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The American cranberry (Vaccinium macrocarpon Ait.) is an important part of the cultural heritage and economy of Southeastern Massachusetts, yet water quality concerns and wetland protection laws challenge its commercial production. Here, we report inputs and outputs of water, nitrogen (N), and phosphorus (P) for a 2.12‐ha cranberry bed over a 2‐year period from 2013 to 2015. Water‐budget analysis indicated that precipitation contributed 40%, floodwater 37%, irrigation 15%, and groundwater 8% of water inputs to the cranberry bed. Minor annual variation in surface water discharge (~90 mm·year?1 or 3%) contrasted with large decreases in net (= outputs ? inputs) nutrient export, from 16.2 to 9.1 kg N·ha?1·year?1 for total (dissolved + suspended particulate) nitrogen (TN) and from 3.34 to 1.47 kg P·ha?1·year?1 for total phosphorus (TP) between Years 1 and 2. Annual variation in net TN and TP export was tied to decreases in spring and summer nutrient export and controlled by the combined effects of fertilizer management, soil biogeochemistry, and hydrology. The relatively high spring TN export in Year 1 was associated with coincident increases in soil temperature and rainfall. A second factor was the timing of fertilizer application, which occurred 1 day prior to a major summer storm (i.e., third largest daily rainfall since 1926) and was responsible for up to 15% and 9% of the Year 1 TN and TP export, respectively. Nutrient budgets, which balanced water and fertilizer inputs with water, fruit, and vegetative outputs, were consistent with the burial of 21.6 kg N·ha?1·year?1 and 7.27 kg P·ha?1·year?1. Field measurements indicated that burial would increase TN and TP in the shallow (0–5 cm) rooting zone by 14% and 6%, respectively, which seemed plausible based on the relatively young age of the bed (4–5 years) and new root growth patterns in Vaccinium plants. 相似文献
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Understanding the temporal and spatial variability of water sources within a basin is vital to our ability to interpret hydrologic controls on biogeochemical processes and to manage water resources. Water stable isotopes can be used as a tool to determine geographic and seasonal sources of water at the basin scale. Previous studies in the Coastal Range of Oregon reported that the variation in the isotopic signatures of surface water did not conform to the commonly observed “elevation effect,” which exhibits a trend of increasing isotopic depletion with rising elevation. The primary purpose of this research is to investigate the mechanisms governing seasonal and spatial variations in the isotopic signature of surface waters within the Marys River Basin, located in the leeward side of the Oregon Coastal Range. Surface water and precipitation samples were collected every 2–3 weeks for isotopic analysis for 1 year. Our results confirmed the lack of elevational variation of surface water isotopes within this leeward basin. Although we find elevational variation in precipitation in the eastern portion of the watershed, this elevation effect is counteracted by rainout with distance from the Pacific coast. In addition, we found significant variation in surface water isotope values between catchments underlain predominantly by basalt or sandstone. The degree of separation was strongest during the summer when low flows reflect deeper groundwater sources. This indicates that baseflow within streams drained by each lithology is being supplied from two distinctly separate water sources. In addition, the flow of the Marys River is dominated by water originating from the sandstone water source, particularly during the low‐flow summer months. We interpreted that the difference in water source results from sandstone catchments having highly fractured geology or locally tipping to the east facilitating cross‐basin water exchange from the windward to the leeward side of the Coast Range. Our results challenge topographic derived watershed boundaries in permeable sedimentary rocks; highlighting the overwhelming importance of underlying geology. 相似文献
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Nickolas Moeckel Ian A. Bonnell 《Monthly notices of the Royal Astronomical Society》2009,396(4):1864-1874
Mass segregation is observed in many star clusters, including several that are less than a few Myr old. Time-scale arguments are frequently used to argue that these clusters must be displaying primordial segregation, because they are too young to be dynamically relaxed. Looking at this argument from the other side, the youth of these clusters and the limited time available to mix spatially distinct populations of stars can provide constraints on the amount of initial segregation that is consistent with current observations. We present n -body experiments testing this idea, and discuss the implications of our results for theories of star formation. For system ages less than a few crossing times, we show that star formation scenarios predicting general primordial mass segregation are inconsistent with observed segregation levels. 相似文献
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A graphic review of the growth and decay of population cohorts 总被引：1，自引：0，他引：1
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Kevin J. Maki Donghee Lee Armin W. Troesch Nickolas Vlahopoulos 《Ocean Engineering》2011,38(4):621-629
In this paper a hydroelastic method for the design of marine structures is used to study the impact of a wedge-shaped body onto a calm free-surface. The method combines computational fluid dynamics and dynamic finite-element techniques to predict the hydroelastic response of a structure in the time domain. The basic idea of the method is to predict the stress field on the fluid-structure interface due to rigid-body impact, and then to transfer the information to a wet modal model. The one-way transfer of information from the fluid simulation to the structure has two important advantages with respect to a fully coupled simulation: a single rigid-body motion computation can be reused for subsequent analyses after the structure has been redesigned, and cost of the fluid dynamic simulation is not increased due to iteration which is required in coupled simulations. The maximum displacement of an elastic wedge during the impact and penetration stages are compared with published results from a fully coupled theoretical model and a fully coupled numerical solver. The present method requires approximation of the flexural added mass, and the comparison with other results shows that the approximation is satisfactory for predicting maximum displacement. 相似文献
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Georgia Pe‐Piper David J.W. Piper Nickolas Zouros George Anastasakis 《Basin Research》2019,31(6):1178-1197
The Petrified Forest of Lesbos comprises silicified tree fossils at multiple stratigraphic levels within the Lower Miocene Sigri Pyroclastic Formation. Our objective was to understand the interplay of tectonic setting, structural evolution, volcanological setting and basin evolution in the preservation of this remarkable natural monument. Sections were logged for lithology, sedimentary structures and hydrothermal alteration. Orientations of fallen fossil trees were measured. Samples were taken for mineralogical and geochemical analysis. 40Ar/39Ar dating was carried out on mineral separates from four samples. Widespread andesite‐dacite domes, the Eressos Formation, intrude and overlie metamorphic basement and are overlain by the Sigri Pyroclastic Formation, which comprises several hundreds of metres of pyroclastic flow tuffs (unwelded ignimbrites) interbedded with fluvial conglomerate and volcaniclastic sandstone. The Sigri Pyroclastic Formation ranges in age from 21.5 to 22 Ma, where it overlies the lacustrine Gavathas Formation, to younger than 18.4 Ma. Tuffs and fluvial conglomerates in the Sigri Pyroclastic Formation coarsen eastwards, and petrified trees and soil horizons occur throughout the Formation. The recurrence of pyroclastic flows was approximately one every 20 ka, so destructive flows were relatively infrequent, allowing the development of climax vegetation between most eruptions. Conglomerate‐filled channels show that rivers flowed westwards. Tree fall directions indicate NW to N movement of pyroclastic flows, implying a source near the younger Mesotopos–Tavari caldera to the south. The basin, which formed in a NNE‐trending dextral strike‐slip regime, provided some topographic steering. Following the Sigri Pyroclastic Formation at ca. 18 Ma, there was a rapid increase in the pace of volcanic activity, with the eruption of thick lava sequences and welded ignimbrites, and intrusion of dykes and laccoliths in SW Lesbos. Rapid burial by permeable tuffs, silica from alteration of volcanic ash, and later hydrothermal circulation all contributed to the preservation of the petrified trees. 相似文献
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In this paper we attempt to reconcile seemingly contradictory research concerning the existence of an El-Niño Southern Oscillation (ENSO) signal in precipitation records from the Gulf of Alaska region. A number of studies based on records from primarily coastal stations and the mass balance of low elevation glaciers suggest there is at best a weak relationship between ENSO and precipitation anomalies in the region. In contrast, an analysis of an ice core extracted from a high elevation site on Mount Logan in the region indicates that a statistically significant ENSO signal exists in its annual snow accumulation time series on both inter-annual and inter-decadal time scales. The ENSO signal in the region is expressed through an atmospheric teleconnection known as the Pacific North America pattern. We show that a statistically significant enhancement in the atmospheric moisture transport into the North Pacific and western North America is associated with the warm phase of ENSO. The maximum transport does not occur at the surface but rather in the lower to middle troposphere. We argue that the high elevation of the Mount Logan site allows it to preferentially sample the vertically distributed moisture transport anomaly associated with warm ENSO events. This study serves to highlight the wealth of information on teleconnection patterns that may be contained in paleoclimate data from mountainous regions. 相似文献
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Timothy G. Fisher Nickolas Waterson Thomas V. Lowell Irka Hajdas 《Quaternary Science Reviews》2009,28(17-18):1608-1624
A field-based reconstruction of the deglacial paleogeography in the Fort McMurray area permits: 1) constraining the timing of meltwater routing to the Arctic from the present Hudson Bay drainage basin; and 2) minimum-age estimates for ice-margin positions that can be used to constrain ice-sheet modeling results. A downslope recession of the Laurentide Ice Sheet resulted in a series of proglacial lakes forming between the ice margin and higher land to the southwest. The paleogeography of these lakes is poorly constrained in part from the masking effect of boreal forest vegetation and map-scale issues. However, recent space-shuttle based DEMs increase the number and spatial extent of moraines identified within the study area resulting in a coherent pattern of ice margin retreat focused on the Athabasca River valley. An intensive lake-coring program resulted in a minimum ten-fold increase in the radiocarbon database used to limit moraine ages. Results indicate that deglaciation in this region was younger than previously reported, and it is likely that the meltwater could not drain northward to the Arctic Ocean from any source southeast of the Fort McMurray area until approximately 9850–9660 14C BP. 相似文献
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