Radiation balance of an isolated holm oak tree (Quercus rotundifolia Lam.) in a mediterranean savannah-type woodland

In closed canopy forests the energy absorbed by the trees can be adequately estimated solely from the vertical radiation fluxes. However, in isolated or widely spaced trees this approach is no longer valid and radiation fluxes in all directions must be accounted for. An adequate estimate of the tree available energy is critical to model and calculate both interception losses and transpiration. Within a study where interception loss in a sparse evergreen oak woodland (montado) of Southern Portugal is evaluated and mod¬elled, the net amount of radiant energy absorbed by an isolated holm oak tree (Q) was measured under different radiation conditions. The measuring and calculating proce¬dure was based on the integration of the flux density of net radiation (Rn) at different points of a cylindrical surface (S) enclosing the tree crown. A set of 4 net radiome¬ters were used: one at a fixed position, on the top of the crown, and the remaining 3 mounted on a standing structure that could be moved around the tree to measure Rn fluxes through the inferior and lateral sides. Measurements of Q were made for 8 dif¬ferent days, during the first 3 months of 2006. Night time measurements of Rn were also done, but with the net radiometers at fixed positions around the tree. The meteoro¬logical conditions during the measurements included clear sky and cloudy days, some of which with light rain. Net radiation at the top of the crown accounted for about 72 % of the total energy absorbed by the tree, and this is reflected by the good linear fit between Q and Rn above the crown. Meteorological conditions seem to have some influence on this relationship, as suggested by the differences on the adjusted linear models when total, clear sky, cloudy or rainy data sets were used. The occurrence of rain tends to cause a slight increase in Q in comparison to dry conditions, for identical levels of Rn. Q also shows a strong linear response to solar radiation (Rs), given the dependence of net radiation upon short wave radiation. The same happens with the component of Q received by the top crown surface. However, energy absorbed lat¬erally is much less dependent on Rs, and the inferior component of Q is completely independent of solar radiation. Under conditions when rainfall interception is most likely to occur, i.e. cloudy/rainy days, the daily time-course of Q follows closely those of Rs and Rn, with a maximum of only 75 W m-2 (expressed per unit of leaf area). Similar maximum daily values were observed in other studies with different species but under similar weather conditions. During the night, net radiation should not have a significant spatial variability and Rn around the canopy should be relatively homo¬geneous. Accordingly, night time estimates of Q were obtained from measurements of Rn at fixed positions, which were considered representative of the Rn fluxes around the tree

Lead (Pb) concentrations in predatory bird livers 2010 and 2011: a Predatory Bird Monitoring Scheme (PBMS) report

The Predatory Bird Monitoring Scheme (PBMS; http://pbms.ceh.ac.uk/) is the umbrella project that encompasses the Centre for Ecology & Hydrology’s National Capability contaminant monitoring and surveillance work on avian predators. By monitoring sentinel vertebrate species, the PBMS aims to detect and quantify current and emerging chemical threats to the environment and in particular to vertebrate wildlife. Lead (Pb) is a highly toxic metal that acts as a non-specific poison affecting all body systems and has no known biological requirement. Sources of Pb in the environment include lead mining, the refining and smelting of lead and other metals, the manufacture and use of alkyl lead fuel additives, and the use of lead ammunition. The present study is the first two years of a PBMS monitoring programme to quantify the scale of exposure to [and associated risk from] Pb in predatory birds. The aim is to quantify the extent of exposure to lead [as assessed from liver residues] in two predatory bird species, the red kite (Mivus milvus) and the sparrowhawk (Accipiter nisus). The red kite is a scavenger and, as such, is particularly at risk from consumption of Pb ammunition in unretrieved game. Sparrowhawks prey predominantly upon live passerine birds that are unlikely to be shot in the UK; likely sources of exposure are diffuse Pb contamination although some individuals may also be exposed to Pb particles ingested by their prey. We also examined the liver Pb isotope ratios in to explore whether they can be used to ascribe likely sources of any Pb detected in the birds. Red kites had significantly higher Pb concentration than those measured in sparrowhawks but the majority of sparrowhawks and all the red kites had liver Pb concentrations below those thought to cause clinical and sub-clinical adverse effects in Falconiforme species. There was overlap in the liver Pb isotope ratios of red kites and sparrowhawks yet there was evidence of separation between the two species. There was also evidence of overlap with the isotope signature for coal and for Pb shot but the isotope signatures in the bird livers were distinct from that of petrol Pb. The Pb isotope pattern observed in the red kites and sparrowhawks in the current study may reflect the fact that liver Pb concentrations were low in the small sample of birds that were analysed and may have been a result of exposure to low-level, diffuse contamination.birds. Red kites had significantly higher Pb concentration than those measured in sparrowhawks but the majority of sparrowhawks and all the red kites had liver Pb concentrations below those thought to cause clinical and sub-clinical adverse effects in Falconiforme species. There was overlap in the liver Pb isotope ratios of red kites and sparrowhawks yet there was evidence of separation between the two species. There was also evidence of overlap with the isotope signature for coal and for Pb shot but the isotope signatures in the bird livers were distinct from that of petrol Pb. The Pb isotope pattern observed in the red kites and sparrowhawks in the current study may reflect the fact that liver Pb concentrations were low in the small sample of birds that were analysed and may have been a result of exposure to low-level, diffuse contamination

Leaf area estimation from tree allometrics in Eucalyptus globulus plantations

Data from five studies on the relationships between dendrometric measurements and leaf area of Eucalyptus globulus Labill. plantations were pooled and analyzed to develop regression models for the estimation of leaf area of individual trees. The data, collected at two sites in west-central and southwestern Portugal, varied in age from 2 to 19 years and in plant density from 481 to 1560 trees/ha and included both first and second rotation coppice stands. A total of 29 nonlinear regression models were tested and ranked with a multicriteria evaluation (MCE) procedure, based on goodness-of-fit statistics, predictive ability statistics, and collinearity diagnostics. The best models were validated using an independent data set. The final model selection was based on comparisons of prediction residuals data, statistical tests, and silvicultural and physiological considerations. One model is proposed as adequate for leaf area estimation of E. globulus plantation trees. This model contains four parameters and independent variables that quantify stem diameter, crown size, and stand density

The effect of drought on energy and water vapour exchange above a mediterranean C3/C4 grassland in Southern Portugal

We studied the seasonal and interannual variation in surface energy fluxes – net radiation (Rn), soil heat (G), sensible heat (H) and latent heat (lE) fluxes – and water vapour exchange above a Mediterranean C3/C4 grassland in Portugal, during two hydrological years, i.e., the period from 1 October to 30 September of the next year, of contrasting rainfall. The first year, 2004–2005, was dry, with total precipitation 45% below the long-term mean (669 mm), whereas the following, 2005–2006, was normal, with total precipitation only 12% above the long-term mean. Soil water availability and plant canopy growth were the most important factors in determining the seasonal and interannual variation in energy partitioning. During autumn, winter and early spring the ratio lE/Rn dominated over H/Rn, in the two years of the study, whereas on an annual basis, the major portion of Rn was consumed in H and lE in the dry and normal years, respectively. The total annual evapotranspiration (E) and its daily maximum were 316 mmand 2.8 mmper day, respectively, for the dry year, and 481mmand 4.5 mmper day for the normal year. After the senescence of the C3 species, the warm-season perennial C4 grass, Cynodon dactylon L., played a preponderant role in maintaining substantial E rates contributing to soil water depletion. In this study, we assessed the effects of the most relevant biophysical factors on surface conductance (gs) and E.We found that the Priestley–Taylor coefficient and gs were substantially reduced when the average volumetric soil moisture content in the top 15 cm of the soil profile dropped below 14%. With abundant soil moisture and leaf area index (LAI) greater than 1, the evaporative fractions (lE/Rn) were linearly related to LAI (R2 = 0.73). The decoupling coefficient (V) ranged from a maximum of about 0.7, under non-limiting soil moisture conditions, to a minimumof about 0.1, under soil moisture deficit. This suggests that E was strongly controlled by the vapour pressure deficit of the air and gs during the periods with limiting soil moisture

Investigation of Co(OH)2 formation during cobalt electrodeposition using a chemometric procedure

AbstractThe mechanism of Co electrodeposition in sulphate solutions containing boric acid was investigated using the EQCM technique and potentiostatic measurements. The effects of solution composition, temperature and deposition potential were studied using factorial design as a chemometric procedure. The boric acid was used as a buffer to prevent pH changes due to the hydrogen evolution reaction (HER) during electrodeposition. The results showed that Co(OH)2 was formed as a parallel reaction to metallic Co formation under some experimental conditions. The analysis of the factorial design revealed that temperature and [Co2+:H3BO3] molar ratio were the critical variables that affect the mechanism of cobalt electrodeposition. At high temperatures (48°C) and using a 5:1 molar ratio of [Co2+:H3BO3], the formation of cobalt hydroxide was detected simultaneously with cobalt deposition

WILDCOMS (Wildlife Disease & Contaminant Monitoring and Surveillance network) annual report 2013-2014

This is the third and final annual report from WILDCOMS, a Natural Environment Research Council collaborative Knowledge Exchange network between ten UK surveillance schemes that monitor disease and contaminants in wild vertebrates. The overall aim of the WILDCOMS network is to foster and facilitate knowledge exchange, harmonisation towards best practice and productive collaboration between: (i) partner organisations; (ii) surveillance schemes and end-users. WILDCOMS aims to facilitate development of a more cost-effective and integrated evidence base for assessing environmental disease and contaminant risk that will benefit end-users and underpin regulatory policy. This report describes the activities of the WILDCOMS network in the third year (2013-14) including an update in the communication tools (wiki, website, quarterly and annual reports for stakeholders) and activities, such as articles in specialised “in-house” publications of key stakeholders and presentations at national and international conferences. This report also describes the development of the inventory on “Specimen archiving” and the recording of the sharing activities across all partners’ schemes as well as between the partners and other organisations. WILDCOMS has met the original goals set out in the grant proposal that was supported by NERC funding. WILDCOMS has established itself as a Knowledge Exchange network with a website that has up to 2000 visits per month and a mailing list of 484 stakeholders to date. The establishment of the network has facilitated greater collaboration and sharing of resources between WILDCOMS partners and has become a point of contact for organisations seeking advice in a wide range of wildlife pollution and disease issues. We have had very successful meetings with stakeholders in England (2012) and Scotland (2013). The funding for WILDCOMS has ceased, but the network will continue to run, albeit with a limited range of activities

Aerodynamic conductances in a sparse mixed oak woodland (Quercus rotundifolia Lam. and Quercus suber L.)

The study of heat and mass exchange between the vegetation and its local environment plays a central role in the analysis of plant-atmosphere interactions. These studies can be undertaken at different scales, ranging from individual leaves to isolated trees or even the canopy scale. In each of these cases, heat and mass fluxes depend on the use of adequate values of transfer conductances. Within a broader study on interception loss from a sparse cork and holm oak woodland (montado) of Southern Portugal, aerodynamic conductances were determined for the boundary layers of both leaves (LBL) and the entire canopy

Reversing of seasonal patterns of carbon uptake in an eucalyptus stand in Portugal after drought and felling

This paper summarizes results between 2002 and 2010 from eddy covariance measurements of carbon uptake in the 12 month annual growing period eucalypt site of Espirra in Southern Portugal (38° 38’N, 8° 36’ W) . This site, aimed for pulp production is part of an intensively 300 ha eucalypt coppice, with about 1100 trees ha–1. The climate is of Mediterranean type. During the measurement period (2002-2010) two main events changed the annual sink pattern of the forest: a drought period of two years (2004-2005) and a tree felling (November and December 2006). Before the felling, annual net ecosystem exchange (NEE) diminished from 865.56 gCm–2 in 2002 to 356.64 gCm–2 in 2005 together with a deep decrease in rainfall from 748 mm in 2002 to 378.58 mm and 396.64 mm in 2004 and 2005, respectively. The eucalypt stand recovered its carbon sink ability in June 2007 with a cumulated NEE of 151 gCm–2 from January to September 2010. A quantitative approach using generalized estimating equations (GEEs) was made to relate monthly NEE, gross primary production (GPP) and soil moisture with the main meteorological variables. Seasonal patterns of carbon uptake were almost opposite in the periods before and after the felling with maxima in April and August, respectively, and this seasonal change is gradually reversing to the pattern before 2006. Drought was the main meteorological driver of these temporal tendencies in carbon uptake