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This article presents an econometric analysis of land‐cover change in western Honduras. Ground‐truthed satellite image analysis indicates that between 1987 and 1996 net reforestation occurred in the 1,015‐km2 study region. While some reforestation can be attributed to a 1987 ban on logging, the area of reforestation greatly exceeds that of previously clear‐cut areas. Further, new area was also deforested between 1987 and 1996. Thus, the observed land‐cover changes represent a complex mosaic of changing land‐use patterns across time and space. The analysis contributes to the literature on land‐cover change modeling in that: (1) it compares two econometric approaches to capture complex and often bidirectional changes in land cover from 1987 to 1996 as a function of agricultural suitability and transportation costs, and (2) it addresses techniques to identify and correct for spatial autocorrelation in a categorical regression framework. 相似文献
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Reducing Emissions from Deforestation and Forest Degradation projects currently cover an area approximately twice the size of Germany and challenge traditional concepts of centralization and decentralization in studies of environmental governance. Emerging from the interactions of a complex network of actors, Reducing Emissions from Deforestation and Forest Degradation demonstrates that transnational governance networks of organizations can become spatially centralized. Using a historical analysis of the development of Reducing Emissions from Deforestation and Forest Degradation, we argue that the evolution of Reducing Emissions from Deforestation and Forest Degradation policy has been directed primarily from donor countries, especially in North America and Europe. Adopting a social network analysis approach, we present findings from a new dataset of collaboration on 276 Reducing Emissions from Deforestation and Degradation, avoided deforestation, and sustainable forest management projects that began some on-the-ground operations between 1989 and June 2012, finding that organizations in donor countries have from the beginning been the central actors in the Reducing Emissions from Deforestation and Forest Degradation network. We conclude that Reducing Emissions from Deforestation and Forest Degradation exhibits spatial centralization within transnational governance architectures despite institutional fragmentation, raising important normative questions about participation in transnational forest governance. 相似文献
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This paper represents the first report of adultG. ginsburgi from Rhode Island waters since 1938. Gobies were collected only from subtidal shell communities in high salinity waters. Seaboard gobies eat a variety of benthic invertebrates but feed most heavily on harpacticoid copepods. Gravid females collected in July contained one size class of ova indicating a single spawning per season. Egg counts ranged from 1268 to 1977 per female. Larval densities indicate that peak spawning occurs in July and suggest thatG. ginsburgi is more abundant in the Sakonnet River and nearby Narragansett Bay than previously reported. 相似文献
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Jeffrey S. Munroe 《第四纪科学杂志》2012,27(6):639-648
The sedimentary records of Nulhegan Pond and Beecher Pond in the Nulhegan Basin of north‐eastern Vermont were analyzed to yield a history of environmental change since the latest Pleistocene. Shoreline landforms indicate that part of the Nulhegan Basin was inundated by Glacial Lake Nulhegan (GLN), which was impounded behind a dam of glacial sediment. Outwash derived from stagnant ice forms the bottom 176 cm of the Nulhegan Pond core. Fine‐grained inorganic sediment deposited between 13.4 and 12.2k cal a BP is interpreted as a deep‐water facies representing GLN, while coarser sediment from 12.2 to 11.8k cal a BP records draining of the glacial lake. Rapid, simultaneous increases in organic matter and biogenic silica signal the onset of productivity following the Younger Dryas. Beecher Pond formed c. 11.3k cal a BP through surface collapse over a buried ice block; buried stagnant ice may have persisted in the vicinity of the pond into the early Holocene. From 8.9 to 5.5k cal a BP, sediment in both lakes became coarser and richer in aquatic organic matter, suggesting a low‐water phase in which previously deposited lacustrine sediments were reworked and the littoral zone shifted basinward. Low water levels at this time are consistent with other records from Maine and southern Quebec, but contrary to records from ～325 km to the south. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Thomas A. Munroe Donald M. Baltz Robert L. Allen Steve W. Ross 《Estuaries and Coasts》2000,23(4):439-448
Two species of tonguefishes,Symphurus plagiusa (Linnaeus 1766) andSymphurus civitatium Ginsburg 1951, occur sympatrically and sometimes syntopically in shallow water habitats in North Carolina and Louisiana estuaries. In North Carolina, approximately 2% of 430 small (<75 mm SL) tonguefishes collected wereS. civitatium, while in Barataria Bay, Louisiana, this species was more abundant and cosmopolitan in distribution than wasS. plagiusa, comprising over 82% of 3,564 tonguefishes collected with a small beam trawl over a 2-yr period. Historical literature has regardedS. plagiusa as the only tonguefish species inhabiting inshore waters in both regions. Presence of a secondSymphurus species in shallow estuaries has been overlooked, most probably due to difficulties in identifying early post-settlement juveniles because both species have similar morphologies and overlapping dorsal-fin and anal-fin ray counts. Juveniles can be readily recognized by differences in number of caudal-fin rays (10 inS. plagiusa versus 12 inS. civitatium), especially when used in combination with pigmentation patterns and posterior extent of the jaws relative to the posterior margin of the lower eye. The most distinctive pigmentation difference between juveniles of these two species (allowing for accurate identifications of over 98% of juveniles) is the absence inS. civitatium (12–61 mm SL) of a series of melanophores overlying pterygiophore regions of the dorsal and anal fins on the blind side. This feature contrasts markedly with that of juvenileS. plagiusa (12–65 mm SL), which are characterized by two interrupted, diagonal series of dark chromatophores converging, but not merging, with posterior tapering of the body. Occurrence of two sympatric species of tonguefishes in estuarine environments in the northcentral Gulf of Mexico and southeastern U.S. potentially compromises results of earlier ecological and distributional studies that assumed presence of only a single tonguefish species in these regions. 相似文献
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Pluvial lakes were abundant in the southwestern United States during Pleistocene glaciations, particularly in the Great Basin. Many of these lakes occupied closed basins; therefore, fluctuations of their water surface elevations are valuable sources of paleoclimate information. Histories of the largest lakes are well constrained, whereas dozens of smaller lakes that were present in this region have received relatively little scientific attention. Given their dimensions, these smaller lakes were climatically sensitive and can offer important information about Quaternary climate variability. Here we present new ages for the highstands of three previously undated small lakes based on radiocarbon dating of gastropod shells recovered from beach ridges. These results are combined with other published and unpublished 14C ages to yield an extensive compilation of highstand shoreline ages for lakes of all sizes throughout the southwestern US. The results indicate that although some lakes reached highstands during the Last Glacial Maximum, the strongest temporal correspondence is between highstands and Heinrich Event H1. These results are consistent with speleothem‐based reconstructions of effective moisture in the southwestern US, which show increased precipitation during stadials of the last glacial cycle. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Radiocarbon-dated sediment cores from subalpine lakes were used to investigate post-glacial dust deposition in the Uinta Mountains (Utah, USA). Lake sediments were geochemically characterized with ICP-OES, ICP-MS and XRF core scanning. Collections from passive samplers constrain the properties of modern dust, and samples of regolith constrain properties of the local material within the watershed. Ca and Eu are more abundant in dust, whereas Ti and Zr are more abundant in local regolith. As a result, the Ca/Ti and Eu/Zr ratios are indices for the dust content of lake sediment. In all records, the dust index rises in the early Holocene as watersheds became stabilized with vegetation, reducing the influx of local material. After this point, values remained above average through the middle Holocene, consistent with an increased dust content in the sediment. Dust index values drop in the late Holocene in most lakes, suggesting a decrease in dust abundance. Generally synchronous shifts in dust index values in cores from lakes in different parts of this mountain range are evidence of enhanced dust deposition in this region during the middle Holocene, and are consistent with a variety of records for increased aridity in the south-western USA at this time. 相似文献
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Jeffrey S. Munroe 《Geomorphology》2006,75(3-4):437
Isolated, laterally extensive, gently sloping surfaces known as summit flats are present at high elevations in many Laramide ranges, and are particularly well developed in the Uinta Mountains of northeastern Utah. To investigate the spatial distribution of these surfaces, and to consider possible controls on this pattern, a map of summit flats in the Uintas was developed from digital elevation data. Summit flats were identified as unglaciated areas of the landscape above an elevation of 3400 m, having a slope of less than 0.3 m m− 1, and an area greater than 5 × 10− 2 km2. As defined, summit flats comprise 43% of the unglaciated land area above 3400 m in the Uintas, with the largest individual flat covering nearly 34 km2. To quantitatively evaluate the distribution of summit flats in the Uintas, the area of summit flats was normalized to the total unglaciated area above 3400 m in 10-km-wide swaths oriented normal to the range axis. Values of percent summit flats obtained by this method decrease dramatically westward, from a high of more than 60% at the eastern end of the Uintas, to 0% at the western end. Given that individual summit flats can be diminished through lateral erosion by surrounding valley glaciers, and that the summit flats themselves were apparently never glaciated, this result suggests that glacial erosion has been more effective in the western Uintas over the course of the Quaternary. Focused glacial erosion at the upwind end of the range is consistent with the hypothesis that the proximity of Lake Bonneville enhanced precipitation over the western Uintas during the Last Glacial Maximum [Munroe, J.S., and, Mickelson, D.M., 2002. Last Glacial Maximum equilibrium-line altitudes and paleoclimate, northern Uinta Mountains, Utah, U.S.A. Journal of Glaciology, 48, 257–266]. 相似文献
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Storm Surges from Extra-Tropical Cyclones 总被引：1，自引：0，他引：1
Danard M. B. Dube S. K. Gönnert G. Munroe Adam Murty T. S. Chittibabu P. Rao A. D. Sinha P. C. 《Natural Hazards》2004,32(2):177-190
The possible influence of climate change on the tracks of the extra-tropical cyclones as well as storm surges is studied. Two differentdata bases have been used: one for the Great Lakes of North America and the otherfor the German Bight in the North Sea of Europe. For the Great Lakes region,significant east-west and north-south shifts in the tracks of ETC'S with decadal periodicities have been observed. However, there was no trend in the amplitudes of storm surges. The most important result for the Great Lakes is that, depending upon its position relative to the constantly shifting storm tracks, a given location could eitherexperience a major storm surge or could miss out completely.The storm surges in the German Bight in general, and at Cuxhaven in particular, appear to show a slightly increasing trend in the latterpart of the 20th century. However, the most significant result for the German Bightis that the number of storm tides (i.e., multiple peaks in a given storm surge event)definitely has shown an increase in the second half of the 20th century. This increase isinterpreted as due to the influence of meso-scale weather systems embedded in the synoptic scale ETCs. 相似文献