bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ozone effects on wheat in relation to CO2: modelling short‐term and long‐term responses of leaf photosynthesis and leaf duration
Authors: Ewert Frank , Porter John R. 
Published: March 2003

SummaryA combined stomatal–photosynthesis model was extended to simulate the effects of ozone exposure on leaf photosynthesis and leaf duration in relation to CO2. We assume that ozone has a short‐term and a long‐term effect on the Rubisco‐limited rate of photosynthesis, Ac. Elevated CO2 counteracts ozone damage via stomatal closure. Ozone is detoxified at uptake rates below a threshold value above which Ac decreases linearly with the rate of ozone uptake. Reduction in Ac is transient and depends on leaf age. Leaf duration decreases depending on accumulated ozone uptake. This approach is introduced into the mechanistic crop simulation model AFRCWHEAT2. The derived model, AFRCWHEAT2‐O3, is used to test the capability of these assumptions to explain responses at the plant and crop level.Simulations of short‐term and long‐term responses of leaf photosynthesis, leaf duration and plant and crop growth to ozone exposure in response to CO2 are analysed and compared with experimental data derived from the literature. The model successfully reproduced published responses of leaf photosynthesis, leaf duration, radiation use efficiency and final biomass of wheat to elevated ozone and CO2. However, simulations were unsatisfactory for cumulative radiation interception which had some impact on the accuracy of predictions of final biomass. There were responses of leaf‐area index to CO2 and ozone as a result of effects on tillering which were not accounted for in the present model. We suggest that some model assumptions need to be tested, or analysed further to improve the mechanistic understanding of the combined effects of changes in ozone and CO2 concentrations on leaf photosynthesis and senescence. We conclude that research is particularly needed to improve the understanding of leaf‐area dynamics in response to ozone exposure and elevated CO2.
Sub‐saharan desertification and productivity are linked to hemispheric climate variability
Authors: Oba Gufu , Post Eric , Stenseth Nils C. 
Published: March 2003

SummaryVegetation productivity and desertification in sub‐Saharan Africa may be influenced by global climate variability attributable to the North Atlantic Oscillation (NAO) and El Niño Southern Oscillation (ENSO). Combined and individual effects of the NAO and ENSO indices revealed that 75% of the interannual variation in the area of Sahara Desert was accounted for by the combined effects, with most variance attributable to the NAO. Effects were shown in the latitudinal variation on the 200 mm isocline, which was influenced mostly by the NAO. The combined indices explained much of the interannual variability in vegetation productivity in the Sahelian zone and southern Africa, implying that both the NAO and ENSO may be useful for monitoring effects of global climate change in sub‐Saharan Africa.
UV‐B effect onQuercus roburleaf litter decomposition persists over four years
Authors: Newsham K. K. , Anderson J. M. , Sparks T. H. , Splatt P. , Woods C. , Mcleod A. R. 
Published: March 2003

SummaryThe effects of elevated UV‐B (280–315 nm) radiation on the long‐term decomposition ofQuercus roburleaf litter were assessed at an outdoor facility in the UK by exposing saplings to elevated UV‐B radiation (corresponding to a 30% increase above the ambient level of erythemally weighted UV‐B, equivalent to that resulting from ac. 18% reduction in ozone column) under arrays of cellulose diacetate‐filtered fluorescent UV‐B lamps that also produced UV‐A radiation (315–400 nm). Saplings were also exposed to elevated UV‐A radiation alone under arrays of polyester‐filtered fluorescent lamps and to ambient solar radiation under arrays of nonenergized lamps. After 8 months of irradiation, abscised leaves were placed into litter bags and allowed to decompose in the litter layer of a mixed deciduous woodland for 4.08 years. The dry weight loss of leaf litter from saplings irradiated with elevated UV‐B and UV‐A radiation during growth was 17% greater than that of leaf litter irradiated with elevated UV‐A radiation alone. Annual fractional weight loss of litter (k), and the estimated time taken for 95% of material to decay (3/k) were respectively increased and decreased by 27% for leaf litter exposed during growth to elevated UV‐B and UV‐A radiation, relative to that exposed to UV‐A alone. The present data corroborate those from a previous study indicating that UV‐B radiation applied during growth accelerates the subsequent decomposition ofQ. roburleaf litter in soil, but indicate that this effect persists for over four years after abscission.
Nitrogen deposition and atmospheric CO2interactions on fine root dynamics in temperate forests: a theoretical model analysis
Authors: Rasse Daniel P. 
Published: March 2003

AbstractFine root turnover is a critical component of below‐ground forest ecology, which regulates nutrient dynamics, forest net primary productivity, carbon input to soils, and soil respiration. Understanding fine root responses to changing environmental conditions is critical for predicting the productivity and carbon sequestration potential of forest ecosystems during the 21st century. The first objective of this study is to demonstrate that a mechanistic model can realistically simulate spatial and temporal fine root demography in temperate forests on the basis of two hypotheses: (1) absorption of mineral N (N) stimulates the production of new roots, and (2) fine root longevity decreases with increasing N availability. Based on this model, my second objective is to predict fine root responses to changing atmospheric CO2levels and N deposition rates. To meet these objectives, an extensive description of the N cycle and the new fine root module were implemented in the ASPECTS model. In agreement with a wide body of literature information, the new model predicted: (1) a preferential colonisation by fine roots of the uppermost soil layer, and (2) a flush of fine root growth in the spring. The simulations indicate that fine root biomass will increase in response to elevated CO2under the double effect of (1) an increase in root longevity due to increased N stress, and (2) larger amounts of assimilates available to the growth of plant tissue due to increased photosynthesis. Although the simulated total fine root biomass increased under both increasing N deposition rates and atmospheric CO2concentrations, the model predicts that the distribution of fine roots among soil layers will be altered. This suggests that experimental studies must consider the full depth of the root system in order to accurately assess effects of environmental changes on fine root dynamics. The model also suggests that fine root longevity is a plastic parameter, which varied from less than 1 year to more than 3 years depending on forcing values of N deposition rates and atmospheric CO2concentrations. Finally, the model indicates that the increase in net ecosystem exchange (NEE) and soil respiration in temperate forests under elevated CO2will be proportional to the amount of available N, with little to no response in low N conditions and up to +28% for both NEE and soil respiration under the highest deposition rate (7.0 g N m−2 y−1).
Effect of springtime solar ultraviolet‐B radiation on growth of Colobanthus quitensis at Palmer Station, Antarctica
Authors: XIONG FUSHENG S. , RUHLAND CHRISTOPHER T. , DAY THOMAS A. 
Published: March 2003

AbstractWe examined the influence of solar ultraviolet‐B radiation (UV‐B; 280–315 nm) on the growth of Colobanthus quitensis plants by placing them under contrasting UV‐B filters at Palmer Station, along the Antarctic Peninsula. The filters reduced diurnal biologically effective UV‐B (UV‐BBE) either by 83% (‘reduced UV‐B’) or by 12% (‘near‐ambient UV‐B’) over the 63 day experiment (7 November 1998–8 January 1999). Ozone column depletion averaged 17% during the experiment. Relative growth and net assimilation rates of plants exposed to near‐ambient UV‐B were 30 and 20% lower, respectively, than those of plants exposed to reduced UV‐B. The former plants produced 29% less total biomass, as a result of containing 54% less aboveground biomass. These reductions in aboveground biomass were mainly the result of a 45% reduction in shoot biomass, and a 31% reduction in reproductive biomass. Reductions in shoot biomass were owing to an 18% reduction in branch production by main shoots, while reductions in reproductive biomass were the result of a 19% reduction in individual capsule mass. Total plant leaf area was reduced by 19% under near‐ambient UV‐B, although total leaf biomass was unaffected because leaves had a greater specific leaf mass. The reduction in plant leaf area under near‐ambient UV‐B was attributable to: (1) production of 11% fewer leaves per main shoot system and plant, which resulted from an 18% reduction in branch production by main shoots. Leaf production per individual main shoot or branch was not affected; (2) shorter leaf longevity—main shoots contained 14% fewer green leaves at a given time; and (3) smaller individual leaves—leaf elongation rates were 14% slower and mature leaves were 13% shorter.
A mechanism of abiotic immobilization of nitrate in forest ecosystems: the ferrous wheel hypothesis
Authors: Davidson Eric A. , Chorover Jon , Dail D. Bryan 
Published: March 2003

AbstractForest soils, rather than woody biomass, are the dominant long‐term sink for N in forest fertilization studies and, by inference, for N from atmospheric deposition. Recent evidence of significant abiotic immobilization of inorganic‐N in forest humus layers challenges a previously widely held view that microbial processes are the dominant pathways for N immobilization in soil. Understanding the plant, microbial, and abiotic mechanisms of N immobilization in forest soils has important implications for understanding current and future carbon budgets. Abiotic immobilization of nitrate is particularly perplexing because the thermodynamics of nitrate reduction in soils are not generally favorable under oxic conditions. Here we present preliminary evidence for a testable hypothesis that explains abiotic immobilization of nitrate in forest soils. Because iron (and perhaps manganese) plays a key role as a catalyst, with Fe(II) reducing nitrate and reduced forms of carbon then regenerating Fe(II), we call this ‘the ferrous wheel hypothesis’. After nitrate is reduced to nitrite, we hypothesize that nitrite reacts with dissolved organic matter through nitration and nitrosation of aromatic ring structures, thus producing dissolved organic nitrogen (DON). In addition to ignorance about mechanisms of DON production, little is known about DON dynamics in soil and its fate within ecosystems. Evidence from leaching and watershed studies suggests that DON production and consumption may be largely uncoupled from seasonal biological processes, although biological processes ultimately produce the DOC and reducing power that affect DON formation and the entire N cycle. The ferrous wheel hypothesis includes both biological and abiological processes, but the reducing power of plant‐derived organic matter may build up over seasons and years while the abiotic reduction of nitrate and reaction of organic matter with nitrite may occur in a matter of seconds after nitrate enters the soil solution.
Plant growth functions and possible spatial and temporal scaling errors in models of herbivory
Authors: Parsons A. J. , Schwinning S. , Carrère P. 
Published: March 2003

Recent studies have provided detail of the mechanisms by which plants and animals interact, but attempts to apply this knowledge to understand function at the scale of whole fields or grazed ecosystems can be fraught with difficulties. Faced with a plethora of detail, and yet demands to make models more comprehensive, modellers face pressure to revert to simplified accounts for what are assumed to be well‐established biological phenomena, for example, for describing plant growth and intake, but this raises the risk that important insights may be lost, or that the analyses may face errors of scaling.The predictions of a previously described spatial model are compared with those of a non‐spatial rendition of the same model to identify the differences in predictions and the sources of these differences. In particular, the use of the conventional empirical growth functions and their interaction with temporal and spatial scaling errors are examined. The comparison exposed how substantial errors could be made in predicting yield and stability under grazing. It is proposed that such errors might be avoided by ensuring that the functional responses used capture the insights of more detailed studies, and by recognizing the difficulties of scaling‐up from the level of processes to the field scale and beyond.
Gasless laparoscopic ovarian cystectomy with minilaparotomy during pregnancy
Authors: Inoue Hiromi , Nabuchi Kaoru , Ishihara Yuki , Fukumoto Yumiko , Kobayashi Masaru 
Published: March 2003

ObjectiveRecently there have been many reports of laparoscopic surgery during pregnancy, despite serious concerns about the possible consequences of fetal damage caused by the pneumoperitoneum and anaesthetics, or the risk of the trauma to the enlarged uterus. We have attempted gasless laparoscopic surgery with extra‐abdominal cystectomy under regional anaesthesia for ovarian cysts in pregnancy to avoid or minimize such risks.InterventionsWe report three cases of laparoscopically assisted abdominal cystectomy during early pregnancy using a gasless method (Laparolift in two cases and surgical wire in one case) and combined spinal‐epidural anaesthesia (CSE). Extra‐abdominal cystectomy was performed after a minilaparotomy directly above the ovarian cyst.ResultsIn all three cases, there were no intraoperative complications and postoperative recoveries were rapid and uneventful for both the mother and the fetus. Intra‐abdominal procedures in gasless laparoscopy are more difficult than those with pneumoperitoneum because of the limited visual field. In respect to anaesthesia, all the patients experienced discomfort with the head‐down tilt during the operation, although this position was maintained for the shortest possible period of time. However, the procedures were performed smoothly and with relative ease with extra‐abdominal cystectomy. All the patients were discharged on the second postoperative day and subsequently completed their normal pregnancies with spontaneous vaginal delivery of healthy full‐term babies.ConclusionGasless laparoscopic cystectomy with a minilaparotomy in early pregnancy may be an alternative approach to ovarian cysts in pregnancy, considering the absence of fetal risk from CO2 pneumoperitoneum and a relatively low risk of trauma to the enlarged uterus. With regard to the choice of anaesthesia in this approach, general anaesthesia may be preferable.
Laparoscopic anterior resection of the rectum and hysterectomy in a patient with extensive pelvic endometriosis
Authors: Reich Harry , Wood Carl , Whittaker Mark 
Published: March 2003

ObjectiveTo assess the feasibility of excising rectal endometriosis using laparoscopic techniques and reanastomosing the rectum using a circular stapling device.SubjectA 41‐year‐old woman with recurrent stage IV endometriosis (revised American Fertility Society classification).InterventionsLaparoscopic excision of stage IV endometriosis, laparoscopic hysterectomy, right salpingo‐oöphorectomy, appendicectomy, anterior rectal resection and reanastomosis with circular stapler.Main outcome measuresSurgical outcome, involvement of endometriosis, operative time, duration of hospital stay, complications, histological involvement of organs with endometriosis and 1‐year follow up.ResultsThe procedure was uncomplicated and took 3 h to complete. The patient was discharged home on day 4. Histological analysis revealed endometriotic involvement through to the rectal mucosa and also of the appendix. The uterus revealed adenomyosis. At 1‐year follow up, the patient was free from the symptoms associated with her pelvic endometriosisConclusionsLaparoscopic anterior resection of the rectum using a stapler fashioned to provide an end‐to‐end anastomosis was performed in association with a total laparoscopic hysterectomy. Advanced rectovaginal endometriosis may involve the full thickness of the rectal wall, the endometriosis may be excised laparoscopically and the rectal disease can be excised without performing a laparotomy. By avoiding the need for laparotomy, this allows the patient the advantages of reductions in pain, hospital stay and duration of convalescence.
Present status of conventional cytoreductive operations
Authors: Heintz  
Published: March 2003

ObjectiveTo evaluate the present status of cytoreductive operations in the treatment of advanced ovarian carcinoma.DesignReview of the relevant literature.ResultAt present it is still accepted that the maximum diameter of the largest tumour mass remaining should optimally not exceed 1.0–1.5 cm because of its influence on survival. Other biological factors may be of equal or greater importance to the outcome as is the extent of surgery. A clear restriction of the procedure is that extensive debulking procedures, such as peritoneal stripping technique, or bowel resections, have so far demonstrated no improvement in survival. In particular, patients with mainly extensive stage III or IV disease, have fared no better after optimal cytoreductive surgery than patients who still had residual disease at the completion of surgery. This observation underlines that the initial tumour burden as well as the tumour residue influences prognosis. It also seems that the particular group of patients with largely irresectable large disease in the abdomen, does not benefit at all from cytoreductive surgery. For this reason intervention cytoreductive surgery after at least three courses of chemotherapy and a proven partial response, seems to be a logical option.ConclusionsAt present it is clear that the residual tumour mass and the initial tumour mass are important factors for prognosis. It seems logical that, especially in patients with large initial tumour masses, neoadjuvant chemotherapy is an option that should seriously be considered. A randomized trial is needed to study the real value of this approach.
Assessment of tissue damage associated with laparoscopic and conventional hysterectomies
Authors: Holub  , Jabor  , Fischlová  , Palásek  
Published: March 2003

ObjectiveTo assess and compare damage to tissue during laparoscopic and conventional hysterectomies.DesignProspective clinical study.SettingDepartment of Gynaecology, Baby‐Friendly Hospital, Kladno, Czech Republic.Subjects95 women who had undergone laparoscopic, abdominal or vaginal hysterectomyMain outcome measuresThe operative trauma and tissue damage were assessed using the enzymatic activity of creatine kinase (CK). Serum levels of CK were measured in 85 patients who had undergone hysterectomy, and the activities of CK, isoenzyme CK‐MB and aspartate aminotransferase (AST) were investigated in seven patients of an additional group.ResultsThe rate of CK activity was significantly greater in 28 patients who underwent abdominal hysterectomy (P < 0.005) compared with that in the patients who underwent laparoscopic or vaginal hysterectomies (34 and 23 patients, respectively). The CK levels in the latter two groups were also significantly different (P < 0.025).ConclusionFollowing total abdominal hysterectomy, tissue damage, as assessed by the activity of creatine kinase, is statistically significantly greater than that following laparoscopic and vaginal hysterectomies. Clinical experience and metabolic changes indicate that the perioperative stress in patients undergoing laparoscopic hysterectomy is lower than that in patients where an abdominal approach is used. Large prospective studies are needed to evaluate the surgical trauma and metabolic changes induced by laparoscopic hysterectomy.
Blind endometrial biopsies: insufficient for diagnosis in women with intrauterine pathology
Authors: Kent Andrew S. H. , Haines Pat , Manners Brian T. B. , Coats Percy M. 
Published: March 2003

ObjectiveTo evaluate blind and directed endometrial biopsies for histological diagnosis in the presence of intrauterine pathology.DesignA prospective study comparing the information obtained at outpatient hysteroscopy with undirected endometrial biopsy with subsequent pathological findings obtained after transcervical resection (TCR) of intrauterine polyps.SettingThe Department of Obstetrics and Gynaecology, The Royal Surrey County Hospital, Guildford, 1991–1996.Subjects414 women who were diagnosed as having intrauterine abnormalities, 177 of whom opted for transcervical resection.Main outcome measuresOutcomes of referrals to a ‘one‐visit clinic’, with particular reference to that group of patients undergoing TCR. Comparisons between the histological findings obtained from blind endometrial biopsy and those from TCR specimens.Results414/1022 women had intrauterine abnormalities identified by flexible hysteroscopy, and 177 (42.8%) opted for TCR. The histological findings from the TCR specimens differed from the endometrial biopsies by 30% overall, and the discrepancies included two carcinomas and three complex hyperplasias with atypia.ConclusionWe suggest that, in women with abnormal uterine bleeding, the use of blind endometrial biopsy alone as a screening technique should be questioned. Outpatient hysteroscopy should be offered to women with abnormal uterine bleeding, with directed biopsy or transcervical resection for those in whom intrauterine polyps have been identified.
The availability of training in the laparoscopic management of ectopic pregnancy
Authors: Bancroft Karen , Whittaker Mark D. , Clayton Richard D. , Garry Ray 
Published: March 2003

ObjectiveTo assess the availability of laparoscopic treatment for ectopic pregnancy, and the availability of training in such laparoscopic techniques, in the Yorkshire Deanery (training region).DesignA postal questionnaire was distributed to all trainees in the Yorkshire Deanery with a national or visiting training number (denoting eligibility for CCST).Results60 trainees were identified of whom 59 (98%) returned completed questionnaires. Whilst the majority of trainees had observed or assisted with laparoscopic surgery for ectopic pregnancy in their current hospital, only 37% had performed such surgery themselves and only 36% considered that they would be able to achieve appropriate training at that hospital. One or more consultants were offering laparoscopic treatment for ectopic pregnancy in 13 out of the 15 hospitals in the deanery. However, in only five of these hospitals did the majority of trainees consider that they would be able to achieve appropriate training in these techniques.ConclusionAlthough the majority of hospitals have at least one consultant able to undertake laparoscopic surgery for the management of ectopic pregnancy, this is not being translated into a routinely available service or into training opportunities for specialist registrars in the Yorkshire Deanery.