ERA

Journal Articles (Renewable Resources)

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  1. Spring flowering response to climate change between 1936 and 2006 in Alberta, Canada [Download]

    Title: Spring flowering response to climate change between 1936 and 2006 in Alberta, Canada
    Creator: Beaubien, E.
    Description: Abstract: In documenting biological responses to climate change, the Intergovernmental Panel on Climate Change has used phenology studies from many parts of the world, but data from the high latitudes of North America are missing. In the present article, we evaluate climate trends and the corresponding changes in sequential bloom times for seven plant species in the central parklands of Alberta, Canada (latitude 52 degrees-57 degrees north). For the study period of 71 years (1936-2006), we found a substantial warming signal, which ranged from an increase of 5.3 degrees Celsius (degrees C) in the mean monthly temperatures for February to an increase of 1.5 degrees C in those for May. The earliest-blooming species' (Populus tremuloides and Anemone patens) bloom dates advanced by two weeks during the seven decades, whereas the later-blooming species' bloom dates advanced between zero and six days. The early-blooming species' bloom dates advanced faster than was predicted by thermal time models, which we attribute to decreased diurnal temperature fluctuations. This unexpectedly sensitive response results in an increased exposure to late-spring frosts.
    Subjects: Flowering, Canada, Global warming, Phenology, Climate change
    Date Created: 2011
  2. Scale-dependent controls on the area burned in the boreal forest of Canada, 1980-2005 [Download]

    Title: Scale-dependent controls on the area burned in the boreal forest of Canada, 1980-2005
    Creator: Parisien, M.A.
    Description: In the boreal forest of North America, as in any fire-prone biome, three environmental factors must coincide for a wildfire to occur: an ignition source, flammable vegetation, and weather that is conducive to fire. Despite recent advances, the relative importance of these factors remains the subject of some debate. The aim of this study was to develop models that identify the environmental controls on spatial patterns in area burned for the period 1980-2005 at several spatial scales in the Canadian boreal forest. Boosted regression tree models were built to relate high-resolution data for area burned to an array of explanatory variables describing ignitions, vegetation, and long-term patterns in fire-conducive weather (i.e., fire climate) at four spatial scales (10(2) km(2), 10(3) km(2), 10(4) km(2), and 10(5) km(2)). We evaluated the relative contributions of these controls on area burned, as well as their functional relationships, across spatial scales. We also assessed geographic patterns of the influence of wildfire controls. The results indicated that extreme temperature during the fire season was a top control at all spatial scales, followed closely by a wind-driven index of ease of fire spread. However, the contributions of some variables differed substantially among the spatial scales, as did their relationship to area burned. In fact, for some key variables the polarity of relationships was inverted from the finest to the broadest spatial scale. It was difficult to unequivocally attribute values of relative importance to the variables chosen to represent ignitions, vegetation, and climate, as the interdependence of these factors precluded clear partitioning. Furthermore, the influence of a variable on patterns of area burned often changed enormously across the biome, which supports the idea that fire-environment relationships in the boreal forest are complex and nonstationary.
    Subjects: Area burned, Climate, Canadian boreal forest, Ignitions, Spatial scale, Boosted regression trees, Topography, Vegetation, Wildfire, Regression modeling
    Date Created: 2011
  3. The soil microbial community and grain micronutrient concentration of historical and modern hard red spring wheat cultivars grown organically and conventionally in the Black soil zone of the Canadian prairies [Download]

    Title: The soil microbial community and grain micronutrient concentration of historical and modern hard red spring wheat cultivars grown organically and conventionally in the Black soil zone of the Canadian prairies
    Creator: Nelson, A. G.
    Description: Abstract: Micronutrient deficiencies in the diet of many people are common and wheat is a staple food crop, providing a carbohydrate and micronutrient source to a large percentage of the world’s population. We conducted a field study to compare five Canadian red spring wheat cultivars (released over the last century) grown under organic and conventional management systems for yield, grain micronutrient concentration, and soil phospholipid fatty acid (PLFA) profile. The organic system had higher grain Zn, Fe, Mg and K levels, but lower Se and Cu levels. There was no trend in the results to suggest that modern western Canadian hard red spring cultivars have lower grain micronutrient content than historical cultivars. Wheat cultivar choice is important for maximizing grain nutrient levels, which was influenced by management system. It is evident that the emphasis on elevated grain quality in the western Canadian hard red spring class has resulted in the retention of micronutrient quality characters. Three fungal PLFAs were indicators for the organic system, and all three of these indicators were positively correlated with grain Cu concentration. In the organic system, percent arbuscular mycorrhizal fungi were negatively correlated with grain Zn and Fe concentrations, and positively correlated with grain Mn, Cu, K concentrations and grain yield. The organic system had higher levels of fungi in the soil, including arbuscular mycorrhizal fungi. Organic management practices appear to result in elevated levels of grain micronutrient concentration. The hard red spring breeding effort in and for the black soil zone of the northern Great Plains also appears to have led to no diminishment of grain micronutrient concentration. It is evident that both the agronomic system and breeding strategies in this region can be exploited for future increases in grain micronutrient concentration.
    Subjects: Micronutrients, Phospholipid fatty acid analysis, Triticum aestivum L., Arbuscular mycorrhizal fungi, Antioxidants, Conventional agriculture, Organic agriculture
    Date Created: 2011
  4. Net ecosystem productivity of temperate and boreal forests after clearcutting - a Fluxnet-Canada measurement and modelling synthesis [Download]

    Title: Net ecosystem productivity of temperate and boreal forests after clearcutting - a Fluxnet-Canada measurement and modelling synthesis
    Creator: Grant, R. F.
    Description: Abstract: Clearcutting strongly affects subsequent forest net ecosystem productivity (NEP). Hypotheses for ecological controls on NEP in the ecosystem model ecosys were tested with CO(2) fluxes measured by eddy covariance (EC) in three post-clearcut conifer chronosequences in different ecological zones across Canada. In the model, microbial colonization of postharvest fine and woody debris drove heterotrophic respiration (R(h)), and hence decomposition, microbial growth, N mineralization and asymbiotic N(2) fixation. These processes controlled root N uptake, and thereby CO(2) fixation in regrowing vegetation. Interactions among soil and plant processes allowed the model to simulate hourly CO(2) fluxes and annual NEP within the uncertainty of EC measurements from 2003 to 2007 over forest stands from 1 to 80 yr of age in all three chronosequences without site- or species-specific parameterization. The model was then used to study the impacts of increasing harvest removals on subsequent C stocks at one of the chronosequence sites. Model results indicated that increasing harvest removals would hasten recovery of NEP during the first 30 yr after clearcutting, but would reduce ecosystem C stocks by about 15% of the increased removals at the end of an 80-yr harvest cycle.
    Subjects: Douglas-fir stand, British Columbia, Spruce stands, Carbon-dynamics, Norway spruce, Vancouver Island, Coarse woody debris, Old-growth, Southern Finland, Scots pine forests
    Date Created: 2010
  5. Diversity of Carabidae (Insecta, Coleoptera) in Epiphytic Bromeliaceae in Central Veracruz, Mexico [Download]

    Title: Diversity of Carabidae (Insecta, Coleoptera) in Epiphytic Bromeliaceae in Central Veracruz, Mexico
    Creator: de Oca, E.M.
    Description: This paper documents the existence of carabid assemblages associated with bromeliads on the Cofre de Perote, Veracruz, Mexico. Based on bromeliads sampled over three altitudinal ranges, the assemblages included at least 26 species with an arboreal lifestyle and another 11 species that are not strictly arboreal. Seven species are new to science, urging us to pay attention to the arboreal fauna in forest conservation studies. Composition of carabid assemblages associated with bromeliads changes with altitude. In lowlands, it is comprised almost entirely of species of Lebiini, with the Platynini dominating assemblages found in bromeliads >1,000 m above sea level. Our data suggest that carabids use bromeliads to reduce stresses associated with drought periods, the exact timing of which depends on altitude. The unexpected low diversity of the carabid fauna associated with bromeliads at middle altitude is explained in terms of anthropogenic conversion of the original forest to pastureland. Given the importance of arboreal elements, further fragmentation of subtropical and tropical mountain forest significantly threatens overall carabid diversity.
    Subjects: Carabids, Bromeliads, Diversity, Altitude, Mexico
    Date Created: 2007
  6. Boreal forest CO2 exchange and evapotranspiration predicted by nine ecosystem process models: Inter-model comparisons and relationships to field measurements [Download]

    Title: Boreal forest CO2 exchange and evapotranspiration predicted by nine ecosystem process models: Inter-model comparisons and relationships to field measurements
    Creator: Amthor, J.S.
    Description: Nine ecosystem process models were used to predict CO2 and water vapor exchanges by a 150-year-old black spruce forest in central Canada during 1994-1996 to evaluate and improve the models. Three models had hourly time steps, five had daily time steps, and one had monthly time steps. Model input included site ecosystem characteristics and meteorology. Model predictions were compared to eddy covariance (EC) measurements of whole-ecosystem CO2 exchange and evapotranspiration, to chamber measurements of nighttime moss-surface CO2 release, and to ground-based estimates of annual gross primary production, net primary production, net ecosystem production (NEP), plant respiration, and decomposition. Model-model differences were apparent for all variables. Model-measurement agreement was good in some cases but poor in others. Modeled annual NEP ranged from -11 g C m(-2) (weak CO2 source) to 85 g C m(-2) (moderate CO2 sink). The models generally predicted greater annual CO2 sink activity than measured by EC, a discrepancy consistent with the fact that model parameterizations represented the more productive fraction of the EC tower \"footprint.\" At hourly to monthly timescales, predictions bracketed EC measurements so median predictions were similar to measurements, but there were quantitatively important model-measurement discrepancies found for all models at subannual timescales. For these models and input data, hourly time steps (and greater complexity) compared to daily time steps tended to improve model-measurement agreement for daily scale CO2 exchange and evapotranspiration (as judged by root-mean-squared error). Model time step and complexity played only small roles in monthly to annual predictions.
    Subjects: Climate variability, Land-surface scheme, Soil, Net primary production, Photosynthesis model, Black spruce forest, General-model, Jack pine forest, Atmospheric carbon-dioxide, Regional applications
    Date Created: 2001
  7. Relationships between stand parameters and understorey light in boreal aspen stands [Download]

    Title: Relationships between stand parameters and understorey light in boreal aspen stands
    Creator: Comeau, P.G.
    Description: Data from six aspen stands in northeastern British Columbia ranging in age from 12 to 40 years were used to examine relationships between understorey light levels and stand attributes (basal area, stand density, and age). Sample points were selected in each stand to characterize the observed range in tree density and size. Fractional transmittance of light (DIFN) was measured at each sample point using a LAI-2000 Plant Canopy Analyzer and a circular plot 3.99 m or 5.64 m in radius was established for density and basal area determination. Results indicated that data from the six stands could be pooled into a single model describing the relationship between understorey light and basal area. Light levels below 40% are found when basal area of aspen in these stands exceeds 14 m2/ha and light levels below 60% are found when basal area of aspen exceeds 8 m2/ha. The potential implications of these light levels to growth of understorey spruce are discussed. A diagrammatic representation of light-density–diameter relationships is presented that could provide a useful tool for management decisions in young mixedwood stands in northeastern British Columbia.
    Subjects: Light, Aspen
    Date Created: 2001
  8. Estimating Economic Carrying Capacity for an Ungulate Guild in Western Canada [Download]

    Title: Estimating Economic Carrying Capacity for an Ungulate Guild in Western Canada
    Creator: Kuzyk, G.W.
    Description: Elk Island National Park in western Canada provides an ideal case study for an economic carrying capacity estimate because it supports high density of four species of ungulates (11/km2), lacks large predators, and is enclosed by a 2.1-meter mesh fence. This high density of ungulates has created persistent management challenges by altering vegetation structure and community composition. Using linear programming, we explored optimal allocation of forage resources for bison (Bison bison bison), moose (Alces andersoni), wapiti (Cervus elaphus manitobensis) and deer (Odocoileus virginianus and O. hemionus) to maximize ungulate biomass and numbers, when constrained by use of the major forage classes and minimum viable populations (MVP) of those ungulate species that do not cross the boundary fence (bison and wapiti). Maximum numbers of animals were achieved by a stocking combination dominated by deer and bison, whereas maximum biomass was attained when bison and moose were abundant but deer were absent. Wapiti remained at MVP during all solutions. Optimal solutions consistent with current ungulate densities were associated with 7 to 11% forage removal. This is less than normally assumed for sustainable forage use, and may reflect the need to account for other biotic and abiotic losses to forage in carrying capacity models for which ungulate densities can be constrained by availability of a preferred forage class (e.g., grass) as well as forage quality. This research extends the conventional animal-unit concept to multispecies systems and provides templates based on forage biomass allocation for resource managers facing similar problems of joint stocking in different environments.
    Subjects: Economic carrying capacity, Ungulates
    Date Created: 2009
  9. Habitat and forage selection of moose in the aspen-dominated boreal forest, central Alberta [Download]

    Title: Habitat and forage selection of moose in the aspen-dominated boreal forest, central Alberta
    Creator: Renecker, L.A.
    Description: Forage and habitat selection of tame moose (Alces alces) in a 65 ha enclosure were studied for an annual cycle. Although the staple winter foods were woody twigs, moose consumed large amounts of leaf litter and bark under some environmental conditions. Foliage dominated the diet following leaf flush in May. Selectivity of moose for plants high in cell solubles was most pronounced during autumn. Moose used a variety of habitats throughout the year. Although relative use varied with foraging returns on an annual basis, habitat choice during late spring and summer because two-fold: to maximize the intake of foods high in cell solubles, and to mitigate thermal imbalances and insect annoyance.
    Subjects: Boreal forest, Moose, Habitat, Forage
    Date Created: 1992
  10. How dinosaurs failed to invent clothes moths, among other things [Download]

    Title: How dinosaurs failed to invent clothes moths, among other things
    Creator: Acorn, J.
    Subjects: Dinosaurs
    Date Created: 2008