Modelling the effect of land management interventions and climate change on sediment loads in the Manawatū–Whanganui region     

Les Basher  Raphael Spiekermann  John Dymond  Alex Herzig  Ella Hayman  Anne-Gaelle Ausseil 《新西兰海洋与淡水研究杂志》2020,54(3):490-511

ABSTRACT

SedNetNZ is used to model the effect of erosion control undertaken under the Sustainable Land Use Initiative (SLUI) and predict the effect of climate change on sediment load in the Manawatū–Whanganui region. Sediment load in 2004 is estimated at 13.4?Mt?yr^?1; by 2018, ≈5000?km² of land had farm plans implemented and annual sediment load reduced by 6.2% of the 2004 load. If SLUI stops at the 2018 level of implementation, by 2038 it is predicted to achieve a 15.7% reduction in annual sediment load. If SLUI continues to implement farm plans, 7949?km² of land will be treated by 2043 and annual sediment load could be reduced by a further 14.7%. Climate change is predicted to substantially increase sediment loads. By 2043 annual sediment load for the region is predicted to increase, compared to 2004, by between 8.3 and 23.7%. However, this can largely be offset by SLUI works. By 2090 an annual sediment load increase of between 53 and 224% due to climate change is predicted. The results suggest climate warming may dominate changes in sediment load in the future.  相似文献   

Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core,and selected auxiliary records     

Mike Walker  Sigfus Johnsen  Sune Olander Rasmussen  Trevor Popp  Jørgen‐Peder Steffensen  Phil Gibbard  Wim Hoek  John Lowe  John Andrews  Svante Björck  Les C. Cwynar  Konrad Hughen  Peter Kershaw  Bernd Kromer  Thomas Litt  David J. Lowe  Takeshi Nakagawa  Rewi Newnham  Jakob Schwander 《第四纪科学杂志》2009,24(1):3-17

The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene–Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in δ¹⁸O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi‐parameter annual layer counting provides an age of 11 700 calendar yr b2 k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene–Holocene boundary have also been recognised. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Midge-inferred temperature reconstructions and vegetation change over the last ~15,000?years from Trout Lake, northern Yukon Territory, eastern Beringia     

Fonya Irvine  Les C. Cwynar  Jesse C. Vermaire  Andrew B. H. Rees 《Journal of Paleolimnology》2012,48(1):133-146

Two cores from Trout Lake, northern Yukon, yielded quantitative estimates of summer air temperatures using fossil midge larvae. Warming began around 14,400?cal?yr BP, with inferred mean July air temperatures reaching values warmer than present by 12,800?cal?yr BP. A 1?°C cooling from 12,200 to 11,200?cal?yr BP closely corresponds with the Younger Dryas chronozone. A broad temperature maximum occurred between 10,800 and 9,800?cal?yr BP, with mean July air temperature about 2.2?°C warmer than present. This represents an early Holocene thermal maximum and coincides with increased organic content of the sediment. Both the shallow- and deep-water cores show similar temperature trends for their overlapping periods. The inferred rise in mean July air temperature at 14,200?cal?yr BP coincides with a shift in vegetation from an herb- to shrub-dominated landscape. In contrast, the increase in Alnus pollen at 6,400?cal?yr BP does not coincide with a change in temperature, but may be a response to a rise in precipitation.  相似文献   

Modeling the adsorption of Cd (II), Cu (II), Ni (II), Pb (II) and Zn (II) onto montmorillonite     

Xueyuan Gu  Les J. Evans 《Geochimica et cosmochimica acta》2010,74(20):5718-5728

The adsorption of five toxic metallic cations, Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II), onto montmorillonite was investigated as a function of pH and ionic strength and a two-site surface complexation model was used to predict the adsorption data. The results showed that in the lower pH range, 3∼6 for Cd, Cu, Ni and Zn, and 3∼4.5 for Pb, the adsorption was greatly affected by ionic strength, while in the higher pH range, the adsorption was not. In the lower pH range, the metallic cations were mainly bound through the formation of outer-sphere surface on the permanently charged basal surface sites (≡X⁻), while in the higher pH range the adsorption occurred mainly on the variably charged edge sites (≡SOH) through the formation of inner-sphere surface complexes. Acid-base surface constants and metal binding constants for the two sites were optimized using FITEQL. The adsorption affinity of the five metallic cations to the permanently charged sites of montmorillonite was Pb > Cu > Ni ≈ Zn ≈ Cd, while that to the variable charged sites was Pb ? Cu > Zn > Cd > Ni.  相似文献   

An Investigation into the role of site and soil characteristics in onsite sewage treatment   总被引：1，自引：1，他引：0  

Les?DawesEmail author  Ashantha?Goonetilleke 《Environmental Geology》2003,44(4):467-477

The onsite treatment of sewage is common in all rural and regional areas of the world. Due to the public health and environmental risks that these treatment systems pose, the need for adopting performance-based management strategies is gaining increasing recognition. This demands the establishment of performance objectives for onsite sewage treatment and disposal which are based on stringent scientific analysis. A research project was undertaken to identify and investigate the role of influential site and soil characteristics in the treatment performance of subsurface effluent disposal areas. The treatment performances of a number of septic systems on a range of site and soil conditions were investigated together with detailed soil analysis. The changes to soil physico-chemical characteristics of the disposal area due to effluent application and its effluent renovation capacity were found to be directly related to the subsurface drainage characteristics. Significant changes to exchangeable cations and chemical parameters such as pH, electrical conductivity and cation exchange capacity (CEC) can result due to subsurface effluent application. A relationship exists between chemical parameters such as exchangeable Na and Ca:Mg ratio and CEC. A strong correlation also exists between the depth to the restrictive subsurface horizon and observed treatment performance. The study confirmed that soil chemistry can be a valuable predictive tool for evaluating the long-term performance of sewage effluent disposal systems particularly in poorly drained sites.  相似文献   

Richness, diversity and succession of late-glacial chironomid assemblages in New Brunswick, Canada     

André J. Levesque  Les C. Cwynar  Ian R. Walker 《Journal of Paleolimnology》1996,16(3):257-274

Chironomid analysis was performed on late-glacial sediment from four New Brunswick lakes in order to gain basic ecological information regarding the richness and diversity of late-glacial chironomid assemblages, and to compare the pattern of succession at each site. At all sites, the richness and diversity of the larval assemblages were lowest immediately following deglaciation and during the Younger Dryas, corresponding to the coldest times of the late-glacial period. Although cold-stenothermous taxa are characteristic of sediments deposited immediately following deglaciation, as well as during the Killarney Oscillation and Younger Dryas cooling events, the constituent taxa are different at each site. During the intervening warm periods, the larval assemblages at each site are also dissimilar, with the more southern sites containing a greater variety of temperate littoral taxa. This raises the possibility that a north-south temperature gradient existed during the warm intervals of the late-glacial period in New Brunswick.  相似文献   

Advances in travel geometry and urban modelling   总被引：1，自引：0，他引：1  

Geoffrey Hyman  Les Mayhew 《GeoJournal》2004,59(3):191-207

Urban travel geometry is a generalization of patterns of movement in cities and regions where route configuration and prevailing traffic speeds constrain or direct movement in distinctive and repeatable patterns. In this paper we use these properties to construct time surfaces on which distance equates to the time of travel in the urban plane. Such surfaces can be two- or three-dimensional and are useful in the study of urban structure, locational analysis, transport planning and traffic management. A particular niche addressed in this paper is non-conformal time surface transformations in which speed or the cost of travel is constrained according to co-ordinate directions. It is argued that such models may be more suited to gridded and orbital-radial cities than previously used conformal transformations. After explaining the rationale behind the approach, a mathematical basis is developed and several calibrated examples are provided based on regions in the UK. The paper concludes with some examples of potential applications, and an annex provides a detailed mathematical framework. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Late-Quaternary history of midge communities and climate from a tundra site near the lower Lena River, Northeast Siberia   总被引：2，自引：0，他引：2  

David F. Porinchu  Les C. Cwynar 《Journal of Paleolimnology》2002,27(1):59-69

Analysis of midge remains in late-Quaternary sediment, recovered from a lake situated north of treeline in northeast Siberia, indicates the occurrence of notable climatic fluctuations during the last 12 ka. The onset of late-glacial warming was disrupted by a marked cooling event – possibly correlative with the Younger Dryas – that occurred between 11,000 and 10,000 yr BP. Increases in the relative abundance of taxa typically found in tundra lakes, such as Hydrobaenus/Oliveridia and Parakiefferiella nigra, and the concurrent decrease in temperate taxa, such as Microtendipes and Corynocera ambigua, suggest climatic deterioration occurred during this interval. At approximately 10,000 yr BP there was a large increase in temperate taxa such as Microtendipes and C. ambigua, and a decline of essentially all cold-water taxa. This suggests that climate was warmer than present since the modern distribution of both Microtendipes and C. ambigua is limited to forested sites in this region. This warm interval lasted until approximately 6000 yr BP when there was a precipitous decline in temperate chironomid taxa and an increase in cold-water chironomid taxa, such as Paracladius, Hydrobaenus/Oliveridia, Abiskomyia, and Parakiefferiella nigra. This cooling continued through the late-Holocene and the modern tundra chironomid assemblage developed by approximately 1400 yr BP.  相似文献   

A global seamount classification to aid the scientific design of marine protected area networks     

Malcolm R. Clark  Les WatlingAshley A. Rowden  John M. GuinotteCraig R. Smith 《Ocean & Coastal Management》2011,54(1):19-36

Seamounts are prominent features of the world's seafloor, and are the target of deep-sea commercial fisheries, and of interest for minerals exploitation. They can host vulnerable benthic communities, which can be rapidly and severely impacted by human activities. There have been recent calls to establish networks of marine protected areas on the High Seas, including seamounts. However, there is little biological information on the benthic communities on seamounts, and this has limited the ability of scientists to inform managers about seamounts that should be protected as part of a network. In this paper we present a seamount classification based on "biologically meaningful" physical variables for which global-scale data are available. The approach involves the use of a general biogeographic classification for the bathyal depth zone (near-surface to 3500 m), and then uses four key environmental variables (overlying export production, summit depth, oxygen levels, and seamount proximity) to group seamounts with similar characteristics. This procedure is done in a simple hierarchical manner, which results in 194 seamount classes throughout the worlds oceans. The method was compared against a multivariate approach, and ground-truthed against octocoral data for the North Atlantic. We believe it gives biologically realistic groupings, in a transparent process that can be used to either directly select, or aid selection of, seamounts to be protected.  相似文献   

Implications of CMIP3 model biases and uncertainties for climate projections in the western tropical Pacific   总被引：1，自引：0，他引：1  

Jaclyn N. Brown  Alex Sen Gupta  Josephine R. Brown  Les C. Muir  James S. Risbey  Penny Whetton  Xuebin Zhang  Alexandre Ganachaud  Brad Murphy  Susan E. Wijffels 《Climatic change》2013,119(1):147-161

Regional climate projections in the Pacific region are potentially sensitive to a range of existing model biases. This study examines the implications of coupled model biases on regional climate projections in the tropical western Pacific. Model biases appear in the simulation of the El Niño Southern Oscillation, the location and movement of the South Pacific Convergence Zone, rainfall patterns, and the mean state of the ocean–atmosphere system including the cold tongue bias and erroneous location of the edge of the Western Pacific warm pool. These biases are examined in the CMIP3 20th century climate models and used to provide some context to the uncertainty in interpretations of regional-scale climate projections for the 21st century. To demonstrate, we provide examples for two island nations that are located in different climate zones and so are affected by different biases: Nauru and Palau. We discuss some of the common approaches to analyze climate projections and whether they are effective in reducing the effect of model biases. These approaches include model selection, calculating multi model means, downscaling and bias correcting.  相似文献