Living on the Edge: Increasing Patch Size Enhances the Resilience and Community Development of a Restored Salt Marsh     

Rachel K. Gittman  F. Joel Fodrie  Christopher J. Baillie  Michelle C. Brodeur  Carolyn A. Currin  Danielle A. Keller  Matthew D. Kenworthy  Joseph P. Morton  Justin T. Ridge  Y. Stacy Zhang 《Estuaries and Coasts》2018,41(3):884-895

Foundation species regulate communities by reducing environmental stress and providing habitat for other species. Successful restoration of biogenic habitats often depends on restoring foundation species at appropriate spatial scales within a suitable range of environmental conditions. An improved understanding of the relationship between restoration scale and environmental conditions has the potential to improve restoration outcomes for many biogenic habitats. Here, we identified and tested whether inundation/exposure stress and spatial scale (patch size) can interactively determine (1) survival and growth of a foundation species, Spartina alterniflora and (2) recruitment of supported fauna. We planted S. alterniflora and artificial mimics in large and small patches at elevations above and below local mean sea level (LMSL) and monitored plant survivorship and production, as well as faunal recruitment. In the first growing season, S. alterniflora plant survivorship and stem densities were greater above LMSL than below LMSL regardless of patch size, while stem height was greatest in small patches below LMSL. By the third growing season, S. alterniflora patch expansion was greater above LMSL than below LMSL, while stem densities were higher in large patches than small patches, regardless of location relative to LMSL. Unlike S. alterniflora, which was more productive above LMSL, sessile marine biota recruitment to mimic plants was higher in patches below LMSL than above LMSL. Our results highlight an ecological tradeoff at ~LMSL between foundation species restoration and faunal recruitment. Increasing patch size as inundation increases may offset this tradeoff and enhance resilience of restored marshes to sea-level rise.  相似文献   

Littoral cladoceran community reassembly following the cessation of disturbance     

Lynn?V.?DupuisEmail author  Brenda?J.?Hann  Michael?Paterson 《Journal of Paleolimnology》2015,54(1):121-135

The process of recovery from environmental impact provides insights into factors that drive community assembly. This study investigated community reassembly following perturbation, using littoral cladoceran microfossils. Whole-lake experimental manipulations of acids and nutrients in Lake 302N (L302N; 1972–1997) and acids in Lake 223 (L223; 1976–1994) at the Experimental Lakes Area (ELA; Ontario, Canada), provided an opportunity to use the sediment record to reconstruct the trajectory of recovery. Comparison was made to unmanipulated Lake 377 (L377) to estimate changes in regional baseline conditions. Recovery was evaluated at both the species and community level, using univariate and multivariate metrics. Up to 14 years after cessation of acid and nutrient additions, and following chemical recovery to pH > 6.5, both L302N and L223 littoral cladoceran communities failed to recover to their pre-manipulation states. Multivariate metrics demonstrated hysteresis along the recovery trajectory, and the movement to alternative states in littoral cladoceran communities in both lakes. The most recent littoral cladoceran community structure, reconstructed from the paleorecord, is driven by the persistence of species from the acidification period, suggesting biological resistance. Recovery states differed between L302N and L223, although their initial, pre-manipulation littoral cladoceran community structures were similar, reflecting multiple, independent recovery trajectories. Independent recovery trajectories are at odds with previous findings, which suggest that dispersal from an egg bank should support deterministic recovery trajectories. We conclude that littoral cladoceran microfossils can be used effectively to determine the community state with recovery and compare it to the pre-manipulation condition, particularly with the use of multivariate metrics.  相似文献   

The case for significant numbers of extraterrestrial impacts through the late Holocene     

Mike Baillie 《第四纪科学杂志》2007,22(2):101-109

When astronomers tell us that there should have been numerous impacts from space during the last five millennia, when impact craters exist on land and more impacts can be assumed over the oceans, why are historians, archaeologists and palaeoecologists not diligently seeking evidence for these impacts, and their effects? This article reviews just some of the relevant evidence for impacts. In turn this suggests that ablation material, background material from space, and micro‐tektites, should all be present in ocean cores, ice cores, peat, and lake sediments. It seems that almost no efforts have been made to find evidence that might link to the known crater fields, or to identify and date periods of enhanced cosmic activity. The question must be, why? Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Scalar fields,fluids and exact Bianchi type-V solutions     

Mark S. Madsen  Grant Baillie 《Astrophysics and Space Science》1985,112(1):203-208

A photometric study of a large sample of Be stars is reported. Infrared homogeneous observational data in theJHKL system are used to derive some photometric characteristics of Be stars, as a class. New infrared observations of 34 Be stars are included in the present paper. Infrared two-colour diagrams are used to investigate the presence of in frared emission in Be stars. The origin of infrared excess in relation to Balmer line emission in Be stars is discussed.  相似文献   

Explaining divided cities in China   总被引：1，自引：0，他引：1  

Brenda Madrazo  Ronald van Kempen 《Geoforum》2012,43(1):158-168

Explanations of the existence of socio-spatial divisions in Western Europe and the United States revolve around the importance of economic, demographic, political, and socio-cultural macro developments and often also on the role of globalization. Much of the literature also emphasizes the role of institutions, especially the national and local state as well as individual and household constraints and opportunities. Many authors explain socio-spatial divisions by a mix of these factors and developments. This paper provides an account of the current state of affairs concerning the literature and theory on divided cities in China. Concentrating on a selection of 88 articles published in international journals during the last decade, we examine how authors explain urban socio-spatial divisions in Chinese cities. The paper indicates that a five-category framework of trends, policies, players, position, and preferences are useful in addressing the complexity of explanations attributed to current urban divisions and inequalities in Chinese cities. While the spatial patterns in the Western and Chinese contexts share rather similar characteristics, the interplay of mechanisms is significantly different. The influence of the state, its institutions, and the cultural background has a much stronger explanatory power in China than in the West.  相似文献   

Singaporeans in China: transnational women elites and the negotiation of gendered identities     

Brenda S.A. Yeoh  Katie Willis 《Geoforum》2005,36(2):211-222

The burgeoning literature on transnationalism involving skilled migrants--based largely on the view from the developed world--have generally paid little heed to “elite” women and the reproductive sphere. We argue that women play many roles in elite transnational migration streams and must be given full consideration as part of the “transnational elite.” Attention is given to the way women--both “tied” and “lead” migrants--negotiate gendered identities as they participate in Singapore's regionalisation process, a state-driven initiative to extend the national economy by leveraging on growth in the region. Empirical material for the paper is mainly based on in-depth interviews with married women who were part of a larger project involving interviews with 150 Singaporeans who had lived, or were living, in China. In examining the movements through transnational space between Singapore and China, it is clear that patriarchal norms continue to shape women's understandings of their own identities vis--vis men's. Singapore women who move as accompanying spouses (the majority) find themselves giving up careers to focus on their domestic role in China (in the absence of access to “suitable” paid domestic service), and are not so much “deskilled” but “re-domesticated”. The exceptional few women who ventured into China as entrepreneurs experienced considerable strain holding together geographically separate spheres of productive and reproductive work across the transnational terrain. Both sets of “stories” alert us to the need to include “elite” women--whether accompanying spouses or independent entrepreneurs--in our understanding of “transnational elites.” This will contribute to the urgent task of ensuring that both productive and reproductive work are valorized in equal measure in conceptualizing transnationalism.  相似文献   

Dating ancient wood by high-sensitivity liquid scintillation counting and accelerator mass spectrometry—Pushing the boundaries     

Alan G. Hogg  L. Keith Fifield  Chris S.M. Turney  Jonathan G. Palmer  Rex Galbraith  Mike G.K. Baillie 《Quaternary Geochronology》2006,1(4):241-248

It is critical that a comprehensive terrestrial radiocarbon (¹⁴C) calibration curve is developed beyond 26 ka for high-precision calibration and correlation of climatic, environmental and archaeological records. Abundant sub-fossil New Zealand kauri (Agathis australis) wood, preserved in Oxygen Isotope Stage-2 and 3 peat swamps, provides an important resource for ¹⁴C calibration; nowhere else in the world does such an extensive collection of ancient wood exist. Although finite ¹⁴C ages beyond 50 ka are becoming routinely reported, few attempts have been made to demonstrate their accuracy or precision. Finite ages beyond 50 ka require optimization of all elements involved in sample preparation and ¹⁴C analysis. Here we discuss the methodology employed for optimizing the ¹⁴C dating of near-background wood samples by both benzene synthesis for liquid scintillation counting (LSC) or graphite synthesis for accelerator mass spectrometry (AMS). We report the mean background blank activities for both methods and present a statistical model for assigning blank standard errors when blank activity variation is over and above counting statistics. We also present duplicate analyses (using LSC and AMS) of nine successive samples of wood obtained from a sub-fossil kauri log near-background in age to investigate the significance of the measured blank levels and variability.  相似文献   

A new formation process for calcic pendants from Pahranagat Valley, Nevada, USA, and implication for dating Quaternary landforms     

Amy L. Brock  Brenda J. Buck 《Quaternary Research》2005,63(3):359-367

It has been assumed that soil pendants form in a similar manner as stalactites, in which innermost laminae are the oldest and outer laminae are the youngest. This study presents a new interpretation for soil pendant development. Pahranagat Valley, Nevada, pendants contain features indicating continued precipitation through time at the clast–pendant contact, implying that the oldest deposits are not always found at the pendant–clast contact, as other studies have assumed. These features include a void at the clast–pendant contact where minerals such as calcium carbonate, silica, and/or fibrous silicate clays precipitate. In addition, fragments of the parent clast and detrital grains are incorporated into the pendant and are displaced and/or dissolved and result in the formation of sepiolite. This study indicates that pendants are complex, open systems that during and after their formation undergo chemical changes that complicate their usefulness for dating and paleoenvironmental analyses.  相似文献   

Population Belongs on the Johannesburg Agenda     

Wolfgang Lutz  Mahendra Shah  Richard E. Bilsborrow  John Bon-gaarts  Partha DasGupta  Barbara Entwisle  Günther Fischer  Brigida Garcia  Daniel J. Hogan  Arne Jernelöv  Zhenghua Jiang  Robert W. Kates  Sanjaya Lall  F. Landis MacKellar  P.K. Makinwa-Adebusoye  Anthony J. McMichael  Vinod Mishra  Norman Myers  Nebojsa Nakicenovic  Sten Nilsson  Brian C. O'Neill  Xizhe Peng  Harriet B. Presser  Nafis Sadik  Warren C. Sanderson  Gita Sen  Barbara Torrey  Dirk van de Kaa  Hans J.A. van Ginkel  Brenda Yeoh  Huda Zurayk 《Global Change & Human Health》2002,3(1):33-35

The forthcoming World Summit on Sustainable Development (WSSD) in Johannesburg (August 26-September 4, 2002) has been set by the United Nations to consider strategies toward sustainable development in all its dimensions. Hence, its mandate is broader than that of the Rio 1992 United Nations Conference on Environment and Development (UNCED). Population issues have so far been discussed in a separate series of World Population Conferences (Bucharest 1974, Mexico City 1984, Cairo 1994). With no new World Population Conference scheduled for 2004 and Johannesburg having a mandate that is stated to explicitly include social and economic aspects, population as a key component of sustainable development should figure prominently on the Johannesburg agenda. Yet, after the third of four preparatory meetings for Johannesburg (which ended in New York on April 5th), consideration of population is completely absent. The reasons for this are not entirely clear. We assume that they have to do with the fear of entering into political controversies over abortion. We are concerned that, despite its broader mandate, in most countries inputs to Johannesburg are being prepared mainly by environment ministries who have little experience in dealing with population questions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Editorial Note     

Teo Siew Eng  Brenda Yeoh 《Singapore journal of tropical geography》1997,18(1):no-no

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