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11.
The zonation patterns ofAvicennia bicolor andRhizophora racemosa were studied in a mangrove forest on the Pacific Coast of Costa Rica. Comparisons were made between the establishment, survival, and growth of both species in three plots, 1 ha each, located along the flooding gradient. Based on cohort analysis and reciprocal planting observations, it was concluded that species zonation was primarily regulated by the depth of tidal inundation and the differential ability of the propagules to become established. However, tidal sorting was not the only operative factor related to inundation. Drought and probably high soil salinities limited the survival and growth ofR. racemosa in the landward sections of the forest. Tidal sorting, however, confined propagules to zones where they probably had the highest likelihood of contributing to another generation. 相似文献
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Thomas M. Leschine Bridget E. Ferriss Kathleen P. Bell Krista K. Bartz Sarah MacWilliams Michelle Pico Andrew K. Bennett 《Estuaries and Coasts》2003,26(4):1189-1204
Numerous studies have concluded that better use of scientific information could improve the quality of coastal and estuarine environmental management. Approaches for effecting such a change include ecosystem-based, integrated, and adaptive management, but such basic re-orientation of estuarine and coastal management has proved difficult to achieve. Even environmental indicators, seemingly straightforward ways of injecting scientific information into decision making, have achieved broad on-the-ground use in relatively few instances—principally the largest estuary management programs. A conceptual framework useful for examining environmental management systems affecting the five PNCERS (Pacific Northwest coastal Ecosystems Regional Study) estuaries conceives of environmental managers, researchers, and interested and affected parties in the public as interacting through the multi-layered institutional arrangements that currently promote the utilization, management, or protection of coastal and estuarine resources. Considerable variation exists in the approach and effectiveness of the region's environmental management organizations. Interaction between science and management in the region appears to be limited to an extent by high transaction costs; a cultural divide between environmental scientists and environmental managers is perceived by members of both groups who work with the PNCERS estuaries as inhibiting communications between them. Mechanisms that both groups identify as useful for improving the flow of information between science and management are little used, perhaps as a result. The two groups have very different patterns of information dissemination and acquisition, and though both chose agency archives and databases as their top methods for disseminating information, neither group relies much on these vehicles for information they seek. Both residents' and practitioners' perceptions of threats to the PNCERS estuaries show patterns of estuary-to-estuary variation. One theme that emerges is that problems associated with poor land management in adjacent uplands are common to most of these estuaries, potentially providing a sense of commonality through which a more regional approach to estuary management could emerge. A common set of estuarine environmental indicators implemented for all estuaries could help instigate such a regional approach, but resource constraints, especially at the local level, will have to be overcome for that to occur. There is currently substantial lack of common vision among coastal practitioners as to the purpose and desirability of indicators, and relatively little experience or knowledge of their use, particularly at the local level. Use of estuarine science in the management of these estuaries appears to be greatest during periods in which the largest programmatic shifts in environmental management approaches occur, an observation consistent with other studies that have concluded that the use of environmental science in environmental management tends to be episodic. 相似文献
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We use a dataset of 38 field‐mapped channel heads from a semi‐arid environment in western Colorado to examine relationships between contributing drainage area (A) and local hillslope gradient (θ) in relation to dominant process of initiation (surface runoff versus subsurface flow). Channel heads resulting primarily from subsurface flow have significantly greater values of A, longer basin lengths, and shallower local gradients than channel heads resulting primarily from surface runoff. We also compare the data from western Colorado to six analogous datasets from more humid regions in other portions of the United States and in southeast Australia. Comparison of the confidence intervals for the exponent values of A–θ regression lines reveals that the confidence intervals for the exponent of western Colorado channel heads with both surface and subsurface flow overlap with the confidence intervals for the exponent of all other datasets. This suggests that A–θ relationships do not differ significantly between diverse geographic locations. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
15.
Entanglement records of hauled out pinnipeds are useful for monitoring trends in impacts of synthetic materials, a principal contaminant, upon pinniped populations. This report documents entanglement of five species (California Sea Lions, Northern Elephant Seals, Steller Sea Lions, Pacific Harbor Seals, and Northern Fur Seals) at South-east Farallon Island (SEFI), an island in Northern California, 1976–1998, when a total of 914 pinnipeds were observed entangled in or with body constrictions from synthetic material. There was a significant decrease in entangled Northern Elephant Seals over the study period. Of the 27 Steller Sea Lions observed entangled, 37% were adult Steller Sea Lions entangled in salmon fishing gear. This report highlights an ongoing problem of entanglement of pinnipeds in synthetic materials in Northern California. 相似文献
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Krista M. Mckinzey John F. Orwin Tom Bradwell 《Geografiska Annaler: Series A, Physical Geography》2004,86(4):319-335
Little Ice Age (LIA) moraines along the margins of Skálafellsjökull and Heinabergsjökull, two neighbouring outlet glaciers flowing from the Vatnajökull ice‐cap, have been re‐dated to test the reliability of different lichenometric approaches. During 2003, 12 000 lichens were measured on 40 moraine fragments at Skálafellsjökull and Heinabergsjökull to provide surface age proxies. The results are revealing. Depending on the chosen method of analysis, Skálafellsjökull either reached its LIA maximum in the early 19th century (population gradient) or the late 19th century (average of five largest lichens), whereas the LIA maximum of Heinabergsjökull occurred by the mid‐19th century (population gradient) or late‐19th century (average of 5 largest lichens). Discrepancies (c. 80 years for Skálafellsjökull and c. 40 years for Heinabergsjökull) suggest that the previously cited AD 1887 LIA maxima for both glaciers should be reassessed. Dates predicted by the lichen population gradient method appear to be the most appropriate, as mounting evidence from other geochronological reconstructions and sea‐ice records throughout Iceland tends to support an earlier LIA glacier maximum (late 18th to mid‐19th century) and probably reflects changes in the North Atlantic Oscillation. These revised chronologies shed further light on the precise timing of the Icelandic LIA glacier maximum, whilst improving our understanding of glacier‐climate interactions in the North Atlantic. 相似文献
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Consolidating measurement data for use by data models or in inter-comparison studies frequently requires transforming the data onto a common grid. Standard methods for interpolating multidimensional data are often not appropriate for data with non-homogenous dimensionality, and are hard to implement in a consistent manner for different datastreams. These challenges are increased when dealing with the automated procedures necessary for use with continuous, operational datastreams. In this paper we introduce a method of applying a series of one-dimensional transformations to merge data onto a common grid, examine the challenges of ensuring consistent application of data consolidation methods, present a framework for addressing those challenges, and describe the implementation of such a framework for the Atmospheric Radiation Measurement (ARM) program. 相似文献
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David G. Blackburn Kathryn L. Bryson Vincent F. Chevrier Krista F. White 《Planetary and Space Science》2010,58(5):780-791
Dynamic models of the martian polar caps are in abundance, but most rely on the assumption that the rate of sublimation of CO2 ice can be calculated from heat transfer and lack experimental verification. We experimentally measured the sublimation rate of pure CO2 ice under simulated martian conditions as a test of this assumption, developed a model based on our experimental results, and compared our model's predictions with observations from several martian missions (MRO, MGS, Viking). We show that sun irradiance is the primary control for the sublimation of CO2 ice on the martian poles with the amount of radiation penetrating the surface being controlled by variations in the optical depth, ensuring the formation and sublimation of the seasonal cap. Our model confirmed by comparison of MGS-MOC and MRO-HiRISE images, separated by 2-3 martian years, shows that ∼0.4 m are currently being lost from the south perennial cap per martian year. At this rate, the ∼2.4-m-thick south CO2 perennial cap will disappear in about 6-7 martian years, unless a short-scale climatic cycle alters this rate of retreat. 相似文献
19.
The forests of southeastern Africa are vulnerable to damage imposed by tropical cyclones operating in the South Indian Ocean. We undertook a geographical analysis to determine the relative vulnerability of forests given tropical cyclones recorded during the 1959–2008 storm seasons. From this analysis, eastern coastal forests of Madagascar seem to be the most vulnerable, although return intervals for severe storms vary along the eastern coast, and are shorter (about 10 years) through the central portion of the country. Therefore, the central lowland to upper montane rainforests on the eastern coast seem to be more vulnerable to damage from tropical cyclones than others in the area. While not as extensive, western coastal forests of Madagascar are also as vulnerable in part due to the recurvature of storms in the Mozambique Channel. Though the coastal forests of Mozambique are all nearly equal in terms of vulnerability, the return interval for severe storms to this area is highly variable. The inland Miombo forests of southeast Africa are less vulnerable to damage from tropical cyclones; however, portions of western Mozambique and Zimbabwe have experienced strong tropical storms in the last 50 years. A number of caveats and limitations associated with the data and analyses are noted. Given the broad scale of the study, the relative vulnerability and the return intervals for severe storms should be considered general representations of these phenomena for the southeastern African coast and the island of Madagascar. 相似文献
20.
Composition of dissolved organic matter in groundwater 总被引：1，自引：0，他引：1
Groundwater constitutes a globally important source of freshwater for drinking water and other agricultural and industrial purposes, and is a prominent source of freshwater flowing into the coastal ocean. Therefore, understanding the chemical components of groundwater is relevant to both coastal and inland communities. We used electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to examine dissolved organic compounds in groundwater prior to and after passage through a sediment-filled column containing microorganisms. The data revealed that an unexpectedly high proportion of organic compounds contained nitrogen and sulfur, possibly due to transport of surface waters from septic systems and rain events. We matched 292 chemical features, based on measured mass:charge (m/z) values, to compounds stored in the Kyoto Encyclopedia of Genes and Genomes (KEGG). A subset of these compounds (88) had only one structural isomer in KEGG, thus supporting tentative identification. Most identified elemental formulas were linked with metabolic pathways that produce polyketides or with secondary metabolites produced by plants. The presence of polyketides in groundwater is notable because of their anti-bacterial and anti-cancer properties. However, their relative abundance must be quantified with appropriate analyses to assess any implications for public health. 相似文献