bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controls over carbon storage and turnover in high‐latitude soils
Authors: Hobbie Sarah E. , Schimel Joshua P. , Trumbore Susan E. , Randerson James R. 
Published: March 2003

SummaryDespite the importance of Arctic and boreal regions in the present carbon cycle, estimates of annual high‐latitude carbon fluxes vary in sign and magnitude. Without accurate estimates of current carbon fluxes from Arctic and boreal ecosystems, predicting the response of these systems to global change is daunting. A number of factors control carbon turnover in high‐latitude soils, but because they are unique to northern systems, they are mostly ignored by biogeochemical models used to predict the response of these systems to global change. Here, we review those factors. First, many northern systems are dominated by mosses, whose extremely slow decomposition is not predicted by commonly used indices of litter quality. Second, cold temperature, permafrost, waterlogging, and substrate quality interact to stabilize soil organic matter, but the relative importance of these factors, and how they respond to climate change, is unknown. Third, recent evidence suggests that biological activity occurring over winter can contribute significantly to annual soil carbon fluxes. However, the controls over this winter activity remain poorly understood. Finally, processes at the landscape scale, such as fire, permafrost dynamics, and drainage, control regional carbon fluxes, complicating the extrapolation of site‐level measurements to regional scales.
Detection of vegetation change using reconnaissance imagery
Authors: Shugart Herman H. , French Nancy H. F. , Kasischke Eric S. , Slawski James J. , Dull Charles W. , Shuchman Robert A. , Mwangi Joe 
Published: March 2003

SummaryVegetation occurs at its highest elevations on equatorial mountains. Inspection of archival and recent high‐resolution reconnaissance imagery of tropical mountains shows, in all cases, features indicating an increase in the elevation of mountain vegetation zones and an increase in vigour in the high‐elevation vegetation. These changes are consistent with an increased plant performance from increased levels of carbon dioxide in the atmosphere as well as with a warmer or more favourable climate.
Lake diatom response to recent Arctic warming in Finnish Lapland
Authors: Sorvari Sanna , Korhola Atte , Thompson Roy 
Published: March 2003

AbstractHigh‐resolution palaeolimnological data from a number of remote and nonpolluted lakes in Finnish Lapland reveal a distinct change in diatom assemblages. This parallels the post‐19th century Arctic warming detected by examination of long‐term instrumental series, historical records of ice cover and tree‐ring measurements. The change was predominantly from benthos to plankton and affected the overall diatom species richness. A particularly strong relationship was found between spring temperatures and compositional structure of diatoms. The change is irrespective of the lake type and catchment characteristics, and is reflected by several other biological indicators, such as chrysophytes and zooplankton, suggesting that entire lake ecosystems have been affected. No corresponding change in the diatom‐inferred lake‐water pH was observed; hence, atmospheric fallout of acid substances cannot have been the driving force for the observed biological change. The mechanism behind the diatom response is unclear, but it may be related to decreased ice‐cover duration, prolonged growing season and increased thermal stability. We postulate that 19th century Arctic warming, rather than acidic or other anthropogenic deposition, is responsible for the recent ecological changes in these high latitude lakes.
Inversion of net ecosystem CO2 flux measurements for estimation of canopy PAR absorption
Authors: Hanan Niall P. , Burba George , Verma Shashi B. , Berry Joseph A. , Suyker Andrew , Walter‐Shea Elizabeth A. 
Published: March 2003

AbstractThe fractional absorption of photosynthetically active radiation (fPAR) is frequently a key variable in models describing terrestrial ecosystem–atmosphere interactions, carbon uptake, growth and biogeochemistry. We present a novel approach to the estimation of the fraction of incident photosynthetically active radiation absorbed by the photosynthetic components of a plant canopy (fChl). The method uses micrometeorological measurements of CO2 flux and incident radiation to estimate light response parameters from which canopy structure is deduced. Data from two Ameriflux sites in Oklahoma, a tallgrass prairie site and a wheat site, are used to derive 7‐day moving average estimates of fChl during three years (1997–1999). The inverse estimates are compared to long‐term field measurements of PAR absorption. Good correlations are obtained when the field‐measured fPAR is scaled by an estimate of the green fraction of total leaf area, although the inverse technique tends to be lower in value than the field measurements.The inverse estimates of fChl using CO2 flux measurements are different from measurements of fPAR that might be made by other, more direct, techniques. However, because the inverse estimates are based on observed canopy CO2 uptake, they might be considered more biologically relevant than direct measurements that are affected by non‐physiologically active components of the canopy. With the increasing number of eddy covariance sites around the world the technique provides the opportunity to examine seasonal and inter‐annual variation in canopy structure and light harvesting capacity at individual sites. Furthermore, the inverse fChl provide a new source of data for development and testing of fPAR retrieval using remote sensing. New remote sensing algorithms, or adjustments to existing algorithms, might thus become better conditioned to ‘biologically significant’ light absorption than currently possible.
Growth and carbon stock change in eucalypt woodlands in northeast Australia: ecological and greenhouse sink implications
Authors: Burrows W. H. , Henry B. K. , Back P. V. , Hoffmann M. B. , Tait L. J. , Anderson E. R. , Menke N. , Danaher T. , Carter J. O. , . McKeon G. M 
Published: March 2003

AbstractData from 57 permanent monitoring sites are used to document the growth in woody vegetation and estimate the carbon sink in 27 M ha of eucalypt woodlands (savannas), contained within c. 60 M ha of grazed woodlands in Queensland (northeast Australia). The study sites are shown to be representative of the environment and structure of the eucalypt woodlands in the defined study area. Mean basal area increment for all live woody plants in 30 long‐term sites, with an average initial basal area of 11.86 ± 1.38 (SE) m2 ha−1, was 1.06 m2 ha−1 over a mean 14 years timeframe. The majority of the measurement period, commencing between 1982 and 1988, was characterized by below‐average rainfall. The increase in live tree basal area was due primarily to growth of existing trees (3.12 m2 ha−1) rather than establishment of new plants (0.25 m2 ha−1) and was partly offset by death (2.31 m2 ha−1). A simple but robust relationship between stand basal area and stand biomass of all woody species was developed for the eucalypt dominant woodlands. Analysis of above‐ground carbon stocks in live and standing dead woody plants gave a mean net above‐ground annual carbon increment for all 57 sites of 0.53 t C ha−1 y−1, similar to values estimated elsewhere in world savannas. Published root : shoot ratios were used to infer C flux in woody root systems on these sites. This results in an estimated sink in above‐ and below‐ground biomass of 18 Mt C y−1 over the eucalypt woodlands studied, and potentially up to 35 Mt C y−1 if extended to all grazed woodlands in Queensland. It is suggested that introduction of livestock grazing and altered fire regimes have triggered the change in tree‐grass dominance in these woodlands. Thus, change in carbon stocks in the grazed woodlands of Queensland is identified as an important component of human‐induced greenhouse gas flux in Australia, equivalent in magnitude to c. 25% of the most recently published (1999) total estimated national net emissions. The latter inventory takes into account emissions from land clearing, but does not include the sink identified in the present study. This sequestration also represents a small but significant contribution to the global terrestrial carbon sink.
Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils
Authors: Neff Jason C. , Hooper David U. 
Published: March 2003

AbstractClimatic change may influence decomposition dynamics in arctic and boreal ecosystems, affecting both atmospheric CO2 levels, and the flux of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) to aquatic systems. In this study, we investigated landscape‐scale controls on potential production of these compounds using a one‐year laboratory incubation at two temperatures (10° and 30 °C). We measured the release of CO2, DOC and DON from tundra soils collected from a variety of vegetation types and climatic regimes: tussock tundra at four sites along a latitudinal gradient from the interior to the north slope of Alaska, and soils from additional vegetation types at two of those sites (upland spruce at Fairbanks, and wet sedge and shrub tundra at Toolik Lake in northern Alaska). Vegetation type strongly influenced carbon fluxes. The highest CO2 and DOC release at the high incubation temperature occurred in the soils of shrub tundra communities. Tussock tundra soils exhibited the next highest DOC fluxes followed by spruce and wet sedge tundra soils, respectively. Of the fluxes, CO2 showed the greatest sensitivity to incubation temperatures and vegetation type, followed by DOC. DON fluxes were less variable. Total CO2 and total DOC release were positively correlated, with DOC fluxes approximately 10% of total CO2 fluxes. The ratio of CO2 production to DOC release varied significantly across vegetation types with Tussock soils producing an average of four times as much CO2 per unit DOC released compared to Spruce soils from the Fairbanks site. Sites in this study released 80–370 mg CO2‐C g soil C−1 and 5–46 mg DOC g soil C−1 at high temperatures. The magnitude of these fluxes indicates that arctic carbon pools contain a large proportion of labile carbon that could be easily decomposed given optimal conditions. The size of this labile pool ranged between 9 and 41% of soil carbon on a g soil C basis, with most variation related to vegetation type rather than climate.
Solar UV‐B radiation affects below‐ground parameters in a fen ecosystem in Tierra del Fuego, Argentina: implications of stratospheric ozone depletion
Authors: Zaller Johann G. , Caldwell Martyn M. , D. Flint Stephan , Scopel Ana L , Salo Osvaldo E. , Ballaré Carlos L. 
Published: March 2003

AbstractStratospheric ozone depletion caused by the release of chlorofluorocarbons is most pronounced at high latitudes, especially in the Southern Hemisphere (including the so‐called ‘ozone hole’). The consequent increase in solar ultraviolet‐B radiation (UV‐B, 280–315 nm) reaching the earth's surface may cause a variety of alterations in terrestrial ecosystems. Most effects might be expected to occur above‐ground since sunlight does not penetrate effectively below‐ground. Here, we demonstrate that solar UV‐B radiation in a fen in Tierra del Fuego (Argentina), where the ozone hole passes overhead several times during the Austral spring, is causing large changes of below‐ground processes of this ecosystem. During the third and fourth year of a manipulative field experiment, we investigated root systems in these plots and found that when the ambient solar UV‐B radiation was substantially reduced, there was a 30% increase in summer root length production and as much as a threefold decrease in already low symbiotic mycorrhizal colonization frequency of the roots compared with plots receiving near‐ambient solar UV‐B. There was also an apparent shift toward older age classes of roots under reduced solar UV‐B. Such large changes in root system behaviour may have decided effects on competition and other ecological interactions in this ecosystem.
Nitrogen input together with ecosystem nitrogen enrichment predict nitrate leaching from European forests
Authors: MacDonald J. A. , Dise N. B. , Matzner E. , Armbruster M. , Gundersen P. , Forsius M. 
Published: March 2003

AbstractThe IFEF database (Indicators of Forest Ecosystem Functioning), consisting of nitrogen deposition, nitrate leaching fluxes, and soil and ecosystem characteristics, is analysed to evaluate the C/N ratio in the organic horizon as an indicator of nitrate leaching. One hundred and eighty one forests are examined, from countries across Europe ranging from boreal to Mediterranean regions, encompassing broadleaf and coniferous sites and plot and catchment studies. N input in throughfall ranges from less than 1 kg N ha−1 y−1 in northern Norway and Finland to greater than 60 kg N ha−1 y−1 in the Netherlands and Czech Republic. The amount of NO3– leached covers a smaller range, between 1 and 40 kg N ha−1 y−1. Nitrate leaching is strongly dependent on the amount of nitrogen deposited in throughfall (N input) and simply adding the C/N ratio in the organic horizon to a regression equation does not improve this relationship. However, when the data are stratified based on C/N ratios less than or equal to 25 and greater than 25, highly significant relationships (P < 0.05) are observed between N input and NO3– leached. The slope of the relationship for those sites where C/N ratio is  ≤ 25 (′nitrogen enriched′ sites) is twice that for those sites where C/N ratio is > 25. These empirical relationships may be used to identify which forested ecosystems are likely to show elevated rates of nitrate leaching under predicted future nitrogen deposition scenarios. Elevated NO3– leaching also shows a relationship with soil pH, with high rates of NO3– leaching only observed at sites with a pH < 4.5 and N inputs > 30 kg N ha−1 y−1. Tree age and species have no significant impact on the ecosystem response to N input at a regional scale.
Interannual variability in net CO2 exchange of a native tallgrass prairie
Authors: Suyker Andrew E. , Verma Shashi B. , Burba George G. 
Published: March 2003

AbstractYear‐round eddy covariance flux measurements were made in a native tallgrass prairie in north‐central Oklahoma, USA during 1997–2000 to quantify carbon exchange and its interannual variability. This prairie is dominated by warm season C4 grasses. The soil is a relatively shallow silty clay loam underlined with a heavy clay layer and a limestone bedrock. During the study period, the prairie was burned in the spring of each year, and was not grazed. In 1997 there was adequate soil moisture through the growing season, but 1998 had two extended periods of substantially low soil moisture (with concurrent high air temperatures and vapor pressure deficits), one early and one later in the growing season. There was also moisture stress in 1999, but it was less severe and occurred later in the season. The annual net ecosystem CO2 exchange, NEE (before including carbon loss during the burn) was 274, 46 and 124 g C m−2 yr−1 in 1997, 1998, and 1999, respectively (flux toward the surface is positive), and the associated variation seemed to mirror the severity of moisture stress. We also examined integrated values of NEE during different periods (e.g. day/night; growing season/senescence). Annually integrated carbon dioxide uptake during the daytime showed the greatest variability from year to year, and was primarily linked to the severity of moisture stress. Carbon loss during nighttime was a significant part of the annual daytime NEE, and was fairly stable from year to year. When carbon loss during the burn (estimated from pre‐ and post‐burn biomass samples) was incorporated in the annual NEE, the prairie was found to be approximately carbon neutral (i.e. net carbon uptake/release was near zero) in years with no moisture stress (1997) or with some stress late in the season (1999). During a year with severe moisture stress early in the season (1998), the prairie was a net source of carbon. It appears that moisture stress (severity as well as timing of occurrence) was a dominating factor regulating the annual carbon exchange of the prairie.
Laparoscopic management of an unsuspected unusual ovarian malignancy
Authors: Bevan  , Farthing  
Published: March 2003

DesignCase report.MethodA 32‐year‐old lady with a large complex ovarian cyst was treated by laparoscopic oöphorectomy. The cyst was removed intact, utilizing an impermeable bag retrieval system. The cyst proved to be malignant and laparoscopic surgical staging was performed as a second procedure.ConclusionThe majority of ovarian cysts in younger women will be benign and should be removed laparoscopically to reduce morbidity. The routine use of an impermeable bag retrieval system reduces the risk of tumour spillage into the peritoneal cavity when unexpected malignancy occurs. We report the first instance of laparoscopic management of a malignant granulosa cell tumour found coincidentally in a dermoid cyst.
The incidence of entry‐related laparoscopic injuries in Finland
Authors: Härkki‐Sirén Päivi 
Published: March 2003

ObjectiveTo analyse entry‐related laparoscopic complications in Finland.SubjectsData from the Finnish Hospital Discharge Register and the National Patient Insurance Association were used.Results51 entry‐related laparoscopic injuries were reported from 1990 through 1996, accounting for 22% of all major laparoscopic complications, the incidence being 0.5/1000 procedures. Of the entry injuries, 57% were bowel injuries, 15% incisional hernias, 12% large‐vessel injuries, 10% small‐vessel injuries and 6% bladder injuries. Altogether, 92% of the complications were treated by laparotomy.ConclusionsLaparoscopic procedures are associated with complications related to laparoscopic access and the operation itself. Safety guidelines should be followed during laparoscopic procedures to reduce the complication risk.
Scottish audit of ectopic pregnancy
Authors:   Scottish Laparoscopic Surgery Audit Group, Brechin Susan , Farquharson David M. , Hawthorn Robert , Davis Jonathon , Fisher Peter , Philips William , Lumsden Mary A. 
Published: March 2003

ObjectiveTo evaluate the use of laparoscopic procedures in the treatment of ectopic pregnancies by a cross‐section of gynaecologists in ScotlandDesignA prospective registration of cases of laparoscopically treated ectopic pregnancy by gynaecologists. Case‐note review was also performed in selected hospitals.Setting13 hospitals in seven Scottish Health Board areas.SubjectsWomen having laparoscopic treatment of ectopic pregnancy.ResultsBetween April 1994 and March 1996, 85 ectopic pregnancies were treated laparoscopically. Contraindications for laparoscopic surgery were most commonly size of the ectopic gestation (53%), presence of intraperitoneal bleeding (42%) and tubal rupture (44%). Salpingotomy was performed in 16% overall with only 86% of consultants monitoring serial human chorionic gonadotrophin levels.ConclusionsLaparoscopic treatment of ectopic pregnancies in Scotland is infrequent. Lack of availability of adequate equipment and trained staff was often quoted as the reason preventing surgeons from developing their skills in these techniques. Complication rates were low and patient satisfaction high.
Microwave endometrial ablation (MEATM): a safe technique? Complication data from a prospective series of 1400 cases
Authors: Parkin David E. ,   MEA Users' Group
Published: March 2003

ObjectiveTo determine the safety of microwave endometrial ablation when used for the treatment of excessive menstrual loss.DesignProspective observational study of all microwave endometrial ablations, describing all the complications associated with this method.SettingA total of 13 gynaecological units in both teaching and general hospitals in the United Kingdom and Canada.ResultsIn 1433 cases there was only one major complication, a small bowel burn, giving an incidence of 0.7/1000. There were few minor complications.ConclusionMicrowave endometrial ablation appears to be safer than hysteroscopic methods of endometrial ablation.
Complications of laparoscopic hysterectomy: comparison of the first 250 cases with the second 250
Authors: Jones Robert A. 
Published: March 2003

ObjectiveA comparison of the complications of the first and second halves of a series of 500 laparoscopic hysterectomies using a constant stapling technique.DesignA prospective study of a series of patients followed by retrospective data analysis by the author and an independent audit.SettingSpecialist gynaecological practice at two private hospitals.SubjectsPatients presented randomly and were offered the procedure, unless preoperative assessment precluded the use of the technique because of anticipated technical difficulty. This would have been for example, on account of excessive uterine size, coincidental abdominoplasty, patient preference or invasive pelvic cancer. In these cases conventional abdominal hysterectomy was offered instead.ResultsThe complication rates were reduced with the passage of time and increasing experience. This was despite more difficult procedures being undertaken and the inclusion of other procedures, such as bladder neck suspension, appendicectomy and laparoscopic repair of prolapse. My rates compared favourably with those in other published reports on laparoscopic hysterectomy.ConclusionA single operator has used a constant surgical stapling technique for laparoscopic hysterectomy over 7 years. There is demonstrated in the series a steady improvement in complication rates.
Accuracy of hysterosalpingography and hysteroscopy for diagnosis of intrauterine lesions in infertile patients in an assisted fertilization programme
Authors: Cunha‐Filho João S.L. , De Souza Carlos A. B. , Salazar Cristiano C. , Facin Andréa C. , Freitas Fernando M. , Passos Eduardo P. 
Published: March 2003

Objective To determine the accuracy of hysterosalpingography compared with hysteroscopy for detection of intrauterine abnormalities in infertile patients.Design Cross‐sectional study.Setting University hospital.Subjects 296 women undergoing an assisted fertilization programme.Intervention Patients Underwent to hysteroscopy and hysterosalpingography prior to intrauterine insemination or in vitro fertilization.Main outcome measures Hysterosalpingographic and hysteroscopic findings.Results Hysteroscopy proved satisfactory in 90.5% of cases. Of the patients, 121 (40.9%) had an abnormal hysteroscopic evaluation. The most prevalent hysteroscopic findings were: cervical stenosis (n = 28); chronic endometritis (n = 17); synechiae (n = 16); suspected endometrial hyperplasia (n = 14); polyps (n = 11); and myomas (n = 7). The comparison of hysteroscopic and hysterosalpingographic findings revealed a sensitivity of 75.21% and a specificity of 41.14% for hysterosalpingography; the positive and negative predictive values were 47% and 70.60%, respectively.Conclusions Hysterosalpingography is not sufficiently accurate, with regard to specificity or sensitivity, for screening pathologies of the endometrial cavity in infertile patients. Hysteroscopy should be performed in all patients before IVF and artificial insemination.