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Diurnal cycles of streamflow in snow-fed rivers can be used to infer the average time a water parcel spends in transit from the top of the snowpack to a stream gauge in the river channel. This travel time, which is measured as the difference between the hour of peak snowmelt in the afternoon and the hour of maximum discharge each day, ranges from a few hours to almost a full day later. Travel times increase with longer percolation times through deeper snowpacks, and prior studies of small basins have related the timing of a stream's diurnal peak to the amount of snow stored in a basin. However, in many larger basins the time of peak flow is nearly constant during the first half of the melt season, with little or...
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Synopsis: Researchers measured the effects of grassland amount and fragmentation on upland and wetland songbird and duck densities and nest success across 16 landscapes in southern Alberta. By comparing these landscape-level effects with local-scale responses, including distance to various edges and vegetation characteristics, the study demonstrated that few species were in fact influenced by grassland amount or fragmentation. In contrast, distance to edge and local vegetation characteristics had significant effects on densities and nest success of many species. Landscape level effects were much less apparent when local characteristics were included in the models. Therefore, researchers concluded that local habitat...
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Conclusions: Successional changes resulting from a legacy of fire suppression and other agricultural and access disturbances combine to create the current hetergeneous landscape mosaic. Thresholds/Learnings: Synopsis: Disturbance is considered to be a major factor influencing landscape pattern and vegetation composition. However, the presettlement vegetation composition of three Ohio (U.S.A) counties was controlled largely by soil texture, soil drainage, and topography. In most cases, both disturbance regime and local site conditions can explain presettlement landscape pattern. This study examines the roles of edaphic conditions landscape features such as topography, and fire in contributing to (1) the abundance,...
Physical ecosystem engineers are organisms that physically modify the abiotic environment. They can affect biogeochemical processing by changing the availability of resources for microbes (e.g., carbon, nutrients) or by changing abiotic conditions affecting microbial process rates (e.g., soil moisture or temperature). Physical ecosystem engineers can therefore create biogeochemical heterogeneity in soils and sediments. They do so via general mechanisms influencing the flows of materials (i.e., modification of fluid dynamic properties, fluid pumping, and material transport) or the transfer of heat (i.e., modification of heat transfer properties, direct heat transfer, and convective forcing). The consequences of physical...
Conclusions: Structurally complex landscapes support more species than simple landscapes, implying that habitat patches in complex landscapes receive a higher diversity of potential colonists from the overall species pool than do patches of the same size and quality in less complex landscapes. Thresholds/Learnings: Synopsis: Structurally complex landscapes support more species than simple landscapes, implying that habitat patches in complex landscapes receive a higher diversity of potential colonists from the overall species pool than do patches of the same size and quality in less complex landscapes. Movement across habitats is a common phenomenon in many species and the spillover of organisms from natural habitats...
Four-level Braun-Blanquet vegetation type hierarchies of an arctic (a section of the Arctic Coastal Plain at Atkasook, Alaska) and an alpine (Indian Peaks area, Colorado Southern Rocky Mountains) area were compared through their vascular plant taxa composition. Vegetation types at all hierarchy levels were more numerous, less well defined, and less clearly distributed along the controlling environmental gradients in the Arctic than in the alpine. This greater environmental and vegetational heterogeneity and relatively poor definition of vegetation types are probably controlled by the surface disturbances of the thaw-lake cycle, rivers, cryoturbation, and wind, which cause significant horizontal movement of materials...
Conclusions:Habitat heterogeneity is often perceived as fragmentation by certain species depending on spatial scales.Thresholds/Learnings:
Conclusions:The effects of adjacent land-use on wetland sediment and water quality can extend over comparatively large distances. As such, sustaining high wetland water quality will not be achieved merely through the creation of narrow buffer zones between wetlands and more intensive land-uses, but rather by maintaining a heterogeneous regional landscape containing relatively large areas of natural forest and wetlands.Thresholds/Learnings:Water nitrogen and phosphorous levels were negatively correlated with forest cover at 2250m from the wetland edge. Sediment phosphorous levels were negatively correlated with wetland size and forest cover at 4000m from the wetland edge, and positively correlated with the proportion...
    map background search result map search result map Effects of site, landscape features, and fire regime on vegetation patterns in presettlement southern Wisconsin A multi-scale analysis of avian response to habitat amount and fragmentation in the Canadian dry mixed-grass prairie. Effects of site, landscape features, and fire regime on vegetation patterns in presettlement southern Wisconsin A multi-scale analysis of avian response to habitat amount and fragmentation in the Canadian dry mixed-grass prairie.