Investigating flow mechanisms in a forest soil by mixed‐effects modelling

Uniform and preferential flow produces typical infiltration patterns. We made three tracer experiments in a Norway spruce forest soil and qualitatively identified the dominant flow regime based on stained patterns. We analysed soil texture, fine root density and soil bulk density from preferential flow paths and the soil matrix by means of linear mixed‐effects models. These models can account for dependences in the data structure caused by hierarchical sampling and can deal with missing values. There were between 44% (topsoil) and 76% (subsoil) larger root densities in preferential flow paths than in the soil matrix. No significant differences in soil texture were detected. The bulk density was greater in the soil matrix by 0.12 g cm⁻³, which is probably because of a greater soil organic matter content of preferential flow paths. Using flow patterns and model results we identified the dominant flow mechanisms. At this study site, roots constituted the main preferential flow paths and induced macropore flow, especially in the topsoil. In the subsoil, root density decreased and inhomogeneous infiltration from preferential flow paths into the soil matrix caused unstable flow.     

Liquid chromatographic determination of zearalenone and zearalenol in animal feeds and grains, using fluorescence detection

A liquid chromatographic (LC) method was developed for the determination of zearalenone and zearalenol in grains and mixed animal feeds. Samples are extracted with chloroform and purified by a base-acid liquid-liquid partition. Zearalenone and zearalenol are separated by reverse phase LC and determined by fluorescence detection, excitation wavelength 236 nm with a 418 nm cutoff filter. The method was applied to the determination of zearalenone and zearalenol in 395 survey samples of corn, oats, barley, sorghum, silage, and finished feeds. The limit of detection is 10 ng/g for both toxins. The range of naturally occurring toxins found was 10-4,000 ng/g. Average recoveries were 84% for zearlenone and 69% for zearalenol. Coefficients of variation were 24.6% for zearalenone and 30.8% for zearalenol for crop year 1980, and 28.3% for zearalenone and 22.0% for zearalenol for crop year 1981.     

Effects of experimental drought on the fine root system of mature Norway spruce

Norway spruce (Picea abies (L.) Karst.) is an economically important, but relatively drought-sensitive tree species that might suffer from increasing drought intensities and frequencies, which are predicted to occur in parts of central Europe under future climatic change. In a throughfall exclusion experiment using sub-canopy roofs, we tested the hypothesis that enhanced drought leads to an increase in fine root mortality, and also to a higher, subsequent fine root growth. Fine root production and mortality were assessed using two independent approaches, sequential soil coring (organic layer) and direct observations in minirhizotrons (organic layer plus upper mineral soil). Six weeks of throughfall exclusion resulted in mild drought stress, i.e. a reduction in average soil moisture from 20 to 12 vol.% during the treatment. Based on the sequential coring data, experimental drought did not result in significant changes in fine root biomass during the 6-week treatment period, but caused an increase in fine root mortality by 61% in the 6 weeks following the drought treatment. Remarkably, fine root production showed a synchronous increase in this period, which more than compensated for the loss due to increased mortality. The minirhizotron data confirmed that the drought treatment increased fine root loss in the organic layer. Based on this method, however, root loss occurred during the drought period and was not compensated by increased root production. The mild drought stress was mainly restricted to the organic layer and did not significantly influence fine root dynamics in the mineral soil. We calculated that the drought event resulted in an extra input of about 28 g C m⁻² and 1.1 g N m⁻² to the soil due to increased fine root mortality. We conclude that even periods of mild drought significantly increase fine root mortality and the associated input of root-derived C to the soil organic matter pool in temperate Norway spruce forests.     

Effects of experimental soil frost on the fine‐root system of mature Norway spruce

Soil‐frost events may influence the dynamics of fine roots and therefore affect root‐derived C fluxes to the soil. We studied the impact of soil frost on the fine‐root dynamics of Norway spruce (Picea abies [L.] Karst.) by a replicated snow‐removal experiment in a mature forest in SE Germany. Snow removal in the three treatment plots reduced soil temperature significantly with minima <–5.5°C in the O layer while the snow‐covered control plots never reached temperatures below the freezing point. Sequential soil coring in the O layer at the beginning and at the end of the soil‐frost period as well as after thawing revealed that the soil frost treatment increased fine‐root mortality by 29%. However, enhanced fine‐root production in the snow‐removal plots nearly compensated for the fine‐root losses caused by low temperatures. These findings were confirmed by minirhizotron observations in the O layer and the upper 25 cm of the mineral soil showing that relative fine‐root loss was by far higher in the snow‐removal plots than in the control plots. Compensatory fine‐root production in the snow‐removal plots exceeded fine‐root production in the control plots during a period of 8 weeks after the soil frost application by 39% in the O layer while it was similar in both plot types in the mineral soil. Sequential coring and minirhizotron observations led to substantially different fine root–longevity estimates for the soil frost period. However, in both cases, the snow‐removal treatment was characterized by a significant reduction in root longevity indicating a faster fine‐root turnover. As a consequence, experimental soil frost enhanced the C input to the soil via root death at our study site by approx. 42 g m^–2 and stimulated the C investment towards the root system of the spruce trees due to a higher sink activity.     

Present aspects of induced mutations in plant breeding

The present status of the utilization of induced mutations in plant breeding is briefly reviewed. It is concluded that with induced mutations in principle successes can be expected similar to those with the conventional breeding methods. Owing to the relatively small yield of progressive mutations the efficiency of mutation breeding, however, is rather poor at present. Greater efficiency may be expected with increased knowledge of both control of original mutation production and of selection.Control of mutation production seems to be possible in at least three ways, (a) by raising the total mutation frequency (b) by changing the relative frequency of chromosome versus point mutations and (c) by altering the spectrum of point mutations. The possibilities of such control through the diverse action of different radiations given with or without modifying agents is reviewed and various mutagenic chemicals are mentioned.Control of mutation selection may be achieved in two ways, (a) by a better understanding of diplontic selection (intrasomatic selection) of mutated cells and (b) by developing appropriate screening methods. A working hypothesis concerning the diplontic selection is briefly outlined. The one initial cell theory means that the greatest efficiency of mutation production can be expected after radiation of primordia or young buds with only one or a few initial cells which will form the tissue of interest. It is hoped that by this the intercellular competition is restricted and a reduced elimination of mutated cells will result.Procedures for selection of mutants, at least in barley, can already start with M₁-spikes. It was shown that completely fertile M₁-spikes possess the same frequency of point mutations (chlorophyll mutations) as those with disturbed fertility. Selection of fertile M₁-spikes should, therefore, eliminate to a large extent the undesirable chromosome mutations and in this way increase the efficiency of screening for progressive mutations. Maximum mutation frequencies of fertile M₁-spikes can, however, only be achieved if the tillering is reduced.It is suggested that more emphasis be put on screening of small mutations, which may generally be expected to have a greater importance for practical purposes than drastic deviations. Usually screening of micro vital-mutations will be advisable in the M₃-generation. Indicator characters may be found through mass selection methods which by their pleiotropic gene action also effect properties eventually of breeding value.Samenvatting Na een kort overzicht van de perspectieven voor toepassing van kunstmatige mutatie bij de plantenveredeling wordt nader ingegaan op enige problemen die thans de aandacht hebben. Voor het beheersen van de kunstmatige mutaties is het van veel belang de frequentie van mutatie te kunnen vergroten en te kunnen bevorderen dat relatief minder chromosoom- en meer gen-mutaties tot stand komen. Vooral van de micromutaties verwacht schrijver vooruitzichten voor de plantenveredeling. Het is echter thans nog zeer moeilijk daarop te selecteren.(Lecture delivered at the organizational meeting of the section Mutation and Polyploidy of EUCARPIA in Lund and Svalöf, July 9–11, 1958).     

Charge separation in a reaction center incorporating bacteriochlorophyll for photoactive bacteriopheophytin

Site-directed mutagenic replacement of M subunit Leu214 by His in the photosynthetic reaction center (RC) from Rhodobacter sphaeroides results in incorporation of a bacteriochlorophyll molecule (BChl) in place of the native bacteriopheophytin (BPh) electron acceptor. Evidence supporting this conclusion includes the ground-state absorption spectrum of the (M)L214H mutant, pigment and metal analyses, and time-resolved optical experiments. The genetically modified RC supports transmembrane charge separation from the photoexcited BChl dimer to the primary quinone through the new BChl molecule, but with a reduced quantum yield of 60 percent (compared to 100 percent in wild-type RCs). These results have important implications for the mechanism of charge separation in the RC, and rationalize the choice of (bacterio)pheophytins as electron acceptors in a variety of photosynthetic systems.     

Role of the New South Wales Department of Primary Industries' Laboratory Information Management System (LIMS) in the 2007 equine influenza emergency animal disease response

A Laboratory Information Management System (LIMS) was used to manage the laboratory data and support planning and field activities as part of the response to the equine influenza outbreak in Australia in 2007. The database structure of the LIMS and the system configurations that were made to best handle the laboratory implications of the disease response are discussed. The operational aspects of the LIMS and the related procedures used at the laboratory to process the increased sample throughput are reviewed, as is the interaction of the LIMS with other corporate systems used in the management of the response. Outcomes from this tailored configuration and operation of the LIMS resulted in effective provision and control of the laboratory and laboratory information aspects of the response. The extent and immediate availability of the information provided from the LIMS was critical to some of the activities of key operatives involved in controlling the response.     

Evaluation of current and novel protocols for disinfection of airplane passenger footwear under simulated conditions

Aerobic bacterial culture was used to compare the effectiveness of the current USDA footwear disinfection protocol for airplane passengers contacting livestock to a novel protocol. The current protocol consists of brushing and dipping shoe soles in 1% Virkon S. The number of bacteria was not different between shoes treated with the current protocol and untreated shoes. No shoes met the standard for disinfection after the current disinfection protocol was completed. The novel protocol consisted of brushing shoe soles, wiping soles with a cotton towel soaked in 1% Virkon S, and drying soles with paper towels. The number of bacteria was less (P<0.0001) on treated shoes compared to control shoes. Eighteen of 20 shoes (90%) cleaned using the novel protocol met the standard for disinfection. Direct comparison of the current and novel protocols found that the number of bacteria cultured was less (P<0.0001) after implementing the novel protocol compared to implementing the current protocol. Again, no shoes treated using the current protocol met the standard for disinfection after the current protocol was completed. Sixteen and 17 of 20 shoes (80--85%), respectively, met the standard for disinfection after the novel protocol was completed. Under conditions of this study, current US airport footwear disinfection protocols were inadequate to disinfect footwear when using aerobic bacteria as a marker for disinfection. We recommend implementation of the novel footwear disinfectant protocol for select passengers from international flights.     

Effect of diets containing sulfate or chloride-based anionic salts,fed to grazing prepartum dairy cows,on concentrations of Ca in plasma,disease incidence and milk yield

AIMS: To compare the effect of two partial mixed ration diets containing either sulfate or chloride-based anionic salts, fed to grazing prepartum dairy cows, on concentrations of Ca, Mg, P and beta-hydroxybutyrate (BHB) in plasma, disease incidence and milk yield during the early postpartum period.

METHODS: The study was conducted on a seasonal-calving grazing dairy farm located in Benton (MO, USA). In August 2016, two groups of 200 cows were randomly assigned at 30 days before expected parturition to receive either a sulfate or chloride-based anionic diet, to achieve a dietary cation–anion difference (DCAD) of ?25?mEq/kg DM. Cows were fed partial mixed rations to provide 50% of their DM intake, with 50% provided by grazing fescue pasture. Urine samples were collected from 20 cows from each group once a week for 5 weeks until calving for pH assessment. At parturition, 42 cows per group were selected at random and blood samples collected on Days 1, 2, 3 and 7 postpartum. The study continued until 100 cows per group calved. Health events and cumulative milk yield until 30 days postpartum were recorded. Concentrations of Ca, P, and Mg in plasma at Days 1, 2, 3, and 7, and BHB in plasma at Day 7 postpartum were assessed.

RESULTS: Mean urine pH was lower in cows in the chloride than sulfate group (p≤0.06) on four of five sampling occasions. Mean concentrations of Ca in plasma on Day 1 were 2.00 (95% CI=1.94–2.05) and 1.91 (95% CI=1.88–1.97) mmol/L for the chloride and sulfate groups, respectively (p=0.15), and on Day 3 were 2.03 (95% CI=1.97–2.08) and 1.90 (95% CI=1.84–1.96) mmol/L, respectively (p=0.038). Concentrations of Mg, P and BHB in plasma and incidence of diseases postpartum were similar in both groups (p>0.05). There were no cases of clinical hypocalcaemia in either group.

CONCLUSIONS AND CLINICAL RELEVANCE: Prepartum cows fed a partial mixed ration with a negative DCAD containing chloride-based anionic salts and free access to a fescue pasture had lower prepartum urine pH, and higher concentrations of total Ca in plasma during the first week postpartum, than cows receiving a partial mixed ration containing sulfate-based anionic salts.