Climates of the soviet union | P.E. Lydolph, 1977. World survey of climatology, 7. Elsevier,Amsterdam, 443 pp., U.S. $ 81.75, Dfl. 200.00     

F. Kenneth Hare 《Earth》1978,14(2):174-175

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A time evolution study of limb spicule spectra     

Kenneth R. Krall  R. J. Bessey  Jacques M. Beckers 《Solar physics》1976,46(1):93-114

Time sequences of simultaneous spectra of limb spicules, obtained using the Sacramento Peak Observatory's tower telescope and echelle spectrograph are analyzed. Intensity determinations of H and K, H, 8498 and 8542 of calcium are tabulated for three observing heights. Electron densities averaged over the entire visible lifetimes of spicules are -6 × 10¹⁰ cm^–3 at observing heights of 6000km, while maximum and minimum values were -1.1 × 10¹¹ cm^–3 at 6000km and - 2 × 10¹⁰ cm^–3 at 10000km. Electron temperatures range between 12 000 K and 16 000 K. Profile halfwidths indicate turbulent velocities of 12 to 22 km s^–1, and spectral tilts are interpreted as caused by differential velocity fields of -3 km s^–1 per 1000 km. No large scale spicule expansions or contractions are observed, although possible expulsions or accretions of material are observed. Spicules may be wider in the calcium K and H lines than in H.Now at School of Science and Engineering, The University of Alabama in Huntsville, Huntsville, Alabama.  相似文献   

The Vivian Thompson Stereo-planigraph     

Kenneth  Mason 《The Photogrammetric Record》1975,8(45):371-371

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BRITISH FARMING IN THE GREAT DEPRESSION 1870–1914: AN HISTORICAL GEOGRAPHY. By Peter J. Perry     

Kenneth  Jackson 《New Zealand geographer》1975,31(1):93-94

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Cosmogenic nuclide methods for measuring long-term rates of physical erosion and chemical weathering     

James W. Kirchner  Clifford S. Riebe  Kenneth L. Ferrier  Robert C. Finkel 《Journal of Geochemical Exploration》2006,88(1-3):296

Understanding the evolution of geochemical and geomorphic systems requires measurements of long-term rates of physical erosion and chemical weathering. Erosion and weathering rates have traditionally been estimated from measurements of sediment and solute fluxes in streams. However, modern sediment and solute fluxes are often decoupled from long-term rates of erosion and weathering, due to storage or re-mobilization of sediment and solutes upstream from the sampling point. Recently, cosmogenic nuclides such as ¹⁰Be and ²⁶Al have become important new tools for measuring long-term rates of physical erosion and chemical weathering. Cosmogenic nuclides can be used to infer the total denudation flux (the sum of the rates of physical erosion and chemical weathering) in actively eroding terrain. Here we review recent work showing how this total denudation flux can be partitioned into its physical and chemical components, using the enrichment of insoluble tracers (such as Zr) in regolith relative to parent rock. By combining cosmogenic nuclide measurements with the bulk elemental composition of rock and soil, geochemists can measure rates of physical erosion and chemical weathering over 1000- to 10,000-year time scales.  相似文献   

Responses of resident marsh fishes to stages ofPhragmites australis invasion in three mid Atlantic estuaries     

Karen L. Hunter  Dewayne A. Fox  Lori M. Brown  Kenneth W. Able 《Estuaries and Coasts》2006,29(3):487-498

Modification of brackish marshes by nonindigenousPhragmites australis has occurred across a broad geographical area in eastern North America. Among its effects on marsh processes,Phragmites may be increasingly unfavorable to marsh surface fishes as its invasion progresses within an estuary. We assessed the effect of thePhragmites invasion on resident marsh surface fishes by examining the population response ofFundulus heteroclitus (mummichog, 5–48 mm TL) andF. luciae (spotfin killifish, 5–41 mm TL) to four distinct invasion stages in three estuaries of the U.S. mid Atlantic region (New Jersey, Delaware, and Maryland). We documented precipitous declines in mean catch per unit effort ofF. heteroclitus in pit traps from natural marsh (51.6), through initial (33.8), early (12.3), and late invasion stages (2.4) across all sites. A similar pattern was documented forF. luciae, with mean catch per unit effort in pit traps declining from natural marsh (48.9), through initial (39.1), early (9.3), and late invasion stages (2.7). Population structure of both species also changed somewhat across invasion stages such that we collected a narrower size range of individuals of both species from late invasion stages. Patterns suggest that as thePhragmites invasion progresses, there is a decline in habitat function for larval and juvenileF. heteroclitus and an increased risk of extirpation ofF. luciae from brackish marshes along the east coast of the U.S.  相似文献   

Variability in drift macroalgal abundance in relation to biotic and abiotic factors in two seagrass dominated estuaries in the Western Gulf of Mexico     

Andrea L. Kopecky  Kenneth H. Dunton 《Estuaries and Coasts》2006,29(4):617-629

We examined the spatial and temporal variability in drift macroalgal abundance in two seagrass dominated estuarine systems on the Texas coast: Redfish Bay (in the Copano-Aransas Estuary) and Lower Laguna Madre. Measurements of benthic macroalgal variability were made in conjunction with a suite of biotic (seagrass biomass, percent cover, blade width and length, shoot density, epiphyte biomass, seagrass blade C:N ratios, and drift macroalgal abundance and composition) and abiotic (inorganic nitrogen and phosphorus concentrations, chlorophylla, total suspended solids, light attenuation, salinity, temperature, total organic carbon and porewater NH₄ ⁺) indicators. All parameters were measured at 30 sites within each estuary semiannually from July 2002 to February 2004. Principal components analysis (PCA) was used to examine relationships between drift macroalgal abundance and biotic and abiotic parameters. In both Redfish Bay and Lower Laguna Madre, drift macroalgal distribution was widespread, and during three of four sampling periods, abundance was equal to abovegro und biomass ofThalassia testudinum, the dominant seagrass. Drift macro algal abundance was highly variable within sites, between sites, and between seasons in both estuaries. No significant differences in drift macroalgal abundance were found between Redfish Bay and Lower Laguna Madre. In Redfish Bay, drift macroalgae (90.1±10.2 gm⁻²) tended to accumulate in bare patches within seagrass beds. In Lower Laguna Madre, drift macroalgae (72.7±10.7 gm⁻²) tended to accumulate in areas of dense seagrass cover rather than in bare areas. We found no relationship between drift macroalgal abundance and low (<2μM) water column nutrient concentrations, and although several of our measured parameters were related to drift macroalgal abundance, none alone sufficiently explained the variability in abundance noted between the two estuarine systems. The contrasting patterns of macroalgal accumulation between Redrish Bay and Lower Laguna Madre likely reflect differences in water circulation characteristics between the two regions as dictated by local physiography, in cluding the shape and orientation of the lagoons, with seasonal variations in macroalgal abundance related to changes in freshwater inflow and nutrient loading.  相似文献   

Response of a subtropical estuarine marsh to local climatic change in the southwestern Gulf of Mexico     

Margaret G. Forbes  Kenneth H. Dunton 《Estuaries and Coasts》2006,29(6):1242-1254

We examined the contrasting, effects of floods and droughts produced by large changes in local climatology on vegetation patterns in Nueces marsh, a semi-arid subtropical salt marsh in south Texas from 1995 to 2005. Climate variations during the study included an initial 4-yr period of moderate conditions, followed by a 2-yr interval of drought, and a recent 4-yr wet period that included large-scale floods. Variation in freshwater inflow, rainfall, and potential evapotranspiration were used in conjunction with field measurements of salinity, inorganic nitrogen, and vegetation structure collected at sites located at varying distances from Nueces Bay. Tidal creek salinities varied with Nueces Bay salinity, with strength of effect inversely related to distance from the bay. Mean (±standard deviation) pore water salinities ranged from 59±54‰ at two high, marsh stations farthest from the bay (10.1 km distant) to 30±21‰ in soil at a low marsh site closest to the bay (0.5 km distant). Mean pore water ammonium was also higher at stations most distant from the bay; nitrate + nitrite did not exhibit a high marsh to low marsh gradient. Nueces Bay salinity decreased substantially when the 10-d cumulative mean daily Nueces River flows exceeded 10 m³ s⁻¹. During periods of low and moderate flood frequency (flows mostly below 10 m³ s⁻¹), vegetation assemblages were dominated by stress-tolerant clonal plants. A catastrophic flood, which immersed vegetation for several weeks between July and September 2002, resulted in extensive plant mortality, but within months, unvegetated areas were rapidly colonized by the obligate annualSalicornia bigelovii. With the end of major flooding by late 2004, plant community structure began a return to pre-drought assemblages at high and middle marsh stations by summer 2005. At the low marsh station, new conditions favored clonal dominants (Spartina alterniflora andBorrichia frutescens), with the latter replacingSalicornia virginica as the dominant species. Our results support the theory that the importance of competition and abiotic stress in determining community composition are inversely related.  相似文献   

Kaleidoscoping Landscapes,Shifting Perspectives     

Kenneth R. Young  Richard Aspinall 《The Professional geographer》2006,58(4):436-447

Landscapes change in complex ways, creating surface patterns reminiscent of forms seen through a kaleidoscope. On the Earth's surface, those forms are linked to, and caused by, processes that originate with bedrock‐soil‐vegetation‐atmosphere interactions. Human‐caused alterations to landscapes are additionally tied to socioeconomic processes. Evaluation of landscape‐level processes can benefit from examining (1) the influence of disturbance regimes in altering landscape patterns, (2) the importance of considering surficial processes, (3) the subtle and cryptic spatial relations that may be present, (4) the reciprocal relationships among local processes and regional consequences, (5) the increased likelihood of some land cover transitions compared to others, and (6) the special case of landscapes with long histories of human use. These are all examples of potential fruitful arenas for interactions and represent a path for expansion of landscape ecology through accommodation of a broad range of content covered by the international GIScience community.  相似文献   

Effective and Equitable Dissemination of Seasonal-to-Interannual Climate Forecasts: Policy Implications from the Peruvian Fishery during El Niño 1997–98     

Kenneth Broad  Alexander S. P. Pfaff  Michael H. Glantz 《Climatic change》2002,54(4):415-438

The development of seasonal-to-interannual climate predictions has spurred widespread claims that the dissemination of such forecasts will yield benefits for society. Based on the use as well as non-use of forecasts in the Peruvian fishery during the 1997–98 El Niño event, weidentify: (1) potential constraints on the realization of benefits, such aslimited access to and understanding of information, and unintended reactions; (2) theneed for an appropriately detailed definition of societal benefit, considering whose welfare counts as a benefit among groups such as labor, industry, consumers, citizens of different regions, and future generations.We argue that consideration of who benefits, and an understanding of potential socioeconomic constraints and how they might be addressed, should be brought to bear on forecast dissemination choices. We conclude with examples of relevant dissemination choices made using this process.  相似文献