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Freeze–thaw cycles can promote soil N losses as a result of microbial and root cell lysis; however, minimal freeze–thaw effects have typically been observed in studies that have imposed moderate temperature cycles. We conducted laboratory incubations on surface soil (top 3 cm) collected in a temperate old field from late fall through mid-winter to examine how variation in freeze–thaw amplitude, number, timing of collection, and freezing rate altered soil extractable N. We varied freeze–thaw amplitude by imposing minimum cycle temperatures of 0, −1, −2, −5, and −10°C for a series of either one or two cycles and held control samples constant at 3°C. We also examined the effects of freezing rates of 1, 3, and 30°C...
Abstract The importance of snow and related cryospheric processes as an ecological factor has been recognized since at least the beginning of the twentieth century. Even today, however, many observations remain anecdotal. The research to date on cold-lands ecosystems results in scientists being unable to evaluate to what extent changes in the cryosphere will be characterized by abrupt changes in local and global biogeochemical cycles, and how these changes in seasonality may affect the rates and timing of key ecological processes. Studies of gas exchanges through snow have revealed that snow plays an important role in modulating wintertime soil biogeochemical processes, and that these can be the driving processes...
Although freeze–thaw cycles can alter soil physical properties and microbial activity, their overall impact on soil functioning remains unclear. This review addresses the effects of freeze–thaw cycles on soil physical properties, microorganisms, carbon and nutrient dynamics, trace gas losses and higher organisms associated with soil. I discuss how the controlled manipulation of freeze–thaw cycles has varied widely among studies and propose that, despite their value in demonstrating the mechanisms of freeze–thaw action in soils, many studies of soil freeze–thaw cycles have used cycle amplitudes, freezing rates and minimum temperatures that are not relevant to temperature changes across much of the soil...
Although freeze?thaw cycles can alter soil physical properties and microbial activity, their overall impact on soil functioning remains unclear. This review addresses the effects of freeze?thaw cycles on soil physical properties, microorganisms, carbon and nutrient dynamics, trace gas losses and higher organisms associated with soil. I discuss how the controlled manipulation of freeze?thaw cycles has varied widely among studies and propose that, despite their value in demonstrating the mechanisms of freeze?thaw action in soils, many studies of soil freeze?thaw cycles have used cycle amplitudes, freezing rates and minimum temperatures that are not relevant to temperature changes across much of the soil profile in...
Freeze–thaw cycles can promote soil N losses as a result of microbial and root cell lysis; however, minimal freeze–thaw effects have typically been observed in studies that have imposed moderate temperature cycles. We conducted laboratory incubations on surface soil (top 3 cm) collected in a temperate old field from late fall through mid-winter to examine how variation in freeze–thaw amplitude, number, timing of collection, and freezing rate altered soil extractable N. We varied freeze–thaw amplitude by imposing minimum cycle temperatures of 0, −1, −2, −5, and −10°C for a series of either one or two cycles and held control samples constant at 3°C. We also examined the effects of freezing rates...
Abstract (from http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0099604): Across the globe, species distributions are changing in response to climate change and land use change. In parts of the southeastern United States, climate change is expected to result in the poleward range expansion of black mangroves ( Avicennia germinans) at the expense of some salt marsh vegetation. The morphology of A. germinans at its northern range limit is more shrub-like than in tropical climes in part due to the aboveground structural damage and vigorous multi-stem regrowth triggered by extreme winter temperatures. In this study, we developed aboveground allometric equations for freeze-affected black mangroves which...
There is widespread evidence that multiple drivers of global change, such as habitat degradation, invasive species, and climate change, are influencing wildlife. Understanding how these drivers interact with and affect species may be difficult because outcomes depend on the magnitude and duration of environmental change and the life history of the organism. In addition, various environmental drivers may be evaluated and managed at different spatial scales. We used a historical dataset from 1991 to 1994 and current information from 2010 to 2012 to examine whether occupancy patterns of wintering raptors were consistent with regional changes in distribution or habitat conditions within a local management unit, the...
Whole air drawn from four heights within the high elevation (3,340 m asl), deep, winter snowpack at Niwot Ridge, Colorado, were sampled into stainless steel canisters, and subsequently analyzed by gas chromatography for 51 volatile inorganic and organic gases. Two adjacent plots with similar snow cover were sampled, one over bare soil and a second one from within a snow-filled chamber where Tedlar/Teflon-film covered the ground and isolated it from the soil. This comparison allowed for studying effects from processes in the snowpack itself versus soil influences on the gas concentrations and fluxes within and through the snowpack. Samples were also collected from ambient air above the snow surface for comparison...
Recent energy development has resulted in rapid and large-scale changes to western shrub-steppe ecosystems without a complete understanding of its potential impacts on wildlife populations. We modeled winter habitat use by female greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB) of Wyoming and Montana, USA, to 1) identify landscape features that influenced sage-grouse habitat selection, 2) assess the scale at which selection occurred, 3) spatially depict winter habitat quality in a Geographic Information System, and 4) assess the effect of coal-bed natural gas (CBNG) development on winter habitat selection. We developed a model of winter habitat selection based on 435 aerial relocations...
Although freeze?thaw cycles can alter soil physical properties and microbial activity, their overall impact on soil functioning remains unclear. This review addresses the effects of freeze?thaw cycles on soil physical properties, microorganisms, carbon and nutrient dynamics, trace gas losses and higher organisms associated with soil. I discuss how the controlled manipulation of freeze?thaw cycles has varied widely among studies and propose that, despite their value in demonstrating the mechanisms of freeze?thaw action in soils, many studies of soil freeze?thaw cycles have used cycle amplitudes, freezing rates and minimum temperatures that are not relevant to temperature changes across much of the soil profile in...
The effect of snow cover on surface-atmosphere exchanges of nitrogen oxides (nitrogen oxide (NO) + nitrogen dioxide (NO2); note, here ?NO2? is used as surrogate for a series of oxidized nitrogen gases that were detected by the used monitor in this analysis mode) was investigated at the high elevation, subalpine (3,340 m asl) Soddie site, at Niwot Ridge, Colorado. Vertical (NO + NO2) concentration gradient measurements in interstitial air in the deep (up to ~2.5 m) snowpack were conducted with an automated sampling and analysis system that allowed for continuous observations throughout the snow-covered season. These measurements revealed sustained, highly elevated (NO + NO2) mixing ratios inside the snow. Nitrogen...
Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a large, regional scale and have little to do with the habitats within the management unit. We examined the latitudinal center of abundance for the winter distributions of six western North America raptor species using Christmas...
Fisheries managers have often suggested that survival of trout during the winter is a major factor affecting population densities in many stream ecosystems in the Rocky Mountains. In Wyoming, trout population reductions from fall to spring in excess of 90% have been documented in some reservoir tailwaters. Though biologists have surmised that these reductions were the result of either mortality or emigration from some river sections, the specific mechanisms have not been defined and the factors leading to the trout loss are unknown. This is a review of four studies that were conducted or funded between 1991 and 1998 by the Wyoming Game and Fish Department to understand the extent of overwinter losses, identify some...