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971.
An experiment was conducted to determine the influence the time of brush-cutting can have on plant regrowth and attractiveness
to herbivores that browse in linear corridors. The influence of cutting time on leaf flush and senescence, shoot morphometry,
and biomass was measured for 3 consecutive years after initial brush-cutting. Results indicate that morphological and phenological
attributes of three woody deciduous plants were influenced by the timing of brush-cutting for up to 3 years after initial
cutting. Brush-cutting generally stimulated plants to produce larger than normal shoots and delay leaf senescence. The degree
to which plants were affected, however, varied with the timing of initial cutting and the species in question. Generally,
plants cut later in the year resprouted more vigorously and were taller in the third year after cutting but produced less
overall biomass than when cut earlier. In the years following brush-cutting, plants cut earlier flushed leaves earlier in
the spring but delayed leaf senescence in the fall when compared to uncut controls. Results of these trials suggest that brush-cutting
time influences plant response and several plant attributes known to influence plant attractiveness to moose and other herbivores.
We therefore recommend that roadside and railside vegetation management plans consider the influence of cutting time on plant
regrowth. Such considerations can ensure that brush is cut to reduce the attractiveness of plant regrowth in these linear
corridors, reduce the utilization of such brush by herbivores, and, as such, mitigate collision risk between motorists and
herbivores such as moose. 相似文献
972.
Yanca CA Barth DC Petterson KA Nakanishi MP Cooper JA Johnsen BE Lambert RH Bivins DG 《Journal of the Air & Waste Management Association (1995)》2006,56(12):1733-1742
Three new methods applicable to the determination of hazardous metal concentrations in stationary source emissions were developed and evaluated for use in U.S. Environmental Protection Agency (EPA) compliance applications. Two of the three independent methods, a continuous emissions monitor-based method (Xact) and an X-ray-based filter method (XFM), are used to measure metal emissions. The third method involves a quantitative aerosol generator (QAG), which produces a reference aerosol used to evaluate the measurement methods. A modification of EPA Method 301 was used to validate the three methods for As, Cd, Cr, Pb, and Hg, representing three hazardous waste combustor Maximum Achievable Control Technology (MACT) metal categories (low volatile, semivolatile, and volatile). The modified procedure tested the methods using more stringent criteria than EPA Method 301; these criteria included accuracy, precision, and linearity. The aerosol generation method was evaluated in the laboratory by comparing actual with theoretical aerosol concentrations. The measurement methods were evaluated at a hazardous waste combustor (HWC) by comparing measured with reference aerosol concentrations. The QAG, Xact, and XFM met the modified Method 301 validation criteria. All three of the methods demonstrated precisions and accuracies on the order of 5%. In addition, correlation coefficients for each method were on the order of 0.99, confirming the methods' linear response and high precision over a wide range of concentrations. The measurement methods should be applicable to emissions from a wide range of sources, and the reference aerosol generator should be applicable to additional analytes. EPA recently approved an alternative monitoring petition for an HWC at Eli Lilly's Tippecanoe site in Lafayette, IN, in which the Xact is used for demonstrating compliance with the HWC MACT metal emissions (low volatile, semivolatile, and volatile). The QAG reference aerosol generator was approved as a method for providing a quantitative reference aerosol, which is required for certification and continuing quality assurance of the Xact. 相似文献
973.
The risk to non-human biota from exposure to ionizing radiation is of current international interest. In calculating radiation doses to humans, it is common to multiply the absorbed dose by a factor to account for the relative biological effectiveness (RBE) of the radiation type. However, there is no international consensus on the appropriate value of such a factor for weighting doses to non-human biota. This paper summarizes our review of the literature on experimentally determined RBEs for internally deposited alpha-emitting radionuclides. The relevancy of each experimental result in selecting a radiation weighting factor for doses from alpha particles in biota was judged on the basis of criteria established a priori. We recommend a nominal alpha radiation weighting factor of 5 for population-relevant deterministic and stochastic endpoints, but to reflect the limitations in the experimental data, uncertainty ranges of 1-10 and 1-20 were selected for population-relevant deterministic and stochastic endpoints, respectively. 相似文献
974.
Degradation of warmwater streams in agricultural landscapes is a pervasive problem, and reports of restoration effectiveness
based on monitoring data are rare. Described is the outcome of rehabilitation of two deeply incised, unstable sand-and-gravel-bed
streams. Channel networks of both watersheds were treated using standard erosion control measures, and aquatic habitats within
1-km-long reaches of each stream were further treated by addition of instream structures and planting woody vegetation on
banks (“habitat rehabilitation”). Fish and their habitats were sampled semiannually during 1–2 years before rehabilitation,
3–4 years after rehabilitation, and 10–11 years after rehabilitation. Reaches with only erosion control measures located upstream
from the habitat measure reaches and in similar streams in adjacent watersheds were sampled concurrently. Sediment concentrations
declined steeply throughout both watersheds, with means ≥40% lower during the post-rehabilitation period than before. Physical
effects of habitat rehabilitation were persistent through time, with pool habitat availability much higher in rehabilitated
reaches than elsewhere. Fish community structure responded with major shifts in relative species abundance: as pool habitats
increased after rehabilitation, small-bodied generalists and opportunists declined as certain piscivores and larger-bodied
species such as centrarchids and catostomids increased. Reaches without habitat rehabilitation were significantly shallower,
and fish populations there were similar to the rehabilitated reaches prior to treatment. These findings are applicable to
incised, warmwater streams draining agricultural watersheds similar to those we studied. Rehabilitation of warmwater stream
ecosystems is possible with current knowledge, but a major shift in stream corridor management strategies will be needed to
reverse ongoing degradation trends. Apparently, conventional channel erosion controls without instream habitat measures are
ineffective tools for ecosystem restoration in incised, warmwater streams of the Southeastern U.S., even if applied at the
watershed scale and accompanied by significant reductions in suspended sediment concentration. 相似文献
975.
Silva Wesley Douglas Oliveira Morais Danielle Costa Urtiga Marcella Maia 《Environment, Development and Sustainability》2022,24(8):10443-10469
Environment, Development and Sustainability - An integrative negotiation model is proposed so that watershed committees (WSC) can deal better with conflicts over alternatives for protecting water... 相似文献