On Critical Realism,Human Geography,and Arcane Sects!     

Victoria A. Lawson  Lynn A. Staeheli 《The Professional geographer》1991,43(2):231-233

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Biological modulation of the Earth's atmosphere     

Lynn Margulis  J.E. Lovelock 《Icarus》1974,21(4):471-489

We review the evidence that the Earth's atmosphere is regulated by life on the surface so that the probability of growth of the entire biosphere is maximized. Acidity, gas composition including oxygen level, and ambient temperature are enormously important determinants for the distribution of life. We recognize that the earth's atmosphere deviates greatly from that of the other terrestrial planets in particular with respect to acidity, composition, redox potential and temperature history as predicted from solar luminosity. These deviations from predicted steady state conditions have apparently persisted over millions of years. We explore the concept that these anomalies are evidence for a complex planet-wide homeostasis that is the product of natural selection. Possible homeostatic mechanisms that may be further investigated by both theoretical and experimental methods are suggested.  相似文献   

Assessing urban rainfall-runoff response to stormwater management extent     

Andrew J. Miller  Claire Welty  Jonathan M. Duncan  Mary Lynn Baeck  James A. Smith 《水文研究》2021,35(7):e14287

We report an empirical analysis of the hydrologic response of three small, highly impervious urban watersheds to pulse rainfall events, to assess how traditional stormwater management (SWM) alters urban hydrographs. The watersheds vary in SWM coverage from 3% to 61% and in impervious cover from 45% to 67%. By selecting a set of storm events that involved a single rainfall pulse with >96% of total precipitation delivered in 60 min, we reduced the effect of differences between storms on hydrograph response to isolate characteristic responses attributable to watershed properties. Watershed-average radar rainfall data were used to generate local storm hyetographs for each event in each watershed, thus compensating for the extreme spatial and temporal heterogeneity of short-duration, intense rainfall events. By normalizing discharge values to the discharge peak and centring each hydrograph on the time of peak we were able to visualize the envelope of hydrographs for each group and to generate representative composite hydrographs for comparison across the three watersheds. Despite dramatic differences in the fraction of watershed area draining to SWM features across these three headwater tributaries, we did not find strong evidence that SWM causes significant attenuation of the hydrograph peak. Hydrograph response for the three watersheds is remarkably uniform despite contrasts in SWM, impervious cover and spatial patterns of land cover type. The primary difference in hydrograph response is observed on the recession limb of the hydrograph, and that change appears to be associated with higher storm-total runoff in the watersheds with more area draining to SWM. Our findings contribute more evidence to the work of previous authors suggesting that SWM is less effective at attenuating urban hydrographs than is commonly assumed. Our findings also are consistent with previous work concluding that percent impervious cover may have greater influence on runoff volume than percent SWM coverage.  相似文献   

Cultural impacts to tribes from climate change influences on forests     

Garrit Voggesser  Kathy Lynn  John Daigle  Frank K. Lake  Darren Ranco 《Climatic change》2013,120(3):615-626

Climate change related impacts, such as increased frequency and intensity of wildfires, higher temperatures, extreme changes to ecosystem processes, forest conversion and habitat degradation are threatening tribal access to valued resources. Climate change is and will affect the quantity and quality of resources tribes depend upon to perpetuate their cultures and livelihoods. Climate impacts on forests are expected to directly affect culturally important fungi, plant and animal species, in turn affecting tribal sovereignty, culture, and economy. This article examines the climate impacts on forests and the resulting effects on tribal cultures and resources. To understand potential adaptive strategies to climate change, the article also explores traditional ecological knowledge and historical tribal adaptive approaches in resource management, and contemporary examples of research and tribal practices related to forestry, invasive species, traditional use of fire and tribal-federal coordination on resource management projects. The article concludes by summarizing tribal adaptive strategies to climate change and considerations for strengthening the federal-tribal relationship to address climate change impacts to forests and tribal valued resources.  相似文献   

Geology of the High Sulfidation Copper Deposits,Monywa Mine,Myanmar     

Andrew H. G. Mitchell  Win Myint  Kyi Lynn  Myint Thein Htay  Maw Oo  Thein Zaw 《Resource Geology》2011,61(1):1-29

The 50 km² Monywa copper district lies near the Chindwin River within the northward continuation of the Sunda‐Andaman magmatic arc through western Myanmar. There are four deposits; Sabetaung, Sabetaung South, Kyisintaung, and the much larger Letpadaung 7 km to the southeast. Following exploration drilling which began in 1959, production of copper concentrates from a small open pit started at Sabetaung in 1983. Since 1997, when resources totaled 7 million tonnes contained copper in 2 billion tonnes ore, a heap leach–electro‐winning operation has produced over 400,000 t copper cathode from Sabetaung and Sabetaung South. Ore is hosted by mid‐Miocene andesite or dacite porphyry intrusions, and by early mid‐Miocene sandstone and overlying volcaniclastics including eruptive diatreme facies which the porphyries intrude. District‐wide rhyolite dykes and domes with marginal breccias probably post‐date andesite porphyries in the mine area and lack ore‐grade copper. Host rocks to mineralization are altered to phyllic and advanced argillic hydrothermal assemblages within an outer chlorite zone; hypogene alunite is most abundant at Letpadaung and Kyisintaung. Most mineralization is structurally‐controlled with digenite‐chalcocite in breccia dykes, in steeply dipping NE‐trending sheeted veins, and in stockwork and low‐angle sulfide veins. A high‐grade pipe at Sabetaung grades up to 30% Cu, and much of the ore at Sabetaung South is in a NE‐trending zone of mega‐breccia and stockworked sandstone. The hydrothermal alteration, together with replacement quartz, alunite and barite in breccia dykes and veins, the virtual absence of vein quartz, and the presence of chalcopyrite and bornite only as rare veins and as inclusions within the abundant pyrite, indicate that the deposits are high sulfidation. Regional uplift, resistance to erosion and leaching of the altered and mineralized rocks have resulted in porous limonite‐stained leached caps over 200 m thick forming the Letpadaung and Kyisintaung hills. The barren caps pass abruptly downwards at the water table into the highest grade ore at the top of the supergene enrichment zone, within which copper grade, supergene kaolinite and cubic alunite decrease, and pyrite increases with depth; in contrast, marcasite is mostly shallow. Much of the copper to depths exceeding 200 m below the water table occurs as supergene digenite‐chalcocite and minor covellite. Disseminated chalcocite is mostly near‐surface and hence almost certainly supergene. We infer that during prolonged uplift at all four deposits, oxidation of residual pyrite at the water table generated enough acid to leach all the copper from earlier supergene‐enriched ore; below the water table the resulting acid sulfate solutions partly replaced enargite, covellite, chalcopyrite, bornite and pyrite with supergene chalcocite. Undeformed upward‐fining cross‐bedded conglomerates and sands of the ancestral Chindwin River floodplain overlie the margins of the Sabetaung deposits, form a major aquifer up to 40 m thick, and are a potential host for exotic copper mineralization. A mid‐Miocene pluton is inferred to underlie the Monywa deposits, but the possibility of porphyry‐type mineralization within the district is at best highly speculative.  相似文献   

Dolomite Versus Calcite Weathering in Hydrogeochemically Diverse Watersheds Established on Bedded Carbonates (Sava and So?a Rivers, Slovenia)     

Kathryn Szramek  Lynn M. Walter  Tja?a Kandu?  Nives Ogrinc 《Aquatic Geochemistry》2011,17(4-5):357-396

The relative contributions of dolomite to calcite weathering related to riverine fluxes are investigated on a highly resolved spatial scale in the diverse watersheds of Slovenia, which previous work has shown have some of the highest carbonate-weathering intensities in the world and suggests that dolomite weathering is favored over limestone weathering in mixed carbonate watersheds. The forested Sava and So?a River watersheds of Slovenia with their headwaters in the Julian Alps drain alpine regions with thin soils (<30 cm) and dinaric karst regions with thicker soils (0 to greater than 70 cm) all developed over bedded Mesozoic carbonates (limestone and dolomite), and siliclastic sediments is the ideal location for examining temperate zone carbonate weathering. This study extends previous work, presenting geochemical data on source springs and documenting downstream geochemical fluctuations within tributaries of the Sava and So?a Rivers. More refined sampling strategies of springs and discrete drainages permit directly linking the stream Mg²⁺/Ca²⁺ ratios to the local bedrock lithology and the HCO₃ ^? concentrations to the relative soil depths of the tributary drainages. Due to differences in carbonate source lithologies of springs and tributary streams, calcite and dolomite weathering end members can be identified. The Mg²⁺/Ca²⁺ ratio of the main channel of the Sava River indicates that the HCO₃ ^? concentration can be attributed to nearly equal proportions by mass of dolomite relative to calcite mineral weathering (e.g., Mg²⁺/Ca²⁺ mole ratio of 0.33). The HCO₃ ^? concentration and pCO₂ values increase as soil thickness and alluvium increase for discrete spring samples, which are near equilibrium with respect to calcite. Typically, this results in approximately 1.5 meq/l increase in HCO₃ ^? from the alpine to the dinaric karst regions. Streams in general do not change in HCO₃ ^?, Mg²⁺/Ca²⁺, or Mg²⁺/HCO₃ ^? concentrations down course, but warming and degassing of CO₂ produce high degrees of supersaturation with respect to calcite. Carbonate-weathering intensity (mmol/km²-s) is highest within the alpine regions where stream discharge values range widely to extreme values during spring snowmelt. Overall, the elemental fluxes of HCO₃ ^?, Ca²⁺, and Mg²⁺ from the tributary watersheds are proportional to the total water flux because carbonates dissolve rapidly to near equilibrium. Importantly, dolomite weathers preferentially over calcite except for pure limestone catchments.  相似文献   

Pavements along memory lane and castles of sand long before “Man”     

Lynn Margulis   《Earth》2009,96(3):v

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Entrainment rates during ACE‐2 Lagrangian experiments calculated from aircraft measurements     

Michael J. Sollazzo  Lynn M. Russell  Derek Percival  Simon Osborne  Robert Wood  Douglas W. Johnson 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):335-347

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First science with the Southern African Large Telescope: peering at the accreting polar caps of the eclipsing polar SDSS J015543.40+002807.2     

J. V. Smoker  B. B. Lynn  D. J. Christian  F. P. Keenan 《Monthly notices of the Royal Astronomical Society》2006,372(1):151-162

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Introduction     

Lynn A. Staeheli  Lorraine Dowler 《GeoJournal》2002,58(2-3):73-75

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