Modelling landscape evolution   总被引：5，自引：0，他引：5  

Gregory E. Tucker  Gregory R. Hancock 《地球表面变化过程与地形》2010,35(1):28-50

Geomorphology is currently in a period of resurgence as we seek to explain the diversity, origins and dynamics of terrain on the Earth and other planets in an era of increased environmental awareness. Yet there is a great deal we still do not know about the physics and chemistry of the processes that weaken rock and transport mass across a planet's surface. Discovering and refining the relevant geomorphic transport functions requires a combination of careful field measurements, lab experiments, and use of longer‐term natural experiments to test current theory and develop new understandings. Landscape evolution models have an important role to play in sharpening our thinking, guiding us toward the right observables, and mapping out the logical consequences of transport laws, both alone and in combination with other salient processes. Improved quantitative characterization of terrain and process, and an ever‐improving theory that describes the continual modification of topography by the many and varied processes that shape it, together with improved observation and qualitative and quantitative modelling of geology, vegetation and erosion processes, will provide insights into the mechanisms that control catchment form and function. This paper reviews landscape theory – in the form of numerical models of drainage basin evolution and the current knowledge gaps and future computing challenges that exist. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Estimating benthic invertebrate production in lakes: a comparison of methods and scaling from individual taxa to the whole-lake level     

Katrina J. Butkas  Yvonne Vadeboncoeur  M. Jake Vander Zanden 《Aquatic Sciences - Research Across Boundaries》2011,73(1):153-169

Studies of aquatic invertebrate production have been primarily conducted at the level of individual taxa or populations. Advancing our understanding of the functioning and energy flow in aquatic ecosystems necessitates scaling-up to community and whole-lake levels, as well as integrating across benthic and pelagic habitats and across multiple trophic levels. In this paper, we compare a suite of non-cohort based methods for estimating benthic invertebrate production at subpopulation, habitat, and whole-lake levels for Sparkling Lake, WI, USA. Estimates of the overall mean benthic invertebrate production (i.e. whole-lake level) ranged from 1.9 to 5.0 g DM m⁻² y⁻¹, depending on the method. Production estimates varied widely among depths and habitats, and there was general qualitative agreement among methods with regards to differences in production among habitats. However, there were also consistent and systematic differences among methods. The size-frequency method gave the highest, while the regression model of Banse and Mosher (Ecol Monogr 50:355–379, 1980) gave the lowest production estimates. The regression model of Plante and Downing (Can J Fish Aquat Sci 46:1489–1498, 1989) had the lowest average coefficients of variation at habitat (CV = 0.17) and whole-lake (CV = 0.08) levels. At the habitat level, variance in production estimates decreased with sampling effort, with little improvement after 10–15 samples. Our study shows how different production estimates can be generated from the same field data, though aggregating estimates up to the whole-lake level does produce an averaging effect that tends to reduce variance.  相似文献   

Policy relevance of biogeographic classification for conservation and management of marine biodiversity beyond national jurisdiction, and the GOODS biogeographic classification     

Jake Rice  Kristina M. Gjerde 《Ocean & Coastal Management》2011,54(2):110-122

This article 1) examines the policy context that created a demand for biogeographic information, 2) describes early national and regional experiences in applying biogeographic classifications, 3) extracts lessons about their usefulness, 4) introduces a broad-scale biogeographic classification for the open ocean and deep seabed called the Global Open Ocean and Deep Seabed (GOODS) biogeographic classification and explains its relevance in this policy context. In so doing it highlights potential uses of biogeographic classifications for the open ocean and deep seabed: these include ecosystem-based management approaches, marine spatial planning and identification of representative networks of MPAs. It also discusses approaches for dealing with problems of uncertainty and connectivity. The article concludes with recommendations for the further development of the GOODS and finer-scale biogeographic classifications.  相似文献   

The ‘humped’ soil production function: eroding Arnhem Land,Australia     

Arjun M. Heimsath  David Fink  Greg R. Hancock 《地球表面变化过程与地形》2009,34(12):1674-1684

We report erosion rates and processes, determined from in situ‐produced beryllium‐10 (¹⁰Be) and aluminum‐26 (²⁶Al), across a soil‐mantled landscape of Arnhem Land, northern Australia. Soil production rates peak under a soil thickness of about 35 cm and we observe no soil thicknesses between exposed bedrock and this thickness. These results thus quantify a well‐defined ‘humped’ soil‐production function, in contrast to functions reported for other landscapes. We compare this function to a previously reported exponential decline of soil production rates with increasing soil thickness across the passive margin exposed in the Bega Valley, south‐eastern Australia, and found remarkable similarities in rates. The critical difference in this work was that the Arnhem Land landscapes were either bedrock or mantled with soils greater than about 35 cm deep, with peak soil production rates of about 20 m/Ma under 35–40 cm of soil, thus supporting previous theory and modeling results for a humped soil production function. We also show how coupling point‐specific with catchment‐averaged erosion rate measurements lead to a better understanding of landscape denudation. Specifically, we report a nested sampling scheme where we quantify average erosion rates from the first‐order, upland catchments to the main, sixth‐order channel of Tin Camp Creek. The low (～5 m/Ma) rates from the main channel sediments reflect contributions from the slowly eroding stony highlands, while the channels draining our study area reflect local soil production rates (～10 m/Ma off the rocky ridge; ～20 m/Ma from the soil mantled regions). Quantifying such rates and processes help determine spatial variations of soil thickness as well as helping to predict the sustainability of the Earth's soil resource under different erosional regimes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

A soil chronosequence in Late Glacial and Neoglacial moraines, Humboldt Glacier, northwestern Venezuelan Andes     

W.C. Mahaney  V. Kalm  B. Kapran  M.W. Milner  R.G.V. Hancock   《Geomorphology》2009,109(3-4):236-245

Late Glacial and Neoglacial (Little Ice Age) deposits on the Humboldt Massif were analyzed for relative-age dating parameters, including geomorphic and weathering characteristics, geochemical and soil properties. The soil chronosequence, formed in chemically uniform parent materials, provides an important database to study soil evolution in a tropical alpine environment. Extractable and total Fe and Al concentrations, examined to assess their use in relative-age determination, and as paleoenvironmental indicators, provide an important measure of the accumulation and downward profile movement over time of organically-bound Al, ferrihydrite and other crystalline forms (hematite and goethite) of extractable Fe. Ferrihydrite is particularly useful in determining former perched water levels in soils with relation to paleoclimate. The ratios of most Fe extracts are time dependent. The Fe_d/Fe_t ratio, within statistical limits, shows a slow increase from LIA (Little Ice Age) to Late Glacial soils, which closely correlates with other alpine soil studies in the middle latitudes and other tropical alpine locales. Values of Al_d (dithionite) and Al_o (oxalate extractable) generally do not correlate with time; however, Al_p (pyrophosphate extractable) measured against Al_t (total) provides insight on the downward translocation over time of organically-bound Al. Low leaching rates in this chronosequence are further supported by clay mineralogy trends and the geochemical data.  相似文献   

People’s capacities in facing hazards and disasters: an overview     

Gaillard  J. C.  Cadag  Jake Rom D.  Rampengan  Mercy M. F. 《Natural Hazards》2019,95(3):863-876

Natural Hazards - This article constitutes an effort towards providing an academic overview and grounding for the concept of capacities in the context of disaster studies and disaster risk...  相似文献   

Do explicit criteria help in selecting indicators for ecosystem-based fisheries management?   总被引：1，自引：1，他引：1  

Rochet  Marie-Joelle; Rice  Jake C. 《ICES Journal of Marine Science》2005,62(3):528-539

  相似文献   

Estimation of Annual Growth in the Edible Crab (Cancer pagurus L.)     

Hancock  D. A.; Edwards  E. 《ICES Journal of Marine Science》1967,31(2):246-264

  相似文献   

Line P ocean temperature and salinity, 1956-2005     

William Crawford  Jake Galbraith 《Progress in Oceanography》2007,75(2):161-178

Vertical profiles of temperature and salinity have been measured for 50 years along Line P between the North American west coast and mid Gulf of Alaska. These measurements extend 1425 km into the gulf at 13 or more sampling stations. The 10-50-m deep layer of Line P increased in temperature by 0.9 °C from 1958 to 2005, but is significant only at the 90% level due to large interannual variability. Most of this increase in temperature accompanies the 1977 shift in wind patterns. Temperature changes at 100-150 m and salinity changes in both layers are not statistically significant. Much of the variance in temperature is in the upper 50 m of Line P, and temperature changes tend to be uniform along Line P except for waters on the continental margin. Salinity changes are dominated by variability in the halocline between 100 and 150 m depth and are less uniform along Line P. Largest oscillations in temperature and salinity are between 1993 and 2003. These events can be understood by considering changes in eastward wind speed and wind patterns that are revealed in the first two modes of the Pacific Decadal Oscillation. Changes in these patterns are indicators for both Ekman surface forcing (Surface ocean currents flow to the right of the wind direction) and Ekman pumping (Surface waters diverge away from regions of positive wind stress curl, leading to upwelling of colder saltier water). Changes in temperature along the nearshore part of Line P suggest Ekman surface forcing is the stronger of the two processes in the upper layer. The change in salinity anomalies in the halocline along the seaward end of Line P, following the wind shift in 1977, is in agreement with enhanced upwelling caused by stronger Ekman pumping in this region.  相似文献   

Reply by the authors     

J.M. Hurst  N.J. Hancock  W.S. McKerrow 《Proceedings of the Geologists' Association. Geologists' Association》1979,90(4):231-232

  相似文献