Net ecosystem productivity of boreal aspen forests under drought and climate change: Mathematical modelling with Ecosys

The net ecosystem productivity (NEP) of boreal aspen is strongly affected by comparative rates of annual potential evapotranspiration (E_a) and precipitation (P_a). Changes in E_a versus P_a during future climate change will likely determine changes in aspen NEP and consequently the magnitude of the carbon sink/source of a significant part of the boreal forest. We hypothesize that the effects of E_a versus P_a on aspen NEP can be modelled with a soil–root–canopy hydraulic resistance scheme coupled to a canopy energy balance closure scheme that determines canopy water status and thereby CO₂ uptake. As part of the ecosystem model ecosys, these schemes were used to model diurnal declines in CO₂ and latent heat (LE) exchange during a 3-year drought (2001–2003) at the Fluxnet-Canada Research Network (FCRN) southern old aspen site (SOA). These declines were consistent with those measured by eddy covariance (EC) at SOA, except that ecosystem CO₂ effluxes modelled during most nights were larger that those measured by EC or gap-filled from other EC measurements. Soil CO₂ effluxes in the model were close to, but sometimes smaller than, those measured by automated surface chambers at SOA. Diurnal declines in CO₂ exchange during the drought caused declines in annual NEP in the model, and in gap-filled EC measurements (model versus EC in g C m⁻²: 275 versus 367 ± 110 in 2001, 82 versus 144 ± 43 in 2002 and 23 versus 104 ± 31 in 2003). Lower modelled NEP was attributed to the larger modelled CO₂ effluxes. Ecosys was then used to predict changes in aspen net biome productivity (NBP = NEP − C lost from disturbance) caused by 6-year versus 3-year recurring droughts during 100-year fire cycles under current climate versus climate change projected under the IPCC SRES A1B scenario. Although NBP was adversely affected during recurring 6-year droughts under current climate, it recovered quickly during non-drought years so that long-term NBP was maintained at 4 g C m⁻² year⁻¹. NBP rose by 10, 108 and 126 g C m⁻² year⁻¹ during the first, second and third centuries under climate change with recurring 3-year droughts, indicating a gradual rise in sink activity by boreal aspen. However recurring 6-year droughts during climate change caused recurring negative NBP (C losses), gradually depleting aspen C reserves and eventually causing dieback of the aspen overstory during the third century of climate change. This dieback was followed by a large decline in NBP.We conclude that NBP of boreal aspen will rise gradually under current projections of climate change, except under prolonged (e.g. 6 years) recurring droughts, which would eventually cause aspen to die back and substantial amounts of C to be lost.     

Direct and indirect effects of Johne's disease on farm and animal productivity in an Irish dairy herd

Johne's disease (JD) is caused by infection with the organism Mycobacterium avium spp. paratuberculosis, leading to chronic diarrhoea and ill thrift in adult cattle. JD is considered to adversely affect farm performance and profitability. This retrospective case study was undertaken on a single commercial dairy herd in the south west of Ireland. Animal production records were interrogated to assess the effect of JD on milk yield (total kg per lactation), somatic cell count (the geometric mean over the lactation), reasons for culling, cull price and changes in herd parity structure over time. JD groups were defined using clinical signs and test results. One control animal was matched to each case animal on parity number and year. Specific lactations (clinical, pre-clinical and test-positive only) from 1994 to 2004 were compared between JD case and control cows. A significantly lower milk yield (1259.3 kg/lactation) was noted from cows with clinical JD in comparison to their matched control group. Clinical animals had an average cull price of €516 less than animals culled without signs of clinical disease. In contrast, little effect was noted for sub-clinical infections. These direct effects of JD infections, in combination with increased culling for infertility and increasing replacement rates, had a negative impact on farm production. Results from this study provide preliminary information regarding the effects of JD status on both herd and animal-level performance in Ireland.     

Evapotranspiration and water use efficiency in different-aged Pacific Northwest Douglas-fir stands

We used the eddy-covariance technique to measure evapotranspiration (E) and gross primary production (GPP) in a chronosequence of three coastal Douglas-fir (Pseudotsuga menziesii) stands (7, 19 and 58 years old in 2007, hereafter referred to as HDF00, HDF88 and DF49, respectively) since 1998. Here, we focus on the controls on canopy conductance (g_c), E, GPP and water use efficiency (WUE) and the effect of interannual climate variability at the intermediate-aged stand (DF49) and then analyze the effects of stand age following clearcut harvesting on these characteristics. Daytime dry-foliage Priestley–Taylor α and g_c at DF49 were 0.4–0.8 and 2–6 mm s^?1, respectively, and were linearly correlated (R² = 0.65). Low values of α and g_c at DF49 as well at the other two stands suggested stomatal limitation to transpiration. Monthly E, however, showed strong positive linear correlations to monthly net radiation (R² = 0.94), air temperature (R² = 0.77), and daytime vapour pressure deficit (R² = 0.76). During July–September, monthly E (mm) was linearly correlated to monthly mean soil water content (θ, m³ m^?3) in the 0–60 cm layer (E = 453θ ? 21, R² = 0.69), and GPP was similarly affected. Annual E and GPP of DF49 for the period 1998–2007 varied from 370 to 430 mm and from 1950 to 2390 g C m^?2, respectively. After clearcut harvesting, E dropped to about 70% of that for DF49 while ecosystem evapotranspiration was fully recovered when stand age was ～12 years. This contrasted to GPP, which varied hyperbolically with stand age. Monthly GPP showed a strong positive linear relationship with E irrespective of the stand age. While annual WUE of HDF00 and HDF88 varied with age from 0.5 to 4.1 g C m^?2 kg^?1 and from 2.8 to 4.4 g C m^?2 kg^?1, respectively, it was quite conservative at ～5.3 g C m^?2 kg^?1 for DF49. N-fertilization had little first-year response on E and WUE. This study not only provides important results for a more detailed validation of process-based models but also helps in predicting the influences of climate change and forest management on water vapour and CO₂ fluxes in Douglas-fir forests.     

The status of the world's land and marine mammals: diversity, threat, and knowledge

Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action.     

Spectral Properties of Near-Earth Asteroids: Evidence for Sources of Ordinary Chondrite Meteorites

Although ordinary chondrite (OC) meteorites dominate observed falls, the identification of near-Earth and main-belt asteroid sources has remained elusive. Telescopic measurements of 35 near-Earth asteroids ( approximately3 kilometers in diameter) revealed six that have visible wavelength spectra similar to laboratory spectra of OC meteorites. Near-Earth asteroids were found to have spectral properties that span the range between the previously separated domains of OC meteorites and the most common (S class) asteroids, suggesting a link. This range of spectral properties could arise through a diversity of mineralogies and regolith particle sizes, as well as through a time-dependent surface weathering process.     

Pharmacokinetics of meloxicam in koalas (Phascolarctos cinereus) after intravenous,subcutaneous and oral administration

The pharmacokinetic profile of meloxicam in clinically healthy koalas (n = 15) was investigated. Single doses of meloxicam were administered intravenously (i.v.) (0.4 mg/kg; n = 5), subcutaneously (s.c.) (0.2 mg/kg; n = 1) or orally (0.2 mg/kg; n = 3), and multiple doses were administered to two groups of koalas via the oral or s.c. routes (n = 3 for both routes) with a loading dose of 0.2 mg/kg for day 1 followed by 0.1 mg/kg s.i.d for a further 3 days. Plasma meloxicam concentrations were quantified by high‐performance liquid chromatography. Following i.v. administration, meloxicam exhibited a rapid clearance (CL) of 0.44 ± 0.20 (SD) L/h/kg, a volume of distribution at terminal phase (V_z) of 0.72 ± 0.22 L/kg and a volume of distribution at steady state (V_ss) of 0.22 ± 0.12 L/kg. Median plasma terminal half‐life (t_1/2) was 1.19 h (range 0.71–1.62 h). Following oral administration either from single or repeated doses, only maximum peak plasma concentration (C_max 0.013 ± 0.001 and 0.014 ± 0.001 μg/mL, respectively) was measurable [limit of quantitation (LOQ) >0.01 μg/mL] between 4–8 h. Oral bioavailability was negligible in koalas. Plasma protein binding of meloxicam was ~98%. Three meloxicam metabolites were detected in plasma with one identified as the 5‐hydroxy methyl derivative. This study demonstrated that koalas exhibited rapid CL and extremely poor oral bioavailability compared with other eutherian species. Accordingly, the currently recommended dose regimen of meloxicam for this species appears inadequate.     

Clinical pathology of Australian bluetongue virus serotype 16 infection in Merino sheep

SUMMARY Viraemic blood from an ox naturally infected with Australian bluetongue (BLU) virus serotype 16 was passaged twice in sheep. Twelve 2- to 4-years-old Merino ewes, negative in a bluetongue agar gel Immunodiffusion test, were Inoculated with viraemic blood from the second sheep passage. They were examined for 18 days and compared with a control group. Significant changes in haematological measurements, namely packed cell volume, total white cell count and lymphocyte count, and in plasma enzyme concentrations, namely aspartate transaminase and creatine kinase, occurred in the infected sheep. All Infected sheep became sick. The antibody response, and clinical and necropsy findings were consistent with other reports of mild to moderate disease with Australian BLU serotypes.     

GRASSLAND FERTILIZER PRACTICE AND HYPOMAGNESAEMIA

The effects of N and K fertilizers on the yield and chemical composition of herbage and the serum Mg and Ca levels of grazing ruminants were investigated, using 64 lactaling ewes in a 4x4 Latin square arrangement of plots. During the 2-year experiment there was no evidence that application of N alone has a depressing effect on the Mg content of either herbage or blood serum. The sheep grazing plots treated with combined N and K fertilizer had significantly (P<0·01) lower serum Mg levels during the early spring grazing period of 1961. It is suggested that individual variability within a group of animals may considerably influence the results of investigations of this kind.