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Western juniper was often historically restricted to fire refugia such as rocky outcrops but has since Euro-American settlement expanded into areas previously dominated by sagebrush steppe. Wildfires in developed woodlands have been rare. In 2007, the Tongue-Crutcher Wildland Fire burned 18,890 ha in southwestern Idaho along a woodland development gradient, providing unique research opportunities. To assess fire effects on vascular plants, field data were collected in 2012/2013 and 2019/2020. Species richness was uniform along the sere, while species diversity declined in late woodland stages attributed to juniper dominance. The greatest changes in species composition following fire occurred in later woodland development phases. Herbaceous vegetation increased following fire, but sagebrush cover was still lower in burned plots 12–13 years post-fire. Many stands dominated by juniper pre-fire became dominated by snowbrush ceanothus post-fire. Juniper seedlings were observed post-fire, indicating that juniper will reoccupy the area. Our research demonstrates resilience to fire and resistance to annual grasses particularly in early successional stages, which provides opportunities for fire use as a management tool on cool and moist ecological sites. Loss of old-growth juniper to wildfire underlines the importance of maintaining and provisioning for future development of some old growth on the landscape given century-long recovery times.

Background Prairie–forest ecotones are ecologically important for biodiversity and ecological processes. While these ecotones cover small areas, their sharp gradients in land cover promote rich ecological interaction and high conservation value. Our objective was to understand how historical and current fire occurrences and human development influenced the Palouse Prairie–forest ecotone. We used General Land Office survey field notes about the occurrence of bearing trees to locate historical (1870s to 1880s) prairie, pine savanna, and forest at the eastern edge of the bioregion. We combined LANDFIRE Existing Vegetation classes to contrast historical land cover with current land cover. We reconstructed historical fire occurrence (1650 to 1900) from fire-scarred trees. We used fire and lightning records from 1992 to 2015 to interpret the role of people and lightning. Results Historically, the ecotone was a matrix of prairie with extensive savanna and some forest. More than half of the ecotone area was prairie, which is now dominated by agriculture, with some residential development. The 16% of the landscape that was pine savanna is now forest or shrubs, agriculture, perennial vegetation under the Conservation Reserve Program, or developed; no savanna now exists. Forests covered 12% of the ecotone and these are still mostly forest. Fires were historically frequent, occurring on average every 5 to 8 years at most sites. Lightning was not frequent but could likely have been sufficient to ignite fires that could spread readily given the rolling terrain and long fire season. Conclusions Fire was far more frequent historically than currently. Conservation, restoration, and other ongoing land-use changes will likely result in more continuous vegetation and hence fuel for fires. Lightning and people may ignite fires that therefore spread readily in the future. Understanding the past and potential future of fire in the Palouse Prairie bioregion may help us live with fire while conserving ecological values here and in similar prairie–forest ecotones.

Woody plant expansion is a global phenomenon that alters the spatial distribution of nutrients, biomass, and fuels in affected ecosystems. Altered fuel patterns across the landscape influences ecological processes including fire behavior, fire effects, and can impact post-fire plant germination and establishment. The purpose of this study was to determine how accumulations of ground fuels beneath western juniper (Juniperus occidentalis ssp. occidentalis) canopies, composed of litter and duff, affect post-fire species response in sagebrush steppe and to quantify fuel loading patterns. Field sampling and analysis was conducted across environmental gradients following the 2007 Tongue-Crutcher Wildfire in southwestern Idaho to determine conditions that were most influential in post-fire vegetation recovery patterns. Duff depth and fire severity were determined to be the most influential factors affecting post-fire vegetation response. Decreasing species richness and native perennial grass cover was represented along the increasing duff depth gradient. Species response grouped by fire severity revealed significant presence of cheatgrass (Bromus tectorum) in low severity sites and a dominance of snowbrush ceanothus (Ceanothus velutinus) in higher severity sites. Determining sub-crown surface fuel characteristics offers the potential to predict future patterns and processes as they relate to burn severity and vegetation recovery components in developing woodlands.

Expansion of juniper (Juniperus spp. L.) and pinyon (Pinus spp. L.) into sagebrush steppe habitats has been occurring for over a century across western United States. Vegetation and fuel treatments, with the goal of increasing landscape diversity and herbaceous productivity, and reducing woody fuels are commonly implemented to mitigate effects of woodland encroachment in sagebrush ecosystems. This study was conducted in conjunction with the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) and was designed to determine the impact of vegetation treatments on fuel variables two years post treatment in sagebrush steppe with an expanding juniper or pinyon −juniper woodland component. Ten locations that characterize common sagebrush steppe sites with an expanding woodland component in the Intermountain West were chosen for analysis. These woodland sites, covering a gradient of juniper development phases, were treated with mechanical (cut and leave) and prescribed fire treatments. Two years post treatment, prescribed fire increased herbaceous biomass and reduced shrub biomass and down woody debris, but was not as effective in woodlands with higher juniper densities. Mechanical treatments increased herbaceous biomass and were effective in preserving the shrub biomass but increased down woody debris, which could lead to severe fire effects in the future. We conclude that both prescribed fire and mechanical treatments are important management tools for maintenance and restoration of sagebrush steppe in areas that support juniper woodland expansion, but the differences in effects on shrub biomass and woody debris must be considered. A combination of the two treatments could lead to desirable effects in many areas.

Numerous studies have been conducted that evaluate the utility of remote sensing for monitoring and assessing vegetation and ground cover to support land management decisions and complement ground measurements. However, few comparisons have been made that evaluate the utility of object-based image analysis (OBIA) to accurately classify a landscape where rule sets (models) have been developed at various scales. In this study, OBIA rule sets used to estimate land cover from high–spatial resolution imagery (0.06-m pixel) on Pinus L. (pinyon) and Juniperus L. (juniper) woodlands were developed using eCognition Developer at four scales with varying grains—1) individual plot, 2) individual sites, 3) regions (western juniper vs. Utah juniper sites), and 4) pinyon-juniper woodland network (all plots)—that were within the same study extent. Color-infrared imagery was acquired over five sites in Oregon, California, Nevada, and Utah with a Vexcel UltraCamX digital camera in June 2009. Ground cover measurements were also collected at study sites in 2009 on 80 0.1-ha plots. Correlations between OBIA and ground measurements were relatively high for individual plot and site rule sets (ranging from r¼0.52 to r¼0.98). Correlations for regional and network rule sets were lower (ranging from r¼0.24 to r¼0.63), which was expected due to radiance differences between the images as well as vegetation differences found at each site. All site and plot OBIA average cover percentage estimates for live trees, shrubs, perennial herbaceous vegetation, litter, and bare ground were within 5% of the ground measurements, and all region and network OBIA average cover percentage estimates were within 10%. The trade-off for decreased accuracy over a larger area (region and network rule sets) may be useful to prioritize management strategies but will unlikely capture subtle shifts in understory plant communities that site and plot rule sets often capture.

Western juniper (Juniperus occidentalis Hook. var. occidentalis) has been expanding into sagebrush (Artemisia L. spp.) steppe over the past 130 yr in Idaho, Oregon, and California. Fuel characteristics and expected fire behavior and effects change as sagebrush steppe transitions into juniper woodlands. Little is currently known about how wildfire influences burn severity and ecosystem response in steppe altered by woodland conversion. In 2007, the Tongue-Crutcher Wildland Fire burned 18 890 ha along a successional gradient ranging from sagebrush steppe to mature juniper woodlands, providing a unique opportunity to evaluate the effects of prefire vegetation on burn severity and ecosystem response across spatial scales. Plot-scale burn severity was evaluated with the composite burn index (CBI) in locations where prefire vegetation data were available, and landscape-scale burn severity was estimated via remotely sensed indices (differenced normalized burn ratio [dNBR] and relative differenced normal...

Land managers need to rapidly assess vegetation composition and bare ground to effectively evaluate and manage shrub steppe communities that have been encroached by pinyon and juniper trees. We used an object-based image analysis (OBIA) approach to estimate land cover classes found in pinyon-juniper woodlands, and evaluated the relationship between ground measurements and OBIA land cover measurements. We acquired high-spatial resolution color-infrared imagery for five sites with a Vexcel UltraCamX digital camera in June 2009. We simultaneously collected ground-based cover measurements within 30 m × 33 m subplots. OBIA mean land cover class differences by site ranged from underestimating litter by 3 percent to overestimating live trees by 1 percent when compared to ground-based measurements. Overall accuracy for thematic maps was 84 percent with a Kappa statistic of 0.80. Although OBIA cover estimates varied slightly from ground cover estimates, methods provide land managers with options for prioritizing management practices and enabling monitoring at an operational scale.

Q uaking aspen ( Populus tremuloides ) habitats con- tribute to species diversity, provide forage and shade for wildlife and livestock, and are highly valued by humans for their productivity and beau- ty. Aspen decline has been observed in the western United States over the past 50 years and has been mainly attributed to a decrease in re frequency, caused by effective re suppres- sion. 1 Changing re regimes have allowed conifer species to expand into aspen stands. Another phenomenon, commonly referred to as “Sudden Aspen Decline” (SAD), has been ob- served within the past decade in the western mountains and in the Canadian aspen parklands. 2 Mature aspen stems begin to die at rates beyond what is expected, which if aspen regen- eration is limited, can eventually lead to the loss of the aspen roots and stands. Excessive browsing by livestock and wildlife can also inhibit aspen regeneration. DOI: 10.2458/azu_rangelands_v34i5_strand

Evaluating vegetation cover is an important factor in understanding the sustainability of many ecosystems. Remote sensing methods with sufficient accuracy could dramatically alter how biotic resources are monitored on both public and private lands. Idaho National Laboratory (INL), in conjunction with the University of Idaho, evaluated whether unmanned aerial vehicles (UAVs) are sufficiently accurate and more efficient than the point-frame field method for monitoring vegetative cover and bare ground in sagebrush steppe ecosystems. These values are of interest to land managers because typically there are limited natural resource scientists and funding for comprehensive ground evaluations. In this project, unmanned helicopters were used to collect still-frame imagery to determine vegetation cover during June and July 2005. The images were used to estimate percent cover for six vegetative cover classes (shrub, dead shrub, grass, forbs, litter, and bare ground). Field plots used to collect imagery and on-the-ground measurements were located on the INL site west of Idaho Falls, Idaho. Ocular assessments of digital imagery were performed using SamplePoint, and the results were compared with field measurements collected using a point-frame method. The helicopter imagery evaluation showed a high degree of agreement with field cover class values for grass, litter, and bare ground and reasonable agreement for dead shrubs. Shrub cover was often overestimated, and forbs were generally underestimated. The helicopter method took 45% less time than the field method. This study demonstrates that UAV technology provides a viable method for monitoring selective types of cover on rangelands and could save time and resources.

In this study, the use of unmanned aerial vehicles (UAVs) as a quick and safe method for monitoring biotic resources was evaluated. Vegetation cover and the amount of bare ground are important factors in understanding the sustainability of many ecosystems. Methods that improve speed and cost efficiency could greatly improve how biotic resources are monitored on western lands. Sagebrush steppe ecosystems provide important habitat for a variety of species including sage grouse and pygmy rabbit. Improved methods of monitoring these habitats are needed because not enough resource specialists or funds are available for comprehensive on-the-ground evaluations. In this project, two UAV platforms, fixed-wing and helicopter, were used to collect still-frame imagery to assess vegetation cover in sagebrush steppe ecosystems. This paper discusses the process for collecting and analyzing imagery from the UAVs to 1) estimate percentage of cover for six different vegetation types (shrub, dead shrub, grass, forb, litter, and bare ground) and 2) locate sage grouse using representative decoys. The field plots were located on the Idaho National Laboratory site west of Idaho Falls, Idaho, in areas with varying amounts and types of vegetation cover. A software program called SamplePoint was used along with visual inspection to evaluate percentage of cover for the six cover types. Results were compared against standard field measurements to assess accuracy. The comparison of fixed-wing and helicopter UAV technology against field estimates shows good agreement for the measurement of bare ground. This study shows that if a high degree of detail and data accuracy is desired, then a helicopter UAV may be a good platform to use. If the data collection objective is to assess broad-scale landscape level changes, then the collection of imagery with a fixed-wing system is probably more appropriate.

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 burn- ing 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 < 0.03). 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. RESUMEN.—Los mosaicos de vegetacion nativa y no nativa son comunes en los pastizales del occidente de Norteamerica. Si los administradores de tierras pudieran predecir mejor los cambios en la abundancia de especies nativas y no nativas despues de las perturbaciones, se podria 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 canon durante la supresion de un incendio cerca de Lewiston, Idaho. Un estudio previo registro la composicion y cobertura de especies antes del incendio, por lo que pudimos evaluar los cambios en la composicion y abundancia de especies en determinados terrenos antes y despues del incendio. En general, las quemas de verano no afectaron mucho a las comunidades de pradera. Para el tercer ano despues del incendio, Pseudoroegneria spicata se habia repuesto al nivel de cobertura que tuvo antes del incendio y la cobertura de especies anuales nativas y no nativas fue significativamente mayor (P < 0.03) en los sitios quemados que en los no quemados. Tal como se esperaba, la cobertura de Bromus tectorum aumento en los terrenos quemados. Los niveles de cobertura de Centaurea solstitialis antes y despues 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 anos. Como parte de este estudio, tambien 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 tamano de muestra, solo reportamos tendencias a nivel de comunidad, pero sugerimos que esta clase de analisis de comunidades podrian servir como modelo para estudios interesantes en el futuro.

Stands of quaking aspen ( Populus tremuloides ) rank among the most biologically diverse plant communities across the intermountain region of western North America. Marked declines of aspen have occurred in recent decades, likely due to a combination of effects from changes in fire regimes, herbivory, climate (e.g. drought), and interspecific competition with conifer species. However, it is poorly understood how the effects of these factors are manifested at a landscape scale over decadal time periods. Analysis of field data combined with topographic information collected across the 500,000 ha Owyhee Plateau in southwestern Idaho revealed that aspen in the area occur in three different biophysical settings; First, aspen stands exist at high altitudes on south-facing slopes where local conifer species are not likely to occur because of limiting temperature or precipitation levels under current climate conditions. In these areas aspen is the potential vegetation type rather than conifers. Second, aspen grow on anomalously wet microsites (e.g. near springs), and third, aspen grow within upland mixed aspen/conifer stands, which are experiencing rapid rates of conifer establishment. Based on a paired t -test ( α = 0.05) we conclude that stands growing on wet microsites show significantly slower successional rates of conifer establishment relative to upland aspen stands. We developed a conceptual state-and-transition model for upland aspen/conifer stands occurring across a range of topographic positions. We then parameterized the model using extensive field data in the vegetation dynamics computer simulation model Vegetation Dynamics Development Tool (VDDT), and examined the current and future aspen distribution under varying fire regimes. Model results indicate that average fire return intervals of 50–70 years are desirable for maintenance of aspen in upland areas where conifers are present. Under the current fire regime in the area many upland aspen/conifer stands will likely be lost within 80–200 years. Thresholds for the effect of conifer encroachment and browsing on aspen regeneration identified through this research are similar to those described by others across the West. We therefore suggest that the results presented for the Owyhee Plateau are likely applicable to semi-arid aspen woodlands across the American West where succession to conifers is a cause of aspen decline.

Quaking aspen (Populus tremuloides) is declining across the western United States. Aspen habitats are among the most diverse plant communities in this region and loss of these habitats can result in shifts in biodiversity, productivity, and hydrology across a range of spatial scales. Western aspen occurs on the majority of sites seral to conifer species, and long-term maintenance of these aspen woodlands requires periodic fire. Over the past century, fire intervals, extents, and intensities have been insufficient to regenerate aspen stands at historic rates; however the effects of various fire regimes and management scenarios on aspen vegetation dynamics at broad spatial and temporal scales are unexplored. Here we use field data, remotely sensed data, and fire atlas information to develop a spatially explicit landscape simulation model to assess the effects of current and historic wildfire regimes and prescribed burning programs on landscape vegetation composition across two mountain ranges in the Owyhee Plateau, Idaho. Model outputs depict the future structural makeup and species composition of the landscape at selected time steps under simulated management scenarios. We found that under current fire regimes and in the absence of management activities, loss of seral aspen stands will continue to occur over the next two centuries. However, a return to historic fire regimes (burning 12–14% of the modeled landscape per decade) would maintain the majority of aspen stands in early and mid seral woodland stages and minimizes the loss of aspen. A fire rotation of 70–80 years was estimated for the historic fire regime while the current fire regime resulted in a fire rotation of 340–450 years, underscoring the fact that fire is currently lacking in the system. Implementation of prescribed burning programs, treating aspen and young conifer woodlands according to historic fire occurrence probabilities, are predicted to prevent conifer dominance and loss of aspen stands.

Aspen woodland is an important ecosystem in the western United States. Aspen is currently declining in western mountains; stressors include conifer expansion due to fire suppression, drought, disease, heavy wildlife and livestock use, and human development. Forecasting of tree species distributions under future climate scenarios predicts severe losses of western aspen within the next 50 years. As a result, aspen has been selected as one of 14 vital signs for long-term monitoring by the National Park Service Upper Columbia Basin Network. This article describes the development of a monitoring protocol for aspen including inventory mapping, selection of sampling locations, statistical considerations, a method for accounting for spatial dependence, field sampling strategies, and data management. We emphasize the importance of collecting pilot data for use in statistical power analysis and semi-variogram analysis prior to protocol implementation. Given the spatial and temporal variability within aspen stem size classes, we recommend implementing permanent plots that are distributed spatially within and among stands. Because of our careful statistical design, we were able to detect change between sampling periods with desired confidence and power. Engaging a protocol development and implementation team with necessary and complementary knowledge and skills is critical for success. Besides the project leader, we engaged field sampling personnel, GIS specialists, statisticians, and a data management specialist. We underline the importance of frequent communication with park personnel and network coordinators.

With the encroachment of piñon (Pinus ssp.) and juniper (Juniperus ssp.) woodlands onto sagebrush steppe rangelands, there is an increasing interest in rapid, accurate, and inexpensive quantification methods to estimate tree canopy cover and aboveground biomass. The objectives of this study were 1) to evaluate the relationship and agreement of piñon and juniper (P-J) canopy cover estimates, using object-based image analysis (OBIA) techniques and National Agriculture Imagery Program (NAIP, 1-m pixel resolution) imagery with ground measurements, and 2) to investigate the relationship between remotely-sensed P-J canopy cover and ground-measured aboveground biomass. For the OBIA, we used eCognition® Developer 8.8 software to extract tree canopy cover from NAIP imagery across 12 P-J woodlands within the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) network. The P-J woodlands were categorized based on the dominant tree species found at the individual sites for the analysis (western juniper, Utah juniper, and mixed P-J community). Following tree canopy cover extractions, relationships were assessed between remotely-sensed canopy cover and ground-measured aboveground biomass. Our OBIA estimates for P-J canopy cover were highly correlated with ground-measured tree canopy cover (averaged across all regions r = 0.92). However, differences between methods occurred for western and Utah juniper sites (P 40%. There were high degrees of correlation between predicted aboveground biomass estimates with the use of remotely-sensed tree canopy cover and ground-measured aboveground biomass (averaged across all regions r = 0.89). Our results suggest that OBIA methods combined with NAIP imagery can provide land managers with quantitative data that can be used to evaluate P-J woodland cover and aboveground biomass rapidly, on broad scales. Although some accuracy and precision may be lost when utilizing aerial imagery to identify P-J canopy cover and aboveground biomass, it is a reasonable alternative to ground monitoring and inventory practices.

Analysis of the spatial patterns of woody plants is important to better understand the ecological processes that govern the worldwide expansion of woody plants across semi-arid ecosystems. Second-order characteristics of a marked spatial point pattern of western juniper (Juniperus occidentalis subsp. occidentalis) were analyzed using Ripley’s K-functions and the pair-correlation function g. The marked point process of crown diameters was produced via two-dimensional wavelet analysis of a fine scale aerial photograph at the woodland-steppe ecotone in the Reynolds Creek watershed in the Owyhee Mountains, southwestern Idaho. Colonization of J. occidentalis stems from mature juniper trees growing in rocky, fire resistant areas. Although these areas introduce components of natural heterogeneity within the landscape, the selected study area is situated within a single soil type, and we modeled the expansion of juniper plants into previously juniper-free sagebrush steppe as a homogeneous point process with constant intensity. Through this research we have identified two statistically significant spatial scales characteristic of J. occidentalis on the woodland/steppe ecotone: (1) We observed inhibition between J. occidentalis plants at distances

Wavelet analysis represents a powerful set of image processing techniques that have considerable potential to quantify ecologically relevant patterns at multiple scales. This paper provides a preliminary assessment of whether two‐dimensional wavelets convolved with 1 m panchromatic aerial photography can be used to detect automatically the location and crown diameters of western juniper (Juniperus occidentalis) plants as they encroach upon a sagebrush (Artemisia spp.) steppe landscape. The juniper crown diameters derived from wavelet analysis produced a strong correlation with crown diameters measured via comparable hand‐digitizing in a geographic information system (r = 0.96, n = 69) with a 5% commission and an 8% omission error. Through comparison with historical photography, we found that juniper plant cover increased 2.7 fold (from 2.7% to 7.3% total cover) during the period from 1939 to 1998 within the 15 ha study area. This approach has considerable potential for the long‐term monitoring of vegetati...

Fire is a major driving force of landscape change in the Mediterranean region. The objectives of this paper were to explore the implications of landscape change and wildfires in a region of northwestern Portugal for the diversity of breeding birds. Land use cover for the years 1958, 1968, 1983 and 1995 was obtained from aerial photography for a study area of 3700 ha. Breeding bird assemblages in each of six land use categories were characterized in 1998 using point counts. The main landscape changes in the study area across the 40 years were a decrease in the area of agricultural land and low shrublands (respectively 29% and 48%) and an increase in forests and tall shrublands (both over 95%). Bird assemblages showed increased richness and diversity across the gradient: low shrublands → tall shrublands → conifer → mixed → deciduous → agricultural areas. Many of the species with narrow niche breadth (specialists) were associated with agricultural areas and deciduous forests. In spite of the low diversity of burned areas (mostly shrublands) a few specialist species depend on this habitat. Thus, the current fire regime probably contributes to maintaining bird diversity at the landscape level. There was an inverse relationship between landscape diversity and estimated bird diversity across the last 40 years. Landscape management actions to preserve bird diversity should focus on the maintenance of agricultural land and deciduous forests. In parallel, a wider use of prescribed burning and grazing is suggested. This would contribute to maintaining low shrublands in the landscape, useful both as an habitat for some bird species and as fuel breaks for preventing the occurrence of large wildfires.

Fire has historically been an important ecological component of forests in the Intermountain Region of the northwestern United States, This study is set in a small biogeographically disjunct mountain range. Our research objectives were to (1) investigate the historical frequency, severity, size, and spatial pattern of fire: (2) determine if and how fire regimes have changed since Euro-American settlement; and (3) compare how fire regimes of a small isolated range compare to nearby, but considerably larger, mountain agglomerations. Our findings suggest that this mountain range has historically supported fires typified by small size and high frequency, resulting in a high degree of spatial pattern complexity compared to mountain agglomerations. We also found disparity in size and burn severity solely within the study area based on the bisecting Continental Divide. Since the advent of Euro-American settlement in the 1870s, fire frequency and sizes of individual fires in the West Big Hole Range have significantly decreased resulting in an estimated 87% reduction in area burned. We discuss potential relationships of mountain range isolation and fire regimes in the Intermountain Region. Furthermore, we suggest that the relative small size of this mountain range predisposes it to greater anthropogenic effects upon fire occurrence.

Mechanical and prescribed fire treatments are commonly used to reduce fuel loads and maintain or restore sagebrush steppe rangelands across the Great Basin where pinyon (Pinus) and juniper (Juniperus) trees are encroaching and infilling. Geospatial technologies, particularly remote sensing, could potentially be used in these ecosystems to (1) evaluate the longevity of fuel reduction treatments, (2) provide data for planning and designing future fuel-reduction treatments, and (3) assess the spatial distribution of horizontal fuel structure following fuel-reduction treatments. High-spatial resolution color-infrared imagery (0.06-m pixels) was acquired for pinyon and juniper woodland plots where fuels were reduced by either prescribed fire, tree cutting, or mastication at five sites in Oregon, California, Nevada, and Utah. Imagery was taken with a Vexcel UltraCam X digital camera in June 2009. Within each treatment plot, ground cover was measured as part of the Sagebrush Steppe Treatment Evaluation Project. Trimble eCognition Developer was used to classify land cover classes using object-based image analysis (OBIA) techniques. Differences between cover estimates using OBIA and ground-measurements were not consistently higher or lower for any land cover class and when evaluated for individual sites, were within ±5 % of each other. The overall accuracy and the K hat statistic for classified thematic maps for each treatment were: prescribed burn 85 % and 0.81; cut and fell 82 % and 0.77, and mastication 84 % and 0.80. Although cover assessments from OBIA differed somewhat from ground measurements, they are sufficiently accurate to evaluate treatment success and for supporting a broad range of management concerns.

Secondary succession of understory communities in Pinus pinaster forests after prescribed fire is evaluated in terms of changes in cover and frequency. To have some information on density changes, relationships were established between percentage of absence and density for the major species. Frequency composition is not significantly affected by fire. However, cover composition is affected but rapidly recovers to preburn levels. Diversity is almost unaffected by fire. From the analysis of the individual species it is concluded that in general, forb and grass cover increase initially after fire. Shrub cover decreases after fire but changes in density and rate of recovery are dependent upon species' sprouting ability. Pine seedlings increase greatly after fire. It is concluded that postfire communities are easily predicted from preburn composition because of the adaptations of the major species to fire.

[1] Although regional increases in woody plant cover in semiarid ecosystems have been identified as a worldwide phenomenon affecting the global carbon budget, quantifying the impact of these vegetation shifts on C pools and fluxes is challenging. Challenges arise because woody encroachment is governed by ecological processes that occur at fine spatial resolutions (1–10 m) and, in many cases, at slow (decadal-scale) temporal rates over large areas. We therefore analyzed time series aerial photography, which exhibits both the necessary spatial precision and temporal extent, to quantify the expansion of western juniper into sagebrush steppe landscapes in southwestern Idaho. We established upper and lower bounds of aboveground woody carbon change across the landscape via two-dimensional spatial wavelet analysis, image texture analysis, and field data collection. Forty-eight 100-ha blocks across a 330,000-ha region were stratified by topography, soil characteristics, and land stewardship for analyses. Across the area we estimate aboveground woody carbon accumulation rates of 3.3 gCm−2yr−1 and 10.0 gCm−2yr−1 using the wavelet and texture method, respectively, during the time period 1946–1998. Carbon accumulation rates were significantly affected by soil properties and were highly dependent on the spatial and temporal scales of analysis. For example, at a 100-ha scale the aboveground carbon accumulation varied from −1.7 to 9.9 gCm−2yr−1, while at the 1-ha scale the range of variability increased to −11 to 22 gCm−2yr−1. These values are an order of magnitude lower than those previously suggested due to woody encroachment, highlighting the need for examining multiple spatial scales when accounting for changes in terrestrial carbon storage.

Juniper (Juniperus spp.) and piñon (Pinus spp.) trees have encroached millions of hectares of sagebrush (Artemisia spp.)–bunchgrass communities. Juniper–piñon trees are treated to reduce canopy fuel loads and crown fire potential. We measured the effects of juniper–piñon infilling and fuel-reduction treatments on fuel load characteristics at four locations in Utah. At each location, treatment areas were burned, left untreated, or trees were cut or masticated in a randomised complete-block design. We measured standing and downed fuels by size and type along 30-m transects on 15 subplots (30 × 33 m) per location before and 1–3 years after treatment. Increased tree cover was associated with decreased shrub and herbaceous fuel loads (P

Expansion of western juniper (Juniperus occidentalis Hook. var. occidentalis) has altered vegetation composition, fire behaviour and fire potential throughout south-western Idaho and eastern Oregon. Utilising GIS-derived products and fire-simulation software, the influence of the spatial arrangement of different woodland developmental stages on simulated surface fire occurrence was evaluated. Custom fuel models and a recent vegetation map processed in FARSITE under moderate fire conditions were used to create a fire-occurrence grid in three sixth-order watersheds on the Owyhee Plateau of south-western Idaho. Landscape pattern metrics were selected to quantify the spatial arrangement of plant communities within a neighbourhood around points from each successional stage randomly placed within each watershed. Linear regression analysis of fire occurrence and each of the selected landscape metrics was compared for four successional stages of western juniper encroachment to assess the effect of landscape-scale vegetation arrangement on fire occurrence. The landscape structure had little influence on whether an early-successional area burns in a surface fire, whereas the surrounding landscape structure influenced whether a late-successional or mature woodland area burned. Landscape metrics that showed significance in late-successional and mature woodland stages include patch density, mean area and Simpson’s diversity.

Plant mortality and productivity in semiarid grasslands may be affected by the length of time grazing is excluded during the postfire regeneration period. The degree of grazing tolerance for the semiarid bunchgrass species, Festuca idahoensis and Agropyron spicatum, exposed to fire, and how the variation in grazing tolerance was affected by the length of time allowed for undisturbed plant regeneration after fire, were central questions addressed in this study. We examined the degree of plant mortality and productivity that resulted from the interaction of fire and grazing. Plants exposed to fire alone, i.e., without subsequent defoliation, exhibited low plant mortality, although culm production was reduced relative to unburned plants. An early-season-defoliation treatment after fire resulted in the plant mortality as high as 50% for Festuca and 70% for Agropyron bunchgrasses. Plant height and the number of vegetative and reproductive culms were also most affected by this defoliation treatment. These detrimental effects were lessened when defoliation was delayed by one growing season after the fire. Although our results suggest that one growing season seems to be enough for both species to recover after the fire, more studies will be necessary to confirm these trends, and induce changes in current grazing management policies.

Book Review: The Landscapes of Craters of the Moon National Monument, R. Gerald Wright, Stephen C. Bunting. University of Idaho Press, Moscow, Idaho (1994).

A study was conducted in 1984 to determine the effect of fall prescribed burning on seed production of bluebunch wheatgrass (Agropyron spicatum), Idaho fescue (Festuca idahoensis), and Columbia needlegrass (Stipa columbiana) in the sagebrush (Artemisia spp.)/grassland region. Plots were located on 7 burns of ages 1 to 5 years, with plots in adjacent unburned areas serving as controls. Seed production (seeds per plant) of bluebunch wheatgrass was greater on 2 of four 1-year-old burns and on one 3-yearold burn than on unburned comparison areas. Idaho fescue seed production was greater on a 5-year old burn than on the control plot, but not statistically different from the controls on 1or 3-year-old burns. Columbia needlegrass seed production was markedly greater on a 2-year-old burn than on adjacent unburned areas. The percentage of filled florets and the number of seeds per inflorescence tended to be greater on burned plots for all 3 species. Bluebunch wheatgrass showed a variable response in the number of inflorescences produced per plant 1 year after burning, but there were significantly (P?0.05) more inflorescences per plant on the 3-year-old burn than the control. Idaho fescue plants produced fewer inflorescences on both 1-year-old burns than on the control plots, but more on the 5-year-old burn than on the control. Columbia needlegrass plants produced more inflorescences on the burn than on the control.

Few brownspine pricklypear were immediately killed by the direct effects of fire. Most plants resprouted after burning in the spring, but mortality averaged 70% by the end of the fourth year after burning. Interactions of fire with insects and rodents caused most of the brownspine pricklypear mortality. V>alkingstick cholla and tasajillo were more directly affected by fire than brownspine pricklypear. First-year mortality was 40 to 65%, respectively; and fourth year mortality was 57 to 80%. Mortalities of other minor species of cactus varied from 49 to 100%. The increase of cactus on grassland ranges, particularly in the Southwest, has been a problem for many years. During a 17-year period (1932-1949) in southern Arizona, jumping cholla (Opuntia fulgida) increased from 5 to 368 plants/ha, cane cholla (0. spinosior) increased from 14 to 785 plants/ha, and Engelmann pricklypear (0. engelmnannii) increased from 0 to 74 plants/ha in a grazed area (Glendening 1952). On an ungrazed area, percentage increase for cane cholla and Engelmann pricklypear were similar to the increases on a grazed area over the same period of time (Glendening 1952). These data indicate that neither reduced grazing pressure nor increasd grass competition will prevent the increase of cacti density. However, Cook (1942), working in the Central Great Plains with pricklypear (0. humifusa), observed that ranges with dense stands of grass also supported high populations of Melitera dle,tcitca, a cactus feeding moth, during years with aboveaverage precipitation. The cactus feeding moth was a major factor in reducing cactus density. Ranges in poor condition did not have high enough populations of moths to cause cactus mortality. Thus, reduced grazing pressure in combination with above-normal moisture can reduce the density of cacti, at least on the eastem edge of cacti ranges. Drouths favor cacti throughout their range (Cook 1942; Houston 1963), and fire and animal use are left as the primary factors to control their density (Humphrey 1958). High densities of cactus plants can reduce forage production and utilization. Rea and Pieper (1973) found that controlling walkingstick cholla (0. imbricata) on blue grama (Bouteloua grtacilis) range increased herbage production by 20% and utilization by 9%. Bement (1968), however, was unable to show an increase in herbage production after control of plains pricklypear (0. polyacantha). Authors are assistant professor of range management, College of Forestry, Wildlife, and Range Sciences, University of Idaho, Moscow 83843 and Horn professor of range management, Texas Tech University, Lubbock, Texas 79409; and assistant professor of Forestry, College of Forestry, Wildlife, and Range Sciences, University of Idaho, Moscow 83843. This research is a contribution of the College of Agricultural Sciences, Texas Tech University, Publication Number T-9-184. Manuscript received February 16, 1978. Cactus plants vary in their response to fire, depending on species, size, and how soon they are observed after a fire. In Arizona, Humphrey and Everson (1951) found that 1 year after a fire the densities of Englemann pricklypear, jumping cholla, and cane cholla had decreased 9, 29, and 7%, respectively. However, Reynolds and Bohning (1956) reported that a prescribed fire reduced densities of barrel cactus (Feroca(ctus JtiSlizeni) 67%, jumping cholla 44%, cane cholla 45% and Engelmann pricklypear 28% after 2 years. Similarly, Cable (1967) found that fire reduced densities of jumping cholla 63%, cane cholla 45%, and Engelmann pricklypear 32% by the second year after a fire. In Texas, mortality of brownspine pricklypear (0. phaeicanitha) was 20% the year after burning and 68% after the second year (Heirman and Wright 1973). Thus, first year mortality is not an adequate indication of the effect of fire on cacti mortality. Small cacti are more susceptible to fire damage than the taller plants (Dwyer and Pieper 1967; Heirman and Wright 1973). Density of walkingstick cholla less than 0.3 m tall was reduced 50%, but larger plants were not severely damaged by fire (Dwyer and Pieper 1967). Hierman and Wright (1973) found that the mortality of walkingstick cholla less than 0.3 m tall was 81%, and for those greater than 0.3 m tall, mortality was 45%. They observed little difference in the mortality of large (>10 pads) and small ( 25) and cholla and tasajillo by height (?0.6 m and >0.6 m tall). Mortality was recorded during July and December each year until December, 1976. Mortality was determined by the absence of living tissue above ground on permanently marked plants on each sampling date. Subsequent mortalities were accumulative for every species on each prescribed burn. An individual cactus plant might be recorded as "dead" on one date and then resprout and be recorded as "living" on a following date. This resulted in a decline in mortality for tasajillo during some years. Chi-square analysis was used to test for differences in mortality between burned and unburned treatments and between size classes of cacti plants. Results and Discussion Brownspine Pricklypear Fire caused little immediate mortality of brownspine pricklypear. The plants were usually top-killed, but within a few weeks after the burn all had resprouted. Average mortality was only 20% at 6 months after the fire. By the end of the third year, however, mortality exceeded 70% (Fig. 1). After the third year, mortality of pricklypear increased about the same rate as it did for the unburned plants. Mortality during the first 3 years apparently was caused primarily by fire weakening the plant and making it more susceptible to damage by insects, rodents, and rabbits. Insects entered the plant through fire-scarred tissue and spread to the young living pads, opening the plant to bacterial and fungal infections. Pads sprouting from burned plant tissue often lost their vascular connection to the root system because of insect damage and decay. Plants sprouting from the root crown survived for a longer period but many of these also died. Most of the plants that survived after 3 years, however, had sprouted from the root crown. Young pads require several weeks before the spines are fully developed. During this time they are frequently browsed by lagomorphs and rodents. This is particularly important during the winter and dry summers when other green material is scarce. The mortality of both burned and control (unburned) plants increased during years when precipitation was below average. Over 50% of one set of control pricklypear plants located on a shortgrass site died during one drought year, probably because they were easily visible and eaten by lagomorphs and rodents. Only 8% of the control plants on tobosagrass sites died during this period. The taller grasses on these sites seem to provide 100 OPUNT IA PHAEACANTHA

Highlight: Based on this research and other work that has been reported, honey mesquite is very difficult to kill with fire on the High Plains and along river bottoms in the Rolling Plains. On upland sites in the Rolling Plains, 27% of the mesquite trees were killedfollowing single fires. Using repeated fires on upland sites at 5 to 10 year intervals, the potential exists to kill 50% of the older mesquite trees. Seedlings of honey mesquite were easy to kill with moderate fires until they reached 1.5 years of age, severely harmed at 2.5 years of age, and very tolerant of intense fires after 3.5 years of age.

Prescribed burning in Pinus pinaster forests was evaluated in terms of the effects on Chamaespartium tridentatum. Postfire forage quantity and quality were studied. Total biomass production, current year's shoot production, and nutritive value were studied in relation to time since rue. Chamaespartium, a vigorous resprouter, achieved 50%O of its preburn biomass level in 2 years. Current year's shoot production reached a maximum 3 to 4 years after fire. Nutritive value of Chamaespartium was briefly enhanced by burning but returned to preburn levels. Seasonal variations of forage quality were very important with lower values in summer or fall. Short-lived increases in protein, cellulose, and hemi-cellulose contents after fire in Chamaespartium shoots returned to preburn levels in 4 years. This supported the traditional fire frequency in the shrublands of 3 to 7 in order to maintain forage quality and productivity.

The effect of fire intensity on understory vegetation on serri stands of ponderosa pine are presented. Vegetational recovery for 2 burn intensities and unburned sites were compared. The results suggest a change in the understory dominance structure foilowhrg underburning is related to the amount of duff consumed by the fire and independent of fire line intensity and flame length. A significantly greater proportion of duff was removed on high fire intensity sites (80%) than on low intensity sites (40%). However, the variation in fire line intensity was great, with some overlap. Fire line intensity ranged from 30 to 3,034 kcai/m-s on high intensity sites and from 25 to 194 kcai/m-s on low intensity sites. Flame length ranged from 0.1 to 1.7 m on both high and low intensity sites. Graminoid canopy coverage was lowest on high intensity sites. The reduction was apparently the result of prolonged smoldering of the duff layer. There was no significant difference in coverage among treatments for shrubs or forbs. A significant change in frequency among treatments was noted for 11 of 54 species sampled. Prescribed burning can be an effective tool in managing seral stands of ponderosa pine (Pinusponderosa). Fire may be used to reduce fuel loading, thin thickets of saplings, create mineral seedbed for seed germination, remove shade tolerant trees from the understory, prune the lower branches from trees, and reduce needle litter on the soil surface (Biswell et al. 1973). Prescribed burning can also be an effective tool for understory vegetation management. Herbaceous yields are dependent on the percent tree overstory canopy closure and the amount of accumulated litter (Wright 1978). Different intensity fires may be used to manipulate the total tree canopy and litter depth. The effect fire intensity may have on understory development has not been previously studied. The objective of this study was to evaluate the effect of fire intensity on early vegetational development in ponderosa pine communities of the Douglas-fir/ ninebark (Pseudotsuga menriesiij Physocarpus

Although a useful method for monitoring changes in species composition, frequency sampling does not provide herbage production or cover data needed to use existing range condition guides. Responding to this need, frequency sampling procedures were investigated for determining range condition. Eighteen mountain meadow sites were sampled with 100 nested frequency quadrats. These quadrats had 5 plot sizes contained (nested) within 1 frame: 5X5 cm, 1OX10 cm, 25X25 cm, 25X50 cm, and 50X50 cm. Rooted frequency of occurrence within each plot size was recorded by species. Discriminant analysis related a site's frequency data to its known range condition class, resulting in 2 range condition guides for mountain meadows based on frequency data. One guide was formulated with data from the 1OX10-cm quadrat size, and a second guide was based on summed data from the 4 largest plot sizes. Both guides had equal resolution, correctly classifying 15 of 18, or 83%, of sites examined. Our procedures should prove valuable in developing condition guides based on frequency data in other areas and in other vegetation types. Among the first to recognize that plants could be used as indicators of successional stages were Sampson (1919) and Jardine and Anderson (1919). Dyksterhuis (1948, 1949) refined the idea of plants as successional indicators and developed range condition classes based on a site's existing vegetation in relation to the site's potential climax. Continuing the work of Weaver and Hansen (1941), Dyksterhuis used the terms decreasers, increasers, and invaders to describe a species' ecological response to grazing presAuthors are research assistant, Range and Wildlife Management Department, Texas Tech University, Lubbock 79409; associate professor and professor of range resources, University of Idaho, Moscow 83843. At the time of the research, the senior author was research assistant, Range Resources Department, University of Idaho, Moscow 83843. Research was funded in part by USDA Science and Education Administration Grant No. 59-2161-1-2-082-0 and Forest, Wildlife and Range Exp. Sta., University of Idaho Contribution No. 278. The authors gratefully acknowledge personnel of the Boise, Payette, and Sawtooth National Forests for their assistance with this study. Manuscript accepted 17 February 1986. sure. Decreasers and increasers are species of undisturbed climax communities, whereas invaders are nonclimax species. Greater relative proportions of decreasers and increasers to invaders indicate higher successional stages. Current U.S. Soil Conservation Service (SCS) range analysis procedures use the decreaser, increaser, and invader concepts (USDA 1976). In contrast to Dyksterhuis' purely ecological approach, Parker (Parker, K.W. 1951. A method for measuring trend in range condition on national forest range. USDA, Forest Service Mimeo.) introduced a condition classification concept that included livestock production and soil stability as additional criteria for evaluating plant species. Similar to the decreasers, increasers, and invaders presented by Dyksterhuis, Parker developed categories of desirables, intermediates, and least desirables. But Parker, instead of relying solely on a species' ecological role, included forage quality, palatability, and rooting characteristics as criteria for classifying species into his desirability groups. Most U.S. Forest Service (USFS) regions use Parker's desirable, intermediate, and least desirable categories in their range analysis procedures. Because different criteria are employed to judge plant species, the USFS and SCS methods may differ dramatically in their condition ratings of the same plant community. Whichever species classes are used in evaluating a site's range condition, those of Dyksterhuis or those of Parker, an investigator must first record the plant community's species composition. Species composition is the relative abundance of the species present in a plant community and is usually determined by measuring yield, cover, density, or frequency. It is important to realize that composition estimates will differ depending upon which measure is used. Since species composition is a relative comparison, it describes a community only in relation to the parameter upon which the composition estimates are based. Estimates of composition based on different parameters are not equivalent. For sampling ease and repeatability, a stable, objective measure is preferred for estimating JOURNAL OF RANGE MANAGEMENT 39(6), November 1986 561 This content downloaded from 157.55.39.147 on Sun, 07 Aug 2016 06:05:33 UTC All use subject to http://about.jstor.org/terms species composition. Estimates based on yield or cover, however, fluctuate with seasonal and yearly climatic changes (Craddock and Forsling 1938, Odum 1960). And density, although a stable vegetation parameter, is often difficult and time consuming to measure, especially when plants reproduce vegetatively (Strickler and Stearns 1963). In contrast to these other parameters, perennial plant frequencies are simple to obtain, objective, and relatively stable from season to season and year to year (Hyder et al. 1966, MuellerDombois and Ellenburg 1974). Frequency is based on presence or absence of a species in a given number of repeatedly placed small quadrats. A species' frequency is the percentage of quadrats in which it occurs, varying from 0 to 100%. Because frequency is simple to obtain, objective, and relatively stable from season to season and year to year, frequency sampling is advantageous for monitoring changes in species composition. But as mentioned above, species composition based on frequency is not equivalent to composition by yield or cover-the inputs needed to use many current range condition guides. Frequency sampling can be used to monitor changes of individual species, but there is presently no way to describe these changes in terms of range condition classes. Development of condition guides based on frequency data would preclude the need to use 2 different sampling methods, 1 for monitoring changes of particular species and an additional method for classifying a site's range condition.