Relationships between elm spanworm, Ennomos subsignaria, juvenile density and defoliation on mature sycamore maple in an urban environment

Using field surveys, we established sampling procedures for estimating defoliation resulting from elm spanworm, Ennomos subsignaria (Hübner) (Lepidoptera: Geometridae), feeding on mature sycamore maple, Acer pseudoplatanus L. (Aceraceae), in St. John's, Newfoundland and Labrador. We also determined whether densities of E. subsignaria eggs, egg masses, early- or late-instar larvae could predict the amount of defoliation at the end of the larval feeding period. Defoliation estimates acquired by sampling branches from only the lower, mid or upper crown explained ≥80% of the variation in tree-level defoliation, suggesting that density–defoliation relationships established using defoliation data from any crown level would also be useful for predicting tree-level defoliation. In linear regressions, egg and egg mass densities explained ≤20% of variation in defoliation and thus only provide a crude relative estimate of the amount of defoliation that will occur. Early- and late-instar larval density in the lower crown explained 53 and 29%, respectively, of the variation in defoliation in the lower crown, where defoliation levels were highest. Thus monitoring early-instar density in the lower crown should provide pest managers with reliable information for decisions regarding whether to apply suppression tactics while allowing enough time to implement these tactics, if necessary.     

Grassland yield response to knife/tine slurry injection equipment – benefit or crop damage?

Slurry injection into grassland has advantages as it decreases ammonia losses, but may harm grassland plants. In two field experiments, four different types of knife/tine equipment were tested on three different grassland species (monocultures of red clover, perennial ryegrass and red fescue), with or without added mineral nitrogen (N), but without slurry application. During 2 years, in two separate experiments, the injection treatments were applied in spring or in summer to different plots. Crop damage was assessed by a range of methods. It was concluded that both the timing and the design of the knife/injector equipment had a significant influence on yield when used in grassland, with the greatest decrease in yield after spring use. Mean total yield over 2 years (no treatment = 100) for timing and species, with N added, was 94 (vertical knife), 92 (vertical and horizontal knife), 96 (double disc tine) and 94 (tubulator tine). With no N added, the relative yield decrease caused by equipment was less. Red fescue seemed to be a little more sensitive than the other species at spring treatment in one of the 2 years. Leaf area index could be useful for measuring crop damage.     

The dynamics of biomass production in relation to foliar and root traits in a grey alder (Alnus incana (L.) Moench) plantation on abandoned agricultural land

The dynamics of the above-ground biomass production of a greyalder plantation on abandoned farmland was investigated during11 years after establishment. In the 12-year-old stand, thetotal biomass of the above-ground part of the stand was 68.8t dry matter (DM) ha^–1 and the current annual production(CAP) was 14.0 t DM ha^–1 year^–1. The predicted meanannual increment (MAI) reached is maximum at the age of 16 years,which indicates bulk maturity (the stand age when CAI = MAI)and appropriate rotation time for obtaining maximum biomassproduction. In the case of short-rotation forestry, initialstand density should not be higher than 6500–6000 treesper hectare. Below-ground biomass accounted for 18 and 16 percent of total stand biomass at a stand age of 5 and 10 years,respectively. The biomass of the nodules was estimated at 155± 63 kg DM ha^–1 and the biomass of the fine rootswas estimated at 870 ± 130 kg DM ha^–1 in the 10-year-oldgrey alder stand. Of the fine roots, 80 per cent and almostall nodules were located in the upper 0–20 cm soil layerin both the 5-year-old and the 10-year-old stand. The valueof leaf area index increased with stand age, ranging between1.38 and 5.43 m² m^–2 during the development of the stand.Specific leaf area varied in different years from 11.1 to 13.5m² kg^–1.     

Resistance of microbial and soil properties to warming treatment seven years after boreal fire

Boreal forests store a large fraction of global terrestrial carbon and are susceptible to environmental change, particularly rising temperatures and increased fire frequency. These changes have the potential to drive positive feedbacks between climate warming and the boreal carbon cycle. Because few studies have examined the warming response of boreal ecosystems recovering from fire, we established a greenhouse warming experiment near Delta Junction, Alaska, seven years after a 1999 wildfire. We hypothesized that experimental warming would increase soil CO₂ efflux, stimulate nutrient mineralization, and alter the composition and function of soil fungal communities. Although our treatment resulted in 1.20 °C soil warming, we found little support for our hypothesis. Only the activities of cellulose- and chitin-degrading enzymes increased significantly by 15% and 35%, respectively, and there were no changes in soil fungal communities. Warming resulted in drier soils, but the corresponding change in soil water potential was probably not sufficient to limit microbial activity. Rather, the warming response of this soil may be constrained by depletion of labile carbon substrates resulting from combustion and elevated soil temperatures in the years after the 1999 fire. We conclude that positive feedbacks between warming and the microbial release of soil carbon are weak in boreal ecosystems lacking permafrost. Since permafrost-free soils underlie 45-60% of the boreal zone, our results should be useful for modeling the warming response during recovery from fire in a large fraction of the boreal forest.     

Response of fungal and actinobacterial communities to water-level drawdown in boreal peatland sites

We used PCR-DGGE fingerprinting and direct sequencing to analyse the response of fungal and actinobacterial communities to changing hydrological conditions at 3 different sites in a boreal peatland complex in Finland. The experimental design involved a short-term (3 years; STD) and a long-term (43 years; LTD) water-level drawdown. Correspondence analyses of DGGE bands revealed differences in the communities between natural sites representing the nutrient-rich mesotrophic fen, the nutrient-poorer oligotrophic fen, and the nutrient-poor ombrotrophic bog. Still, most fungi and actinobacteria found in the pristine peatland seemed robust to the environmental variables. Both fungal and actinobacterial diversity was higher in the fens than in the bog. Fungal diversity increased significantly after STD whereas actinobacterial diversity did not respond to hydrology. Both fungal and actinobacterial communities became more similar between peatland types after LTD, which was not apparent after STD. Most sequences clustered equally between the two main fungal phyla Ascomycota and Basidiomycota. Sequencing revealed that basidiomycetes may respond more (either positively or negatively) to hydrological changes than ascomycetes. Overall, our results suggest that fungal responses to water-level drawdown depend on peatland type. Actinobacteria seem to be less sensitive to hydrological changes, although the response of some may similarly depend on peatland type.     

Chemical composition and nutritional quality of soybean meals prepared by extruder/expeller processing for use in poultry diets

This research examined variation in chemical composition and nutrient quality of soybeans (SBs) and soybean meals (SBMs) produced at seven commercial extruder/expeller plants in the United States (experiment 1), as well as differences in amino acid digestibilities when roosters were fed SBMs extruded at 121, 135, 150, or 160 degrees C at a U.S. pilot processing plant (experiment 2). In experiment 1, limited variation existed in the composition of SBs arriving at the plants, whereas substantial differences were noted in amino acid composition and protein quality of the resultant SBMs. In experiment 2, the SBMs extruded at 121 and 135 degrees C were underprocessed as noted by high urease activities and lower amino acid digestibilities. Soybean meals extruded at 150 and 160 degrees C resulted in higher amino acid digestibilities and lower urease activities, indicating adequate processing. Large variation exists in the nutritional quality of extruder/expeller SBMs currently in the marketplace. Optimal processing temperatures should be >135 degrees C, and temperatures as high as 165 degrees C do not result in overprocessing.     

Responses of sugar maple and hemlock seedlings to elevated carbon dioxide under altered above- and belowground nitrogen sources

Various human-induced changes to the atmosphere have caused carbon dioxide (CO?), nitrogen dioxide (NO?) and nitrate deposition (NO??) to increase in many regions of the world. The goal of this study was to examine the simultaneous influence of these three factors on tree seedlings. We used open-top chambers to fumigate sugar maple (Acer saccharum) and eastern hemlock (Tsuga canadensis) with ambient or elevated CO? and NO? (elevated concentrations were 760 ppm and 40 ppb, respectively). In addition, we applied an artificial wet deposition of 30 kg ha?1 year?1 NO?? to half of the open-top chambers. After two growing seasons, hemlocks showed a stimulation of growth under elevated CO?, but the addition of elevated NO? or NO?? eliminated this effect. In contrast, sugar maple seedlings showed no growth enhancement under elevated CO? alone and decreased growth in the presence of NO? or NO??, and the combined treatments of elevated CO? with increased NO? or NO?? were similar to control plants. Elevated CO? induced changes in the leaf characteristics of both species, including decreased specific leaf area, decreased %N and increased C:N. The effects of elevated CO?, NO? and NO?? on growth were not additive and treatments that singly had no effect often modified the effects of other treatments. The growth of both maple and hemlock seedlings under the full combination of treatments (CO??+?NO??+?NO??) was similar to that of seedlings grown under control conditions, suggesting that models predicting increased seedling growth under future atmospheric conditions may be overestimating the growth and carbon storage potential of young trees.     

Fine-root rhizosphere and morphological adaptations to site conditions in interaction with tree mineral nutrition in young silver birch (<Emphasis Type="Italic">Betula pendula</Emphasis> Roth.) stands

Limited nutrient acquisition from soil is a key process limiting productivity in boreal forest. We investigated short-root morphological adaptations and rhizosphere effect in relation to site conditions in interaction with tree mineral nutrition. We studied seven young (8- to 14-year-old) silver birch (Betula pendula Roth.) stands on abandoned agricultural land in Estonia. Soil pH varied from 3.8 to 7.0, and soil N % from 0.07 to 0.26%. Tree nutrient (NPK) status was expressed by leaf nutrient concentrations. Leaf N correlated negatively with short-root specific length and area. Summed activity (SA) and metabolic diversity of bacteria (by BIOLOG Ecoplate™), bacterial community diversity (by DGGE) and pH_KCl were determined for rhizosphere (R) and bulk soil (S) to reveal the extent of the rhizosphere effect. Bacterial activity in rhizosphere was 1.4–4.7 times higher than in bulk soil. Ratio SA_R/SA_S indicating root support to the rhizosphere bacterial communities decreased with increasing bulk soil pH; however, when bulk soil pH was ≥5, the decrease in SA_R/SA_S was insignificant, i.e. the rhizosphere effect stayed at a stable level. Diversity of bacterial community was 6% higher in bulk soil than in rhizosphere. Rhizosphere acidification occurred in studied stands when bulk soil pH_KCl ≥ 5. Short-root N % correlated positively with SA_R/SA_S. We concluded that tree N-nutritional status was related to short-root morphological parameters but not to studied microbiological characteristics in the soil of young silver birch stands.     

Pharmacokinetics of chloramphenicol base in horses and comparison to compounded formulations

Chloramphenicol is commonly used in horses; however, there are no studies evaluating the pharmacokinetics of veterinary canine‐approved tablets. Studies using different formulations and earlier analytical techniques led to concerns over low bioavailability in horses. Safety concerns about human health have led many veterinarians to prescribe compounded formulations that are already in suspension or paste form. The objective of this study was to evaluate the pharmacokinetics of approved chloramphenicol tablets in horses, along with compounded preparations. The hypothesis was that chloramphenicol has low absorption and a short half‐life in horses leading to low serum concentrations and that compounded preparations have lower relative bioavailability. Seven horses were administered chloramphenicol tablets (50 mg/kg orally). In a crossover design, they were administered two compounded preparations to compare all three formulations at the same dose (50 mg/kg). C_max was 5.25 ± 4.07 μg/ml at 4.89 hr, 4.96 ± 3.31 μg/ml at 4.14 hr, and 3.84 ± 2.96 μg/ml at 4.39 hr for the tablets, paste, and suspension, respectively. Elimination half‐life was 2.65 ± 0.75, 3.47 ± 1.47, and 4.36 ± 4.54 hr for tablets, paste, and suspension, respectively. The AUC_0→∞ was 17.93 ± 7.69, 16.25 ± 1.85, and 14.00 ± 5.47 hr*μg/ml for the tablets, compounded paste, and compounded suspension, respectively. Relative bioavailability of compounded suspension and paste was 78.1% and 90.6%. C_max after administration of all formulations did not reach the recommended MIC target of 8 μg/ml set by the Clinical Laboratory Standards Institute (CLSI) for most bacteria. Multidose studies are warranted, but the low serum concentrations suggest that bacteria with MIC values lower than CLSI recommendations should be targeted in adult horses.