Management impacts on the dissolved organic carbon release from deadwood, ground vegetation and the forest floor in a temperate Oak woodland.

The forest floor is often considered the most important source of dissolved organic carbon (DOC) in forest soils, yet little is known about the relative contribution from different forest floor layers, understorey vegetation and deadwood. Here, we determine the carbon stocks and potential DOC production from forest materials: deadwood, ground vegetation, leaf litter, the fermentation layer and top mineral soil (Ah horizon), and further assess the impact of management. Our research is based on long-term monitoring plots in a temperate deciduous woodland, with one set of plots actively managed by thinning, understorey scrub and deadwood removal, and another set that were not managed in 23 years. We examined long-term data and a spatial survey of forest materials to estimate the relative carbon stocks and concentrations and fluxes of DOC released from these different pools. Long-term soil water monitoring revealed a large difference in median DOC concentrations between the unmanaged (43.8 mg L-1) and managed (18.4 mg L-1) sets of plots at 10 cm depth over six years, with the median DOC concentration over twice as high in the unmanaged plots. In our spatial survey, a significantly larger cumulative flux of DOC was released from the unmanaged than the managed site, with 295.5 and 230.3 g m-2, respectively. Whilst deadwood and leaf litter released the greatest amount of DOC per unit mass, when volume of the material was considered, leaf litter contributed most to DOC flux, with deadwood contributing least. Likewise, there were significant differences in the carbon stocks held by different forest materials that were dependent on site. Vegetation and the fermentation layer held more carbon in the managed site than unmanaged, whilst the opposite occurred in deadwood and the Ah horizon. These findings indicate that management affects the allocation of carbon stored and DOC released between different forest materials.

Atmospheric deposition of phosphorus to land and freshwater.

We compiled published and newly-obtained data on the directly-measured atmospheric deposition of total phosphorus (TP), filtered total phosphorus (FTP), and inorganic phosphorus (PO4-P) to open land, lakes, and marine coasts. The resulting global data base includes data for c. 250 sites, covering the period 1954 to 2012. Most (82%) of the measurement locations are in Europe and North America, with 44 in Africa, Asia, Oceania, and South-Central America. The deposition rates are log-normally distributed, and for the whole data set the geometric mean deposition rates are 0.027, 0.019 and 0.14 g m(-2) a(-1) for TP, FTP and PO4-P respectively. At smaller scales there is little systematic spatial variation, except for high deposition rates at some sites in Germany, likely due to local agricultural sources. In cases for which PO4-P was determined as well as one of the other forms of P, strong parallels between logarithmic values were found. Based on the directly-measured deposition rates to land, and published estimates of P deposition to the oceans, we estimate a total annual transfer of P to and from the atmosphere of 3.7 Tg. However, much of the phosphorus in larger particles (principally primary biological aerosol particles) is probably redeposited near to its origin, so that long-range transport, important for tropical forests, large areas of peatland and the oceans, mainly involves fine dust from deserts and soils, as described by the simulations of Mahowald et al. (Global Biogeochemical Cycles 22, GB4026, 2008). We suggest that local release to the atmosphere and subsequent deposition bring about a pseudo-diffusive redistribution of P in the landscape, with P-poor ecosystems, for example ombrotrophic peatlands and oligotrophic lakes, gaining at the expense of P-rich ones. Simple calculations suggest that atmospheric transport could bring about significant local redistribution of P among terrestrial ecosystems. Although most atmospherically transported P is natural in origin, local transfers from fertilised farmland to P-poor ecosystems may be significant, and this requires further research.

Short and long term changes in carbon, nitrogen and acidity in the forest soils under oak at the Alice Holt Environmental Change Network site.

The dynamics of soil properties within a 70 year old oak plot were assessed every five years (1994-2009), by depth and by horizon to identify short term changes in soil carbon and nitrogen stocks, and acidity. The findings were set within a study of long term changes in soil properties in a 180 year chronosequence of oak plots from the same forest. Carbon stock increased significantly in the top mineral horizon - overall increase was 5 t C ha(-1), at a mean accumulation rate of 0.34 t C ha(-1)y(-1), which was mainly due to increase in horizon thickness. No increase was seen when soils were sampled by depth. Differences obtained by depth or horizon sampling due to changes in horizon thickness over time highlight the importance of horizon in the correct evaluation of soil property change in small scale sampling programs. This is particularly important in forest soils with high litter accumulation and low turnover rates when compared to other land uses. Nitrogen stock increases below 10cm soil depth were attributed to insect activity, litterfall variation and a change in water table. Findings were confirmed in the chronosequence study of oak across the forests; increases in soil C stocks of 0.1-0.2 t C ha(-1)y(-1) were calculated across young (~25 years), mid-rotation (~60 years) and old (120+ years) stands. Soil nitrogen increased significantly with canopy age whilst pH increased significantly between young-mid rotation stands but decreased between mid rotation and old stands. Significant increases in pH were also recorded before 2004 in the ECN 70 year old oak plots reflecting overall pollution recovery.

The effects of phytophagous insects on water and soil nutrient concentrations and fluxes through forest stands of the Level II monitoring network in the UK.

The effects of insect defoliators on throughfall and soil nutrient fluxes were studied in coniferous and deciduous stands at five UK intensive monitoring plots (1998 to 2008). Links were found between the dissolved organic carbon (DOC), nitrogen (N) and potassium (K) fluxes through the forest system to biological activity within the canopy. Underlying soil type determined the leaching or accumulation of these elements. Under oak, monitored at two sites, frass from caterpillars of Tortrix viridana and Operophtera brumata added direct deposition of ~16kgha(-1)extra N during defoliation. Peaks of nitrate (NO(3)-N) flux between 5 and 9kgha(-1) (×5 usual winter values) were recorded in consecutive years in shallow soil waters. Synchronous rises in deep soil NO(3)-N fluxes at the Grizedale sandy site indicate downward flushing, not seen at the clay site. Under three Sitka spruce stands, generation of honeydew (DOC) was attributed to two aphid species (Elatobium abietinum and Cinara pilicornis) with distinctive feeding strategies. Throughfall DOC showed mean annual fluxes (6 seasons) ~45-60kgha(-1) compared with rainfall values of 14-22kgha(-1). Increases of total N in throughfall and NO(3)-N fluxes in shallow soil solution were detected - soil water fluxes reached 8kgha(-1) in Llyn Brianne, ~25kgha(-1) in Tummel, and ~40kg NO(3)-Nha(-1) in Coalburn. At Tummel, on sandy soil, NO(3)-N leaching showed increased concentration at depth, attributed to microbiological activity within the soil. By contrast, at Coalburn and Llyn Brianne, sites on peaty gleys, soil water NO(3)-N was retained mostly within the humus layer. Soil type is thus key to predicting N movement and retention patterns. These long term analyses show important direct and indirect effects of phytophagous insects in forest ecosystems, on above and below ground processes affecting tree growth, soil condition, vegetation and water quality.

Chemical fluxes in time through forest ecosystems in the UK - soil response to pollution recovery.

Long term trend analysis of bulk precipitation, throughfall and soil solution elemental fluxes from 12 years monitoring at 10 ICP Level II forest sites in the UK reveal coherent national chemical trends indicating recovery from sulphur deposition and acidification. Soil solution pH increased and sulphate and aluminium decreased at most sites. Trends in nitrogen were variable and dependant on its form. Dissolved organic nitrogen increased in bulk precipitation, throughfall and soil solution at most sites. Nitrate in soil solution declined at sites receiving high nitrogen deposition. Increase in soil dissolved organic carbon was detected - a response to pollution recovery, changes in soil temperature and/or increased microbial activity. An increase of sodium and chloride was evident - a possible result of more frequent storm events at exposed sites. The intensive and integrated nature of monitoring enables the relationships between climate/pollutant exposure and chemical/biological response in forestry to be explored.

Relationship of inspiratory and expiratory times to upper airway resistance during pulsatile needle cricothyrotomy ventilation with generic delivery circuit.

BACKGROUND: Narrow-bore cricothyrotomy retains a clinical role, due to the availability of its component equipment in acute clinical environments, ease of assembly, and operator preference. However, due to infrequent use, there is a need to model this for research and teaching. We present mathematical and laboratory models. METHODS: Using electrical analogy, we mathematically modelled a generic cannula cricothyrotomy circuit, relating inspiratory and expiratory times to the upper airway resistance (R(u)). We constructed a laboratory model to support our mathematical model. The simulated lung is a smooth-bore tube on a tilting table. The upper airway is simulated by 20 G cannulae. Inspiratory and expiratory times for the water meniscus to travel a preset distance (corresponding to tidal volume) were measured and plotted against the number of cannula. RESULTS: From the mathematical model, inspiratory time increases hyperbolically with decreasing R(u), such that there is a minimum R(u) beyond which most of the fresh gas flow leaks out without inflating the chest. Conversely, as R(u) increases, inspiratory time decreases to a plateau. Expiratory time is limited by respiratory factors at low R(u) and by the resistance of the transtracheal expiratory pathway at high R(u), producing a sigmoid-shaped expiratory curve. The experimental results seem consistent with these predictions, although direct theory-experiment mapping is problematic because of the difficulty in assigning a single value to the dynamically changing upper airway resistance. CONCLUSIONS: We can exploit the contrasting changes in inspiratory and expiratory times with the upper airway resistance to optimize conditions for emergent cannula cricothyrotomy ventilation.

Management of unanticipated difficult intubation: a survey of current practice in the Oxford region.

BACKGROUND AND OBJECTIVE: Unanticipated difficulty in tracheal intubation in an anaesthetized patient has always been a cause of concern to anaesthesiologists. This difficulty may lead to morbidity and mortality. This survey was carried out to determine the technique commonly favoured in centres in the Oxford region in the UK for the management of unanticipated difficult intubation. METHODS: We conducted a clinical scenario-based questionnaire survey of 181 anaesthesiologists in the Oxford region. In this scenario, difficulty in endotracheal intubation is recognized only after induction of anaesthesia. A number of options were available to deal with this situation. We used this scenario as a tool to gain insight into the training and the training needs of anaesthesiologists at various levels of training. RESULTS: Of the 181 questionnaires sent, we received 143 (79%) completed replies. The vast majority (141/143 (99%)) of anaesthesiologists would use a gum-elastic bougie together with head and neck positioning and optimal external laryngeal manipulation to gain the best attempt at intubation. If intubation still failed, overall 129/143 (90%) had a back-up plan, while 14/143 (10%) had no plan. Flexible fibreoptic techniques were more commonly planned by 92/143 (64%) anaesthesiologists compared to blind techniques which were less commonly planned by 37/143 (26%) anaesthesiologists. Differences in choice of technique among anaesthesiologists in teaching and district general hospitals were not significant (P = 0.87). Overall, trainees were less likely to choose fibreoptic techniques compared to consultants (P = 0.0009) and would use blind techniques or ask a more experienced colleague to take over. The main reason for the choice was previous experience with the technique. CONCLUSIONS: Although fibreopric techniques were most commonly planned, these were less often chosen by trainees than consultants due to lack of experience/training, while unavailability of intubating laryngeal mask airway (Intavent) was an additional issue precluding its use as an adjunct to intubation.

The value of blood lactate measurements in ICU: an evaluation of the role in the management of patients on haemofiltration.

In response to clinical demand some point-of-care analysers now provide blood lactate measurements, but recently concern has been expressed about the value and interpretation of these measurements. We undertook this study to evaluate blood lactate measurements in patients with acute renal failure undergoing haemofiltration (HF) with lactate replacement fluid. At baseline, 27 patients had base deficits of >5 mmol/l and 14 (52%) had blood lactates of >3.5 mmol/l. Lactate 'tolerance' was monitored by peak changes in these parameters during the procedure. There was a worsening of base deficit in only three of the patients in whom lactate rises exceeded 10 mmol/l with one survivor. Twelve patients with rises of blood lactate greater than 5 mmol/l improved their base deficit (+1 to +17) with eight (67%) survivors. Of the remaining 12 patients with improved base deficit (+2 to +20), 10 (83%) survived. Lactate tolerance was compromised in patients with co-incidental liver disease, those on inotropic support, and in patients with initial blood lactate measurements of >10 mmol/l and large base deficits. The data suggest that blood lactate and simultaneous acid-base response measurements during HF help to assign correct buffer replacement and should be performed on all patients.

The Value of Blood Lactate Measurements in ICU: An Evaluation of the Role in the Management of Patients on Haemofiltration.

In response to clinical demand some point-of-care analysers now provide blood lactate measurements in critical care. Recent literature has raised concerns about the value and interpretation of these measurements. Two particular concerns relate to over-interpretation of lactate rises as equating tissue hypoxia and also the failure to recognise the contribution from inotropic support. We undertook this study to evaluate blood lactate measurements in intensive care unit (ICU) patients in the assessment of response to, and requirements for, haemofiltration (HF) with lactate replacement fluid and to evaluate influences from hepatic failure and from inotropic supportive therapy. Haemofiltration is a convenient renal replacement therapy widely used in intensive care management as an alternative to haemodialysis. Mainly used for the treatment of acute renal failure the process involves removal by filtration of fluid, electrolytes, metabolites and other substances and simultaneous replacement of essential fluid and electrolytes as well as a buffer, usually in the form of lactate (sodium salt). There is controversy about whether lactate replacement may be harmful to the patient and, if so, when it would be appropriate to use a lactate-free fluid at greater expense. Serial blood lactate with simultaneous blood gas measurements were recorded in 27 patients requiring HF for acute renal failure. At baseline all patients had base deficits of >5mmol/L and 14 (52%) had blood lactates of >3.5mmol/L. Lactate 'tolerance' was monitored by peak changes in these parameters during the procedure. There was a worsening of base deficit in only three of the patients in whom lactate rises exceeded 10 mmol/L at some stage during HF with one survivor. A further twelve patients with rises of blood lactate greater than 5 mmol/L improved their base deficit (+1 to +17) with 8 (67%) survivors. Of the remaining twelve patients with improved base deficit (+2 to +20), 10(83%) survived. The influence on 'lactate tolerance' in patients with co-incidental liver disease and those on inotropic support was studied. In these groups lactate tolerance was compromised, particularly those on adrenaline support. Patients with initial blood lactate measurements of >10mmol/l and large base deficits were also lactate intolerant. The data suggest that rises in blood lactate during HF signal harm if accompanied by inadequate improvement in base deficit. Blood lactate and simultaneous acid-base response measurements during HF help to assign correct buffer replacement and should be performed on all patients.

Diclofenac vs oxybuprocaine eyedrops for analgesia in paediatric strabismus surgery.

Forty children undergoing strabismus surgery as day patients were randomly allocated to receive oxybuprocaine 0.4% eyedrops or 0.1% diclofenac eyedrops for perioperative analgesia. A non-invasive anaesthetic technique using the reinforced laryngeal mask airway was used. The study demonstrated that both topical analgesics provided good to excellent analgesia and the anaesthetic technique was associated with a relatively low incidence of nausea and vomiting. Complications were limited to two children who were admitted with persistent postoperative nausea and vomiting.

Diclofenac vs oxybuprocaine eyedrops for analgesia in paediatric strabismus surgery.

Forty children undergoing strabismus surgery as day patients were randomly allocated to receive oxybuprocaine 0.4% eyedrops or 0.1% diclofenac eyedrops for perioperative analgesia. A non-invasive anaesthetic technique using the reinforced laryngeal mask airway was used. The study demonstrated that both topical analgesics provided good to excellent analgesia and the anaesthetic technique was associated with a relatively low incidence of nausea and vomiting. Complications were limited to two children who were admitted with persistent postoperative nausea and vomiting.

A new hinged tip laryngoscope.

The McCoy laryngoscope undoubtedly improves the view of the vocal cords during difficult tracheal intubation. An inherent design problem with the McCoy blade is the need to relax the grip on the laryngoscope handle at the point when stability is most necessary. A new hinged tip blade is described which is operated by a button mechanism on a secondary handle that runs adjacent to the standard handle. This modification offers the possibility of better stability and ease of manipulation whilst maintaining all the benefits of the McCoy blade.