Managing land-use effects on Northland dune lakes: lessons from the past     

Tom Stephens  Paul Augustinus  Brett Rip  Patricia Gadd  Atun Zawadski 《新西兰海洋与淡水研究杂志》2018,52(3):409-429

The Northland region of New Zealand includes numerous high-value, macrophyte-dominated dune lakes. Recent water policy reforms offer limited guidance on managing for aquatic macrophytes. In addition, dune lake histories are poorly known as regular monitoring dates to 2005 AD. Here, ca. 4000 years of lake functional behaviour is reconstructed from sedimentary archives in two Northland dune lakes (Humuhumu and Rotokawau). Results demonstrated that macrophyte dominance is sensitive to catchment erosion and hydrological drawdown. Degradation of macrophyte communities occurred in the nineteenth and twentieth centuries, earlier at Lake Humuhumu than Lake Rotokawau (post-1880 AD and post-1930 AD, respectively). In both lakes, increased erosional influx reduced macrophyte productivity, before later increases to wider trophic state (post-1970 AD). Lake-level decline is linked to increased nutrient loading at Lake Rotokawau but less so, Lake Humuhumu which is more strongly groundwater-fed. In Northland dune lakes, water-level reduction and erosional influx from land use have driven macrophyte degradation.  相似文献   

Determination of the optimal conditions for inclination maneuvers using a Swing-by     

O. MouraJr.  C. C. Celestino  A. F. B. A. Prado 《Astrophysics and Space Science》2018,363(5):91

The search for methods to reduce the fuel consumption in orbital transfers is something relevant and always current in astrodynamics. Therefore, the maneuvers assisted by the gravity, also called Swing-by maneuvers, can be an advantageous option to save fuel. The proposal of the present research is to explore the influence of some parameters in a Swing-by of an artificial satellite orbiting a planet with one of the moons of this mother planet, with the goal of changing the inclination of the artificial satellite around the main body of the system. The fuel consumption of this maneuver is compared with the required consumption to perform the same change of inclination using the classical approach of impulsive maneuvers.  相似文献   

The droughts of 1996–1997 and 2004–2005 in Amazonia: hydrological response in the river main‐stem     

Javier Tomasella  Laura S. Borma  José A. Marengo  Daniel A. Rodriguez  Luz A. Cuartas  Carlos A. Nobre  Maria C. R. Prado 《水文研究》2011,25(8):1228-1242

Severe hydrological droughts in the Amazon have generally been associated with strong El Niño events. More than 100 years of stage record at Manaus harbour confirms that minimum water levels generally coincide with intense warming in the tropical Pacific sea waters. During 2005, however, the Amazon experienced a severe drought which was not associated with an El Niño event. Unless what usually occurs during strong El Niño events, when negative rainfall anomalies usually affect central and eastern Amazon drainage basin; rainfall deficiencies in the drought of 2005 were spatially constrained to the west and southwest of the basin. In spite of this, discharge stations at the main‐stem recorded minimum water levels as low as those observed during the basin‐wide 1996–1997 El Niño‐related drought. The analysis of river discharges along the main‐stem and major tributaries during the drought of 2004–2005 revealed that the recession on major tributaries began almost simultaneously. This was not the case in the 1996–1997 drought, when above‐normal contribution of some tributaries for a short period during high water was crucial to partially counterbalance high discharge deficits of the other tributaries. Since time‐lagged contributions of major tributaries are fundamental to damp the extremes in the main‐stem, an almost coincident recession in almost all tributaries caused a rapid decrease in water discharges during the 2005 event. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Analytical study of the swing-by maneuver in an elliptical system     

Alessandra F. S. Ferreira  Antônio F. B. A. Prado  Othon C. Winter  Denilson P. S. Santos 《Astrophysics and Space Science》2018,363(2):24

The objective of the present paper is to derive a set of analytical equations that describe a swing-by maneuver realized in a system of primaries that are in elliptical orbits. The goal is to calculate the variations of energy, velocity and angular momentum as a function of the usual basic parameters that describe the swing-by maneuver, as done before for the case of circular orbits. In elliptical orbits the velocity of the secondary body is no longer constant, as in the circular case, but it varies with the position of the secondary body in its orbit. As a consequence, the variations of energy, velocity and angular momentum become functions of the magnitude and the angle between the velocity vector of the secondary body and the line connecting the primaries. The “patched-conics” approach is used to obtain these equations. The configurations that result in maximum gains and losses of energy for the spacecraft are shown next, and a comparison between the results obtained using the analytical equations and numerical simulations are made to validate the method developed here.  相似文献   

Response of the topside ionosphere over Arecibo to a moderate geomagnetic storm     

Diana Prado Garzón  Christiano G.M. Brum  Ezequiel Echer  Néstor Aponte  Michael P. Sulzer  Sixto A. González  Robert B. Kerr  Lara Waldrop 《Journal of Atmospheric and Solar》2011,73(11-12):1568-1574

We analyze the data obtained using the Arecibo incoherent scatter radar to examine the response of the topside ionosphere to a moderate geomagnetic storm that occurred during the period March 7–11, 2008. During this time period a magnetic storm with a non-monotonic main phase decrease in the Dst index occurred. The recovery phase also exhibited a secondary Dst decrease. During the initial phase of the storm, Te and Ti increased coincident with the arrival of the solar wind. The main phase registered an increase in proton concentration proportional to Ne while temperatures reached the lowest values. Variations in O⁺ concentration were not significant but a reduction in helium fraction was observed. Soon after the peak of the storm, the transition height between the topside ionosphere and the protonosphere, where H⁺ ions dominate composition, was lower than would be expected during quiet conditions and this behavior lasted for approximately 12 h.  相似文献   

Late glacial and holocene landscapes of central Beringia     

Anatoly V. Lozhkin  Patricia Anderson  Wendy R. Eisner  Tatiana B. Solomatkina 《Quaternary Research》2011,76(3):383-392

New palynological and sedimentological data from St. Lawrence Island present a rare view into late-glacial and Holocene environments of the central Bering Land Bridge. The late glaciation was a time of dynamic landscape changes in south-central Beringia, with active thermokarst processes, including the formation and drainage of thaw lakes. The presence of such a wet, unstable substrate, if widespread, probably would have had an adverse impact on food sources and mobility for many of the large mammal populations. The establishment of Betula shrub tundra on the island suggests late-glacial summers that were warmer than present, consistent with regional paleoclimatic interpretations. However, the increasing proximity to the Bering Sea, as postglacial sea levels rose, modified the intensity of warming and prevented the establishment of deciduous forest as found in other areas of Beringia at this time. The mid- to late Holocene is marked by more stable land surfaces and development of Sphagnum and Cyperaceae peat deposits. The accumulation of organic deposits, decline of shrub Betula, and decrease in thermokarst disturbance suggest that conditions were cooler than the previous. A recent decline in peat accumulation at the study sites may relate to local geomorphology, but similar decreases have been noted for other arctic regions.  相似文献   

Factors to consider in evaluating the management and conservation effectiveness of a whale sanctuary to protect and conserve the North Atlantic right whale (Eubalaena glacialis)     

Patricia R. Hinch  Elizabeth M. De Santo 《Marine Policy》2011

This paper examines key factors used in protecting the migratory North Atlantic right whale within the context of a marine protected area (MPA) system, using the Grand Manan Whale Conservation Area, in New Brunswick Canada, as a case study example. Designated as a conservation area in 1993, before the Oceans Act came into effect, the Grand Manan conservation area currently does not form part of the Canadian network of MPAs. Given the possibility that MPA designation may occur, the paper examines factors that should be considered in meeting International Union for Conservation of Nature (IUCN) MPA design criteria and IUCN evaluation model requirements. An MPA evaluation framework based on an IUCN evaluation model (Hockings et al., 2000 [1]) is designed to assess the effectiveness of an MPA in protecting a migratory right whale. Case study results indicate that current management and research activities for the Grand Manan conservation area address most governance, biophysical and socio-economic issues under an IUCN evaluation framework. On a site basis, it is recommended that the Grand Manan conservation area be designated as a component of the Canadian network of MPAs and that regulations be developed and implemented under the Species at Risk Act to clearly define activities considered damaging or destructive to right whale critical habitat. Recommendations also suggest the preparation of a combined site management-action plan for the Grand Manan conservation area indicating how activities specified in North Atlantic Right Whale Recovery Strategy will be implemented locally. On a regional and international basis, recommendations call for an internationally coordinated and integrated approach to right whale protection within the context of a network of designated critical habitat areas. Recommended activities include: continued Canadian participation in cross-border research and actions to mitigate threats to the right whales over their migratory range; development of a regional right whale management and monitoring strategy; and designation of additional critical habitats in national/international waters. It is further recommended that the evaluation framework developed by this paper be used as a model in assessing the conservation and management effectiveness of MPAs protecting other migratory marine species.  相似文献   

Geostandards and Geoanalytical Research Bibliographic Review 2014          下载免费PDF全文

Ulrike Weis  Beate Schwager  Uwe Nohl  Laura M. Otter  Brigitte Stoll  Patricia Karlowski  Klaus Peter Jochum 《Geostandards and Geoanalytical Research》2015,39(4):497-500

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Automatically Analyzing Large Texts in a GIS Environment: The Registrar General's Reports and Cholera in the 19th Century          下载免费PDF全文

Patricia Murrieta‐Flores  Alistair Baron  Ian Gregory  Andrew Hardie  Paul Rayson 《Transactions in GIS》2015,19(2):296-320

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Harmful algal blooms and eutrophication: ��strategies�� for nutrient uptake and growth outside the Redfield comfort zone     

Patricia M. GLIBERT  JoAnn M. BURKHOLDER 《中国海洋湖沼学报》2011,29(4):724-738

While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.  相似文献