Erratum to: A Simple Model for the Vertical Transport of Reactive Species in the Convective Atmospheric Boundary Layer     

Leif Kristensen  Donald H. Lenschow  David Gurarie  Niels Otto Jensen 《Boundary-Layer Meteorology》2010,135(1):181-183

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Comparing biodiversity between protected savanna and adjacent non-protected farmland in the southern Kalahari     

Bernd Wasiolka  Niels Blaum 《Journal of Arid Environments》2011,75(9):836-841

In this study we investigated the effect of different land use options (wildlife versus livestock) on species richness of plants and reptiles in the protected Kgalagadi Transfrontier Park (KTP) versus adjacent non-protected farmland within the same savanna habitat type (Aoub dune veld) in the southern Kalahari, South Africa. Our results show that both plant and reptile species richness as well as plant cover and reptile abundance was significantly higher in the protected KTP than in the non-protected farmland. The higher proportion of shrub but lower proportions of perennial grass cover, herb cover, and herb species richness in the farmland can be explained by higher stocking rates and the differences in feeding behaviour between native wild ungulates (e.g. Antidorcas marsupialis, Oryx gazella) and livestock (mainly sheep). The reptile’s prey availability and microhabitats (perennial grass tussocks and rodent burrows) for thermoregulation and protection against predators were significantly lower in the farmland. To conclude, our results clearly show that long term effects of different land use options (wildlife in protected KTP versus extensive livestock production in the non-protected farmland) even within the same habitat type have led to significant changes in vegetation composition, availability of microhabitat structures and in the reptile community.  相似文献   

Estimating resource costs of compliance with EU WFD ecological status requirements at the river basin scale     

Niels Riegels  Roar Jensen  Lisa Bensasson  Stella Banou  Flemming Møller  Peter Bauer-Gottwein 《Journal of Hydrology》2011,396(3-4):197-214

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Landslide impact on organic carbon cycling in a temperate montane forest     

Robert G. Hilton  Patrick Meunier  Niels Hovius  Peter J. Bellingham  Albert Galy 《地球表面变化过程与地形》2011,36(12):1670-1679

In humid, forested mountain belts, bedrock landslides can harvest organic carbon from above ground biomass and soil (OC_modern) while acting to refresh the landscape surface and turnover forest ecosystems. Here the impact of landslides on organic carbon cycling in 13 river catchments spanning the length of the western Southern Alps, New Zealand is assessed over four decades. Spatial and temporal landslide maps are combined with the observed distribution and measured variability of hillslope OC_modern stocks. On average, it is estimated that landslides mobilized 7.6 ± 2.9 tC km^?2 yr^?1 of OC_modern, ~30% of which was delivered to river channels. Comparison with published estimates of OC_modern export in river suspended load suggests additional erosion of OC_modern by small, shallow landslides or overland flow in catchments. The exported OC_modern may contribute to geological carbon sequestration if buried in sedimentary deposits. Landslides may have also contributed to carbon sequestration over shorter timescales (<100 years). 5.4 ± 3.0 tC km^?2 yr^?1 of the eroded OC_modern was retained on hillslopes, representing a net‐carbon sink following re‐vegetation of scar surfaces. In addition, it was found that landslides caused rapid turnover of the landscape, with rates of 0.3% of the surface area per decade. High rates of net ecosystem productivity were measured in this forest of 94 ± 11 tC km^?2 yr^?1, which is consistent with rapid landscape turnover suppressing ecosystem retrogression. Landslide‐OC_modern yields and rates of turnover vary between river catchments and appear to be controlled by gradients in climate (precipitation) and geomorphology (rock exhumation rate, topographic slope). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Erratum     

Rudolf H. Steiger  Gorica Harnik-?optrajanova  Emil Zimmermann  Niels Henriksen 《Mineralogy and Petrology》1991,43(4):315-315

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Urban-waterfront developments: a geographic problem in search of a model     

Niels West   《Geoforum》1989,20(4)

A modified version of the economic rent model is applied to the significant urban-waterfront changes which have characterized most European and North American port cities during the twentieth century. The model is at this stage conceptual, although supported by case studies, and employs elements which are characteristic of the majority of waterfront renewal literature. The model addresses four different conditions, three of which trace the evolution which has characterized the traditional inner-city port. The first analyzes the conditions prevailing prior to the late 1950s, when most ocean cargo still used the traditional harbor. The second application of the model relates to the dynamic changes which started in the late 1950s and lasted approximately 20 years, a period in which many piers and warehouses were abandoned and destroyed. The urban-waterfront renewal efforts which have occurred in both Europe and North America are analyzed in the third phase, which emphasizes boundary changes and potential and real economic rent windfalls accruing to landowners in the path of or adjacent to proposed urban-waterfront renewal efforts. The final application of the model reviews the impact on both economic rents and land uses of improvements to the shore and nearshore marine environment.  相似文献   

The 1991 eruption of Hekla,Iceland     

Agust Gudmundsson  Niels Oskarsson  Karl Gronvold  Kristjan Saemundsson  Oddur Sigurdsson  Ragnar Stefansson  Sigurdur R Gislason  Pall Einarsson  Bryndis Brandsdottir  Gudrun Larsen  Haukur Johannesson  Thorvaldur Thordarson 《Bulletin of Volcanology》1992,54(3):238-246

The eruption that started in the Hekla volcano in South Iceland on 17 January 1991, and came to an end on 11 March, produced mainly andesitic lava. This lava covers 23 km² and has an estimated volume of 0.15 km³. This is the third eruption in only 20 years, whereas the average repose period since 1104 is 55 years. Earthquakes, as well as a strain pulse recorded by borehole strainmeters, occurred less than half an hour before the start of the eruption. The initial plinian phase was very short-lived, producing a total of only 0.02 km³ of tephra. The eruption cloud attained 11.5 km in height in only 10 min, but it became detached from the volcano a few hours later. Several fissures were active during the first day of the eruption, including a part of the summit fissure. By the second day, however, the activity was already essentially limited to that segment of the principal fissure where the main crater subsequently formed. The average effusion rate during the first two days of the eruption was about 800 m³ s^–1. After this peak, the effusion rate declined rapidly to 10–20 m³ s^–1, then more slowly to 1 m³ s^–1, and remained at 1–12 m³ s^–1 until the end of the eruption. Site observations near the main crater suggest that the intensity of the volcanic tremor varied directly with the force of the eruption. A notable rise in the fluorine concentration of riverwater in the vicinity of the eruptive fissures occurred on the 5th day of the eruption, but it levelled off on the 6th day and then remained essentially constant. The volume and initial silica content of the lava and tephra, the explosivity and effusion rate during the earliest stage of the eruption, as well as the magnitude attained by the associated earthquakes, support earlier suggestions that these parameters are positively related to the length of the preceeding repose period. The chemical difference between the eruptive material of Hekla itself and the lavas erupted in its vicinity can be explained in terms of a density-stratified magma reservoir located at the bottom of the crust. We propose that the shape of this reservoir, its location at the west margin of a propagating rift, and its association with a crustal weakness, all contribute to the high eruption frequency of Hekla.  相似文献   

The effectiveness of communicative tools in addressing barriers to municipal climate change adaptation: lessons from the Netherlands     

Heleen Mees  Niels Tijhuis  Carel Dieperink 《Climate Policy》2018,18(10):1313-1326

Little research has been done on the effectiveness of communicative tools for climate change adaptation. Filling this knowledge gap is relevant, as many national governments rely on communicative tools to raise the awareness and understanding of climate impacts, and to stimulate adaptation action by local governments. To address this knowledge gap, this study focuses on the effectiveness of communicative tools in addressing key municipal barriers to climate change adaptation, by conducting a large N-size empirical study in the Netherlands. This study explores the effectiveness of these tools in theory, by checking whether their goals match the perceived barriers to municipal climate change adaptation, and the effectiveness in practice by analysing whether they are used and perceived as useful. Document analyses have clarified the assumptions underlying the tools. By conducting semi-structured interviews with 84 municipalities the key barriers to climate change adaptation and the use and usefulness of the tools in practice were analysed. The research revealed that the key barriers experienced by municipalities are a lack of urgency, a lack of knowledge of risks and measures, and limited capacity, the first being the primary one. Communicative tools, while being effective in theory, are not sufficiently effective in practice in addressing the key barriers. Municipalities that are not experiencing a sense of urgency to take on adaptation planning are not likely to be activated by the tools. Advanced municipalities need more sophisticated tools. This article concludes with some suggestions to improve the effectiveness of communicative tools.

Key policy insights

• Although effective in theory in addressing key barriers to municipal adaptation planning, the effectiveness in practice of communicative tools is limited.

• To increase their effectiveness in practice, municipalities’ awareness of the existence of the communicative tools needs to be raised.

• Advanced municipalities need more sophisticated tools that are context-specific and address a wide range of climate risks.

• The effectiveness of communicative tools can be improved by embedding them in a wider mix of policy instruments.

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Statistical EOF analysis of spatiotemporal glacier mass-balance variability: a case study of Mittivakkat Gletscher,SE Greenland     

Sebastian H. Mernild  Andrew P. Beckerman  Niels Tvis Knudsen  Bent Hasholt  Jacob C. Yde 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2018,118(1):1-16

An Empirical Orthogonal Function (EOF) variance analysis was performed to map in detail the spatiotemporal variability in individual stake mass-balances (ba) on Mittivakkat Gletscher (MG) – in a region where at present five out of ~20.000 glaciers have mass-balance observations. The EOF analysis suggested that observed ba was summarized by two modes: EOF1 and EOF2 represented 80% (significant) and 6% (insignificant) of the explained variance, respectively. EOF1 captured a decline in ba that was uniformly distributed in space at all stakes. The decline was correlated with albedo observations and air temperature observations from nearby stations. EOF2, however, described variations in ba that were heterogeneously distributed among stakes and associated with local slope and aspect. Low elevation stakes (~<400 m a.s.l.) showed relatively negative (out of phase) correlation and higher elevated stakes relatively positive (in phase) eigenvector correlation values with EOF2. Such relatively negative and positive eigenvector correlation values were present where the constituted of exposed glacier ice or snow cover, respectively. The results from this study show how EOF analyses can provide information on spatiotemporal patterns of glacier mass-balance. Understanding such detailed variabilities in mass-balance on a Greenlandic glacier is of interest because a fifth of the Arctic contribution from glaciers and ice caps to sea-level rise originates from Greenland.  相似文献   

南极中山站至Dome A剖面表面雪样氧同位素组成          下载免费PDF全文

阎明  李院生  谭德军  温家洪  汪大立  Claus U.Hammer  孙波  康建成  刘雷保 《极地研究》2001,13(3):159-164

运用质谱技术 ,测定了南极中山站至 Dome A剖面 1 998/1 999年度表面雪样氧同位素组成。结果表明 ,表面雪样氧同位素组成变化范围相当大 (- 2 2 .5 1‰ - - 5 0 .6 7‰ ) ,且具有随距中山站距离逐渐增大、海拔高度逐渐增加而逐渐减小的趋势。线性回归分析显示表面雪样氧同位素组成与距中山站距离、海拔高度和纬度存在着很好的相关性 ,这实际上反映出稳定同位素组成和温度之间的密切联系  相似文献