Radial growth change of temperate tree species in response to altered regional climate and air quality in the period 1901–2008     

Vincent Kint  Wim Aertsen  Matteo Campioli  Dries Vansteenkiste  Andy Delcloo  Bart Muys 《Climatic change》2012,115(2):343-363

Both increasing and decreasing 20th century growth trends have been reported in forests throughout Europe, but only for few species and areas suitable modelling techniques have been used to distinguish individual tree growth (operating on a local scale) from growth change due to exogenous factors (operating on a broad geographical scale). This study relates for the first time observed growth changes, in terms of basal area increment (BAI) of dominant trees of pedunculate oak, common beech and Scots pine, in north-west European temperate lowland forests (Flanders) to climate, atmospheric CO₂ and tropospheric O₃ concentrations, N deposition, site quality and forest structure for more than a century (the period 1901?C2008), applying mixed models. Growth change during the 20th century is observed for oak (increasing growth) and beech (increasing growth until the 1960s, growth decline afterwards), but not for pine. It was possible to relate growth change of oak and beech to climate time series and N deposition trends. Adding time series for CO₂ and O₃ concentration did not significantly improve model results. For oak and beech a switch from positive to negative growth response with increasing nitrogen deposition throughout time is observed. Growth increase for oak is mainly determined by the interaction between growing season temperature and soil water recharge. It is reasonable to assume that the observed growth trend for oak will continue for as long as early season water availability is not compromised. The decreasing trend in summer relative air humidity observed since the 1960s in the study area can be a main cause of recent beech BAI decrease. A further growth decline of beech can be expected, independent of site quality.  相似文献   

Photochemistry in the Arctic Free Troposphere: Ozone Budget and Its Dependence on Nitrogen Oxides and the Production Rate of Free Radicals     

Craig Stroud  Sasha Madronich  Elliot Atlas  Christopher Cantrell  Alan Fried  Brian Wert  Brian Ridley  Fred Eisele  Lee Mauldin  Richard Shetter  Barry Lefer  Frank Flocke  Andy Weinheimer  Mike Coffey  Brian Heikes  Robert Talbot  Donald Blake 《Journal of Atmospheric Chemistry》2004,47(2):107-138

Local ozone production and loss rates for the arctic free troposphere (58–85° N, 1–6 km, February–May) during the TroposphericOzone Production about the Spring Equinox (TOPSE) campaign were calculated using a constrained photochemical box model. Estimates were made to assess the importance of local photochemical ozone production relative to transport in accounting for the springtime maximum in arctic free tropospheric ozone. Ozone production and loss rates from our diel steady-state box model constrained by median observations were first compared to two point box models, one run to instantaneous steady-state and the other run to diel steady-state. A consistent picture of local ozone photochemistry was derived by all three box models suggesting that differences between the approaches were not critical. Our model-derived ozone production rates increased by a factor of 28 in the 1–3 km layer and a factor of 7 in the 3–6 kmlayer between February and May. The arctic ozone budget required net import of ozone into the arctic free troposphere throughout the campaign; however, the transport term exceeded the photochemical production only in the lower free troposphere (1–3 km) between February and March. Gross ozone production rates were calculated to increase linearly with NO_x mixing ratiosup to 300 pptv in February and for NO_x mixing ratios up to 500 pptv in May. These NO_x limits are an order of magnitude higher thanmedian NO_x levels observed, illustrating the strong dependence ofgross ozone production rates on NO_x mixing ratios for the majority of theobservations. The threshold NO_x mixing ratio needed for netpositive ozone production was also calculated to increase from NO_x 10pptv in February to 25 pptv in May, suggesting that the NO_x levels needed to sustain net ozone production are lower in winter than spring. This lower NO_x threshold explains how wintertime photochemical ozone production can impact the build-up of ozone over winter and early spring. There is also an altitude dependence as the threshold NO_x neededto produce net ozone shifts to higher values at lower altitudes. This partly explains the calculation of net ozone destruction for the 1–3 km layerand net ozone production for the 3–6 km layer throughout the campaign.  相似文献   

Numerical Simulation Study on the Scientific and Methodological Aspects of the Brazilian Proposal          下载免费PDF全文

HU Guoquan  DAI Xiaosu  Greg BODEKER  Andy REISINGER 《Acta Meteorologica Sinica》2005,19(4):447-456

1. IntroductionObservations of surface air temperature indicatethat a significant global average warming has occurredduring the 20th century. The Intergovernmental Panelon Climate Change (IPCC, 2001) concludes that thereis new and stronger evidence that man has influencedthe climate. International negotiations have led to afirst step in combating climate change with the UnitedNations Framework Convention on Climate Change(UNFCCC) and the Kyoto Protocol, but further stepsare needed in …  相似文献   

Serendipity is not a strategy: the impact of national climate programmes on greenhouse-gas emissions     

Andy Kerr 《Area》2007,39(4):418-430

This article examines the efficacy of national climate programmes (packages of policies introduced by governments to meet emissions reduction targets set out in the Kyoto Protocol) by considering emissions trends before and after their implementation. Analysis reveals that only four of 21 countries with defined programmes demonstrate improved emissions trends following their inception and in only one is the change statistically significant. The reasons for this are manifold but serendipity appears to play as large a part as strategy in determining national emissions trends in the early years of climate programmes. Inflated claims of success by national governments are unhelpful for effective policy analysis and development.  相似文献   

Effects of Alpine hydropower dams on particle transport and lacustrine sedimentation     

Flavio S. Anselmetti  Raphael Bühler  David Finger  Stéphanie Girardclos  Andy Lancini  Christian Rellstab  Mike Sturm 《Aquatic Sciences - Research Across Boundaries》2007,69(2):179-198

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Analysis of the climate signal contained within δO and growth rate parameters in two Ethiopian stalagmites     

Andy Baker  Asfawossen Asrat  Melanie J. Leng  Peter M. Wynn  Dominique Genty 《Geochimica et cosmochimica acta》2007,71(12):2975-2988

We combine surface and cave climate monitoring with multiple stalagmite parameters to help understand and calibrate the climate records contained within stalagmites from a region with strong rainfall seasonality. Two actively growing stalagmites from Ethiopia were analysed in order to investigate the climate signal contained within δ¹⁸O and growth rate parameters. The δ¹⁸O and growth rate of the two stalagmites give different responses to surface climate due to variations in the climate signal transfer. Both stalagmites (Merc-1 and Asfa-3) have a climate response that is seasonal; however this signal is subsequently smoothed by the mixing of event and storage water within the aquifer. Merc-1 responds more to high frequency (‘event’) climate, due to a greater ratio of event to storage water in this sample, whereas Asfa-3 responds more to low frequency (‘storage’) climate. In addition, different parameters respond to different seasons. For example, stalagmite Asfa-3, from greater depth from the surface and with a slow drip rate, has a growth rate that responds to the amount of summer rain. In contrast, Merc-1, closer to the surface and with a faster drip rate, exhibits no clear response to surface climate, probably due to a more complex climate signal transfer. δ¹⁸O response varies with stalagmite due to the interplay between rainfall forcing factors (amount, seasonality) and disequilibrium kinetics, with opposing correlations between seasonal rainfall and δ¹⁸O between the samples. Our results demonstrate that analysis of seasonal climate forcing, and transfer functions reflecting the mixing of event and storage water, may be the most appropriate approach to develop of transfer functions appropriate for high-resolution, stalagmite climate reconstruction.  相似文献   

The timing of regional Lateglacial events and post-glacial sedimentation rates from Lake Superior     

Andy Breckenridge  Thomas C. Johnson  Suzanne Beske-Diehl  John S. Mothersill 《Quaternary Science Reviews》2004,23(23-24):2355-2367

We analyze both new and previously published paleomagnetic records of secular variation (PSV) from Lake Superior sediment cores and compare these records to correlated rhythmite (varve) thickness records to determine post-glacial sedimentation rates and to reassess the termination of glaciolacustrine varves in the basin. The results suggest that offshore sedimentation rates have exhibited considerable spatial variation over the past 8000 years, particularly during the mid-Holocene. We attribute offshore, mid-Holocene sedimentation changes to alterations in whole basin circulation, perhaps precipitated by a greater dominance of the Gulf of Mexico air mass during the summer season. Nearshore bays are characterized by high sedimentation rates for at least 1000 years after varve cessation and during a period between around 4500 and 2000 cal. BP. After 2000 cal. BP, sedimentation rates subsided to earlier rates. The increases between 4500 and 2000 cal. BP are probably due to lake level fall after the Nipissing II highstand.The older glaciolacustrine varve thickness records suggest that the influx of glacially derived sediment ended abruptly everywhere in the lake, except near the Lake Nipigon inlets. Multiple sediment cores reveal 36 anomalously thick varves, previously ascribed to the formation of the Nakina moraine, which were deposited just prior to varve cessation in the open lake. The PSV records support the observation that the cessation of these thick varves is a temporally correlative event, occurring at 9035±170 cal. BP (calibrated years before 1950, ca 7950–8250 ¹⁴C BP). This date would correlate to the eastern diversion of Lake Agassiz and glacial meltwater into Lake Ojibway.  相似文献   

Using the Internet to Integrate Thematic and Regional Approaches in Geographic Education     

Philip E. Steinberg  Andy Walter  Kathleen Sherman&#x;Morris 《The Professional geographer》2002,54(3):332-348

Geographers have long debated the superiority of regional versus thematic approaches to geographical analysis and geographic education. While most acknowledge that these two approaches are complementary, the task of implementing both approaches in a single introductory course remains challenging. “Global Change, Local Places,” an Internet–based course offered at Florida State University, attempts to fuse thematic and regional approaches using methodological and pedagogical techniques that emphasize student–centered learning and Internet technologies. Results of a student survey and analysis of student assignments suggest that this format was successful. Students expressed a high level of satisfaction with course content, and, although attainment of skills and knowledge was particularly hard to measure given the structure and goals of the course, students appear to have gained country–specific knowledge as well as skills in critical analysis using thematic concepts.  相似文献   

Attenuation and Biodegradation of Chlorophenols in Ground Water at a Former Wood Treating Facility     

Andy Davis  Jim Campbell  Craig Gilbert  Michael V. Ruby  Meridan Bennett  Susan Tobin 《Ground water》1994,32(2):248-257

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Aqueous oxidation-reduction kinetics associated with coupled electron-cation transfer from iron-containing silicates at 25°C     

Art F. White  Andy Yee 《Geochimica et cosmochimica acta》1985,49(5):1263-1275

Mechanisms and kinetics of aqueous $\text{Fe}{}^{\mathrm{+2}}\text{Fe}{}^{\mathrm{+3}}$ oxidation-reduction and dissolved O₂ interaction in the presence of augite, biotite and hornblende were studied in oxic and anoxic solutions at pH 1–9 at 25°C. Oxidation of surface iron on the minerals coincided with both surface release of Fe⁺² and by reduction of Fe⁺³ in solution. Reaction with iron silicates consumed dissolved oxygen at a rate that increased with decreasing pH. Both Fe⁺³ and O₂ consumption were shown to be controlled by coupled electron-cation transfer reactions of the form; and where M is a cation of charge +z. The spontaneous reduction of aqueous Fe⁺³in the presence of precipitated Fe(OH)₃bracketed the surface oxidation standard half cell between +0.33 and +0.52 volts. Concurrent hydrolysis reactions involving cation release from the iron silicates were suppressed by the above reactions. Calculated oxidation depths in the minerals varied between 12 and 80Å and were apparently controlled by rates of solid-state cation diffusion.  相似文献