Response of understory species to changes in ponderosa pine stocking levels in the Black Hills

The objective of this study was to test the hypothesis that there are no differences in understory production, by species, due to stocking levels of Pinus ponderosa (ponderosa pine). Understory production was estimated, by species, on 3 replicates each of 8 growing stock levels, ranging from clearcuts to unthinned stands, in both sapling- and pole-sized pine stands (48 plots) over 3 nonconsecutive years. All stands were approximately 70 yr old when thinning treatments were applied. Production of many herbaceous species, especially Agropyron spp. (wheatgrasses) and Carex spp. (sedges), declined as growing stock levels (measured in terms of basal area) of ponderosa pine increased. While trends in total production were similar, there were specific differences between sapling and pole stands. Sedges and Oryzopsis asperfolia (roughleaf ricegrass) produced more in sapling stands, whereas Danthonia intermedia (timber oatgrass) was more abundant in pole stands. Shrub production, dominated by Acrtostaphylos uva-ursi (bearberry), was relatively consistent across all stocking levels except unthinned. Although the total number of species declined as pine basal area increased, a few species, such as Linnaea borealis (twinflower) and Shepherdia canadensis (buffaloberry), were found only under relatively dense pine canopies. While floristic species richness was greater at lower stocking levels of ponderosa pine, the total number of species would be greater if all stocking levels were present.     

Influence of ponderosa pine overstory on forage quality in the Black Hills, South Dakota

Forage quality was assessed in pole and sapling ponderosa pine ( Pinus ponderosa ) stands growing at five stocking levels—0, 5, 14, 23, and unthinned (which approximated 40 m 2 /ha basal area)—in the Black Hills of South Dakota. Crude protein, acid detergent fiber, acid detergent lignin, ash, calcium, and phosphorus were evaluated for cream peavine ( Lathyrus ochroleucus ), bearberry ( Arctostaphylos uva-ursi ), and timber oatgrass ( Danthonia intermedia ). Acid detergent fiber, acid detergent lignin, and ash showed some significant differences among growing stock levels for cream peavine growing in sapling stands. Crude protein content of timber oatgrass was different among growing stock levels in pole stands. In all cases, however, no trends or patterns relative to stocking levels were evident. When understory forage quality was compared within pole and sapling stands, only 4 of 18 possible comparisons were significant. In general, modifying the overstory of ponderosa pine in the Black Hills by clearcutting or thinning did not result in predictable changes in nutritional values of selected understory species.     

Winter habitat selection patterns of Merriam's turkeys in the southern Black Hills, South Dakota

In northern areas of their expanded range, information on Merriam's turkeys ( Meleagris gallopavo merriami ) is lacking, specifically pertaining to wintering behavior and factors associated with winter habitat selection. Forest managers need detailed quantification of the effects of logging and other management practices on wintering habitats needed by Wild Turkeys and other wildlife. Therefore, we examined winter habitat selection patterns within ponderosa pine ( Pinus ponderosa ) forests and determined factors associated with use of farmsteads by Merriam's turkeys in the southern Black Hills, South Dakota. We radio-marked 86 female Merriam's turkeys (70 adults and 16 yearlings) and monitored them during winter (1 December–31 March), 2001–2004. Female Wild Turkeys used recently burned pine forest less than expected but selected farmsteads and stands of mature ponderosa pine ( 22.9 cm diameter at breast height [DBH] trees) for foraging sites. Within forests, female Wild Turkeys selected foraging sites with less understory vegetation and visual obstruction, and larger-diameter ponderosa pine. Ponderosa pine seed abundance varied among years, and pine seeds were most abundant in stands of 30–35 cm DBH with basal area of 22–28 m2 ? ha–1. Abundance of pine seeds may have influenced use of farmsteads by Wild Turkeys, more so than ambient temperatures or snow depth. In the southern Black Hills, management should emphasize open- to mid-canopy and mature-structural-stage pine stands, where seed production was greatest. During winters when mast from pine is unavailable, farmsteads likely provide nutritional supplementation and may be important for maintaining Merriam's turkey populations.     

Characteristics of white-tailed deer fawn beds, Black Hills, South Dakota

Forty-two white-tailed deer fawns ( Odocuileus virginianus dakotensis ) were captured and fitted with radio transmitters and observed from June through September 1991 and 1992 to determine diurnal bed site use in the Black Hills of South Dakota. Fawns were monitored biweekly during daylight hours and 259 bed sites were located. In addition, 301 random sites were measured for comparison. Of 31 habitat variables measured, 8 were significant to determine use by fawns for a bed site when compared with random sites. Sites used by fawns were in relatively open stands of ponderosa pine ( Pinus ponderosa ) with mean basal area of approximately 11 m 2 /ha compared to 16 m 2 /ha in random sites. Fawn bed sites had greater mean vegetation cover, which ranged from 28.1% to 36.0%, compared with 19.9% and 33.8% at random sites in 1991 and 1992, respectively. Mean vegetation height was 101 cm at bed sites compared to 75 cm at random sites. Current timber harvest standards for stocking levels of pine range from 14 m 2 /ha to 18 2 /ha in the Black Hills, which are similar to our random sites. These levels preclude adequate development of understory characteristics used by white-tailed deer fawns for bed sites.     

Understory vegetation in fully stocked pinyon-juniper stands

Ten fully stocked pinyon-juniper stands contained a total of 73 species in the understory, but the number of understory species in any one stand was moderately low (mean = 20). On each stand, species of at least five different plant groups were present in the understory (shrub, perennial grass, perennial forb, annual grass, or annual forb). A perennial grass, Sandberg bluegrass ( Poa sandbergii ), and a group of annual forbs with relatively high cover and constancy among stands appeared best adapted to coexist with the pinyon-juniper overstory. The proportion of total plant cover was greater on tree-associated microsites (duff and transition) than in the interspace between trees because of the greater surface area of the former in most stands. The transition microsite was the most favorable for understory species and provided understory cover in disproportionately greater amounts than the area it occupied.     

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.     

Impacts of nonnative plant species on production and diversity in the front range of Colorado

Nonnative plant species are considered one of the greatest threats to biodiversity, yet we still are unable to predict how production and diversity of a community will change once a species has invaded. Ponderosa pine woodlands in the Front Range of Colorado are ideal for studying the impacts of nonnative plants on production and species richness. We selected 5 sites along the northern Front Range with varying proportions of nonnative and native species and compared understory production and species richness along the gradient of nonnative species dominance. Total species production was positively and significantly related to total species richness, and total species production increased significantly with increasing nonnative species richness. There was a negative relationship between native and nonnative species production, and there was no relationship between nonnative species richness and native species richness. This study demonstrates the complex nature of species richness and productivity relationships and should serve as a starting point for future research in which a variety of other variables are considered.     

Dynamic responses of a British Columbian forest-grassland interface to prescribed burning

Ponderosa pine Pinus ponderosa and Douglas-fir Pseudotsuga menziesii forests in the Interior of British Columbia, Canada, are adjacent to grasslands. Forest ingrowth and tree encroachment, mainly due to fire suppression, represent threats to both forest and ranching industries in the region. The use of prescribed burning for ecological restoration is being practiced, but the associated ecosystem effects of restoration treatments have been little studied in the region. We used a randomized complete block design in a prescribed burning experiment. Tree survival and the responses of understory vegetation to burning were monitored for 3 years. The transect method along with crown projection areas (onto the ground) were used in comparisons between areas inside and outside of the burned area. Fire was effective in eliminating small ponderosa pine (dbh Artemisia tridentata ssp. wyomingensis was observed in grassland sites, while reduction in rabbitbrush Chrysothamnus nauseosus in the forest was observed. Data trends indicate that 3 years after burning, total biomass and forb biomass increased in grasslands, but graminoid biomass in forests was reduced and total understory biomass was not affected by burning. Burning also reduced the shrub component in these ecosystems. While aboveground biomass production may be enhanced by burning in grasslands, the impact of burning on forest understory was minimal and burning may result in reduction of graminoids. Therefore, burning can be used to control tree encroachment and forest ingrowth in this region. Management plans must incorporate topography, species diversity, and tree survival to target areas that are most susceptible to tree encroachment and to achieve desired results. Extended monitoring is necessary to determine the long-term effects of burning on species diversity in and productivity of these ecosystems.     

Effects of Douglas-fir beetle (Coleoptera: Scolytidae) infestations on forest overstory and understory conditions in western Wyoming

Douglas-fir beetle ( Dendroctonus pseudotsugae Hopk.) infestations frequently result from disturbance events that create large volumes of weakened Douglas-fir trees, Pseudotsuga menziesii (Mirb.) Franco. Previous research has focused on determining susceptibility of forest stands to Douglas-fir beetle and predicting the amount of tree mortality from Douglas-fir beetle infestations following disturbance events. Little work has been done on consequent changes in the forest overstory and understory. In the early 1990s, populations of Douglas-fir beetle increased in fire-scorched trees, subsequently infesting undamaged neighboring stands in the Rocky Mountains of western Wyoming, USA. In 1999 transect sampling and 25 pairs of previously infested and uninfested plots were used to quantify changes in forest stand conditions and ensuing responses in the understory caused by Douglas-fir beetle infestations. Significant effects of the Douglas-fir beetle infestation comprised 3 general categories: (1) overstory effects: basal area was reduced by 40%-70%, average tree diameter decreased by 8%-40%, and the Douglas-fir component of the overstory decreased by more than 12%; (2) regeneration effects: conifer seedling regeneration increased nearly fourfold in infested plots and 90% of the regeneration was Douglas-fir; (3) understory effects: understory vegetation (forbs, grass, and shrubs) had a threefold increase in infested compared with uninfested plots. In addition, basal area of Douglas-fir killed by the Douglas-fir beetle was significantly correlated with initial Douglas-fir basal area and percentage of Douglas-fir, but not with stand density index, tree diameter, or trees per hectare. Significant inverse relationships also were found between post-infestation basal area and abundance of forbs, grass, and shrubs, and understory height. Thus, we found that Douglas-fir beetle infestations cause significant short-term effects in both the overstory and understory and contribute to an altered mosaic in forest structure.     

Selection of dwarf mistletoe-infected ponderosa pines by Ips species (Coleoptera, Scolytidae) in northern Arizona

Following an Ips bark beetle outbreak in 2002, mortality of ponderosa pine ( Pinus ponderosa Douglas ex C. Lawson) was evaluated in 2 study areas infested with southwestern dwarf mistletoe ( Arceuthobium vaginatum [Willd.] Presl subsp. cryptopodum [Engelm.] Hawksw. & Wiens) in the Coconino and Tonto National Forests, Arizona. A pairwise comparison of dwarf mistletoe ratings for live and dead ponderosa pines was conducted to determine whether dead ponderosa pines had higher dwarf mistletoe ratings than pines that were not attacked. In both study areas, dead ponderosa pines had significantly higher dwarf mistletoe ratings, indicating an association between the severity of dwarf mistletoe infection and susceptibility to attack by Ips spp. We suggest that the probability of ponderosa pine mortality is greater in stands severely infested with southwestern dwarf mistletoe in northern Arizona.     

Density, distribution, and habitat of Flammulated Owls in Idaho

From 1990 to 1992 we surveyed for Flammulated Owls ( Otus flammeolus ) in 3 areas in Idaho: Salmon National Forest (SNF), Payette National Forest and adjacent Hells Canyon National Recreation Area (PNF-HCNRA), and Nez Perce National Forest (NPNF). We also collected and summarized information on all historic and modern records of Flammulated Owls in Idaho. Flammulated Owls were detected on 65% of 68 routes (2-16 km in length) surveyed at densities ranging from 0.04 to 1.25 singing males/40 ha. Owls were detected on survey routes as early as 10 May and as late as 23 July. Mean percent canopy cover estimated at owl locations on the PNF-HCNRA and NPNF study sites ranged from 52% to 64%, while shrub cover ranged from 16% to 21% and ground cover was 39% to 49%. Our surveys and summary of distributional records indicated that Flammulated Owls occur throughout the montane forests of Idaho in old or mature stands of open ponderosa pine ( Pinus ponderosa ), Douglas-fir ( Pseudotsuga menziesii ), and stands co-dominated by those 2 species. Fire suppression and timber harvest activity in ponderosa pine forests represent 2 main threats to the species' future security in Idaho. More research on the effects of various silvicultural treatments on Flammulated Owl populations is warranted.     

A comparison of the spherical densiometer and ocular methods of estimating canopy cover

Percent tree canopy cover in a ponderosa pine ( Pinus ponderosa ) forest of northeastern California was estimated by the point intercept spherical densiometer and ocular methods. Estimates derived by the two methods were similar (P > .05). The ocular method is recommended when understory vegetation is tall or clumped instead of randomly distributed, or if available field time limits sample size.     

Forest health impacts of bark beetles, dwarf mistletoe, and blister rust in a Lake Tahoe Basin mixed conifer stand

Interactions between forest health variables and mensurational characteristics in an uneven-aged eastern Sierra Nevada mixed conifer stand were examined. The stand was located in the Lake Tahoe Basin on a site featuring a coarsely textured granitic soil and numerous rock outcrops. Its composition was dominated by California white fir ( Abies concolor var. lowiana [Gord.] Lemm.), with Jeffrey pine ( Pinus jeffreyi Grev. & Balf.) and sugar pine ( Pinus lambertiana Dougl.) less prominent and incense-cedar ( Libocedrus decurrens Torr.) and mountain alder ( Alnus tenuifolia Nutt.) the most minor constituents. The majority of saplings and seedlings were white fir. The stand exhibited no evidence that its development had been influenced by fire and, overall, it consisted of numerous small trees accruing little radial growth. Nearly one-quarter of all standing stems pole size or larger were dead, with mortality concentrated in white fir. Forestfloor fuel accumulations were excessive, and coarse debris was especially prominent. A fir engraver beetle ( Scolytus ventralis LeConte) epidemic in white fir contrasted against apparent endemic population levels of the Jeffrey pine ( Dendroctonus jeffreyi Hopkins) and red turpentine ( Dendroctonus valens LeConte) beetles in Jeffrey pine and of the mountain pine beetle ( Dendroctonus ponderosae Hopkins) in sugar pine. The severity of fir engraver attack on white fir was weakly related to overall tree size and to the proportion of composition consisting of this host species, while in Jeffrey pine and sugar pine, bark beetle attacks were strongly correlated with the individual proportions of these 2 hosts. Across all species, basal area explained a substantial proportion of the variation in overall attack severity. We found light infestations of true fir dwarf mistletoe ( Arceuthobium abietinum Engelm. ex Munz f. sp. concoloris ) in white fir and western dwarf mistletoe ( Arceuthobium campylopodum Engelm.) in Jeffrey pine, plus an early stage of infection by the white pine blister rust ( Cronartium ribicola J.C. Fischer) in sugar pine. Collectively, this case study characterized and quantified many of the conditions, symptoms, and causative agents inherent in a decadent mixed conifer stand in the eastern Sierra Nevada.     

Ponderosa pine conelet and cone mortality in central Arizona

Ponderosa pine conelets in 10 stands on the Coconino and Kaibab national forests were observed periodically from July 1982 until they matured in September 1983. Abortion, ponderosa pine cone beetles ( Conophthorus ponderosae Hopkins), and ponderosa pine coneworms ( Dioryctria sp., probably Auranticella [Grote]) were the significant mortality factors. Cattle, tip moths, and squirrels rarely destroyed conelets or cones.     

Effects of dwarf mistletoe on spruce in the White Mountains, Arizona

Mortality of spruce in mixed conifer stands moderately to heavily infested with western spruce dwarf mistletoe was two to five times greater than in healthy stands in the White Mountains, Arizona. Ten-year volume growth loss for heavily infected spruce trees ranged from 25% to 40%. Estimates of growth loss for spruce on a stand basis ranged from 10% to 20% in heavily infested stands. Because western spruce dwarf mistletoe is prevalent in the White Mountains and causes increased mortality and reduced growth, its control should be included in management of mixed conifer stands there.     

Native plants dominate understory vegetation following ponderosa pine forest restoration treatments

Dense ponderosa pine forests in the southwestern United States inhibit understory production and diversity and are susceptible to high-severity wildfire. Restoration treatments involving overstory thinning and prescribed burning are being implemented to increase understory productivity and diversity and to reduce the risk of severe wildfire. However, disturbances associated with treatments may favor invasion of nonnative species, and the severity of the disturbance may be related to the level of nonnative species establishment. We examined understory community composition, species richness, and plant cover responses to 3 stand-scale replicates of 4 different tree-thinning intensities. Restoration treatments altered the composition of the understory community regardless of thinning intensity. Understory richness and cover were highly variable among experimental blocks, but we observed strong trends of increasing richness and cover in the treated stands. Immediately following restoration treatments, nonnative species cover comprised 6% of the total cover where treatment-induced disturbances were the greatest. However, the initial increase in nonnative species did not persist and was reduced by half 6 years after treatment. Plant community composition was still in flux by the sixth year after treatment, indicating that continued monitoring is necessary for evaluating whether restoration targets are maintained over time. Los densos bosques de pino ponderosa en el suroeste de los E.U.A. inhiben la producción y diversidad del sotobosque y son propensos a incendios severos. El raleo del dosel y la quema controlada se están implementando como tratamientos de restauración para incrementar la productividad y diversidad del sotobosque y para reducir el peligro de incendios severos. Sin embargo, las perturbaciones asociadas con estos tratamientos podrían favorecer la invasión por especies no nativas, y la severidad de la perturbación puede estar relacionada con el nivel de establecimiento de estas especies. Examinamos la reacción del sotobosque con respecto a la composición de sus comunidades, a la riqueza de especies y a la cobertura de la vegetación, a tres réplicas a nivel de rodal de cuatro distintas intensidades de raleo. Los tratamientos de restauración cambiaron la composición de la comunidad del sotobosque independientemente de la intensidad del raleo. La riqueza y la cobertura del sotobosque variaron mucho entre las áreas estudiadas, pero observamos marcadas tendencias de mayor riqueza y cobertura en los rodales que recibieron el tratamiento. Inmediatamente después de los tratamientos de restauración, la cobertura de especies invasoras constituía el 6% de la cobertura total donde las perturbaciones producidas por los tratamientos fueron más grandes. No obstante, el aumento inicial en la cobertura de especies invasoras no persistió, y se redujo a la mitad en un lapso de seis años después del tratamiento. La composición de las comunidades de plantas aun seguía cambiando en el sexto año después del tratamiento, lo cual indica que será preciso el monitoreo continuo para determinar si se lograron las metas de restauración.     

Vegetation, soils, and hydrogeomorphology of riparian patch types of a dryland river

From a landscape perspective, riparian corridors can be viewed as mosaics of vegetation patches. We delineated 10 patch types within the floodplain of the San Pedro River (Arizona) on the basis of physiognomy, dominant overstory species, and tree size class; and we assessed differences in hydrogeomorphology, vegetation structure, plant species richness, and soil chemistry and texture. Patches of tamarisk ( Tamarix ), an introduced species, fell within the continuum of variation shown by other patch types in the landscape mosaic. Among the tree-dominated types, cottonwood-willow ( Populus-Salix ) and tamarisk patches were inundated more frequently than mesquite ( Prosopis ) patches, while cottonwood-willow patches had shallower groundwater than tamarisk or mesquite patches. Due to the wetter conditions, cottonwood-willow patches had a high relative abundance of wetland and exotic species in the understory. Tamarisk patches and wet shrublands ( Baccharis salicifolia—Salix exigua ) had high woody stem densities while cottonwood-willow patches had dense canopy cover. In association with differences in canopy cover, cottonwood-willow patches had low herbaceous species richness but high woody species richness, while tamarisk patches had high herbaceous and low woody species richness. Soil electrical conductivity, silt content, organic matter content, and available phosphorus increased from young to old stands of both tamarisk and cottonwood-willow, often resulting in greater differences between patches of different size/age class than between patches with different dominant species. Surface soil salinity (electrical conductivity) was low in all patches, including those dominated by tamarisk. Nitrate was abundant in soils of tamarisk patches (perhaps reflecting their high clay content) and wet shrubland patches. Dry shrublands ( Hymenoclea-Ericameria ) and wet shrublands were similar to young forest patches in having coarse soils with little organic matter.     

Relationship between environmental and vegetational parameters for understory and open-area communities

Ten individuals from each of four tree species were selected, and their associated understory and adjacent open-area communities were sampled for both environmental and vegetational parameters, including light intensity, pH, litter depth, soil depth, and percentages of exposed rock, litter cover, living cover, shrubs, forbs, grasses, and annuals. The four tree species were ponderosa pine, Rocky Mountain juniper, Gambel oak, and snowbrush ceanothus. The study site was in the lower Uinta Mountains about 10 miles east of Kamas, Utah. Correlations among the various biotic and abiotic parameters were examined. The interplay of these factors in differentiating the understory and open-area communities is discussed.       

Effects of exotic species on Yellowstone's grizzly bears

Humans have affected grizzly bears ( Ursus arctos horribilis ) by direct mortality, competition for space and resources, and introduction of exotic species. Exotic organisms that have affected grizzly bears in the Greater Yellowstone Area include common dandelion ( Taraxacum officinale ), nonnative clovers ( Trifolium spp.), domesticated livestock, bovine brucellosis ( Brucella abortus ), lake trout ( Salvelinus namaycush ), and white pine blister rust ( Cronartium ribicola ). Some bears consume substantial amounts of dandelion and clover. However, these exotic foods provide little digested energy compared to higher-quality bear foods. Domestic livestock are of greater energetic value, but use of this food by bears often leads to conflicts with humans and subsequent increases in bear mortality. Lake trout, blister rust, and brucellosis diminish grizzly bears foods. Lake trout prey on native cutthroat trout ( Oncorhynchus clarkii ) in Yellowstone Lake; white pine blister rust has the potential to destroy native whitebark pine ( Pinus albicaulis ) stands; and management response to bovine brucellosis, a disease found in the Yellowstone bison ( Bison bison ) and elk ( Cervus elaphus ), could reduce populations of these 2 species. Exotic species will likely cause more harm than good for Yellowstone grizzly bears. Managers have few options to mitigate or contain the impacts of exotics on Yellowstones grizzly bears. Moreover, their potential negative impacts have only begun to unfold. Exotic species may lead to the loss of substantial highquality grizzly bear foods, including much of the bison, trout, and pine seeds that Yellowstone grizzly bears currently depend upon.     

Fire frequency and the vegetative mosaic of a spruce-fir forest in northern Utah

Fire scar and vegetative analysis were used to construct a fire history for the Engelmann spruce/subalpine fir ( Picea engelmannii/Abies lasciocarpa ) vegetation type of Utah State University (USU) T. W. Daniel Experimental Forest. Three distinct periods of fire frequency were established-presettlement (1700-1855), settlement (1856-1909), and suppression (1910-1990). Mean fire interval (MFI) decreased during the settlement period and greatly increased during the suppression era. The difference was attributed to the influx of ignition sources during the settlement of nearby Cache Valley, located 40 km to the west. Logging and livestock grazing appear to have led to the reduced MFI, which in turn worked as a factor to create the vegetative mosaic now observed on the study area. The increase in MFI during the suppression ear permitted the advancement of shade-tolerant species in the understory of the shade-intolerant lodgepole pine ( Pinus contorta var. latifolia ) and quaking aspen ( Populus tremuloides ). Continued suppression of disturbance from wildfire will allow the lodgepole pine cover type, which experience the lowest MFI during the settlement period, to be further invaded by shade-intolerant species, decreasing spatial stand diversity and increasing the risk of more intense fires.