Succession in pinyon-juniper woodlands following wildfire in the Great Basin

Twenty - one areas in pinyon ( Pinus monophylla ) - juniper ( Juniperus osteosperma ) woodlands burned by wildfire from approximately 1 to 60 years prior to sampling and adjacent unburned mature woodland stands were studied in Nevada and California to determine successional patterns and individual species responses to burning and to changing plant communities through time. One year after burning, all late successional woodland species were present in postburn plant communities except tree species. Increases in both cover and occurrence of annual and perennial forbs resulted in their dominance on early successional sites. Shrubs and annual grasses dominated midsuccessional sites, subsequently giving way to tree, shrub, and perennial grass dominance in late succession. North and east slopes generally supported high cover and occurrence of shrubs, perennial grasses, and perennial forbs, and south and west slopes generally supported high cover and occurrence of annual forbs and annual grasses. The ability to group species according to preferential occurrence on various aspects and successional stages can be used to predict plant community composition in time and space in the pinyon - juniper woodlands.         

Understory seed rain in harvested pinyon-juniper woodlands

Seed rain was collected on six paired tree harvest and undisturbed plots in singleleaf pinyon ( Pinus monophylla )–Utah juniper ( Juniperus osteosperma ) stands. Approximately 14,600 seeds were collected during four years. Seed rain in undisturbed plots was similar to levels in mixed forest communities. Seed rain on harvest plots was similar to disturbed sites and grasslands. Seed rain levels reflect the current successional stage rather than the climax community type for the site. Seed rain increased in numbers and seed production per unit of plant cover following tree removal and especially on transition soil microsites. Only three to four of the plant species present on a site contributed greater than 10% of the total seed rain. Seed rain composition was similar on harvest and undisturbed plots (Jaccard Similarity Index Values = 47% to 67%) and explains in part the rapid reestablishment of predisturbance understory communities.     

Comparative habitat use in a juniper woodland bird community

We compared vegetation structure used by 14 bird species during the 1998 and 1999 breeding seasons to determine what habitat features best accounted for habitat division and community organization in Utah juniper ( Juniperus osteosperma ) woodlands of southwestern Wyoming. Habitat use was quantified by measuring 24 habitat variables in 461 bird-centered quadrats, each 0.04 ha in size. Using discriminant function analysis, we differentiated between habitat used by 14 bird species along 3 habitat dimensions: (1) variation in shrub cover, overstory juniper cover, mature tree density, understory height, and decadent tree density; (2) a gradient composed of elevation and forb cover; and (3) variation in grass cover, tree height, seedling/sapling cover, and bare ground/rock cover. Of 14 species considered, 9 exhibited substantial habitat partitioning: Mourning Dove ( Zenaida macroura ), Bewick's Wren ( Thryomanes bewickii ), Blue-gray Gnatcatcher ( Polioptila caerulea ), Mountain Bluebird ( Sialia currucoides ), Plumbeous Vireo ( Vireo plumbeus ), Green-tailed Towhee ( Pipilo chlorurus ), Brewer's Sparrow ( Spizella breweri ), Dark-eyed Junco ( Junco hyemalis ), and Cassin's Finch ( Carpodacus cassinii ). Our results indicate juniper bird communities of southwestern Wyoming are organized along a 3-dimensional habitat gradient composed of woodland maturity, elevation, and juniper recruitment. Because juniper birds partition habitat along successional and altitudinal gradients, indiscriminate woodland clearing as well as continued fire suppression will alter species composition. Restoration efforts should ensure that all successional stages of juniper woodland are present on the landscape.     

Winter habitats and foods of Blue Grouse in the Sheeprock Mountains, Utah

Winter habitat use and food habits of Blue Grouse ( Dendragapus obscurus ) were studied in an isolated Utah desert mountain range that contained little typical Douglas-fir ( Pseudotsuga menziesii ) winter habitat. Habitat use was concentrated in the Douglas-fir and pinyon ( Pinus edulis )-juniper ( Juniperus spp. ) habitat. Douglas-fir and pinyon pine were the most consumed foods. Other foods that represented >15% of the composition of an individual fecal sample were limber pine ( Pinus flexilis ), mahogany ( Cercocarpus ledifoliu ), juniper, and an Anteunaria-Cirsium type. The breadth in winter diet indicates that Blue Grouse may successfully occupy other habitats when typical winter habitat is scarce.     

Fungi associated with soils collected beneath and between pinyon and juniper canopies in New Mexico

The soil fungal community beneath pinyon ( Pinus edulis Engelm.) and one-seeded juniper ( Juniperus monosperma [Engelm.] Sar.) tree canopies is described and compared with fungi from adjacent interspace soils dominated by blue grama ( Bouteloua gracilis [H. B. K.] Lag.). Significantly higher organic matter contents and fungal propagule levels were found in soils beneath pinyon and juniper trees than in interspace soils. Soils under pinyon and juniper trees contained similar chemical, physical, and biological properties and, consequently, many groups of fungi in common (64% of the species isolated were common to both). In contrast soil fungi in adjacent interspace soils were vastly different from those collected in soils beneath pinyon and juniper canopies (44% and 48% species in common, respectively). Soil fungi that were isolated more often from pinyon-juniper soils than from interspace soils included Absidia sspp., Beauvaria spp., Gliocladium spp., Mucor spp., Penicillium cyclopium , P. fasciculata , P. frequentans , P. restrictum , Thamnidium spp., and Trichoderma spp. Soil fungi that were isolated more often in interspace soils than in pinyon or juniper soils included Aspergillus alutaceus spp., A. fumigatus , some Fusarium spp., Penicillium luteum , and P. talaromyces .     

Fishtail Mesa: a vegetation resurvey of relict area in Grand Canyon National Park, Arizona

Relict sites are geographically isolated areas that are undisturbed by direct and indirect human influences. These sites facilitate long-term ecological monitoring by providing a reference for gauging impacts occurring elsewhere. Knowledge gained through comparing vegetation change on matched relict and proximal disturbed areas can help partition the causes of change into natural and human-produced components. Fishtail Mesa in Grand Canyon National Park is a 439-ha relict site that is inaccessible to domestic livestock. Human visitation is infrequent and irregular, and fires have never been suppressed or managed. In 1958, U.S. Forest Service range scientists conducted a survey of Fishtail Mesa to gather reference data on vegetation, wildlife, and soils. Vegetation sampling was conducted using a method called the ";";elb.";"; We returned to Fishtail Mesa in May 1996 to perform a general vegetation and floristic survey, assess the extent of vegetation change after 38 years, and evaluate the suitability of the site as a location for long-term surveillance of ecological change. Fishtail Mesas vegetation consists primarily of a Pinus edulis (pinyon) and Juniperus osteosperma (Utah juniper) woodland with an Artemisia tridentata (sagebrush) understory, or tree-type (310.9 ha), and an Artemisia and Poa fendleriana (mutton grass) steppe, or shrub-type (127.5 ha). Since 1958 vegetation changes in both shrub- and tree-types have been limited to only a few species. In the shrub-type we detected slight increases from 1958 to 1996 in both Pinus and Juniperus , and reexamination of 1958 photo sites confirmed that Pinus and Juniperus are reoccupying the shrub-type. Artemisia cover declined from 1958 to 1996, whereas Poa increased from near trace amounts in 1958 to moderate cover in 1996. In the tree-type, Poa has increased from 1958 to 1996, while Artemisia , Juniperus , and Pinus showed no apparent change. Other species such as Ephedra torreyana (Torrey joint-fir), Opuntia polyacantha (prickly pear), and Gutierrezia sarothrae (snakeweed) have decreased. Vegetation analysis aided by TWINSPAN revealed that the shrub-type is defined more on the basis of absence of Pinus and Juniperus rather than any special association of differential species with a high preference for this type. We interpret the ";";invasion";"; of the shrub-type by Pinus and Juniperus as a ";";reoccupation.";"; Indirect ordination using DECORANA inferred 2 environmental gradients, a moisture gradient and perhaps a substrate texture gradient, that appeared to influence vegetation distribution on Fishtail Mesa. Fishtail Mesa is a valuable relict area for studying the effects of livestock grazing and prescribed fire. It should be designated a Federal Research Natural Area based on its vegetation communities, size, and protection afforded by its location in Grand Canyon National Park.     

Estimates of the incidence of mistletoes in pinyon-juniper woodlands of the Coconino National Forest, Arizona

The relative incidence of mistletoes found in pinyon-juniper woodlands is estimated for the Coconino National Forest, Arizona, using a roadside survey. Approximately 50% of the pinyon-juniper woodlands surveyed were infested with juniper mistletoes ( Phoradendron juniperinum or P. capitellatum ). In contrast, only about 12% of the areas surveyed were infested with pinyon dwarf mistletoe ( Arceuthobium divaricatum ). In these infested woodlands, 70% with juniper mistletoes and 44% with pinyon dwarf mistletoe were lightly infested. Most areas where pinyon dwarf mistletoe populations were observed (90%) also had juniper mistletoe ( P. juniperinum ) present, but many juniper mistletoe populations observed had no pinyon dwarf mistletoe (50%), although pinyon pine was common at those locations. Therefore, pinyon dwarf mistletoe is frequently co-distributed with juniper mistletoe as has been suggested by other investigators, but juniper mistletoe frequently occurs where there is no pinyon dwarf mistletoe present.     

Long-term vegetation dynamics in a cut western juniper woodland

Western juniper ( Juniperus occidentalis spp. occidentalis Hook.) expansion in the northern Great Basin has reduced shrubsteppe productivity and diversity. Chainsaw cutting of western juniper woodlands is commonly applied to remove tree interference and restore sagebrush plant communities. Studies assessing understory response following cutting have been limited to early successional stages and have not evaluated the effects of western juniper debris on plant succession. Cutting western juniper produces a large amount of debris which is commonly left on site, occupying a significant portion of treated areas. This study evaluated successional dynamics spanning 13 years after western juniper cutting. Four 0.45-ha blocks were selected on Steens Mountain in southeastern Oregon. Western juniper cover averaged 26% and mature tree density averaged 250 trees ? ha –1 . Blocks were cut in late summer 1991. Understory standing crop, cover, and density were compared among 3 locations: old canopy litter mats (canopy), interspace, and area underneath cut western juniper (debris). In the interspace, perennial grasses increased in cover and in standing crop relative to other functional groups. In canopy and debris locations, species composition shifted in the 6th year after cutting as annual grass cover, density, and standing crop increased. However, by 2003, perennial grass biomass was 2 times greater than annual grass biomass in canopy and debris locations. Because annual grasses increased in areas of debris accumulation, managers need to be cognizant of western juniper treatments that create safe sites that are favorable to the establishment of weedy species. Retaining western juniper debris on this site did not increase establishment and growth of perennial grasses compared to the interspace. A shift in perennial grass dominance from Thurber's needlegrass ( Achnatherum thurberianum [Piper] Barkworth) to bottlebrush squirreltail ( Elymus hystrix [Nutt.] Smith) occurred in areas of debris accumulation. Our results demonstrated that long-term vegetation evaluations are necessary to properly assess management activities and disturbance.     

Foliage biomass and cover relationships between tree- and shrub-dominated communities in pinyon-juniper woodlands

Woodlands dominated by singleleaf pinyon ( Pinus monophylla Torr.and Frem.) and Utah ( Juniperus osteosperma [Torr.] Little) cover extensive areas in the Great Basin and Southwest. Both species are aggressive and can nearly eliminate the previous shrub-dominated community. Successional pathways from shrub-dominated communities before tree establishment to the tree-dominated communities that follow are known only for a few specific sites. How site growing conditions affect successional patterns needs further study. We compared the relationship of foliage biomass and percentage of cover between paired shrub-dominated and tree-dominated plots over several sites. Sites studied are from different elevation and topographic conditions on one mountain range. Foliage biomass in shrub-dominated plots had about a three-to-one variation over the range of site conditions sampled. Tree-dominated plots varied by about two-to-one. Cover in shrub-dominated plots had a four-to-one variation; cover in the tree-dominated plots varied by about two-to-one. Total foliage biomass in both tree- and shrub-dominated plots correlated best with the site index of height at 200 years of age. Variation in percentage of cover in both tree and shrub-dominated plots correlated best with elevation. Foliage biomass variation in shrub-dominated plots was proportional to the variation in the paired tree-dominated plots. A similar proportional relationship was present for percentage of cover between paired tree- and shrub-dominated plots. Foliage biomass was more sensitive to topographic differences than to cover. Variation in plant species sampled in the shrub-dominated plots correlated with total foliage biomass of the same plots. Species sampled also correlated with pinyon height at 200 years of age and total foliage biomass in the paired tree-dominated plots.     

Full-glacial shoreline vegetation during the maximum highstand at Owens Lake, California

Owens Valley, California, was markedly different during the Wisconsin glacial stage from what it is today. Alpine glaciers bounded the Sierra Nevada, and pluvial Owens Lake reached highstands and overflowed its natural basin. We analyzed three layers from two packrat middens, dated to ca 23,000-14,500 yr BP, obtained from Haystack Mountain (1155 m) only 10 m above and Juniperus osteosperma ) and single-needle pinyon pine ( Pinus monophylla ) woodland existed at the site. In the layers dated to ca 17,500 and 16,000 yr BP, macrofossils document the presence of Rocky Mountain juniper ( Juniperus scopulorum ), a species that no longer occurs in California. It is suggested that meltwater from the retreating glacial ice inundated the Owens River Lake chain causing pluvial Owens Lake to reach its highstand. This caused an increase in effective moisture, due to high groundwater, allowing the mesophytic Rocky Mountain juniper to exist at the site.     

Human trampling effects on regeneration and age structures of Pinus edulis and Juniperus monosperma

We examined effects of human foot traffic on age structures and densities of seedlings and saplings of Pinus edulis (Colorado pinyon) and Junisperus monosperma (one-seed juniper) in a heavily used urban park, Garden of the Gods, Colorado. Age structures show no stand-destroying disturbances, but they do contain small peaks 85-95 yr ago (minimum age), which have been interpreted as responses to heavy grazing. For Pinus edulis reverse J-shaped age structures indicate a strongly reproducing population, while flat age structures of J. monosperma show low present reproduction. Young trees showed strong preferences for establishing under existing trees and shrubs and not among herbs or on bare soil. Pinus edulis seedling density was reduced by 73% in heavily trampled areas compared to lightly trampled areas. However, there were no differences in density when only the area protected by rocks, shrubs, or trees was considered. This indicates that direct effects such as physical damage and soil erosion kill young trees, and indirect effects, such as lower seed production, do not cause the lower densities in heavily trampled areas. Pinus edulis saplings and J. monosperma seedlings and saplings showed no differences in density across trampling intensities. In heavily trampled areas of Garden of the Gods Park, recent increases in use have apparently reduced Pinus edulis seedling establishment enough that long-term regeneration is threatened. Managers of all pinyon-juniper woodlands must recognize that in areas strongly impacted by foot traffic, and also presumably by similar disturbances such as vehicle traffic, sufficient regeneration likely does not occur to replace trees. The areal extent of severely disturbed areas should be limited, and managers should seek to avoid further degradation of less damaged areas.     

Holocene vegetation and historic grazing impacts at Capitol Reef National Park reconstructed using packrat middens

Mid- to late-Holocene vegetation change from a remote high-desert site was reconstructed using plant macrofossils and pollen from 9 packrat middens ranging from 0 to 5400 yr in age. Presettlement middens consistently contained abundant macrofossils of plant species palatable to large herbivores that are now absent or reduced, such as winterfat ( Ceratoides lanata ) and ricegrass ( Stipa hymenoides ). Macrofossils and pollen of pinyon pine ( Pinus edulis ), sagebrush ( Artemisia spp.), and roundleaf buffaloberry ( Shepherdia rotundifolia ) were recently reduced to their lowest levels for the 5400-yr record. Conversely, species typical of overgrazed range, such as snakeweed ( Gutierrezia sarothrae ), viscid rabbitbrush ( Chrysothamnus visidiflorus ), and Russian thistle ( Salsola sp.), were not recorded prior to the historic introduction of grazing animals. Pollens of Utah juniper ( Juniperus osteosperma ) also increased during the last 200 yr. These records demonstrate that the most sever vegetation changes of the last 5400 yr occurred during the past 200 yr. The nature and timing of these changes suggest that they were primarily caused by the 19th-century open-land sheep and cattle ranching. The reduction of pinyon and sagebrush concurrent with other grazing impacts suggests that effects of cattle grazing at modern stocking levels may be a poor analog for the effects of intense sheep grazing during drought.     

Host-based morphometric differentiation in three Cinara species (Insecta: Hemiptera: Aphididae) feeding on Pinus edulis and P. monophylla

Cinara edulis (Wilson), C. terminalis (Gillette and Palmer), and C. wahtolca Hottes were all larger when feeding on Pinus monophylla Torr. & Frem. than when feeding on P. edulis Engelm. Almost all nonsetal morphometric characters were longer in aphids on the former of these pinyon pines. Although mouthpart characters also followed this pattern of size in C. edulis and C. wahtolca , rostrum length showed the opposite pattern in C. terminalis and was shorter when on P. monophylla . This reversal in size pattern suggests that mouthpart size can be independent of overall aphid size. Principal components analyses corroborate the univariate statistics and we discuss the contribution of various characters to the principal components. We compare environmental induction and environmental selection as explanations for the observed size differences and discuss the taxonomic implications of our results.     

Rodent weights in modified pinyon-juniper woodlands of southwestern New Mexico

Changing habitat structure in pinyon ( Pinus edulis )—one-seed juniper ( Juniperus monosperma ) stands by (1) pushing trees down with a bulldozer and leaving them in place, (2) pushing, then piling and burning slash, or (3)thinning to a spacing of 6. 1 m and leaving slash did not affect weights of individuals of nine rodent species. Previous studies have shown that habitat modifications influence kinds of species and numbers of individuals, but changes in total rodent biomass are a function of sizes of different species occupying different habitats, not changes in weights of individuals.     

Late Pleistocene-early Holocene history of coniferous woodlands in the Lucerne Valley region, Mohave Desert, California

The composition of four radiocarbon-dated, late Pleistocene woodrat middens is reported and analyzed. A date of 11,850 ±550 BP records the first reported macrofossil occurrence in this region of late Pleistocene Pinus monophylla-Juniperus osteosperma woodlands. A 7,800 ±350 BP date documents the most recent J. osteosperma woodlands in this presently coniferless desert area, while a date of 12,100 ±400 BP is the oldest record of juniper woodlands among the four middens. Other juniper and creosote bush desert flora radiocarbon dates along with six pollen profiles were obtained. The research suggests that as recently as 7,800 BP this part of the Mohave Desert was subject to a cooler, moister climate than at present, and that the aboriginal food resources of pinyon seeds and juniper berries were probably available to early prehistoric man in this area.     

Understory patterns in cut western juniper ( Juniperus occidentalis spp. occidentalis Hook.) woodlands

Western juniper ( Juniperus occidentalis spp. occidentalis ) has rapidly expanded into shrub steppe communities in the intermountain Northwest during the past 120 yr. Cutting juniper is a management tool used to restore shrub steppe communities. Response of the understory after cutting is strongly influenced by plant species composition existing prior to treatment. This study assessed distribution patterns of understory plants over 2 growing seasons after tree cutting in a western juniper woodland. Cover, density, and diversity of understory species were compared among 3 locations: interspaces, duff zones (previously under tree canopies), and debris zones (beneath cut trees). Plant cover density increased in all zones following tree cutting. Understory vegetation in cut woodlands exhibited strong zonal distribution. Cover and density of Poa sandbergii and Sitanion hystrix and canopy cover of annual forbs were greatest in duff zones ( P P < 0.05). Debris zones tended to have the lowest overall understory cover and plant density values. Under juniper debris many species common to interspaces were reduced in density, although plants that survived or established beneath debris grew larger than their counterparts in interspaces. Species increased in density and cover under debris were plants characteristic of duff zones and whose seeds are typically wind dispersed.     

Species diversity and habitat complexity: does vegetation organize vertebrate communites in the Great Basin?

In this study, we have examined the effect of vegetation structure on the three major vertebrate taxa in Great Basin habitats of southwestern Utah. The effect of increasing vegetation heterogeneity, both horizontally and vertically, on the diversities of lizards, rodents, and postbreeding birds was investigated. We found no statistically significant relationship between diversity of all animal taxa and horizontal vegetation heterogeneity, although lizard diversity tended to decrease with increasing heterogeneity and rodent diversity tended to increase. Bird species diversity was positively correlated with vertical habitat heterogeneity. Abundances were highest for rodents in pinyon/juniper habitat and highest for lizards and birds in areas with the highest grass cover. Species richness was highest in sagebrush habitat for rodents but highest for lizards and birds in pinyon/juniper. Evenness values were relatively similar and high for birds and rodents and were relatively high for lizards in all habitats except for pinyon/juniper, which had an evenness value of 0.38. For rodents and lizards, abundance was significantly correlated with the index for horizontal habitat heterogeneity. After logarithmic transformation, abundance of lizards was positively correlated with increasing vegetation complexity. Combined abundance of lizards and rodents was also positively correlated with vegetation complexity. Rodent and lizard abundances, however, were affected by different aspects of the habitat. After logarithmic transformation, lizard abundances increased significantly with increasing grass cover, whereas rodent abundances increased significantly with increasing shrub cover.     

Tree densities on pinyon-juniper woodland sites in Nevada and California

The densities of sing le leaf pinyon and Utah juniper trees in four diameter classes (1&ndash;9, 10&ndash;19, 20&ndash;29, and &ge; 30 cm) were measured on 522 plots of 1/10 ha each throughout the Great Basin. Density distribution patterns of pinyon and juniper varied with aspect, elevation, and eastern (EGB) versus western Great Basin (WGB) locations. On most locations north and, to a lesser extent, west slopes supported higher densities of pinyon than south and east slopes, with high relative densities of small diameter trees on north slopes and large diameter trees on west slopes. Pinyon densities were higher on EGB than on WGB sites and on higher elevation than on lower elevation sites. Juniper densities were higher on EGB than on WGB sites and on lower elevation than on higher elevation sites. Juniper densities on low-elevation WGB sites were higher on south and west aspects than on north and east, with higher relative densities in the 20&ndash;29 cm diameter class than in other diameter classes. On low elevation EGB sites, east and south slopes supported higher juniper densities than did north and west slopes, with comparatively higher relative densities in the 10&ndash;19 cm diameter class. Differences in relative densities between diameter classes were not significant among aspects on high elevation sites.     

Herbaceous succession after burning of cut western juniper trees

The expansion of western juniper ( Juniperus occidentalis spp. occidentalis Hook.) in the northern Great Basin has resulted in the wide-scale conversion of sagebrush-steppe communities to juniper woodlands. Prescribed fire and mechanical cutting are the 2 main methods used to remove juniper and restore sagebrush steppe. Mechanical treatments commonly leave cut juniper on site. Disadvantages of leaving cut juniper are the increased fuel hazard and the potential for increased establishment and growth of invasive species. This study evaluated the response of herbaceous plants to winter burning of cut western juniper. Vegetation response was compared among 2 burning treatments (burning trees the first winter after cutting and burning the second winter after cutting), a control (cut-unburned juniper), and the interspace between cut trees. To minimize fire impacts to herbaceous perennials, cut trees were burned in the winter when soils and ground litter were frozen and/or soils were at field capacity. Only felled trees were burned, as fire did not carry into interspaces or litter mats around western juniper stumps. We hypothesized that winter season burning would increase herbaceous perennials and would reduce cheatgrass establishment when compared to the cut-unburned control. After 10 years, total herbaceous and perennial grass cover was 1.5- to 2-fold greater, respectively, in burned treatments compared to cut-unburned controls. Perennial grass density was 60% greater in the burned treatments than in the cut-unburned treatment and the interspace. Cheatgrass cover was twice as great in the control than in the 2 burn treatments and the interspace. We concluded that burning cut western juniper when soils were wet and frozen in winter enhanced community recovery of native perennials compared to leaving cut juniper unburned.     

Habitat of three rare species of small mammals in juniper woodlands of southwestern Wyoming

Southwestern Wyoming constitutes the northern limit of the ranges of the cliff chipmunk ( Tamias dorsalis ), pinyon mouse ( Peromyscus truei ), and canyon mouse ( P. crinitus ). In addition to trying to determine their presence in the region, we wanted to identify habitat characteristics commonly used by each of these species. We used Sherman live-traps to sample 14 sites representing 2 distinct habitat types in 1998 and 1999: juniper-rocky slopes and juniper cliffs. Seventeen habitat characteristics were measured at capture locations for each species and compared with randomly located points. Best subsets multiple logistic regression was used to construct models that distinguish between used and available habitat for each species. The cliff chipmunk occurred in both rocky slopes and cliffs. The pinyon mouse was also captured in rocky slopes and cliffs and was most often captured in locations in the interior of the juniper woodland with high tree canopy cover, high forb cover, and low density of rock outcrops. The canyon mouse was captured only in cliffs at sites consisting of high forb cover, high rock cover, and high tree density.