Investigations of vegetation stress along non-paved roads treated with a range of magnesium chloride (MgCl 2 ) application rates utilized 60 roadside and 79 drainage plots on 15 and 18 roads, respectively. Evaluations were completed of foliar damage, plant health, biotic and abiotic damage incidence and severity, soil and foliar chemistry and other common site and stand characteristics of Pinus contorta, Populus tremuloides, Picea engelmannii, Abies lasiocarpa, and lower elevation plots dominated by shrubs and grasses. High concentrations of soil magnesium and chloride (400-500 ppm), high foliar chloride (2,000-16,000 ppm depending on species) and high incidence of foliar damage were measured in roadside plots along straight road segments in the first 3 to 6.1 m adjacent to treated roads. In drainage plots, where water is channeled off roads, high concentrations of both magnesium and chloride ions and associated foliar damage were measured between 3 and 98 m from the road. High incidence of foliar damage and elevated ion concentrations were not apparent in control plots along non-treated roads. Lodgepole pine appeared to be the most sensitive species, while aspen accumulated the most chloride and exhibited the least amount of damage. Foliar chloride concentrations strongly correlated with percent foliar damage for all species (r=0.53 to 0.74, p< 0.0001) while the incidence of biotic damages did not correlate well. Positive relationships between foliar chloride and magnesium chloride application rates were strong and can be used to predict foliar concentrations and subsequent damage to roadside trees.

Success of extensive green roof vegetation depends primarily on associated plant species' ability to survive the low moisture content of the substrate. As a result of the well-drained nature of the substrate, plants adaptable to dry, porous soils are primarily used in extensive green roof applications. Although Sedum species have dominated the plant palette for extensive green roofs, there is growing interest in expanding the plant list for extensive green roof systems. To effectively select suitable plants, species need to be evaluated in terms of their response to gradual and prolonged dry down of the substrate. A study to determine the relative rates of dry down for 15 species was conducted in greenhouse trials. During dry downs that extended over 5 months, the substrate of succulent and herbaceous species dried down at different rates. The change in moisture content of the substrate was not consistent among succulent and herbaceous plant species during the initial 18 d of dry down. Despite differences in rate of dry down, the succulent species, as a group, maintained viable foliage for over five times longer than the herbaceous species. The revival rates of the succulent species were nearly double those of the herbaceous species. Therefore, not only are succulent species more likely to survive during periods of drought, but these species are more likely to resume growth soon after water is again made available.

The smaller European elm bark beetle, Scolytus multistriatus, has been the primary vector of the Dutch elm disease fungus, Ophiostoma novo-ulmi, in elm trees in Colorado since 1948. An exotic from Asia, the banded elm bark beetle, Scolytus schevyrewi, was found in Siberian elm, Ulmus pumila, in Colorado in April of 2003; this was the first report of S. schevyrewi in North America. S. schevyrewi is now found throughout much of Colorado and in at least 21 other states. The similarities in breeding and feeding habits between S. schevyrewi and S. multistriatus have raised concerns about the ability of S. schevyrewi to serve as a vector for O. novo-ulmi. The objective of this preliminary study was to determine if O. novo-ulmi could be isolated from adult S. schevyrewi emerging from diseased elm trees. S. schevyrewi and S. multistriatus were allowed to infest diseased stem segments of American elm, Ulmus americana. The infested stem segments were caged and isolations were made from the adult brood that emerged. O. novo-ulmi was isolated from most of the adults of both beetle species, showing that S. schevyrewi could acquire the pathogen as effectively as S. multistriatus. Future studies are needed to determine if S. schevyrewi can effectively transmit the pathogen to healthy trees.

This research examined plant area covered (plant cover) for six plant species on an existing modular extensive green roof in a semiarid climate. Species evaluated were Antennaria parvifolia Nutt., Bouteloua gracilis (Kunth) Lag., Delosperma cooperi (Hook. f.) L. Bol., Eriogonum umbellatum Torr. aureum ‘Psdowns’, Opuntia fragilis Nutt., and Sedum lanceolatum Torr. Many methods for measuring plant cover are subjective and based on semiquantitative measurements. This study compared digital image analysis data (DIA) with manually collected converted two-dimensional data (C2D) for plants grown on an extensive green roof. For each plant in the study, digital images and manual two-dimensional measurements were taken on four dates (at 6-week intervals) in 2008 and on four dates (at 6-week intervals) in 2009. Additionally, comparisons between DIA data and final biomass, and C2D and final biomass, were performed. Plant cover increased for all six species during the 2008 growing season. However, E. umbellatum aureum ‘Psdowns’ had a low overwintering rate (12.5%) and was removed from analysis in 2009. In the spring of 2009, four of the five remaining species exhibited decreased plant cover as a result of winter dieback; the one exception was O. fragilis. In terms of plant cover, both quantification methods (C2D and DIA) revealed that B. gracilis and D. cooperi had more plant cover than A. parvifolia, O. fragilis, and S. lanceolatum by the end of the study. Thus, five of the six species evaluated in this study are appropriate for use in extensive green roof applications in semiarid regions. High levels of correlation were found between the DIA and C2D data sets (r = 0.77) averaged over the five species on all eight data collection dates. The groundcover species (A. parvifolia, D. cooperi, and S. lanceolatum) had a higher correlation on average (r = 0.83) than the upright (B. gracilis, r = 0.70) and decumbent (O. fragilis, r = 0.65) species. Additionally, DIA and final biomass correlations showed parallel trends with groundcovers averaging r = 0.83, upright r = 0.64, and decumbent r = 0.41. Therefore, using DIA to evaluate plant cover and biomass accumulation is especially appropriate for groundcover species.

A multi-faceted research project was conducted on a modular green roof in semi-arid, high elevation Denver, Colorado U.S.A. A photovoltaic (PV) array ran along the southeastern edge of the research area and visibly influenced the plant growth, cover and biomass. Plants grown near the PV prospered compared to plants in the exposed area. Average summer temperatures in the modules under the PV array were cooler with less temperature variation compared to the modules located in the exposed areas of the green roof. Shading structures integrated on green roofs may produce effects that resemble natural ecotones tending towards greater plant coverage and biomass, and therefore greater green roof resilience.

Summary Dutch Elm Disease (DED) is a vascular wilt disease of Ulmus species (elms) incited in North America primarily by the exotic fungus Ophiostoma novo‐ulmi. The pathogen is transmitted via root grafts and elm bark beetle vectors, including the native North American elm bark beetle, Hylurgopinus rufipes and the exotic smaller European elm bark beetle, Scolytus multistriatus. The banded elm bark beetle, Scolytus schevyrewi, is an exotic Asian bark beetle that is now apparently the dominant elm bark beetle in the Rocky Mountain region of the USA. It is not known if S. schevyrewi will have an equivalent vector competence or if management recommendations need to be updated. Thus the study objectives were to: (i) determine the type and size of wounds made by adult S. schevyrewi on branches of Ulmus americana and (ii) determine if adult S. schevyrewi can transfer the pathogen to American elms during maturation feeding. To determine the DED vectoring capability of S. schevyrewi, newly emerged adults were infested with spores of Ophiostoma novo‐ulmi and then placed with either in‐vivo or in‐vitro branches of American elm trees. The inoculation of trees via feeding wounds was successful 30% of the time for in‐vivo trials and 33% for in‐vitro trials. Although the infection rate of DED has declined in Colorado over the past 10 years, the disease is still present in urban elms. While it appears that S. schevyrewi is another vector of the DED pathogens, it appears that S. schevyrewi is no more efficient than S. multistriatus. Thus, management programs that remove elm bark beetle breeding sites, rapidly remove DED‐infected elms and include the planting of DED‐resistant elms should continue to be effective management tactics.

Magnesium chloride (MgCl2)-based dust suppression products are commonly used throughout western United States on nonpaved roads for dust suppression and road stabilization by federal, state, and county transportation agencies. The environmental implications of annually applying these products throughout spring and summer months on adjacent stream chemistry are not known. Sixteen streams were monitored biweekly for 1 to 2 yr in two Colorado counties for a suite of water quality variables up and downstream of nonpaved roads treated with MgCl2-based dust suppression products. Eight of 16 streams had significantly higher downstream than upstream concentrations of chloride or magnesium over the entire monitoring period (p

This research examined soilless green roof substrate blends on an existing modular extensive green roof in Denver, Colorado, USA. Substrate blends evaluated include an extensive green roof substrate, Green Grid® and Green Grid® plus varying percentages of ZeoPro™ H-Plus. Plant taxa used included Sedum acre L., Sedum album L., Sedum spurium Marsch-Bieb. ‘Dragon's Blood’ and S. spurium ‘John Creech’. Substrate blends were evaluated based on plant taxa growth performance. Data collected included digital images to measure plant area covered using digital image analysis (DIA) and substrate volumetric moisture content (VMC). All data were analyzed over two growing seasons using the GLIMMIX procedure in SAS as multiple comparisons of substrate blends for each taxa, DIA data were analyzed from eight dates and VMC data were analysed from seven dates. The addition of zeolite (ZeoPro™) to the typical extensive green roof substrate improved establishment year plant cover for S. acre and S. album but hindered overwintering. Conversely, the two cultivars of S. spurium did not show a benefit of plant cover from the addition of ZeoPro™ in the first year but did the second year. As the percentage of ZeoPro™ in the substrate increased, VMC also increased.