A multicatchment analysis of headwater and downstream temperature effects from contemporary forest harvesting          下载免费PDF全文

Kevin D. Bladon  Catalina Segura  Nicholas A. Cook  Sharon Bywater‐Reyes  Maryanne Reiter 《水文研究》2018,32(2):293-304

Stream temperature is a key physical water‐quality parameter, controlling many biological, chemical, and physical processes in aquatic ecosystems. Maintenance of cool stream temperatures during summer is critical for high‐quality aquatic habitat. As such, transmission of warm water from small, nonfish‐bearing headwater streams after forest harvesting could cause warming in downstream fish‐bearing stream reaches with negative consequences. In this study, we evaluate (a) the effects of contemporary forest management practices on stream temperature in small, headwater streams, (b) the transmission of thermal signals from headwater reaches after harvesting to downstream fish‐bearing reaches, and (c) the relative role of lithology and forest management practices in influencing differential thermal responses in both the headwater and downstream reaches. We measured summer stream temperatures both preharvest and postharvest at 29 sites—12 upstream sites (4 reference, 8 harvested) and 17 downstream sites (5 reference, 12 harvested)—across 3 paired watershed studies in western Oregon. The 7‐day moving average of daily maximum stream temperature (T_7DAYMAX) was greater during the postharvest period relative to the preharvest period at 7 of the 8 harvested upstream sites. Although the T_7DAYMAX was generally warmer in the downstream direction at most of the stream reaches during both the preharvest and postharvest period, there was no evidence for additional downstream warming related to the harvesting activity. Rather, the T_7DAYMAX cooled rapidly as stream water flowed into forested reaches ~370–1,420 m downstream of harvested areas. Finally, the magnitude of effects of contemporary forest management practices on stream temperature increased with the proportion of catchment underlain by more resistant lithology at both the headwater and downstream sites, reducing the potential for the cooling influence of groundwater.  相似文献   

A middle–late Ediacaran volcano‐sedimentary record from the eastern Arabian‐Nubian shield     

David Nettle  Galen P. Halverson  Grant M. Cox  Alan S. Collins  Mark Schmitz  James Gehling  Peter R. Johnson  Khalid Kadi 《地学学报》2014,26(2):120-129

The Ediacaran Jibalah Group comprises volcano‐sedimentary successions that filled small fault‐bound basins along the NW–SE‐trending Najd fault system in the eastern Arabian‐Nubian Shield. Like several other Jibalah basins, the Antaq basin contains exquisitely preserved sedimentary structures and felsic tuffs, and hence is an excellent candidate for calibrating late Ediacaran Earth history. Shallow‐marine strata from the upper Jibalah Group (Muraykhah Formation) contain a diversity of load structures and intimately related textured organic (microbial) surfaces, along with a fragment of a structure closely resembling an Ediacaran frond fossil and a possible specimen of Aspidella. Interspersed carbonate beds through the Muraykhah Formation record a positive δ¹³C shift from ?6 to 0‰. U‐Pb zircon geochronology indicates a maximum depositional age of ~570 Ma for the upper Jibalah Group, consistent with previous age estimates. Although this age overlaps with that of the upper Huqf Supergroup in nearby Oman, these sequences were deposited in contrasting tectonic settings on opposite sides of the final suture of the East African Orogen.  相似文献   

Incorporating climate change and morphological uncertainty into coastal change hazard assessments     

Heather M. Baron  Peter Ruggiero  Nathan J. Wood  Erica L. Harris  Jonathan Allan  Paul D. Komar  Patrick Corcoran 《Natural Hazards》2015,75(3):2081-2102

  相似文献   

The Meteoritical Bulletin,No. 100, 2014 June     

Alex Ruzicka  Jeffrey N. Grossman  Laurence Garvie 《Meteoritics & planetary science》2014,49(8):E1-E101

Meteoritical Bulletin 100 contains 1943 meteorites including 8 falls (Boumdeid [2011], Huaxi, Ko?ice, Silistra, So?tmany, Sutter's Mill, Thika, Tissint), with 1575 ordinary chondrites, 139 carbonaceous chondrites, 96 HED achondrites, 25 ureilites, 18 primitive achondrites, 17 iron meteorites, 15 enstatite chondrites, 11 lunar meteorites, 10 mesosiderites, 10 ungrouped achondrites, 8 pallasites, 8 Martian meteorites, 6 Rumuruti chondrites, 3 enstatite achondrites, and 2 angrites, and with 937 from Antarctica, 592 from Africa, 230 from Asia, 95 from South America, 44 from North America, 36 from Oceania, 6 from Europe, and 1 from an unknown location. This will be the last Bulletin published in the current format. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available online at http://www.lpi.usra.edu/meteor/  相似文献   

Situating corporate framings of child labor: Toward grounded geographies of working children in globalized agriculture     

《Geoforum》2015

The expansion of multinational corporations into agricultural production around the world is resulting in new forms of engagement in specific places. In the context of neoliberal restructuring, these engagements are tied to shifting landscapes of societal, governmental and industry-based perceptions on the role of corporations in labor regimes. But how are these engagements developed and how do they connect to the everyday lives of workers? In India, when Monsanto expanded into hybrid cotton seed production in the early 2000s, the corporation came under pressure to address concerns over the widespread employment of children and young workers for seed pollination. In response, the corporation developed an approach to child labor that, I argue, works to reinforce generalized and problematic notions of childhood and work. Corporate engagements in global agriculture need to be situated in time and space, and alongside the experiences of workers. Children experience attempts to shape their patterns of work and mobility as a series of surmountable obstacles, disconnected from the process of deciding whether or not they will engage in this work. Drawing on qualitative fieldwork in Gujarat and Rajasthan, and documentary analysis of public documents, I outline the development of a corporate response to child labor and place it within the context of the rise of corporate social responsibility, global ideas of child labor, and in the specific case of cotton seed production in western India. I demonstrate that contextualized geographies of working children in globalized agriculture reveal the nature of multinational corporations’ engagements in specific places.  相似文献   

Assessment of future runoff trends under multiple climate change scenarios in the Willamette River Basin,Oregon, USA     

Il‐Won Jung  Heejun Chang 《水文研究》2011,25(2):258-277

We investigated trends in future seasonal runoff components in the Willamette River Basin (WRB) of Oregon for the twenty‐first century. Statistically downscaled climate projections by Climate Impacts Group (CIG), eight different global climate model (GCM) simulations with two different greenhouse gas (GHG) emission scenarios, (A1B and B1), were used as inputs for the US Geological Survey's Precipitation Runoff Modelling System. Ensemble mean results show negative trends in spring (March, April and May) and summer (June, July and August) runoff and positive trends in fall (September, October and November) and winter (December, January and February) runoff for 2000–2099. This is a result of temperature controls on the snowpack and declining summer and increasing winter precipitation. With temperature increases throughout the basin, snow water equivalent (SWE) is projected to decline consistently for all seasons. The decreases in the centre of timing and 7‐day low flows and increases in the top 5% flow are caused by the earlier snowmelt in spring, decreases in summer runoff and increases in fall and winter runoff, respectively. Winter runoff changes are more pronounced in higher elevations than in low elevations in winter. Seasonal runoff trends are associated with the complex interactions of climatic and topographic variables. While SWE is the most important explanatory variable for spring and winter runoff trends, precipitation has the strongest influence on fall runoff. Spatial error regression models that incorporate spatial dependence better explain the variations of runoff trends than ordinary least‐squares (OLS) multiple regression models. Our results show that long‐term trends of water balance components in the WRB could be highly affected by anthropogenic climate change, but the direction and magnitude of such changes are highly dependent on the interactions between climate change and land surface hydrology. This suggests a need for spatially explicit adaptive water resource management within the WRB under climate change. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Are managed retreat programs successful and just? A global mapping of success typologies,justice dimensions,and trade-offs     

《Global Environmental Change》2022

As managed retreat programs expand across the globe, there is an urgent need to assess whether these programs are reducing exposure to climatic hazards, enhancing adaptive capacity, and improving the living conditions of communities in a just and equitable manner or are they exacerbating existing risks and vulnerabilities? Strictly speaking, are retreat programs successful? Using an expansive intersectional justice approach to examine 138 post-resettlement case studies published between 2000 and 2021 across the Global North and South, we identified five typologies of success – techno-managerial, eco-restorative, compensatory, reformative, and transformative – and their trade-offs and synergies. Our meta-analysis incorporated a variety of metrics: relocation types, funding, decision making, socio-economic class, land use change, livelihood options, and social impacts. We found 26% of cases failed, 43% were successful, and 30% are on-going and therefore success was undetermined. The techno-managerial cases, while successful in the limited terms of relocating residents, paid little attention to equity and justice. The eco-restorative and compensatory cases reduced hazard exposure but revealed the synergies and tensions associated with social, ecological, and intergenerational justice. The reformative and transformative cases improved community wellbeing, rootedness, and access to livelihoods while incorporating diverse justice concerns to different degrees. By intersecting these typologies with multiple dimensions of justice, this study advances a novel planning and analytical tool for assessing the potential success or failure of current and future retreat programs.  相似文献   

Protoconch morphology of Conoteuthis (Diplobelida,Coleoidea) and its implications on the presumed origin of the Sepiida     

《Cretaceous Research》2012

The phylogenetic origin of the Sepiida is still unclear. The presumed derivation from diplobelid belemnoids can be tested by comparison of their initial chambers (protoconchs). The first investigation of a juvenile phragmocone of the diplobelid Conoteuthis hayakawai from the Cenomanian of Hokkaido (northern Japan) yielded surprising insights into the internal protoconch morphology of the Diplobelida. The Conoteuthis protoconch exhibits in many aspects a mosaic of the belemnitid and the spirulid protoconch types. Whereas the sepiid protoconch represents most probably a modification of the spirulid type, the Conoteuthis protoconch is unique in having a closed (imperforated) proseptum. Apart from this, Conoteuthis differs in many other characters from the earliest sepiids (Ceratisepia, Belosepia), which makes a closer relationship unlikely.  相似文献   

Long‐term trend of precipitation and runoff in Korean river basins     

Deg‐Hyo Bae  Il‐Won Jung  Heejun Chang 《水文研究》2008,22(14):2644-2656

The spatial and temporal variations of precipitation and runoff for 139 basins in South Korea were investigated for 34 years (1968–2001). The Precipitation‐Runoff Modelling System (PRMS) was selected for the assessment of basin hydrologic response to varying climates and physiology. A non‐parametric Mann–Kendall's test and regression analysis are used to detect trends in annual, seasonal, and monthly precipitation and runoff, while Moran's I is adapted to determine the degree of spatial dependence in runoff trend among the basins. The results indicated that the long‐term trends in annual precipitation and runoff were increased in northern regions and decreased in south‐western regions of the study area during the study period. The non‐parametric Mann–Kendall test showed that spring streamflow was decreasing, while summer streamflow was increasing. April precipitation decreased between 15% and 74% for basins located in south‐western part of the Korean peninsula. June precipitation increased between 18% and 180% for the majority of the basins. Trends in seasonal and monthly streamflow show similar patterns compared to trends in precipitation. Decreases in spring runoff are associated with decreases in spring precipitation which, accompanied by rising temperatures, are responsible for reducing soil moisture. The regional patterns of precipitation and runoff changes show a strong to moderate positive spatial autocorrelation, suggesting that there is a high potential for severe spring drought and summer flooding in some parts of Korea if these trends continue in the future. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

The value of water supply reliability in California:: a contingent valuation study     

《Water Policy》2001,3(2):165-174

Water agencies are often faced with the need to estimate the value of water service reliability. Since no explicit market for water supply reliability exists, this study indirectly measures consumers’ valuation of water supply reliability using the contingent valuation method (CVM). Respondents were asked to indicate their willingness to pay in order to avoid the occurrence of water shortages of a given frequency and severity. We employed a “double bounded” dichotomous choice model. The results indicate that customers are willing to pay as much as $16.92/month to avoid a 50% water shortage occurring every 20 years. The goal of such a study is to provide a framework with which water agencies can determine and pursue policies appropriate to the level of reliability desired by customers. The values resulting from the analysis can be assessed in terms of options and the practical bounds of options.  相似文献