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251.
252.
Total captures, species richness, diversity, and assemblages of adult carabids (Coleoptera: Carabidae) in a boreal mixed-wood ecosystem study were compared among unharvested, and clear-cut plots untreated or treated with herbicides (Vision® and Release®), mechanical treatments (brush saw and Silvana Selective). Carabids were sampled using unbaited pitfall traps for one growing season 7 and 9 years after clear-cutting, in the second growing season after competition control was applied. A total of 5032 individuals representing 30 species were collected between June 1 and September 25, 1995. Total catches were not affected by the harvest or the conifer release alternatives applied. Species richness and diversity increased following conifer release alternatives. Ten species showed habitat preferences after treatment whereas the remaining 20 species were not significantly affected by treatment.  相似文献   
253.
A key driver of rain forest degradation is rampant commercial logging. Reduced-impact logging (RIL) techniques dramatically reduce residual damage to vegetation and soils, and they enhance the long-term economic viability of timber operations when compared to conventionally managed logging enterprises. Consequently, the application of RIL is increasing across the tropics, yet our knowledge of the potential for RIL also to reduce the negative impacts of logging on biodiversity is minimal. We compare the impacts of RIL on birds, leaf-litter ants, and dung beetles during a second logging rotation in Sabah, Borneo, with the impacts of conventional logging (CL) as well as with primary (unlogged) forest. Our study took place 1-8 years after the cessation of logging. The species richness and composition of RIL vs. CL forests were very similar for each taxonomic group. Both RIL and CL differed significantly from unlogged forests in terms of bird and ant species composition (although both retained a large number of the species found in unlogged forests), whereas the composition of dung beetle communities did not differ significantly among forest types. Our results show little difference in biodiversity between RIL and CL over the short-term. However, biodiversity benefits from RIL may accrue over longer time periods after the cessation of logging. We highlight a severe lack of studies investigating this possibility. Moreover, if RIL increases the economic value of selectively logged forests (e.g., via REDD+, a United Nations program: Reducing Emissions from Deforestation and Forest Degradation in Developing Countries), it could help prevent them from being converted to agricultural plantations, which results in a tremendous loss of biodiversity.  相似文献   
254.
Although the passion that people demonstrate at work would appear to be a topic of considerable interest and importance to organizational scholars and practitioners, we know virtually nothing about it. In response, we introduce the work passion construct, discuss what we currently understand, and provide needed directions for future research. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
255.
To aid the recovery of a species, understanding the extent to which populations are connected is useful for targeting conservation efforts. Pacific hake within waters of Puget Sound, Washington State, USA, and Georgia Strait, British Columbia, Canada are listed as a species of concern under the U.S. Endangered Species Act due to dramatic declines in the Puget Sound population. To assess the role of dispersal in the recovery of Pacific hake, we sought to quantify patterns of connectivity between populations in Puget Sound and Georgia Strait. Using natural chemical markers from otoliths of fish sampled from these two populations, we linked natal signatures of fish to signatures of individuals from known spawning grounds. Results indicated that 82 % of individuals collected from Puget Sound (n = 78) were estimated to have originated there, while 40 and 92 % of the individuals collected from two cohorts within Georgia Strait (n = 9 and 24, respectively) had originated from Puget Sound. A trend of “population abandonment” of fish from Puget Sound suggests that recovery of this Pacific hake population will depend on local management practices.  相似文献   
256.
The harvesting of communal natural resources by ‘outsiders’ (i.e. harvesters from other villages or towns) was investigated in ten rural villages in South Africa. Participatory Rural Appraisal (PRA) techniques were used to collect data in focus groups in each village. A case study quantifying the outflow of fuelwood was also conducted in one of the villages. Harvesting by outsiders was reportedly widespread and, in the case of fuelwood, a cause for concern. Of 13 recorded resources, the three most commonly harvested by outsiders were fuelwood, plants for traditional medicine and river sand for brick-making. An increase in harvesting by outsiders over the last decade was widely reported. This was related to socio-economic changes, largely associated with the first democratic elections in 1994. Key socio-economic drivers of this increased harvesting were: 1) the breakdown of institutional control of resources, 2) rising unemployment, and 3) a pervasive sense of entitlement associated with new-found political freedom and democracy. Evidence suggests that the increased harvesting by outsiders is a reality, rather than a xenophobic accusation, and that it poses a threat to the sustainability of communal resources in rural areas. This is discussed within the context of South Africa as a society in transition.  相似文献   
257.
Coral reefs worldwide are declining at an alarming rate and are under continuous threat from both natural and anthropogenic environmental stressors. Warmer sea temperatures attributed to global climate change and numerous human activities at local scales place these valuable ecosystems at risk. Reefs provide numerous services, including shoreline protection, fishing, tourism and biological diversity, which are lost through physical damage, overfishing, and pollution. Pollution can be controlled under provisions of the Clean Water Act, but these options have not been fully employed to protect coral reefs. No U.S. jurisdiction has implemented coral reef biocriteria, which are narrative or quantitative water quality standards based on the condition of a biological resource or assemblage. The President’s Ocean Action Plan directs the U.S. Environmental Protection Agency (EPA) to develop biological assessment methods and biological criteria for evaluating and maintaining the health of coral reef ecosystems. EPA has formed the Coral Reef Biocriteria Working Group (CRBWG) to foster development of coral reef biocriteria through focused research, evaluation and communication among Agency partners and U.S. jurisdictions. Ongoing CRBWG activities include development and evaluation of a rapid bioassessment protocol for application in biocriteria programs; development of a survey design and monitoring strategy for the U.S. Virgin Islands; comprehensive reviews of biocriteria approaches proposed by states and territories; and assembly of data from a variety of monitoring programs for additional metrics. Guidance documents are being prepared to assist U.S. jurisdictions in reaching protective and defensible biocriteria.  相似文献   
258.
We predicted the effects of sulfate (SO(4)) deposition on wilderness areas designated as Class I air quality areas in western North Carolina using a nutrient cycling model (NuCM). We used three S deposition simulations: current, 50% decrease, and 100% increase. We measured vegetation, forest floor, and root biomass and collected soil, soil solution, and stream water samples for chemical analyses. We used the closest climate stations and atmospheric deposition stations to parameterize NuCM. The areas were: Joyce Kilmer (JK), Shining Rock (SR), and Linville Gorge (LG). They differ in soil acidity and nutrients, and soil solution and stream chemistry. Shining Rock and LG have lower soil solution base cation and higher acidic ion concentrations than JK. For SR and LG, the soil solution Ca/Al molar ratios are currently 0.3 in the rooting zone (A horizon), indicating Al toxicity. At SR, the simulated Ca/Al ratio increased to slightly above 1.5 after the 30-yr simulation regardless of S deposition reduction. At LG, Ca/Al ratios ranged from 1.6 to 2.4 toward the end of the simulation period, the 100% increase scenario had the lower value. Low Ca/Al ratios suggest that forests at SR and LG are significantly stressed under current conditions. Our results also suggest that SO(4) retention is low, perhaps contributing to their high degree of acidification. Their soils are acidic, low in weatherable minerals, and even with large reductions in SO(4) and associated acid deposition, it may take decades before these systems recover from depletion of exchangeable Ca, Mg, and K.  相似文献   
259.
Sorption of dissolved organic matter (DOM) plays an important role in maintaining the fertility and quality of soils in agricultural ecosystems. Few studies have examined the effects of decomposition on DOM sorption and chemical characteristics. This study investigated the sorption to goethite (alpha-FeOOH) of fresh and decomposed hydrophilic (HPL) and hydrophobic (HPB) DOM fractions extracted from the shoots and roots of crimson clover (Trifolium incarnatum L.), corn (Zea mays L.), soybean [Glycine max (L.) Merr.], hairy vetch (Vicia villosa L.), and dairy and poultry manures. Sorption was positively related to apparent molecular weight (MWAP), aromaticity as measured by absorptivity at 280 nm, and phenolic acid content. A 10-d laboratory microbial decomposition of the source organic matter generally increased the sorption of the extracted DOM onto goethite. The decomposition effect on sorption was greater for the HPL fractions than for the HPB fractions. There was a decrease in the MWAP values of the DOM samples following sorption to goethite. In many cases the reduction in MWAP was large, indicating a strong preference by goethite for the higher MWAP DOM fractions. The results of this laboratory-based research demonstrate that microbial processes affect the chemical characteristics of DOM which may affect the distribution of soil organic C pools.  相似文献   
260.
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