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151.
Isolating the role of soil resources,defoliation, and interspecific competition on early establishment of the late successional bunchgrass Festuca campestris
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Native grasslands are valued for biodiversity and supporting dormant season grazing, but are prone to invasion. In western Canada, revegetation of Festuca campestris grasslands may be hindered by Poa pratensis, an invasive grass. To determine the competitive interaction of these species during establishment, two greenhouse experiments were conducted where F. campestris seedlings were planted in monocultures or mixtures with P. pratensis. The first experiment used equal‐aged (3‐month old) seedlings of both species, while the second experiment used unequal‐aged seedlings (4‐month‐old F. campestris and 2‐month‐old P. pratensis). Seedling performance was measured in response to manipulations of water and nitrogen, defoliation, and plant neighbor. While water and nitrogen reduced the biomass and vegetative reproduction (tillering) of F. campestris, exposure to P. pratensis most strongly limited the growth of F. campestris seedlings regardless of other treatments. More frequent and consistent decreases in F. campestris due to P. pratensis were observed in older F. campestris seedlings than younger seedlings. Defoliation also reduced the growth of F. campestris, and the added presence of P. pratensis during defoliation further enhanced these reductions in younger, equal‐aged bunchgrass seedlings. Overall, these results suggest that when restoring native F. campestris grasslands, early establishment may be improved by reducing the negative impacts of P. pratensis, and avoiding severe defoliation. 相似文献
152.
Sarah Kimball Megan Lulow Quinn Sorenson Kathleen Balazs Yi‐Chin Fang Steven J. Davis Michael O'Connell Travis E. Huxman 《Restoration Ecology》2015,23(6):800-810
Ecological restoration is a multibillion dollar industry critical for improving degraded habitat. However, most restoration is conducted without clearly defined success measures or analysis of costs. Outcomes are influenced by environmental conditions that vary across space and time, yet such variation is rarely considered in restoration planning. Here, we present a cost‐effectiveness analysis of terrestrial restoration methods to determine how practitioners may restore the highest native plant cover per dollar spent. We recorded costs of 120 distinct methods and described success in terms of native versus non‐native plant germination, growth, cover, and density. We assessed effectiveness using a basic, commonly used metric (% native plant cover) and developed an index of cost‐effectiveness (% native cover per dollar spent on restoration). We then evaluated success of multiple methods, given environmental variation across topography and multiple years, and found that the most successful method for restoring high native plant cover is often different from the method that results in the largest area restored per dollar expended, given fixed mitigation budgets. Based on our results, we developed decision‐making trees to guide practitioners through established phases of restoration—site preparation, seeding and planting, and maintenance. We also highlight where additional research could inform restoration practice, such as improved seasonal weather forecasts optimizing allocation of funds in time or valuation practices that include costs of specific outcomes in the collection of in lieu fees. 相似文献
153.
B. Christian Schmidt 《ZooKeys》2015,(527):103-126
The Lacinipolia
vicina (Grote) species complex, previously consisting of Lacinipolia
vicina, Lacinipolia
teligera (Morrison), Lacinipolia
pensilis (Grote), and Lacinipolia
subalba Mustelin is revised to six species: Lacinipolia
vicina (eastern USA), Lacinipolia
teligera (southern Great Plains), Lacinipolia
pensilis (Pacific Northwest and northern Rocky Mountains), Lacinipolia
acutipennis (Grote), stat. rev. (= Lacinipolia
subalba
syn. n.) (western North America), Lacinipolia
sareta (Smith), stat. rev. (Canada and western USA) and Lacinipolia
dimocki, sp. n. (California and Pacific Northwest). Lectotypes are designated for Lacinipolia
vicina, Lacinipolia
teligera and Lacinipolia
pensilis. 相似文献
154.
155.
Productivity enhances benthic species richness along an oligotrophic Indian Ocean continental margin
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156.
Bycatch in artisanal gill nets threatens the vaquita, Phocoena sinus, with extinction. In 2008 the Mexican government announced a conservation action plan for this porpoise, with three options for a protected area closed to gill net fishing. The probability of success of each of the three options was estimated with a Bayesian population model, where success was defined as an increase in vaquita abundance after 10 yr. The model was fitted to data on abundance, bycatch, and fishing effort, although data were sparse and imprecise. Under the first protected area option, the existing Refuge Area for the Protection of the Vaquita, bycatch was about 7% of population size, and probability of success was 0.08. Under the second option with a larger protected area, the probability of success was 0.35. The third option was large enough to eliminate vaquita bycatch and had a probability of success >0.99. Probability of success was reduced if elimination of vaquita bycatch was delayed or incomplete. Despite considerable efforts by the Mexican government to support vaquita conservation, abundance will probably continue to decline unless additional measures to reduce vaquita bycatch are taken, such as banning gill nets within the vaquita's range and developing effective alternative fishing gear. 相似文献
157.
Nathan J. P. Wintle Deborah A. Duffield Nélio B.
Barros Ronald D. Jones James M. Rice 《Marine Mammal Science》2011,27(4):E268-E278
Muscle samples from 105 marine mammals stranded along the Oregon and Washington coasts (2002–2009) were tested for levels of total mercury (THg) by Cold Vapor Atomic Fluorescence Spectrometry. The THg present is in the form of the highly toxic methylmercury. After normalizing tissue to 75% water weight, Steller sea lions and northern elephant seals exhibited the highest mean concentrations of THg followed by harbor seals, harbor porpoises, and California sea lions, 0.34 ± 0.278, 0.34 ± 0.485, 0.21 ± 0.216, 0.17 ± 0.169, and 0.15 ± 0.126 mg/kg normalized wet weight (ww), respectively. The mean normalized values demonstrate limited muscle methylmercury accumulation in these species in the Pacific Northwest. However, actual ww concentrations in some of the stranded carcasses may pose a risk to scavengers. Normalizing muscle mercury concentrations eliminated the variability from desiccation, and allowed for a clearer indication of the amount of mercury the animal accumulated before stranding. 相似文献
158.
159.
Xavier López‐Medellín Exequiel Ezcurra Charlotte González‐Abraham Jon Hak Louis S. Santiago James O. Sickman 《植被学杂志》2011,22(1):143-151
Question: Although mangrove forests are generally regarded as highly threatened, some studies have shown that mangrove canopies in the Pacific coast of Mexico have been increasing in recent decades. We investigated the possible causes driving this reported mangrove expansion. Location: The mangrove lagoons of Magdalena Bay in Baja California, Mexico. Methods: We used 50‐year‐old aerial photographs and 24‐year‐old satellite images to compare long‐term vegetation change, surveyed a coastal vegetation transect to analyse flooding levels, compiled six decades of tidal and oceanographic information, as well as hurricane data to analyse changes in storm frequency or sea‐level conditions, and used isotopic analysis to date the age of trees along the gradient. Results: A significant increase in mangrove cover has occurred in backwaters of the lagoons during the last 40 years, and especially during the El Niño anomalies of the 1980s and 1990s, while at the same time the mangrove fringe has been receding. Conclusions: The observed change can be attributed to the combined action of the warm surface waters of El Niño events and sea‐level rise. Jointly, these two effects are sufficient to flood large areas of previously non‐flooded salt flats, dispersing mangrove seedlings inland. The inland expansion of mangroves, however, does not ease conservation concerns, as it is the seaward fringes, and not the inland margins, that provide the most valuable environmental services for fisheries and coastal protection. 相似文献
160.
Hoffecker JF 《Evolutionary anthropology》2011,20(1):24-39
Artifacts of Paleolithic age were first recognized in eastern Europe during the 1870s. Archeologists have struggled ever since to integrate them into the better known record of western Europe, where the interpretive framework of Paleolithic archeology was originally developed. The essential elements of both the Middle and Upper Paleolithic were recognized quickly in eastern Europe, and a close connection with a major middle Upper Paleolithic industry of central Europe (Gravettian) was established many years ago. The early Upper Paleolithic (EUP) has remained a major challenge, however; it is represented primarily by a bewildering array of local archeological cultures that exhibit limited similarity to contemporaneous industries of western and central Europe.6-9. 相似文献