Neil E. West

Ecology and management of sage-grouse and sage-grouse habitat

Abstract Sage-grouse (Centrocercus urophasianus and C. minimus) historically inhabited much of the sagebrush-dominated habitat of North America. Today, sage-grouse populations are declining throughout most of their range. Population dynamics of sage-grouse are marked by strong cyclic behavior. Adult survival is high, but is offset by low juvenile survival, resulting in low productivity. Habitat for sage-grouse varies strongly by life-history stage. Critical habitat components include adequate canopy cover of tall grasses (≥ 18 cm) and medium height shrubs (40–80 cm) for nesting, abundant forbs and insects for brood rearing, and availability of herbaceous riparian species for late-growing season foraging. Fire ecology of sage-grouse habitat changed dramatically with European settlement. In high elevation sagebrush habitat, fire return intervals have increased (from 12–24 to > 50 years) resulting in invasion of conifers and a consequent loss of understory herbaceous and shrub canopy cover. In lower elevation sagebrush habitat, fire return intervals have decreased dramatically (from 50–100 to < 10 years) due to invasion by annual grasses, causing loss of perennial bunchgrasses and shrubs. Livestock grazing can have negative or positive impacts on sage-grouse habitat depending on the timing and intensity of grazing, and which habitat element is being considered. Early season light to moderate grazing can promote forb abundance/availability in both upland and riparian habitats. Heavier levels of utilization decrease herbaceous cover, and may promote invasion by undesirable species. At rates intended to produce high sagebrush kill, herbicide-based control of big sagebrush may result in decreased habitat quality for sage-grouse. Light applications of tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea) can decrease canopy cover of sagebrush and increase grass and forb production which may be locally important to nesting and foraging activities. The ability of resource managers to address sage-grouse habitat concerns at large scales is aided greatly by geomatics technology and advances in landscape ecology. These tools allow unprecedented linkage of habitat and population dynamics data over space and time and can be used to retroactively assess such relationships using archived imagery. The present sage-grouse decline is a complex issue that is likely associated with multiple causative factors. Solving management issues associated with the decline will require unprecedented cooperation among wildlife biology, range science, and other professional disciplines.

Tree Age and Dominance Patterns in Great Basin Pinyon-Juniper Woodlands

Prior studies of pinyon-juniper woodlands at a few locations have indicated considerable historical expansion of the trees and loss of understory. Whether these changes are a widespread phenomenon and related to pervasive, rather than local, influences was the question asked by this research. An objective sampling of 18 randomly selected mountain ranges in the Great Basin was undertaken. Tree age and dominance in the pinyon-juniper woodlands showed definite geographical, elevational, and historical trends. The oldest, most tree-dominated woodlands were located in areas of intermediate topography where disturbances may have been less frequent. Populations of both tree species [Pinus monophylla (Torr.) and Juniperus osteosperma (Torr. and Frem.)] were progressively younger and less dominant in both upslope and downslope directions from the intermediate elevations. Tree densities have also historically increased within the oldest woodlands. Pinyon density has increased faster than that of juniper. Approximately 40 percent of the sampled plots had their trees establishing during the last 150 years. These changes generally coincide with introduction of heavy livestock grazing, tree utilization by the mining industry, and fire suppression that followed settlement of the region. Associated climatic trends were also investigated. The relative importance of these influences on the changes in tree age and dominance cannot be determined without further research. The loss of understory, coincident with increasing tree dominance, has reduced forage production and made the woodlands progressively less susceptible to fire. Barring some major environmental change or management action, this forage reduction and decreased frequency of burning will continue until trees dominate much more area. Pinyon-juniper woodland is an important range type that has apparently increased in area and density over the last century (Plummer 1958, Christensen and Johnson 1964, Murdock and Welsh 1971, West et al. 1975). In the Great Basin, the type now occupies an area of nearly 18 million acres (Tueller et al. 1979). Although changes in tree dominance in these woodlands have been widely discussed, the few existing studies (Cottam and Stewart 1940, Woodbury 1947, Blackburn and Tueller 1970, Barney and Frischknecht 1974, West et al. 1975), have provided only limited documentation of these changes. Many combinations of natural and man-influenced causes have been proposed (West et al. The authors are former graduate research assistant, professor and former graduate fellow, respectively, Department of Range Science, Utah State University, Logan 84322. Tausch’s current address is 401 Manzanita Avenue, Carte Madera, California 94925. Nabi’s current address is Department of Range Science, Colorado State University, Fort Collins 80523. This research was performed under a cooperative agreement with the Intermountain Forest and Range Experiment Station, U.S. Forest Service. McIntire-Stennis Forestry Research Act funding was also provided from the Utah Agricultural Experiment Station, of which this is Journal Paper No. 2328. Nabi’s contributions were financially supported by the Ministry of Education of the Libyan Arab Republic. We are indebted to Mr. Robert Bayn for drafting the figures and to many others too numerous to mention individually for assistance in the collection and processing of these data. Manuscript received November 16, 1979. JOURNAL OF RANGE MANAGEMENT 34(4), July 1981 1975, Burkhardt and Tisdale 1976). Ecologists and land managers have questioned whether the reported thickening of trees in the original stands and invasion of former grasslands and shrubland are a widespread phenomenon controlled by a few wide-reaching factors common to the region or of only local importance. In addition, the rates of change, including the secondary succession resulting from tree re-establishment in areas denuded by tree cutting for mine props and charcoal, has not been totally determined (Lanner 1977, Budy and Young 1979). The following is a report of our attempts to provide an overview of the spatial and elevational variation of tree age and dominance in the Great Basin pinyon-juniper woodlands by describing existing conditions, historical changes, and apparent rates of change.

Vegetation Change after 13 Years of Livestock Grazing Exclusion on Sagebrush Semidesert in West Central Utah

Range managers often assume that release of vegetation from livestock grazing pressure will automatically result in a trend toward the pristine condition. The pathways and time scales for recovery are also sometimes assumed to be the same as for retrogression. These assumptions were examined via monitoring of plant community composition and forage production in five large paddocks of sagebrush semi-desert vegetation in west central Utah over a 13-year interval. No significant increases in native perennial grasses were noted over this period despite a trend toward more favorable precipitation in recent years. Thus, the present brushdominated plant community is probably successionally stable. A return to vegetation similar to the original sagebrush-native grass mixture is unlikely. The possibility of a successional deflection via fire is enhanced by the increase of annual grass. Improvement of forage production in this vegetation will not necessarily follow after livestock exclusion. Direction manipulations are mandatory if rapid returns to perennial grass dominants are desired in such

A Protocol for Retrospective Remote Sensing–Based Ecological Monitoring of Rangelands

Abstract The degree of rangeland degradation in the United States is unknown due to the failure of traditional field-based monitoring to capture the range of variability of ecological indicators and disturbances, including climatic effects and land use practices, at regional to national spatial scales, and temporal scales of decades. Here, a protocol is presented for retrospective monitoring and assessment of rangeland degradation using historical time series of remote sensing data and catastrophe theory as an ecological framework to account for both gradual and rapid changes of state. This protocol 1) justifies the use of time-series satellite imagery in terms of the spatial and temporal scale of data collection; 2) briefly explains how to acquire, process, and transform the data into ecological indicators; 3) discusses the use of time-series analysis as the appropriate procedure for detecting significant change; and 4) explains what reference conditions are appropriate. Landsat data have been collected and archived since 1972, and include complete coverage of US rangelands. Characteristics of land degradation can be retrospectively measured for a nearly 33-year trend using surrogate remote sensing–based indicators that correlate with changes in life-form composition (time series of thematic maps), declines in vegetation productivity (vegetation indices), accelerated soil erosion (soil indices), declines in soil quality (piospheric analysis), and changes in landscape configuration (time series of thematic maps). Aspects of 2 retrospective studies are presented as examples of application of the protocol to considerations of the land use impacts from military training and testing and ranching activities on rangelands.

Recovery of Sagebrush-Grass Vegetation Following Wildfire

Most studies of the impacts of fire in sagebrush-grass vegetation in the Great basin have involved recovery on sites seriously depleted of native perennial bunchgrasses. The usual recommendation is to promptly seed such areas artificially. This is costly, not alwayssuccessful, and if unnecessary, could produce no more than a natural recovery. The natural recovery of a good condition sagebrush-grass site in central Utah was monitored for 2 years after a mid-summer wildfire. Total plant cover 1 year after the fire was similar to that before the fire and on unburned controls. Annual herbaceous growth 1 year later was almost twice that before the fire. Most of the plant growth the first year was due to cheatgrass (Bromus tectorum). By the second year after fire, however, the perennial bunchgrasses had cover and production levels near those recorded prior to the burn. Two years after the Bre, total grazable forage was 2.5 times that before the fire. Total precipitation, however, had been higher than average both years. Sagebrush-grass sites in good condition may be improved for cattle production with a few years of livestock exclusion following wildfire. Prescribed or controlled burns would probably be appropriate on similar high condition rangelands if cattle grazing is the dominant use and conflicts with wildfire are minor. The relative amount of big sagebrush (Artemisia tridentata)’ and perennial grasses in sagebrush-grasslands prior to the coming of European man is thought to have been at least partially related to fire frequency (West 1983). Big sagebrush does not resprout after fire (Young and Evans 1977). Wright and Bailey (1982) conclude that the probable return frequency of fire in such vegetation is between 50100 years for a given piece of ground. Heavy livestock use since European settlement has reduced the proportion of palatable herbaceous species, thereby diminishing competition from the herbs and lessening the amounts of fine fuel. This and The authors are professor, Range Science Department, Utah State University, Logan 84322; and instructor, Veterinary and Animal Husbandry Technicians Institute, Khartoum North, Sudan. At the time of the research the junior author was a graduate fellow, Range Science Department, Utah State University. Research was funded in part by the Utah Agricultural Experiment Station of which this is journal paper No. 2935. The authors appreciate the cooperation of the landowner, Mr. Carl Christensen, Pleasant Grove, Utah. Manuscript accepted May 8, 1984. ‘Latin names for plants follow Welsh et al. (1981). common names follow Bettle

Cover components on long-term seasonal sheep grazing treatments in three-tip sagebrush steppe.

The effects of fall and spring sheep use on cover components and recovery following a change in seasonality of grazing practices, were studied within long-term grazing treatments of three-tip sagebrush (Artemisia tripartita Rydb.) steppe on the U.S. Sheep Experiment Station near Dubois, Ida. Few significant differences existed among treatments within the litter, moss, lichen, and soil components, but several differences in vegetational cover categories occurred. More live shrub and annual grass cover were observed in the long-term (since 1924) and new spring (since 1950) treatments than in the long-term fall (since 1924), new fall (since 1950), old exclosure (since 1940), and new exclosure (since 1950) (P < 0.01). More perennial grass and forb cover, and less dead shrub cover existed in fall-grazed treatments (P < 0.01). The new fall- grazed treatment previously grazed in the spring failed to reach a more uniform mixture of perennial growth forms after 46 years such as was evident in the long-term fall, which suggests low resilience following spring grazing. The exclosure which was heavily spring and fall-grazed prior to 1950 had even less perennial forb cover than the new fall treatment, indicating that the cessation of sheep grazing did not promote herb recovery any better than continued fall use. The direct impact of sheep herbivory and its indirect effects on the competitive relationships among major plants appear to have affected the cover of sagebrush steppe components at this study site.

Effects of Climatic Change on the Edaphic Features of Arid and Semiarid Lands of Western North America

A group of specialists was asked by the Environmental Protection Agency to use their judgment as to which soil variables would be most impacted by five scenarios of climatic change in deserts of North America that could occur over the next 40 years. The following soil characteristics were evaluated in terms of their potential for change: physical, chemical, and biological crusts; the vesicular layer; soil organic matter; organic C and N content; the C/N ratio; carbonate pool; inorganic N, P, and S; salinity levels; micro‐element content; microbial community composition; free‐living microbial N fixation; denitrification; ammonia volatilization; salinization rates; water infiltration; evaporation; lateral flow and leaching; wind and water erosion; and litter decomposition. The Delphi approach was used to reach consensus on expected trends. Computer modeling was used to integrate and project interactive changes. We expect physical and chemical crusting, vesicularity, ammonium volatilization, soil erosion, an...

A COMPARISON OF TECHNIQUES FOR ASSESSING DISPERSION PATTERNS

A series of artificial populations with different types of spatial distribution is used to test the value of a number of published indices in identifying non-randomness. Among tests based on distance measurements, that of Hopkins is generally the most powerful, through there are reasons for preferring that of Pielou where the vegetation has not been completely mapped. Among tests involving quadrat measurements, the variance/mean ratio appears to be best. Where contiguous series of quadrats are available hierarchical analysis of variance is a more powerful test than Monte-Carlo pairing of quadrats, though the latter is a more flexible technique. The value of different methods for describing pattern, once non-randomness has been established, is also discussed.

Rodent-Influenced Establishment of Ponderosa Pine and Bitterbrush Seedlings in Central Oregon

Unrecovered caches of Pinus ponderosa and Purshia tridentata seed made by small rodents frequently result in establishment of seedling clusters. Studies in montane forests of central Oregon indicate that about 90% of the Purshia seedlings that germinate develop in clusters. At least 15% of the pine seedlings result from rodent caches.

Estimation of Phytomass for Ungrazed Crested Wheatgrass Plants Using Allometric Equations

The 8llometric relationship between plant volume and pbytomass 01 crested wheatgrass was studied for the 1981,1983, and 1984 growing seasons in west-central Utah. Basal diameters, canopy diameters, and standing plant beigbts were measured for btdividual plants. Three models of volume (basal elliptical cylinder, canopy elliptical cybnder, and elliptical cone section) were tested as predictors of plant pbytomass usbtg nonlinear regression. Elliptical cone section produced the blgbeat R* and lowest SEE, but requires measurement of canopy diameters which m8y be subject to excessive measurement error. Basal elliptical cylinder produced R* and SEE v8lues nearly comparable to those of the elliptical cone section; moreover, this model does not require measurement of canopy dirmeters, making it the practic81 choice. Nonlinear regressions for plants by sixe class (small, medium and large) were produced using 1983 data. Predictive ability of size class-specific equations was compared to that of tbe equati011 for alI size classes combined. When pbytomass of only small or medium size class plants was predicted, the SEE of s&e class-specific equations was slightly lower than the SEE of the equation for all sixe classes combined. Wben pbytomass of plrnts from all sixe classor was predicted, however, the equation for alI size classes combbted produced the lowest combined SEE for new data (i.e., data not used to generate tbe equation). There were substantial year-to-year differences between equations, which indicates the necessity of producbrg new equations each year.