted of radition for production. The Thematic Mappers Simulator (TMS) normalized difference vegetation index (NDVI) provided a good linear estimate of %IPAR (R2 = 0.97). Vegetation intercepted from 24.8% to 99.9% of incident photosynthetically active radiation (PAR), and aboveground net primary production (ANPP) ranged from 53 to 1310 g·m—2·yr—1. The ANPP was linearly related to annual IPAR across sites (R2 = 0.70). Constraints on the ability of each species to utilize intercepted light, as defined by differential responses to freezing temperatures, drought, and vapor pressure deficit, were quantified from hourly meteorological station measurements near the sites and field physiological measurements. Vegetation could utilize from 30% of intercepted radiation at the eastside semiarid juniper woodland and shrub sites to 97% at the maritime coastal sites. Energy—size efficiency (ϵu), calculated from aboveground production and IPAR modified by the environmental limits, averaged 0.5 g/MJ for the shrub sites and 0.9 g/MJ for the forested sites.

Environmental Limits on Net Primary Production and Light‐Use Efficiency Across the Oregon Transect

Due to climate differences, an extreme range in productivity occurs along a 250—km, west—east transect at °44° north latitude in western Oregon, USA, where coniferous evergreen forests dominate. As part of the Oregon Transect Ecosystem Research (OTTER) project, our objective was to evaluate how climate constrains net primary production (NPP) by limiting the utilization of intercepted photosynthetically active radiation (IPAR). The forests measured along the transect intercepted from 22% to 99.5% of the incident PAR. With data collected from recording meteorological stations installed near each site, we defined the hourly conditions when photosynthesis was partly or completely limited by drought, extreme humidity deficits, or frost. From this analysis we calculated that the fraction of incident PAR that could be utilized throughout the year ranged from 92% in the coastal rainforests to <25% in the juniper woodland. NPP varied from 3 to 26 Mg°ha—1°yr—1 with the fraction of belowground NPP, estimated from litterfall, increasing from 20% to 60% of the total as the environment becomes harsher. Light—use efficiency (°u) calculated under conditions when the environment did not constrain photosynthesis, averaged 0.8 g/MJ for aboveground NPP and 1.3 g/MJ for total NPP.

New Names in California Oaks

The following five names are proposed for California oaks: Quercus john-tuckeri, nom. et stat. nov. for Quercus turbinella subsp. californica J. M. Tucker; Quercus pacifica, sp. nov.; Quercus x kinselae, stat. nov. for Quercus dumosa Nuttall var. kinselae C. H. Muller; Quercus durata var. gabrielensis Nixon & C. H. Muller, var. nov.; and Quercus parvula var. shrevei (C. H. Muller) Nixon, stat. nov. for Quercus shrevei C. H. Muller. In the course of preparing a treatment of the genus Quercus in California, we have found it necessary to provide new names for the following five taxa. We are publishing these names in advance of the full study, in order to make them available for floristic treatments currently in preparation. 1. Quercus john-tuckeri Nixon & C. H. Muller, nom. et stat. nov. Basionym: Quercus turbinella E. Greene subsp. californica J. M. Tucker, Madronio 11: 240. 1952. TYPE: U.S.A. California: San Luis Obispo County, ca. 2 mi. NE of summit of Caliente Mountain, 2 Oct. 1948, J. Tucker 1886-16 (holotype, UC 938396; isotypes, DAV, BH). Shrubs 1-3(-5) m tall, subevergreen or evergreen; bark scaly; twigs yellowish or dingy gray, 11.5(-2) mm thick, densely tomentulose; buds brown, ovoid or globose, 1.5-2(-3) mm long, glabrous except for the ciliate margins of the scales, lowermost scales often yellowish puberulent. Petiole 1-4 mm. Leaf blade unicolored, elliptic or obovate, thick and coriaceous, often brittle, (10-)15-30(-40) mm x (8-)10-15(-20) mm; base squarrose or roundedattenuate, rarely subcordate; secondary veins (3-)47, often some of the veins branching near margin and passing into more than one tooth; margin irregularly spinose-toothed, occasionally shallowly lobate; apex acute or rounded; abaxially waxy grayish or light green, with sparse to moderately dense vestiture of (8-)10-12-rayed (loosely) appressed stellate hairs, these often 0.2-0.5 mm diam., and sparse to dense yellowish glandular hairs; adaxially grayish, stellate similar to abaxial surface. Fruits solitary or paired, subsessile; cup cup-shaped or obconic to hemispheric, thin, 10-15 mm wide x 5-7 mm deep; scales whitish or yellowish, moderately or scarcely tuberculate, puberulent. Nut fusiform, ovoid or conic, apically acute, 20-30 mm long. Cotyledons free. Dry slopes, chaparral, pinion and juniper woodland, margins of oak woodland and sagebrush; 9002,000 m. Endemic to California, from Los Angeles County north in the interior Coast Ranges and Sierra Foothills to the northern edge of the Sacramento Valley. Quercus john-tuckeri bears some resemblance to both Q. turbinella and Q. berberidifolia Liebmann; however, the former has pedunculate fruit and typically cordate leaf bases, while the latter has a glabrate upper leaf surface, substantially smaller stellate trichomes with fewer rays on the lower leaf surface, heavier, tuberculate acorn cups, and typically nonacute acorns. At the species level, the epithet californica is preoccupied by the illegitimate (but validly published) name Quercus californica Torrey ex J. G. Cooper (= Q. kellogii Newberry). 2. Quercus pacifica Nixon & C. H. Muller, sp. nov. TYPE: U.S.A. California: Santa Barbara County, rocky slope E of Pelican Bay, Santa Cruz Island, alt. 100 ft., Ira W. Clokey 4893 (holotype, BH-CHM). Frutices ad 2 m vel raro arbores ad 5 m, subsempervirentes. Petioli 2-5 mm longi. Lamina foliorum obovata vel oblonga, 15-40 mm longa, 7-20(-40) mm lata, margine integra vel dentata; pagina abaxialis ceracea, glandifera, sparsim stellato-pilosa, pilis paginae abaxialis adpressis; pagina adaxialis viridis, glabra. Nux sessilis, cylindrica vel fusiformis, (15-)20-30 mm longa, (6-)915 mm lata, apex acutus. Shrubs to 2 m tall, rarely small trees to 5 m or taller, subevergreen; bark scaly on older branches and trunk; twigs brownish or reddish and minutely NOVON 4: 391-393. 1994. This content downloaded from 157.55.39.138 on Sun, 26 Jun 2016 06:12:46 UTC All use subject to http://about.jstor.org/terms

A break in the nitrogen cycle in aridlands? Evidence from δp15N of soils.

We examined the content and isotopic composition of nitrogen within soils of a juniper woodland and found that a cryptobiotic crust composed of cyanobacteria, lichens, and mosses was the predominant source of nitrogen for this ecosystem. Disturbance of the crust has resulted in considerable spatial variability in soil nitrogen content and isotopic composition; intercanopy soils were significantly depleted in nitrogen and had greater abundance of 15N compared to intra-canopy soils. Variations in the 15N/14N ratio for inter- and intra-canopy locations followed similar Rayleigh distillation curves, indicating that the greater 15N/14N ratios for inter-canopy soils were due to relatively greater net nitrogen loss. Coverage of cryptobiotic crusts has been reduced by anthropogenic activities during the past century, and our results suggest that destruction of the cryptobiotic crust may ultimately result in ecosystem degradation through elimination of the predominant source of nitrogen input.

Packrat Midden Evidence of Late Quaternary Vegetation Change in the White Mountains, California-Nevada

Packrat ( Neotoma spp.) middens from the White Mountains indicate climatic and plant community conditions for the last 19,000 yr. During full-glacial times (ca. 19,000 yr B.P.) and at the Pleistocene/Holocene boundary juniper woodlands were 600 m lower in elevation than at present. Midden assemblages and stable-isotope data suggest lower temperatures and increased precipitation relative to the present into the early Holocene. Two early Holocene middens (ca. 8000 yr B.P.) from lower elevations of the White Mountains contain fragments of pinyon pine and indicate that both pinyon and juniper grew at a site that today supports only a pinyon woodland. Two middle Holocene middens (ca. 5000 yr B.P.) indicate that there was an upward migration of pinyon-juniper woodlands along a high-elevation ecotone, but little change in the middle of the pinyon-juniper woodland. Middens from the late Holocene indicate that present-day plant communities were in place by ca. 2000 yr B.P. or before.

The Effect of Nest Predation on Habitat Selection by Dusky Flycatchers in Limber Pine-Juniper Woodland

Habitat selection by Dusky Flycatchers (Empidonax oberholseri) was examined in limber pine-mountain juniper (Pinus flexilis-Juniperus scopulorum) woodland in western Wyoming during the breeding seasons of 1986, 1987, and 1988. Vegetation characteristics associated with occupied habitat were measured (1) at the nest site, (2) within the 0.04-ha nest patch, and (3) in the breeding territory outside the nest patch; results were evaluated in relation to availability within the habitat type and nesting success. Breeding pairs of Dusky Flycatchers occupied nest patches with greater foliage cover and greater density of trees than was generally available; territories were associated with greater densities of snags and a smaller proportion of trees with dead branches extending outside the canopy than was generally available, although selectivity at the territory scale was relatively weak. Successful pairs of Dusky Flycatchers had nests with greater concealment from below, shorter distances from the nest tree to the nearest tree, and greater densities of small trees in the nest patch than unsuccessful pairs. An experiment using artificial nests suggested that concealment from below the nest site and tree density in the nest patch were selected independently. I speculate that Dusky Flycatchers select nest patches that conceal parental movements from nest predators, and that fewer trees with dead branches may indicate the selection of higher tree or foliage vigor in occupied territories. The possibility of multiple selective factors and processes, differentially affecting the selection of nest-site, nest-patch, and territory-scale habitat is discussed.

Ash-Throated Flycatchers (Myiarchus cinerascens) Raise Mountain Bluebird (Sialia currucoides) Young

Ash-throated Flycatchers (Myiarchus cinerascens) and Mountain Bluebirds (Sialia currucoides) are secondary cavity-nesters that are sympatric in juniper woodlands of northern Nevada. While conducting a study of Mountain Bluebird reproductive strategies during the 1988-1989 breeding seasons, we observed two instances of Ash-throated Flycatchers raising bluebird nestlings in addition to their own young. Our study area is located in partially burned juniper woodlands north of Reno, Nevada, and contains 68 nestboxes. These boxes have been used since 1985 by Mountain Bluebirds and are also used occasionally by Ash-throated Flycatchers. In the first incident, a nestbox which contained two bluebird eggs on 30 May 1989 was taken over by Ashthroated Flycatchers. The adult bluebirds were unbanded, so we are not sure what happened to them after losing the nestbox; they did not use the nestbox again that season. The female flycatcher did little additional nestbuilding (flycatchers in this area use clumps of fur for nest material whereas bluebirds mainly use strips of bark), but laid her clutch of five eggs alongside the two bluebird eggs by 6 June. She incubated the mixed clutch, and all seven eggs hatched on approximately 19 June. In the four times we checked the nest between hatching and 3 July, the rate of nestling development appeared to be equal for both species. Only flycatchers were seen feeding the young. All nestlings presumably fledged on 11 July, except for one almost completely feathered bluebird nestling found mummified in the nestbox on 12 July (cause of death unknown). Despite repeated searches, we did not see the young after fledging. In the second incident, an Ash-throated Flycatcher laid two eggs by 22 June 1989 in a nestbox in which a bluebird pair had previously fledged a clutch of four young. On 5 July there was one Mountain Bluebird egg in the nest, along with two additional Ash-throated Flycatcher eggs. The flycatcher incubated all five eggs. On 12 July, we found one bluebird and two flycatcher young along with a dead flycatcher nestling and an unhatched egg. The young were approximately two days old. Again, only flycatchers were seen caring for the young. On 15 July (five days after hatching), the nest contained only two dead young (one flycatcher and one bluebird). The other nestling and the unhatched egg were missing. The adults were not in the area and were not seen again. Since predation is a major cause of bluebird egg and nestling mortality in our study area (unpubl. data), we assume this was the cause of nest failure, though nest abandonment cannot be completely ruled out. To our knowledge, this is the first report of Ashthroated Flycatchers raising the young of any other species. These two cases are qualitatively different, and we consider two possible explanations for them: 1. competition for suitable nest sites, and 2. facultative brood parasitism. Nest site competition. Two lines of evidence suggest that Mountain Bluebirds and Ash-throated Flycatchers compete for suitable nest sites in this study area. First, we know of four takeovers of bluebird nests by flycatchers since 1985 (two in 1986, one in 1987, one in 1989). There have been no reciprocal takeovers by bluebirds, presumably because flycatchers are much ' Received 15 October 1990. Final acceptance 7 December 1990. SHORT COMMUNICATIONS 461

Effect of species mix on size/density and leaf-area relations in Southwest pinyon/juniper woodlands

The effects of species mix on stand structure and growth are evaluated for 117 pinyon ( Pinus edulis Engelm.) and juniper ( Juniperus monosperma (Engelm.) Sarg and J. osteosperma (Torr.) Little) woodlands of the southwestern United States. Maximum-size/density relations, leaf area and growth of pure and mixed-species woodlands are compared. Structure of pure and mixed-species woodlands appeared to be restricted by maximum-size/density relations. Maximum Stand Density Index ( sdi) for mixed-species woodlands was 30% greater than for pure woodlands. Ceiling leaf areas were 3.6 for mixed-species, 3.5 for pure pinyon and 1.0 for pure juniper woodlands. Ceiling leaf area varied with species mix and soil type. Highest growth of mixed-species woodlands occurred at maximum woodland and pinyon sdi. We suggest that higher size/density, leaf area and growth relations in mixed-species woodlands than in pure woodlands are related to differences in rooting habit and water relations between pinyon and juniper.

Late quaternary arthropod remains from Sonoran Desert packrat middens, southwestern Arizona and northwestern Sonora

A total of 50 arthropod taxa were identified from 41 fossil packrat ( Neotoma sp.) middens from 160 to 625 m elevation in three study areas in the Lower Colorado River Valley subdivision of the Sonoran Desert. Radiocarbon dates associated with the middens range from >43,200 to 610 yr B.P. The fauna in the Tinajas Altas Mountains, southwestern Arizona, was relatively modern by ca. 10,000 yr B.P. in the early Holocene although a California juniper woodland persisted in the area until 8970 yr B.P. In contrast the fauna of the Hornaday Mountains, northwestern Sonora, increased dramatically in species richness after 4000 yr B.P. Although we are limited by poor taxonomic resolution and by insufficient knowledge of current distributions, the arthropod fauna may have been much more conservative than the regional flora during the last glacial/interglacial climatic cycle. Decreasing differences between modern and glacial climates (both temperature and precipitation) at lower latitudes and elevations may have resulted in minimal changes in the arthropod fauna of the Sonoran Desert lowlands.

A Weather Severity Index on a Mule Deer Winter Range

Temperature, wind, and snow conditions predictably affect the nutrition, behavior, distribution, productivity, and mortality of free-ranging cattle and big game in winter. Indexing of data obtained with commonly available weather instruments to reflect episodes of positive and negative energy balances of free-ranging ruminants could aid scheduling of feeding programs and planning of cover-forage manipulations. Such a weather severity index was developed and tested over 11 winters. Plausible levels of stress and episodes of relative severity were depicted during winters when mule deer exhibited low, moderate, and high mortality. The index curves mirrored over-winter declines of fat reserves probably sustained by mule deer. Lesser weather severity was predicted and measured in a western juniper woodland than in an adjacent rabbitbrush steppe community in southcentral Oregon. 32 references, 3 figures, 2 tables.

Evaluation of the Hand-Held Net Gun for Capturing Pronghorns

A hand-held net gun was used to capture pronghorns (Antilocapra americana) on the Pinon Canyon Maneuver Site (PCMS) in southeastern Colorado. Eighteen adult pronghorns were captured successfully during April and December 1984 and March 1985. Two of 20 pronghorns (10%) captured or pursued for capture died of injuries. Capture myopathy (CM) was not obvious during our operations. The net gun proved to be a useful tool for capturing individual pronghorns under certain conditions. Rapid processing of captured animals, experienced pilots and gunner, small herds (3-12 individuals), and open grassland habitats all contributed to the success of this technique. J. WILDL. MANAGE. 50(2):320-322 Free-ranging pronghorn antelope have been captured in corral type traps, linear tangle nets, drop nets, and cannon nets (Amstrup et al. 1980, Moody et al. 1982). These methods are time consuming, labor intensive, and nonselective with respect to age and sex (Barrett et al. 1982). Drug immobilization of pronghorns can be selective but is limited by the effectiveness of available drugs (Copeland et al. 1978, Amstrup et al. 1980) and generally high mortality rates (10-19%) (Amstrup and Segerstrom 1981, Autenrieth et al. 1981). Barrett et al. (1982) described the use of a hand-held net gun for capturing large mammals including pronghorns. Of the 5 pronghorns captured by Barrett et al. (1982), 1 of 3 adult females broke its leg and both fawns captured developed acute metabolic stress; no adult males were captured. They concluded that pronghorns are captured easily with this technique; however, considerable effort may be required to reduce CM and losses from trauma. We evaluated the hand-held net gun for capturing pronghorns and suggest ways to reduce stress and injury related mortality. This work was funded by the U.S. Army, Environ., Energy and Nat. Resour. Div., Fort Carson, Colo.; the U.S. Fish and Wildl. Serv., Va. Coop. Fish and Wildl. Res. Unit; the U.S. Fish and Wildl. Serv., Fish and Wildl. Assist. Off., Golden, Colo.; and the Virginia Polytech. Inst. and State Univ., Dep. Fish. and Wildl. Sci. We thank C. Nobles and the other pilots, the support of Alpha and Delta Co., 4th Aviation Battalian, Fort Carson, Colo., and the field assistance of E. Gese. METHODS During April and December 1984 and March 1985 pronghorns were captured on the PCMS in southeastern Colorado using a hand-held net gun (Coda Enterprises, Mesa, Ariz.). (Reference to this trade name does not imply endorsement by the U.S. Fish and Wildl. Serv.) The maneuver site consists of flat to rolling short grass prairie with pinyon pine (Pinus edulis)-one-seed juniper (Juniperus monosperma) woodlands scattered throughout. All captures were executed from a UH-1 (Bell 212) military helicopter. Pilots and gunner had experience in the net-gun capture of mule deer (Odocoileus hemionus) and coyotes (Canis latrans). Pronghorn herds were hazed until they lined out in single file. A low approach was made, and one of the trailing animals was shot. After a successful shot the aircraft landed and processing began in 530 seconds. All captured animals were aged, eartagged, radiocollared, and released in <10 minutes. RESULTS AND DISCUSSION Eighteen (11 male and 7 female) adult pronghorns were captured successfully using a hand-held net gun during 3 capture operations on t e PCMS, Colorado (Table 1). Twenty-two capture attempts were unsuccessful. Temperatures ranged from 7 to 24 C during the gunning, and snow was not present to slow the animals' movement. Mean pursuit time for successful attempts ( = 3.75 min) was less (P < 0.05) than mean pursuit time for unsuccessful attempts (9 = 5.75).

A Seasonal Analysis of Bird Communities in Southern Nevada

Bird communities were studied on 3 sites in southern Nevada for a period of 15 months, including 2 breeding seasons. Study sites ranged from 975 m to about 1220 m elevation. Vegetation varied from low desert shrub dominated by creosote (Larrea tridentata) and Mohave yucca (Yucca schidigera) to sparse pinyon pine (Pinus monophylla) - California juniper (Juniperus californica) woodland. Twenty-three species bred on 1 or more study sites during 1975 and 1976. Species richness and density of individuals was directly related to elevation in all seasons. Monthly fluctuations in species richness followed a similar pattern on all 3 sites; fluctuations in density were more variable among sites. Spring migration was characterized by more species and individuals than was fall migration; few or no migrants were recorded from the 2 lowest sites in fall. Density and number of species was lowest in winter, particularly January. Seasonal fluctuations in abundance of individuals within major trophic groups differed among groups, probably in response to food availability.

Vegetation dynamics in the Asir woodlands of south-western Saudi Arabia

Woodland vegetation in the Asir mountains of south-western Saudi Arabia was quantitatively surveyed to delineate development patterns associated with topography and elevation. Two tree species and five shrubs dominate the woody vegetation in the juniper woodlands. Plant densities are generally higher in the lower elevations and on south-west and west-facing slopes. Species segregate on the basis of ecological importance depending on slope aspect, elevation, and human impact through wood gathering and grazing activities especially on plateau sites. Regeneration is suppressed with concomitant reduction in species diversity and tree size class distribution.

Paleobiogeography of Montane Islands in the Great Basin since the Last Glaciopluvial

The existing warm (Larrea) deserts of the Southwest are Holocene expansions replacing late—Pleistocene, evergreen woodlands of low—statured junipers, pinyon pines, and live oaks; these woodlands have been isolated by complementary contraction to the slopes of higher mountains that rise like islands from the modern desert sea. Because pinyon—juniper woodland is now so widespread on the similar fault—block mountains of the Great Basin, even as far north as southern Idaho, it would seem reasonable to suppose that the modern "cold" (Artemisia, Atriplex) deserts were similarly wooded during the last glacial. However, conclusive Neotoma macrofossil evidence (45 14C—dated assemblages are reported here) documents major latitudinal displacement of vegetation that precludes pinyon—juniper woodland in the northern and central Great Basin at that time. On the other hand, the entire Mohave Desert sector (south of °37°N) served as an extensive Pleistocene refugium for pinyon—juniper woodland, as documented by an additional 48 dated Neotoma deposits. During the Wisconsinan glacial in the southeastern corner of Oregon, a 42°27'N, there was a subarctic landscape of hyperboreal, prostrate shrublet—junipers (Juniperus horizontalis and J. communis) and widespread patterned ground, even at the near—basal elevation of 1460 m. The pleniglacial vegetation of the central Great Basin at 39°N in eastern Nevada and western Utah, was dominated by a regional subalpine forest of bristlecone pine (Pinus longaeva), associated with minor but consistent boreal juniper (J. communis) down to 1660 m, close to the base level imposed by pluvial Lake Bonneville. Spruce has not been recorded below 1900 m during the last glacial. At a lower range of elevation (1350—1525 m), available south of the southeastern rim of the Bonneville basin at 37°30'N. Pinus longaeva was replaced by limber pine (P. flexilis), Douglas—fir (Pseudotsuga), and montane red cedar (J. scopulorum); existing woodland juniper (J. osteosperma) was lacking, but the subalpine J. communis was present at this local base level. Theory of island biogeography, as applied to ecological islands atop the high mountains of the Great Basin, is reexamined in the light of the drastic vegetational displacements documented in the detailed Quaternary macrofossil record. Species/area plots of montane—subalpine conifers presently distributed on 54 Great Basin mountaintops show an overall insular pattern that is especially well developed on the subset of 38 ecological islands east of 116°W; the slope of z = 0.26 is close to the theoretical value for islands in equilibrium. All 11 taxa of montane—subalpine conifers that penetrate the Great Basin deeply have their main distributions in the Rocky Mountains; only three wide—ranging species occur also in the Sierra Nevada. A long sundering trough in the western Great Basin parallels and isolates the Cascade—Sierran uplift with low—elevation barriers that impede migration, but in the eastern Great Basin there are high connecting divides to the western Rockies, especially via an axial route southeast of the Bonneville basin. There is an east—west pattern of declining species richness of11 montane conifers in the Great Basin that correlates with distance from the rocky Mountain pool of 12 coniferous species. The pleniglacial subalpine forests in the lowlands of the central Great Basin had only one to three species of conifers (e.g., Pinus longaeva, Picea engelmannii, Juniperus communis). During the great late—glacial/Holocene (12 000—8000 yr BP) warming of climate, these shifted upward in elevation and were augmented in the east (but not in the west) by as many as five additional species of montane conifers. Macrofossil evidence indicted that the later Holocene arrivals dispersed across barriers of woodland and desert that by then isolated the shrunken montane islands. Moderately long—range transport of seeds by birds is deduced as follows: a northward latitudinal shift of 500—640 km during the Holocene is documented for several species of relatively thermophilous conifers, including the heavy—seeded, late—maturing pinyon pine. A 640—km migration in 8000 yr (80 m/yr) is indicated for pinyon, but the most generous estimate of its dispersal rate via the wind/gravity mode is a plodding 0.4 m/yr (3.2 km/8000 yr), orders of magnitude too slow. Seed dispersal by Clark's Nutcrackers and Pinyon Jays, however, is both the prevalent mode and amply swift enough to fit the known migrational history. Hence, the islands—in—equilibrium pattern indicated by the typically insular slope (z = 0.26) for montane conifers on the eastern set of mountaintops in the Great Basin is a reflection of Holocene immigration via sweepstakes dispersal being offset by extinction on the smaller islands. Both extinction and immigration of conifers are documented in the late—glacial/early—Holocene Neotoma record from the small Confusion Range in the east—central Great Basin of western Utah.

Analysis of variation in the Elaphrus finitimus complex of North America (Coleoptera: Carabidae)

This is a continuation of a study on geographical variation of the Elaphrus americanus Dejean species complex. This paper is devoted to E. finitimus Casey, which includes at least seven populations: White Mountains of California, Colorado Plateau, western Great Basin, western Arizona, central California, southern California, and southern Sierra Nevada. Three main groups of populations were recognized by means of numerical taxonomic analyses: White Mountains of California (one population), Intermontane (Colorado Plateau and western Great Basin), and southwestern (remaining four populations). The above groups were discerned from clustering by UPGMA (unweighted pair group using arithmetic averages) of Mahalanobis distances, and are characterized in a discriminant analysis. Other geographically distinct populations were recognized by univariate analysis of nominal characters. All seven populations are allopatric and are isolated presently from one another by vast expanses of dry regions (prairies and piñon–juniper woodlands), or by different life zones with altitude. We postulated that during the glacial phases of the Pleistocene similar barriers existed, though the gaps were narrower than at present. The reconstructed glacial ranges of these populations offer a hypothesis as to the origin of some populations, and direction of limited gene flow between some populations.

Cost of Controlling Maturing Western Juniper Trees

A cost evaluation was conducted of four alternatives for improvements on maturing western juniper (Juniperus occidentulis) woodlands. The alternatives were: (a) the use of picloram (4-amino-3,5,6-trichloropicolinic acid) to kill the trees with no further treatment, with a total cost of %78/ha (%3l/acre); (b) picloram with sufficient limbing and/or removal of trees to allow passage of a rangeland drill for seeding at a cost of %448/ha ($179/acre); (c) mechanical clearing and burning of the trees at a cost of %595/ha (%237/acre); and (d) wood harvesting and slash disposal at a cost of %2,08O/ha ($832/acre). The picloram and limb, mechanical, and wood-harvesting treatments provide mechanically seedable sites, but of considerably different quality in terms of ease of seeding and chances of seedling establishment. The mechanical treatment requires a large capital investment, while the wood-harvesting treatment requires a large amount of labor. Based on equivalent energy values, the wood-harvesting operation would produce a profit for the landowner who could afford to invest the labor. For a specific woodland, a combination of treatments would be most cost effective. During the late 19th and early 20th centuries, range sites that formerly supported big sagebrush (Artemisia tridentam)/ bunchgrass communities were suddenly invaded by western juniper (Juniperus occidentalis subsp occidentalis) trees (Burkhardt and Tisdale 1969, 1976; Young and Evans 1980). These stands are now in a successional stage where the trees completely dominate the site and have largely depleted the understory of competing grass and browse species. Juniper roots occupy the soil profile to the extent that the site is effectively closed for seedling establishment of desirable forage or browse species. In many stands the junipers are approaching maturity, with 150 trees/ ha (60/acre); individual trees are 9.2 m (30 ft) tall and 0.5 m (20 inches) in diameter at the base (Young and Evans 1981). The tree canopies are not closed, and projected crown covers range from 36 to 45% in the stands. The density of trees on invasion sites is relatively constant, apparently reflecting an equilibrium with available environmental potential. The purpose of this study is to evaluate alternatives for the improvement and utilization of these stands by ranchers. In other studies, either published or in progress, we have reported on why these invasion stands exist and how to prevent their occurrence. This study concerns the ranch manager’s options given the existing woodlands. The study was designed for western juniper woodlands that are owned by ranchers who are interested in enhancing forage production for livestock. Because of the power units available and the biological conditions of the stands, we did not consider chaining as a treatment. Within these constraints, the treatments evaluThe authors are range scientists, U.S. Dep. Agr., Agr. Res. Serv., Reno. Nev. 89512; assistant professor of forestry; and formerly research associate, agricultural and

Stephens' Woodrat, a Dietary Specialist

The feeding biology of Stephens' woodrat ( Neotoma stephensi ) was studied in juniper woodlands in Arizona. Microscopic examinations were made of fecal samples from live-trapped animals, observations were made on foraging behavior, and data on plant communities occupied by this woodrat were gathered. Stephens' woodrat is a dietary specialist, unique in its ability to utilize juniper throughout the year. Some 90% of the diet is juniper: foliage is most important, but male and female cones are also eaten. This woodrat is a highly selective central-place forager, feeding repeatedly on certain individual junipers and avoiding others. Such finely tuned foraging probably facilitates the exploitation of junipers with unusually low levels of defensive, digestibility-reducing chemicals, and may be the key to this animal's success as a juniper specialist. Stephens' woodrat may be considered a relict species, largely restricted to areas supporting vestiges of a xeric juniper woodland that in the early Holocene was widespread in the southwestern United States.

BIOGEOGRAPHY OF THE GENUSEUXOA(LEPIDOPTERA: NOCTUIDAE) IN NORTH AMERICA

AbstractThe biogeography of 171 North American species ofEuxoa(Lepidoptera: Noctuidae) is reviewed. For biogeographical analysis, species are arranged in groups according to habitat; these are 62 aridland species, 69 forest species, 19 widespread species, and 21 species with special or unknown habitat requirements. Aridland species are distributed primarily in grassland areas in the Great Plains and in sagebrush areas or piñon–juniper woodland in the intermontane region. Ranges in these two regions are connected in arid corridors through the Rocky Mountain region. Forest species in western North America are arranged in two groups: those that occur in both conifer forests and piñon–juniper woodland (17 species), and those that occur only in conifer forests (40 species). Species in the former category occur throughout the mountain ranges of the west including those of the Great Basin wherever suitable habitat occurs. Those of the latter category occur in conifer forests on mountain ranges around the Great Basin but do not occur in the Great Basin, even in mountain ranges that support suitable habitat. Most forest species that occur in the Rocky Mountain region also occur in disjunct woodland areas in the Great Plains.The effect of Wisconsinan glaciation on the biogeographic regions of western North America is reconstructed from a review of fossil pollen and plant macrofossil studies. From this synthesis it is suggested that during the Wisconsinan glacial maximum, forest species were widely distributed in the Great Plains south of the Laurentian ice sheet, and at low elevations in the Sierra Nevada and Rocky Mountain regions. Piñon–juniper woodland species were widespread in the Great Plains. Forest species that do not occur in piñon–juniper woodland were distributed around the Great Basin but were prevented from reaching suitable habitat in mountain ranges within the Basin by unsuitable habitat in the intervening lowlands. The ranges of aridland species were greatly reduced during Wisconsinan time, particularly in the Great Plains. Aridland corridors through the Rocky Mountains were eliminated during the Wisconsinan glacial maximum.The possibility of speciation during Wisconsinan time is reviewed. Although the distribution of many sister-species are what would be expected from speciation during the Wisconsinan, the distributions may reflect allopatric distributions during Wisconsinan time and not speciation.