Stephen C. Bunting

Landscape changes and breeding bird assemblages in northwestern Portugal: the role of fire

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.

Wavelet estimation of plant spatial patterns in multitemporal aerial photography

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 vegetation change via aerial photograph and other remotely sensed imagery.

Comparison of Unmanned Aerial Vehicle Platforms for Assessing Vegetation Cover in Sagebrush Steppe Ecosystems

Abstract 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.

Landscape Trends (1753-1993) of Whitebark Pine (Pinus albicaulis) Forests in the West Big Hole Range of Idaho/Montana, U.S.A.

Pinus albicaulis (whitebark pine) is an important tree species in subalpine forests of the Northern Rocky Mountains. Populations have been declining at unprecedented rates due to the introduction of an exotic pathogen and fire suppression. We initiated this study to evaluate historical trends in Pinus albicaulis abundance along with associated subalpine conifers within a small biogeographically disjunct mountain range. The central objective was to estimate historic trends in subalpine forest composition and structure at the species and community scales. Reconstruction of forest stands reveals an 85% increase in tree volume among all species since the 1870s. Pinus albicaulis has historically dominated most stands associated with Abies bifolia (subalpine fir) and Picea engelmannii (Engelmann spruce) but dominance has shifted to these late-seral species for most of the study area since the early 1900s. We estimate, that since 1753, nearly 50% of the study area has shifted to later successional stages while only 3% has receded to earlier stages. We discuss the implications for Pinus albicaulis and suggest that careful reintroduction of fire can aid in the maintenance of ecological integrity at the community and landscape scales.

Utah juniper and two-needle piñon reduction alters fuel loads

Juniper (Juniperus spp.) and pinon (Pinus spp.) trees have encroached millions of hectares of sagebrush (Artemisia spp.)–bunchgrass communities. Juniper–pinon trees are treated to reduce canopy fuel loads and crown fire potential. We measured the effects of juniper–pinon 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 < 0.01). By 2 years post-treatment, herbaceous fuel loads were greater than pretreatment in all treated areas (P < 0.01). Cut and mastication treatments increased surface woody 10- and 100-h fuel loads and wood/bark cover (P < 0.01). Masticated-tree depth was a good estimator of fuel loads (R2 = 92). The conversion of canopy fuels to surface fuels reduced fuels that enable crown fire and extreme fire intensity. Cool-season prescribed fire may need to follow mechanical treatments to reduce surface fuel and the potential for wildfire damage to perennial understorey vegetation.

Effect of burning on seed production of bluebunch wheatgrass, Idaho fescue, and Columbia needlegrasss.

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.

Assessing the Relationship between Ground Measurements and Object-Based Image Analysis of Land Cover Classes in Pinyon and Juniper Woodlands

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.

Utilizing National Agriculture Imagery Program Data to Estimate Tree Cover and Biomass of Piñon and Juniper Woodlands

Abstract 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 < 0.05), and were more prominent where tree canopy cover was > 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.

Using Unmanned Helicopters to Assess Vegetation Cover in Sagebrush Steppe Ecosystems

Abstract 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. Resumen Evaluar la cobertura vegetal es un importante factor para entender la sustentabilidad de muchos ecosistemas. Métodos de teledetección con suficiente precisión pueden considerablemente alterar la manera en como los recursos bióticos son monitoreados tanto en propiedad privada y pública. El laboratorio Nacional de Idaho (INL), en conjunto con la universidad de Idaho, evaluaron si vehículos aéreos no tripulados (UAVs) son suficientemente precisos y más eficientes que los métodos de campo basados en punto de referencia para monitorear la cobertura de las vegetación y el suelo desnudo en los ecosistemas de pastizales de Artemisia. Estas evaluaciones son de interés para los manejadores de tierra ya que normalmente hay pocos científicos dedicados al estudio de los recursos naturales así como escasos recursos monetarios para evaluaciones integrales. En este proyecto, helicópteros no tripulados fueron usados para recolectar imágenes usadas para determinar la cobertura vegetal durante junio y julio de 2005. Las imágenes fueron usadas para estimar el porcentaje de cobertura de seis clases de cubierta vegetal (arbustos, arbustos muertos, pastos, herbáceas, hojarasca y suelo desnudo). Parcelas de campo que fueron usadas para recolectar las imágenes así como las mediciones en campo fueron localizadas en el sitio INL al oeste de Idaho Falls, Idaho. Evaluaciones oculares de imágenes digitales fueron realizadas usando SamplePoint y los resultados fueron comparados con las mediciones de campo recolectadas usando el método de point-frame. La evaluación de las imágenes recolectadas por el helicóptero mostró un alto grado de correlación con respecto a las evaluaciones de campo para pastos, hojarasca, y suelo desnudo, y una razonable relación para plantas muertas. Las cobertura de los arbustos fue regularmente sobrestimado y para las herbáceas fueron generalmente subestimadas. El método del helicóptero tomo 45% menos tiempo que el método de campo. Este estudio demostró que la tecnología UAV proporciono un método viable para monitorear los tipos selectivos de cobertura en los pastizales y podría salvar tiempo y recursos.

Cover Estimations Using Object-Based Image Analysis Rule Sets Developed Across Multiple Scales in Pinyon-Juniper Woodlands

Abstract 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 r = 0.52 to r = 0.98). Correlations for regional and network rule sets were lower (ranging from r = 0.24 to r = 0.63), 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.