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.     

Production, losses, and germination of Ceanothus fendleri seeds in an Arizona ponderosa pine forest

I quantified seed production and ovule losses for Ceanothus fendleri Gray (Fendler ceanothus) plants protected from large ungulate herbivores in a ponderosa pine ( Pinus ponderosa [Laws]) forest of northern Arizona. I also tested seed germination responses to cold stratification and heat treatments in the laboratory. Fruit production on fecund stems ranged from 7.4 to 38.2 fruits per stem, which equated to 22.2-118.2 potential seeds based on 3 ovules per fruit. Stems that produced fruit were significantly large relative to their expected sizes. Predispersal ovule losses ranged from 70.7% to 91.4% across the 2 years studied. A chalcidoid seed parasite ( Eurytoma squamosa Bugbee) consumed 11%-28% of the total number of seeds produced. Postdispersal seed predation varied from 0% to 24% and was significantly affected by forest floor substrate in 1 study year. Cumulative ovule losses were estimated to be 71%-92%. Cold stratification did not significantly affect seed germination, and exposure to 90°C resulted in the highest germination percentage. Both dormant and nondormant seeds suggested a bet-hedging life history strategy. This study provides basic ecological information important for management of ponderosa pine forest and nursery production of C. fendleri .     

A disjunct ponderosa pine stand in southeastern Oregon

An isolated stand of ponderosa pine ( Pinus ponderosa ) is surviving on an extremely harsh site in southeastern Oregon. Seed production is low because of insects, primarily pine coneworm ( Dioryctria auranticella ), feeding in developing cones. Seedling establishment is infrequent and difficult because of drought and coarse, rocky soils. A rock-mulch soil surface probably reduces interspecific competition. Because stand size is small (     

A seed chalcid ( Eurytoma squamosa Bugbee) parasitizes buckbrush ( Ceanothus fendleri Gray) seeds in a ponderosa pine forest of Arizona

Predispersal seed parasitism rates were quantified for buckbrush ( Ceanothus fendleri Gray) in 3 Arizona ponderosa pine ( Pinus ponderosa Laws.) forest units that had been thinned for ecological restoration objectives. The chalcidoid wasp Eurytoma squamosa Bugbee (Eurytomidae) was responsible for 35% of total seed loss in a single year. These findings represent an expansion of the known range and host list for E. squamosa and increase our understanding of factors that may constrain regeneration of C. fendleri in Southwest ponderosa pine forests.     

Pisolithus Tinctorius , a Gasteromycete, Assiciated with Jeffrey and Sierra Lodgepole Pine on Acid Mine Spoils in the Sierra Nevada

Basidiocarps of Pisolithus tinctorius , a gasteromycetous fungus adapted to harsh sites, were observed in association with Jeffrey and Sierra Lodgepole pine on acid mine spoils in northeastern California. Subterranean mycelial strands were traced from these basidiocarps to the root systems of the two pine species, which had ectomycorrhizae characteristics of those formed by this fungus in symbiotic relationships with conifer hosts.     

Behavioral activities and breeding success of Willow Flycatchers in the Sierra Nevada

Observing survival and how individuals allocate time can provide insight into a species' ability to tolerate environmental constraints. We studied the Willow Flycatcher ( Empidonax trallii ) in the Sierra Nevada to determine if there were behavioral differences between pairs that successfully produced offspring and those that did not. This information will advance understanding of why these birds are declining in the Sierra Nevada and contribute to recommendations that may help to conserve them. We studied birds in 13 meadows in 2000 and 2001 using continuous focal-animal observations. Of the 43 territories we observed, 11 were occupied by males who never paired with a female, leaving 32 pairs for analysis. Of the 32 pairs, 13 were successful at breeding on their 1st attempt, and 9 pairs failed at their initial try but were successful on their 2nd breeding attempt. Throughout the breeding season, Willow Flycatchers spent 77%-78% of the day loafing during territory establishment and nest building, and loafing reached a low of 49% of the time budget during the nestling stage. Unsuccessful pairs spent on average 34% more time perching than their successful counterparts, while successful pairs spent on average 48% more of their time on the nest than unsuccessful pairs. Willow Flycatchers doubled the time spent foraging during the nestling phase because they had to meet the daily intake requirements for their young and themselves. Our results suggest that birds that spent more time on the nest and less time vocalizing had a significantly higher probability of successfully producing young because they were able to protect nests from predators, nest parasites, and inclement weather.     

Spring denitrification rates in soils of four eastside Sierra Nevada plant communities

Denitrification rates in soils of four subalpine plant communities in the Sierra Nevada were determined by the acetylene blockage method. The study area included riparian, meadow, forest, and barren sites. Data were collected during dawn-to-dusk measurements in April 1987. Soil atmosphere samples were analyzed for N 2 O content using gas chromatography. Generally, temporal variability in denitrification rate within each plant community was insubstantial. Denitrification rate and soil temperature were found to be significantly correlated only in the riparian and barren sites. Of the four communities, the riparian site was found to have the lowest rate of denitrification overall. However, differences among sites in denitrification rate could not be conclusively attributed to variation in soil temperature, moisture, organic matter, total C and N, C:N ratio, NO 3 - N, or pH.     

Number and condition of seeds in ponderosa pine cones in central Arizona

Ponderosa pine cones from 10 areas in Arizona were collected prior to natural seed dispersal and dissected to determine the number of sound, hollow, and insect-damaged seeds in each cone. Total and sound seed yields per cone did not vary significantly among areas but did vary significantly among trees within each area. Numbers of hollow and Megastigmus -infested (Hymenoptera: Torymidae) seeds varied significantly among areas and trees within areas. Numbers of sound seed increased significantly with increasing cone length but did not change with increasing numbers of cones per cluster. The percentages of Megastigmus -infested seed did not change significantly with increasing cone length or number of cones per cluster.     

Reproductive ecology of Dusky Flycatchers in montane meadows of the central Sierra Nevada

Avian species with expansive ranges or those that occupy more than one vegetative association may vary in aspects of their life histories across their ranges. The distribution of Dusky Flycatchers encompasses a variety of vegetative associations, including riparian communities. However, much of the literature on this species details studies conducted in upland areas. Our objectives were to describe the breeding ecology and fecundity of Dusky Flycatchers nesting in montane meadows of the central Sierra Nevada, California. We monitored 36 territories and located 37 Dusky Flycatcher nests in 8 meadows. Average clutch size was 3.9 eggs. Egg laying, incubation, and nestling stages were 4, 15.4, and 16.4 days, respectively. Eighteen nests successfully fledged young, with an average of 3.3 fledglings per successful nest. Nest success was 43% and nest predation was the leading cause of nest failure. Estimated annual fecundity was 1.62 fledglings per pair; however, because all renesting attempts were not located, this should be viewed as the minimum annual fecundity. Dusky Flycatchers we monitored may have had higher fecundity than those nesting in upland areas because riparian areas often have higher arthropod abundances. While the importance of riparian conservation to riparian-obligate bird species is obvious, our study indicates that these areas also may be of value to Dusky Flycatchers that breed in riparian areas and upland areas.     

Breeding birds of an ancient bristlecone pine stand in east central Nevada

This paper describes features of the breeding bird population of a Great Basin ancient bristlecone pine stand on Wheeler Peak in White Pine County, east central Nevada. The bird population was determined by spot-mapping methods on a 20-ha plot during June and July 1981. The density of breeding birds was 82 pairs per 40 ha. Fourteen species were territorial. The most abundant species were the Dark-eyed Junco, Mountain Chickadee, Mountain Bluebird, and Townsend’s Solitaire. Other common breeding species included the Cassin’s Finch, Yellow-rumped Warbler, Pine Siskin, and Dusky Flycatcher. There were 410 individual breeding birds per km 2 . When expressed as standing crop biomass, the Townsend’s Solitaire was the predominant species, followed by the Dark-eyed Junco, American Robin, Mountain Bluebird, and Northern Flicker. Total standing crop biomass was 95 g/ha. None of the breeding birds were restricted to the bristlecone pine stand. The structure of the breeding bird community in the bristlecone pine forest compared best to those of the Rocky Mountain and Northern Boreal forest regions.     

Dwarf mistletoe-pandora moth interaction and its contribution to ponderosa pine mortality in Arizona

The interaction between Southwestern dwarf mistletoe, Arceuthobium vaginatum subspecies cryptopodum , infestation and defoliation by the pandora moth, Coloradia pandora pandora , on the Kaibab Plateau in Arizona was evaluated. Heavy defoliation of ponderosa pine, Pinus ponderosa , in 1979 and 1981 resulted in mortality of individual trees in areas of heavy dwarf mistletoe infestation. Postmortem evaluation of ponderosa pines indicated that dead trees had a significantly higher dwarf mistletoe rating than did nearby paired live trees. Of 25 tree pairs evaluated, only two live trees had higher dwarf mistletoe ratings than the paired dead tree. Mean dwarf mistletoe ratings were: live trees 2.9, dead trees 4.6 (6 class dwarf mistletoe rating system). Implications for management of the pandora moth are discussed.        

Factors influencing the frequency of nest parasitism by Brown-headed Cowbirds in the northern Sierra Nevada

Nest parasitism by Brown-headed Cowbirds ( Molothrus ater ) can negatively affect host populations. Landscape-scale factors, such as proximity to residential areas, equestrian riding stables, and grazing allotments, can affect the risk of nest parasitism as well as the abundance of Brown-headed Cowbirds. Recent increases in residential and recreational development along with a reduction in grazing allotments in the northern Sierra Nevada provide an opportunity to reevaluate factors that influence frequency of nest parasitism by Brown-headed Cowbirds. Frequency of nest parasitism increased as the distance to the nearest residential center and distance to the nearest equestrian riding stable decreased. Similarly, Brown-headed Cowbird abundance was negatively correlated with distance to the nearest residential center and distance to the nearest equestrian stable. To reduce the risk of nest parasitism, efforts should be devoted to (1) reducing further residential development at the wildland–urban interface and (2) educating landowners about bird feeders, which frequently attract Brown-headed Cowbirds.     

Composition and abundance of periphyton and aquatic insects in Sierra Nevada, California, stream

The species composition of periphyton and benthic insect communities and abundances of common taxa (&;gt;0.1&;#37; of individuals) were examined during snow-free months in Convict Creek, a permanent snowmelt- and spring-fed stream in the Sierra Nevada of California. The communities were highly diverse. The most abundant taxa in the periphyton were diatoms ( Achnanthes minutissima, Cocconeis placentula lineata, Cymbella microcephala, C. sinuata, Fragilaria construens, F. crotonensis , Navicula spp., Synedra acus , and S. rumpens ), except in late spring and summer when several seasonal blue-green algae ( Chamaesiphon incrustans, Lyngbya spp. and Oscillatoria spp.) are at their maximum densities. Most common periphyton taxa vary systematically in abundance with season, but relative abundances of taxa also appear to be influenced by streambed scouring and by concentrations of ambient nutrients. Data on population densities and length frequencies of larval and nymphal stages of common benthic insects and occurrences of pupal and adult stages were examined to determine life history patterns. Taxa hatching in winter and spring and abundant as immatures in late spring include ephemeropterans ( Epeorus longimanus, Drunella flavilinea , and Caudatella heterocaudata ), plecopterans ( Calineuria californica, Doroneuria baumanni, and Pteronarcys princeps ) and dipterans ( Cryptolabis sp.). Common taxa hatching in late spring or summer are the plecopteran Malenka ( californica? ) and the trichopterans Arctopsyche grandis and Rhyacophila acropedes . Several bivoltine and multivoltine ephemeropterans ( Baetis devinctus and B. tricaudatus ) and dipterans ( Simulium spp. and Chironomidae) have summer cohorts. Taxa hatching in late summer or autumn and most abundant in autumn include ephemeropterans ( Baetis spp., Ephemerella infrequens, Epeorus dulciana, Ironodes lepidus , and Paraleptophlebia pallipes ), trichopterans ( Hydropsyche oslari, Lepidostoma spp., Glossosoma califica, Micrasema sp., Brachycentrus americanus, Neophylax sp., and Rhyacophila vaccua ) and dipterans ( Antocha monticola, Pericoma sp., and Chironomidae). Major recurring events that may influence life history patterns and structure of the benthic insect community are (1) near-freezing, nighttime winter water temperatures and occasional anchor ice, (2) a prolonged period of high discharge in late spring and early summer (3) a brief summer, and (4) a prolonged period of moderate stream discharge in autumn when the substratum is stable and food is abundant.     

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.     

Insect damage, cone dimensions, and seed production in crown levels of ponderosa pine

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Insect damage to second-year cones was generally not significantly different between crown levels, but was significantly different among areas and among trees within areas for Conophthorus, Megastigmus, and Cydia. Both cone length and width were not significantly different between lower and middle crown, but cone length was significantly greater in the upper crown. Seeds per cone ranged from 34 to 66, but the percent of sound seed per cone varied significantly according to the amount of insect damage.        

Forest-floor treatments in Arizona ponderosa pine restoration ecosystems: no short-term effects on plant communities

Leaf litter accumulation during fire exclusion and increases in tree density in postsettlement southwestern Pinus ponderosa forests may limit the establishment of understory vegetation. We performed an experiment in P. ponderosa forests of northern Arizona to ascertain plant community responses to forest-floor scarification and Oi removal on thirty-six 100-m 2 plots overlaid on an existing ecological restoration experiment that involved tree thinning and prescribed burning. Constrasting with findings from many other forest types, forest-floor treatments had no effect on community diversity or composition during the 2-year experiment. S?rensen similarities were as high as 97% between posttreatment years within treatments; and successional vectors also provided little indication that treatments may appreciably affect longer-term successional trajectories. Lack of response to these fairly drastic treatments is surprising given these forests' exceptionally heavy Oi horizons and large proportions of conifer litter. Apparently shading, belowground competition for water or nutrients, or other tree-associated factors more strongly limit understory communities than does leaf litter. Based on sparse A-horizon seed banks averaging <300 seeds ? m –2 and limited aboveground vegetation, we hypothesize that seed shortages, particularly for native perennials, also partly precluded a treatment response. Because extensive unvegetated areas at these restoration sites may be colonized by exotics, conservative management strategies could include testing the seeding or outplanting of desirable native species as an option for filling unoccupied microsites. Reporting of "no treatment effect" experiments such as this one is important to avoid biasing meta-analyses, as is future research to clarify combinations of factors limiting understory communities. Increased understanding of these limiting factors may lead to identification of other treatments that promote recovery of native species during ecological restoration in this region.     

Wood and understory production under a range of ponderosa pine stocking levels, Black Hills, South Dakota

Stemwood and understory production (kg ha -1 ) were estimated during 3 nonconsecutive years on 5 growing stock levels of ponderosa pine including clearcuts and unthinned stands. Stemwood production was consistently greater at mid- and higher pine stocking levels, and understory production was greater in stands with less pine; however, there were no differences in total (stemwood + understory) production. Based on loss of productivity, there is no argument that small clearcuts and unthinned stands should not be included in site plans. They contribute significantly to community structure, particularly to plant and animal species richness.     

Peat depth of Sierra Nevada fens, and profile changes from 1958 to 1972 in Mason Fen

Peat cores along transects of seven minerotrophic peatlands (fens) in the Sagehen Creek basin were made in 1972. The areas were all shallow, sloping peatlands from 67 to 206 cm in maximum depth. Cores from one fen contained layers of charcoal and clay that suggested fire followed by fen regeneration. Profiles from Mason Fen suggested that the peat mass was moving downslope, creating splits and ridges with surface pools at right angles to the slope. Comparison of a profile made in 1958 with 1972 showed further evidence of downslope mass movement and expansion of the surface area.     

Nesting ecology of Yellow Warblers ( Dendroica petechia ) in montane chaparral habitat in the northern Sierra Nevada

The Yellow Warbler ( Dendroica petechia ) is considered a riparian specialist in much of western North America, but in California it also breeds in a second habitat type: montane chaparral of the Sierra Nevada and southern Cascades. We monitored Yellow Warbler nests in montane chaparral and assessed their poorly known nesting ecology in this habitat. We also conducted point counts in upland habitat throughout the region. We determined habitat associations for Yellow Warblers based on nest site and point-count vegetation data; nests were predominantly in bush chinquapin ( Chrysolepis sempervirens ) and greenleaf manzanita ( Arctostaphylos patula ), and point-count abundance was most strongly associated with high overall shrub cover. The importance of montane chaparral for a number of shrub-dependent Sierran birds is well documented, yet the chaparral is threatened by various practices including fire suppression, closed-canopy-focused forest management, and understory fuels-reduction treatments. Although Yellow Warblers are far more abundant in wet mountain meadow riparian habitat in the region, we recommend that management of montane chaparral habitat consider this species and the requirements of other shrub-nesting birds.