Gray fox and coyote abundance and diet responses after a wildfire in central Arizona

There is a paucity of information on the effects of wildfire on carnivores. We studied the effects of a 237-km 2 catastrophic wildfire in the Mazatzal Mountains, Arizona, on gray foxes ( Urocyon cinereoargenteus ) and coyotes ( Canis latrans ). We indexed relative abundance 3 times each year from 1996 to1998 using scat transects in burned and unburned areas. We collected scats to estimate diet and measured small mammal abundance and mast availability in 1997 and 1998. We also measured vegetation cover in burned and unburned sites. Gray fox indices declined 3 months postfire, but after 30 months, indices returned to preburn levels. Coyote indices did not change. Primary foods for both species in burned and unburned sites were mast (fruits of shrubs) and rodents, and diet comparisons between sites became similar as plant succession continued. Scat indices did not correlate with seasonal small mammal abundance. We suspect that the lower abundance indices of gray foxes were related to reduction in cover and food availability, because indices increased as vertical cover and mast crop increased. These data indicate that the effects of this catastrophic fire were short-term but also highlight the importance of preserving shrub and vegetation diversity for gray fox.     

Vegetation response to prescribed fire in Dinosaur National Monument

Much of western North America is dominated by dense, monotypic, late seral stands of big sagebrush ( Artemisia tridentata Nutt.). These stands often have depauperate understories with limited species richness, diversity, and herbaceous cover. The National Park Service at Dinosaur National Monument, Colorado, is using both strategic and natural prescribed fire in Wyoming big sagebrush ( Artemisia tridentata ssp. wyomingensis Beetle and Young) communities to foster intra-community (α -scale) and landscape diversity. This study analyzed an accumulated foliar cover data set between paired burn and control areas on 6 different sites during the last 20 years. Across the monitoring period, mean total vegetation cover of all combined sites was 44% control and 42% burn. Total vegetation cover in burn areas was higher than or equal to paired control areas within 2-3 years post-burn. Shrubs were essentially eliminated in burn areas, but perennial grass cover was 10-35% higher. Mean number of species on all sites and years combined was 17 control and 18 burn. Species richness was different on only 1 site-year, Dry Woman 1995 ( P = 0.001, 15 control, 9 burn). Species similarity by site and between treatments ranged from 44% to 75%. Differences in Shannon-Weiner diversity index values between paired sites occurred in 6 of 20 years ( P < 0.05). Index value differences on these 6 sites were due to a large annual grass component in burn areas. Prescribed burning successfully shifted late successional sagebrushdominated communities to earlier herbaceous-dominated successional stages without lowering total vegetation cover, while maintaining -scale diversity and species richness.     

Vegetation response to fire and postburn seeding treatments in juniper woodlands of the Grand Staircase-Escalante National Monument, Utah

We compared 3 naturally ignited burns with unburned sites in the Grand Staircase-Escalante National Monument. Each burn site was restored with native and nonnative seed mixes, restored with native seeds only, or regenerated naturally. In general, burned sites had significantly lower native species richness (1.8 vs. 2.9 species), native species cover (11% vs. 22.5%), and soil crust cover (4.1% vs. 15%) than unburned sites. Most burned plots, seeded or not, had significantly higher average nonnative species richness and cover and lower average native species richness and cover than unburned sites. Regression tree analyses suggest site variation was equally important to rehabilitation results as seeding treatments. Low native species richness and cover, high soil C, and low cover of biological soil crusts may facilitate increased nonnative species richness and cover. Our study also found that unburned sites in the region had equally high cover of nonnative species compared with the rest of the Monument. Cheatgrass ( Bromus tectorum ) dominated both burned and unburned sites. Despite the invasion of cheatgrass, unburned sites still maintain higher native species richness; however, the high cover of cheatgrass may increase fire frequency, further reduce native species richness and cover, and ultimately change vegetation composition in juniper woodlands.     

Effects of prescribed fall burning on a wetland plant community, with implications for management of plants and herbivores

An important contemporary challenge for adaptive resource management is assessing both the direct and indirect effects of management activities by designing appropriate monitoring programs and sound analysis methods. Here we evaluate the effects of prescribed fall burning on a wetland plant community that is managed primarily for spring-migrating geese. During late fall in 2 consecutive years, we burned vegetation in 4 replicate blocks (2.3 ha each) that traversed a natural moisture and associated vegetation gradient. We used ordination, gradient analysis, and contingency table analysis to evaluate how annual changes in relative abundance of plants were affected by burning as well as other important ecological factors. Burning increased species diversity of plants, especially in the 2 wetter vegetation zones, but had no effect on species richness or on the proportion of native plant species. Wetland plant species responded to prescribed burning independently, and their response often differed by vegetation zone and with annual variation in flooding. Burning enhanced the abundance of native foxtail barley ( Hordeum jubatum ) and reduced the abundance of introduced swamp timothy ( Crypsis shoenoides ). Saltgrass ( Distichlis spicata ), a native plant species, was usually less abundant following burning, although the level of response was different for each of the 3 vegetation zones. Two other introduced plant species, quackgrass ( Elytrigia repens ) and reed canarygrass ( Phalaris arundinaceae ), were less abundant after fall burning, especially when spring flooding was more extensive. Wild geese using the experimental blocks for feeding clearly preferred burned sites, suggesting that fall burning can enhance wetland use by geese during spring. Given that simple manipulations such as burning and flooding of a wetland system may often produce complex results, we suggest that on-going management schemes be regularly evaluated with field experiments such as those conducted in this study.     

Evaluation of wildlife response to a retained mine highwall in south central Wyoming

From 1984 through 1985 a study was made of the influence of a retained mine highwall on a wildlife community in south central Wyoming. Vegetation species richness and diversity were greater near the highwall compared with two adjacent sites 150 m in front of and behind the highwall. However, vegetation abundance (cover) was greater on the two adjacent sites. Small mammal abundance, richness, and diversity were greater on the highwall than on the two adjacent sites. Male bird abundance, richness, and diversity were greatest in front of the highwall (+ 50 m to + 350 m) compared with the highwall and the area behind the highwall.     

Plant community patterns in unburned and burned blackbrush ( Coleogne ramosissima Torr.) shrublands in the Mojave Desert

The blackbrush vegetation type is dominated by Coleogyne ramossisima , which is thought to preclude the coexistence of many other plant species. Fire can remove blackbrush cover and possibly increase plant species richness and evenness. Fire also may increase the frequency and cover of alien annual grasses, thereby intensifying landscape flammability. We tested these predictions in unburned and burned (6-14 years postfire) blackbrush at 3 sites spanning the range of this vegetation type in the Mojave Desert. Species richness in unburned blackbrush was similar to published values for vegetation types in western North America, bur richness varied significantly among the 3 sites and 4 spatial scales (1, 10, 100, and 1000 m 2 ). Richness values declined in order from annual forbs, woody perennials, herbaceous perennials, annual grasses, cacti, to perennial grasses. Fire reduced Coleogyne cover, thus boosting species evenness. In contrast, species richness decreased after burning, although the results varied among spatial scales. Total cover was unaffected by fire because cover of wood perennials decreased, while cover of annual forbs, annual grasses, herbaceous perennials, and perennial grasses increased. Native species richness and cover decreased, whereas alien richness and cover increased after burning especially where the alien forb Erodium cicutarium was present. Fire had no effect on frequency and variable effects on cover of alien annual grasses. These results indicate that in blackbrush species richness can vary among sites and local spatial scales, and effects of fires can vary among plant life-forms and between natives and aliens.     

Variation in ant populations with elevation, tree cover, and fire in a pinyon-juniper–dominated watershed

Climate change and fire suppression have facilitated expansion of pinyon-juniper woodlands into sagebrush-steppe ecosystems of the Great Basin, USA, resulting in a loss of biological diversity. To assess the effects of using prescribed fire in restoration efforts, ant abundance, species richness, and composition were examined pre- and post-burn along the elevation and tree cover gradients encompassed by a pinyon-juniper woodland in a central Nevada watershed. Ants were sampled using pitfall traps in 6 sites for the elevation study and in 2 sites for the tree cover study, representing paired burn and control sites in a randomized block design. Vegetation and ground cover variables were also sampled to determine how variation in ant populations was correlated with differences in vegetation and ground cover. Ant species richness remained unchanged for all treatments. Tree cover had no significant effect on ant populations. Significantly more ants were trapped after the burn treatment on burn plots. Variation in ant populations was not directly correlated with any of the vegetation or ground cover variables. According to ANOVA and multivariate analyses, elevation had the greatest effect on changes in ant communities, likely due to increased moisture availability. Our results suggest that management for conservation of sagebrush-steppe ecosystems in this and similar watersheds should include a range of elevations to ensure maximum ant species diversity.     

Habitat use by small mammals in southeastern Utah, with reference to Mexican Spotted Owl management

We determined temporal and spatial differences in abundance and habitat use by small mammals in southeastern Utah as part of an effort to enhance management of the Mexican Spotted Owl ( Strix occidentalis lucida ), listed by the federal government as threatened. Woodrats ( Neotoma spp.) were captured only in canyons and most frequently in the pinyon-juniper ( Pinus edulis-Juniperus osteosperma ) vegetation type. White-footed mice ( Peromyscus spp.) were found in a variety of vegetation types in both canyons and mesas. The deer mouse ( P. maniculatus ) was generally the most frequently captured species among vegetation types. We found seasonal and yearly differences in relative abundance of each small mammal species. Our data suggest that the pinyon-juniper vegetation type within canyons is an important component of Mexican Spotted Owl habitat.     

Benthic community structure in two adjacent streams in Yellowstone National Park five years after the 1988 wildfires

Physical characteristics, benthic macroinvertebrates, and periphyton assemblages in two adjacent headwater streams in Yellowstone National Park were evaluated five years after the 1988 wildfires. The catchment of one stream was burned by wildfire (burned stream) while the other catchment was unburned (unburned stream). Physical measures revealed channel alteration in the burned stream relative to the unburned stream Periphyton biomass was lower in the burned than the unburned stream (29.2 vs. 50.5 g/m 2 AFDM, respectively), further demonstrating the unstable physical conditions of that system. Kendall's coefficient of concordance (an index of similarity) between diatom assemblages was 0.22, indicating distinct assemblage composition between streams. Navicula permitis Hust. was the most abundant diatom in the burned stream while Hannaea arcus (Ehr.) Patr. was dominant in the unburned stream. Macroinvertebrate taxa richness, density, and biomass were all greater in the unburned stream, although Chironomidae was the most abundant taxon in both streams. Results suggest the removal of terrestrial/riparian vegetation by wildfire can directly influence benthic assemblages by altering the inherent disturbance regime of the physical habitat templet.     

Short-term effects of a prescribed burn on songbirds and vegetation in mountain big sagebrush

I measured songbird abundance and vegetation cover in and around a 420-ha prescribed burn in a mountain big sagebrush community located at 2133 m elevation. Data were collected during the 3rd growing season after the fire. Brewer's Sparrow and Sage Thrasher occurred in lower abundance on sites that were largely or completely burned relative to sites that were outside the fire perimeter or within unburned islands of shrubs. The number of Brewer's Sparrow detections was linearly related to remaining sagebrush cover. In contrast, Horned Lark occurred at higher abundances on sites where shrub cover had been removed in the prescribed burn. Cover of perennial grasses and cover of 4 of the 5 most common forbs was greater on burned sites than on unburned sites.     

Comparison of insects from burned and unburned areas after a range fire

Insect communities at recently burned and unburned sites in the Great Basin of northwestern Utah were studied by weekly sampling with pitfall and Malaise traps. More specimens were consistently collected at the burned site, although the numbers of species between the sites were about equal a month after the fire. Flying insects showing no preference for the sites were sciarids, phorids, and leafminer flies (all Diptera). Insects preferring the unburned site were mostly entomophagous flies such as pipunculids, chamaemyiids, and tachinids. Insects more common at the burned site were mosquitoes and phytophagous species of lygaeid bugs, leafhoppers, and moths. Seasonal trends in relative abundance of major families of flying insects are reported. Ground survivors included gryllacridids, carabids, tenebrionids, and ants. Silphids and buprestids immigrated into the burned area soon after the fire. Interrelationships between the burned area and the insect community are dicussed.     

Canyon grassland vegetation changes following fire in northern Idaho

Native and nonnative vegetation mosaics are common in western rangelands. If land managers could better predict changes in the abundance of native and nonnative species following disturbances, maintenance of native plant cover and diversity may be improved. In August 2000, during suppression of a wildfire near Lewiston, Idaho, a backing fire burned canyon grassland plots. A previous study had recorded species composition and cover prior to the fire, so we were able to evaluate changes in species composition and abundance on established plots before and after the fire. Overall, summer burning had little effect on the grassland communities. Pseudoroegneria spicata recovered to prefire coverage by the third postfire year. In the third postfire year, cover of native and nonnative annual species was significantly greater on burned than unburned sites ( P Bromus tectorum cover increased, as expected, on burned plots. Prefire and postfire cover values for Centaurea solstitialis were nearly equal, and there were no significant cover differences between burned and unburned plots in any year. As part of this study, we also evaluated changes in the cover of dominant native and nonnative species with respect to their prefire seral stage on burned and unburned plots. Because our sample sizes were small, we only report community-level trends but suggest that this type of community analysis could make for an interesting future study. Los mosaicos de vegetaci&oacute;n nativa y no nativa son comunes en los pastizales del occidente de Norteam&eacute;rica. Si los administradores de tierras pudieran predecir mejor los cambios en la abundancia de especies nativas y no nativas despu&eacute;s de las perturbaciones, se podr&iacute;a mejorar el mantenimiento de la cobertura y diversidad de las plantas nativas. En agosto de 2000, los remanentes de un incendio quemaron terrenos de pradera de ca&ntilde;&oacute;n durante la supresi&oacute;n de un incendio cerca de Lewiston, Idaho. Un estudio previo registr&oacute; la composici&oacute;n y cobertura de especies antes del incendio, por lo que pudimos evaluar los cambios en la composici&oacute;n y abundancia de especies en determinados terrenos antes y despu&eacute;s del incendio. En general, las quemas de verano no afectaron mucho a las comunidades de pradera. Para el tercer a&ntilde;o despu&eacute;s del incendio, Pseudoroegneria spicata se hab&iacute;a repuesto al nivel de cobertura que tuvo antes del incendio y la cobertura de especies anuales nativas y no nativas fue significativamente mayor ( P Bromus tectorum aument&oacute; en los terrenos quemados. Los niveles de cobertura de Centaurea solstitialis antes y despu&eacute;s del incendio fueron casi iguales, y no hubo ninguna diferencia significativa en la cobertura de los terrenos quemados y la de los no quemados en ninguno de estos a&ntilde;os. Como parte de este estudio, tambi&eacute;n evaluamos los cambios en la cobertura de especies dominantes nativas y no nativas con respecto a su estado sucesional previo al incendio en terrenos quemados y no quemados. Debido a que tuvimos un reducido tama&ntilde;o de muestra, s&oacute;lo reportamos tendencias a nivel de comunidad, pero sugerimos que esta clase de an&aacute;lisis de comunidades podr&iacute;an servir como modelo para estudios interesantes en el futuro.     

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.     

Examining ecological consequences of feral horse grazing using exclosures

Although feral horses have inhabited western North America since the end of the 16th century, relatively little synecological research has been conducted to quantitatively characterize how they interact with ecosystem components. Because feral horses exhibit watering behavior markedly different from that of domestic cattle, it is particularly important to evaluate response of ecosystem elements near water sources to horse use. To assess this response, we performed live-trapping of small mammals and 2-tiered vegetative sampling in 2 mountain ranges in central Nevada in the interior Great Basin, USA. At low elevations, plots around horse-excluded springs exhibited notably greater plant species richness, percent cover, and abundance of grasses and shrubs, as well as more small mammal burrow entrances than plots at horse-grazed springs. At high elevations, meadows protected from grazing exhibited maximum vegetation heights 2.8 times greater than vegetation grazed by horses only and 4.5 times greater than vegetation grazed by horses and cattle. Species richness in quadrats was most different between the horse-and-cattle-grazed meadow and its ungrazed counterpart, suggesting the possibility of synergistic effects of horse and cattle grazing in the same location. This study, the first in the Great Basin to investigate quantitatively ecosystem consequences of feral horse use with exclosures, represents a preliminary step in identifying factors that determine the magnitude of horse grazing impacts.     

Spatially scaled response of a Lazuli Bunting population to fire

We examined the response of Lazuli Bunting ( Passerina amoena ) to fire in Gambel oak ( Quercus gambelii ) woodland at Camp Williams, Utah, during 1993–1998. Overall, Lazuli Bunting abundance on the study area increased significantly during the 2 years after a stand-replacing wildfire, which covered 800 ha of Gambel oak woodland. This increase suggested that Lazuli Buntings respond positively to fire. However, a comparison of pre- and postfire abundance of Lazuli Bunting for 2 groups of monitoring plots with different fire histories showed that abundance was significantly greater during the post-fire period for both burned and unburned plots. When we examined our data at a spatial scale appropriate to Lazuli Bunting, we found that post-fire increases observed on unburned plots were limited to plots in close proximity to the burned area. A comparison of pre- and post-fire abundance of Lazuli Bunting for 3 groups of monitoring plots located at various distances from the burned area revealed that post-fire abundance was similar only for plots within the fire boundary and for those ≤1000 m from the fire boundary; plots located >1000 m from the fire boundary had fewer individuals per plot post-fire. However, prefire Lazuli Bunting abundance was similar among all 3 categories. This differential, spatially scaled response of Lazuli Bunting to fire at the landscape level may support a hierarchical view of habitat selection.     

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. &nbsp;&nbsp;&nbsp;     

Summer food habits of a small mammal community in the pinyon-juniper ecosystem

Summer food habits of a small mammal community in the Piceance Basin of Colorado were investigated during 1977 and 1978 using a combination of fecal and stomach content analyses. Three species, deer mice ( Peromyscus maniculatus ), least chipmunks ( Eutamias minimus ), and plains pocket mice ( Perognathus flavescens ) consumed arthropods as the majority of their diets. Bushy-tailed woodrats ( Neotoma cinerea ) consumed predominantly woody vegetation, and the diet of golden-mantled ground squirrels ( Spermophilus lateralis ) consisted primarily of forbs and fungi. Mountain cottontails ( Sylvilagus nuttalli ) depended heavily on grasses, with a mix of woody vegetation and forbs composing the remainder of their diet. Most of the species investigated selected different foods and thus avoided competition for food. Plains pocket mice may have competed with deer mice for arthropods in 1977.     

Winter site fidelity and body condition of three riparian songbird species following a fire

The effects of fire on nonbreeding songbird species in riparian habitat have not been studied. We compared body condition, within-year site fidelity, and between-year site fidelity of 3 songbird species ( Passerella iliaca , Fox Sparrow; Catharus guttatus , Hermit Thrush; and Regulus calendula , Ruby-crowned Kinglet) at 2 coastal riparian sites. Wildfire, which is rare in this habitat, had occurred at 1 of the sites before data collection. A significantly larger proportion of Passerella iliaca was recaptured in subsequent winters at the unburned site than at the burned site, but little difference was found between sites for Catharus guttatus or Regulus calendula . Body mass of all 3 species declined during winter at the burned site, but differences between sites were not significant. Similarly, body mass indices of new captures were lower at the burned site than the unburned site for all 3 species, but these differences were not significant. The within-year recapture rate for all 3 species combined declined at the burned site over the course of the study, possibly due to changes in vegetation structure caused by the fire. Overall, our data suggest that wintering songbirds were resilient to this disturbance, but that response to the post-fire environment differed among foraging guilds. Well-replicated studies that include pre-burn data are needed to evaluate the effects of this disturbance in riparian systems.     

Preliminary assessment of velvet ant (Hymenoptera: Mutillidae) diversity in the deserts of southern California

The deserts of southern California house a diverse and unique insect fauna. Velvet ants (Hymenoptera: Mutillidae) are common in these deserts. Velvet ants are important to ecosystem health, particularly in desert environments, because they are parasitic on the bees and wasps that help maintain overall ecosystem function. The goal of this study was to measure velvet ant diversity across the deserts of southern California. We made preliminary collections from 10 sites in a variety of areas in the western Sonoran Desert (Colorado Desert), the Mojave Desert, and the Great Basin Desert. We measured &beta;-diversity using S&oslash;rensen&rsquo;s similarity index to compare velvet ant richness and relative abundance between different sites. To determine how accurate our similarity estimates were, and to gain an understanding of actual velvet ant diversity, we also compared velvet ant richness of 2 sites (Algodones Sand Dunes and Deep Canyon) using data obtained from the examination of museum specimens borrowed from over 12 museums across the West. Comparisons of velvet ant faunas between sites revealed low similarities (0.167&ndash;0.75 species richness only; 0.022&ndash;0.67 both abundance and richness). Low similarity values indicate that a rich velvet ant fauna exists in the deserts of southern California.     

Trapping methods for rangeland insects in burned and unburned sites: a comparison

Different insect trapping methods were compared weekly on recently burned and nearby unburned rangeland in the Great Basin of western Utah. Flight traps (or wing traps) collected the most specimens (total = 4,916 at burned site, 4,384 at unburned site) but represented the fewest species (no more than 11 spp./wk at either site); this method was not recommended because of difficulty in removing specimens from adhesive. Water traps amassed the next largest number of specimens (￣x ± SE/wk = 150.9 ± 75.3 at burned site, 158.0 ± 66.4 at unburned site) and the most species (￣x ± SE/wk = 21.6 ± 6.4 at burned site, 35. 1 ± 4.5 at unburned site). The weekly collections from pitfall traps between the sites were significantly different (P < .05) in number of specimens (￣x ± SE/wk = 8.1 ± 1.5 at burned site, 19.7 ± 4.8 at unburned site) and species (￣x ± SE/wk = 4.7 ± 0.6 at burned site, 9.5 ± 2.0 at unburned site). Malaise traps were the most convenient. Black Malaise traps collected more specimens (￣x ± SE/wk = 99.8 ± 19.4 at burned site, 90.6 ± 16.4 at unburned site) and species (￣x ± SE/wk = 22.9 ± 3.9 at burned site, 19.4 ± 6.5 at unburned site) than white malaise traps (specimens: ￣x ± SE/wk = 72.1 ± 22.4 at burned site, 87.1 ± 31.2 at unburned site; species: ￣x ± SE/ wk = 19.7 ± 6.6 at burned site, 16.4 ± 5.4 at unburned site), although this difference was not significant.