Cool-Season Floodplain Meadow Responses to Shrub Encroachment in Alberta

This study evaluated the impact of shrub encroachment within cool-season floodplain meadows in a portion of the Rocky Mountain Forest Reserve in southwestern Alberta, where nearly half of open grasslands have been lost since 1958. Sample transects situated in meadows, known formerly to be in open grassland, were assessed in 2001 (n = 21) and 2002 (n = 33) in areas ranging from 0% to 92% shrub cover. Shrub cover, density, and height were correlated to understory parameters, including herbaceous production, bunchgrass cover and density, and species richness and diversity. Additional data on soil horizon depths were obtained. Analysis was conducted using regression to assess empirical relationships between understory or soil characteristics and the overstory. Stronger empirical relationships (i.e., greater R²) were found in 2002, coincident with larger sample sizes and greater rainfall. Among independent overstory variables, aggregate shrub cover for all species accounted for the greatest variation in understory characteristics. Significant (P < 0.01) negative nonlinear relationships were observed between shrub cover and herbage production, with the latter declining from 6 629 kg · ha^–1 in meadows containing less than 12% shrub cover, to 2 797 kg · ha^–1 in areas where shrub cover exceeded 35%. Negative linear trends were found (P < 0.01) for bunchgrass density and cover in relation to increasing shrub abundance in 2002. Understory diversity increased with shrub abundance, peaking at 64% shrub cover in 2002. Meadows with low and high shrub cover also coincided with thicker Ah and litter, fibric, and humic soil layer (LFH) horizons, respectively. Collectively, these results indicate shrub encroachment is threatening the sustainability of native bunchgrass communities and reducing forage availability. Meadow conservation in this area will require proactive management to protect or restore open grasslands.     

Effect of variety choice, resistant rootstocks and chitin soil amendments on soil-borne diseases in soil-based, protected tomato production systems

Soil-borne diseases are the most significant crop protection problem in soil-based, low-input and especially organic glasshouse production systems in Europe. While chemical soil disinfestation has been the control method of choice in conventional farming systems, soil steaming has been the main strategy for the control of soil-borne diseases in organic production. Both methods are extremely expensive and have been increasingly restricted for environmental reasons by governments, and integrated and organic farming standard-setting bodies. The use of disease-tolerant varieties, grafting onto resistant rootstocks and chitin soil amendments were evaluated as potential replacements for soil steaming in organic and other low-input tomato production systems. When only Pyrenochaeta lycopersici and/or Meloidogyne spp. were present in soil, grafting and/or chitin soil amendment were found to be as effective in reducing root disease and/or increasing yield as soil steaming, but the efficacy of both treatments was reduced when Verticillum albo-atrum was also present in soil. No additive effects of combining grafting and chitin soil amendments could be detected. A more widespread use of grafting and/or chitin soil amendments may therefore allow significant reductions in the use of steam and chemical soil disinfestation in glasshouse crops. It will also allow integrated and organic farming standard-setting bodies to impose further restrictions on the use of soil disinfestation treatments.     

Growth of Western Australian corals in the anthropocene

Anthropogenic increases of atmospheric carbon dioxide lead to warmer sea surface temperatures and altered ocean chemistry. Experimental evidence suggests that coral calcification decreases as aragonite saturation drops but increases as temperatures rise toward thresholds optimal for coral growth. In situ studies have documented alarming recent declines in calcification rates on several tropical coral reef ecosystems. We show there is no widespread pattern of consistent decline in calcification rates of massive Porites during the 20th century on reefs spanning an 11° latitudinal range in the southeast Indian Ocean off Western Australia. Increasing calcification rates on the high-latitude reefs contrast with the downward trajectory reported for corals on Australia's Great Barrier Reef and provide additional evidence that recent changes in coral calcification are responses to temperature rather than ocean acidification.     

Reducing interactions between seabirds and trawl fisheries: Responses to foraging patches provided by fish waste batches

Seabird bycatch in trawl fisheries is driven by the attraction of birds to foraging opportunities, i.e., the discharge of catch processing waste and the contents of trawl nets. The risk of seabird captures increases with seabird abundance and exposure to fishing gear. We investigated (1) how quickly seabirds responded to discharges of trawl catch processing waste and (2) whether decreasing numbers of seabirds attended trawlers during processing waste discharge events as the time interval between these events increased. Waste was retained onboard the vessel for four different holding periods (30 min, 2 h, 4 h, 8 h), one of which was applied each day using a randomised block design. We determined seabird responses to batch discharge events after the prescribed holding periods using the abundance of large (albatrossses and giant petrels Macronectes spp.) and small (all other petrels except cape petrels Daption capense, shearwaters and prions) seabirds in a semi-circle of 40 m radius, centred on the stern of the experimental trawler. Seabird responses reflected the type of discharge released: birds moved from the air to the water, as the amount of food available increased from no discharge, through sump discharge to batch discharge. When discharge occurred, seabird abundance increased faster than could be resolved with the 5 min sampling period. However, abundance decreased more slowly over a 10-15 min period after the discharge event. The number of large seabirds attending the vessel during discharge events decreased significantly when waste was held for 4 h. For small birds, significant decrease occurred after 8 h. Such holding periods emphasise the tenacity of foraging seabirds, although we have not evaluated any long-term habituation to a particular discharge regime. While holding waste for less than 4 h may not reduce seabird attendance during discharge events, holding for shorter intervals can still reduce bycatch risk, e.g., prior to and during net shooting and hauling.     

Decomposition of aspen leaf litter results in unique metabolomes when decomposed under different tree species

We examined whether the decomposition rate of trembling aspen (Populus tremuloides) leaf litter differed when decomposed for one year in litter bags placed within adjacent monotypic stands of trembling aspen, Engelmann spruce, and lodgepole pine trees in four replicate blocks in the San Juan mountains of Colorado, and whether they were metabolized into different metabolic byproducts. Mass loss was 6-8% lower in pine stands than in spruce or aspen stands, but this trend was not significant (p = 0.27). Water-soluble leaf litter metabolites were characterized using ultra-performance liquid chromatography coupled to a quadrapole time-of-flight mass spectrometer (UPLC-MS). Aspen leaf litter metabolomes were highly chemically complex; thousands of unique molecular features were identified in each sample. Although many of the molecular features were common to litter decomposed in all three forest types, we identified a subset of features that differed in abundance among the forest types. Our results suggest that the decomposer communities associated with each forest type not only affected the overall decomposition rate, but also produced many compounds in the diverse suite of metabolic byproducts at different rates, which could be an important control on the long-term sequestration of C in soil organic matter.     

Isotopic trophic guild structure of a diverse subtropical South American fish community

Characterization of food web structure may provide key insights into ecological function, community or population dynamics and evolutionary forces in aquatic ecosystems. We measured stable isotope ratios of 23 fish species from the Rio Cuareim, a fifth‐order tributary of the Rio Uruguay basin, a major drainage of subtropical South America. Our goals were to (i) describe the food web structure, (ii) compare trophic segregation at trophic guild and taxonomic scales and (iii) estimate the relative importance of basal resources supporting fish biomass. Although community‐level isotopic overlap was high, trophic guilds and taxonomic groups can be clearly differentiated using stable isotope ratios. Omnivore and herbivore guilds display a broader δ¹³C range than insectivore or piscivore guilds. The food chain consists of approximately three trophic levels, and most fishes are supported by algal carbon. Understanding food web structure may be important for future conservation programs in subtropical river systems by identifying top predators, taxa that may occupy unique trophic roles and taxa that directly engage basal resources.     

屋顶开闭自如结构坚固耐用新型温室亮相意大利

最近,一种新型温室出现在意大利,这在意大利园艺生产中心的地中海地区的利古里亚(Liguria)产生了很大反响. 参与新型温室项目的伽斯尼(Giancarlo Cassini)表示,这种新产品的正式投入使用具有历史意义.而这种设施的生产商--加拿大科拉沃设备公司(Cravo Equipment Ltd)的总裁理查德·沃伦布赖特(Richard Vollebregt)则详细介绍了新产品的特性.该新型温室的造价介于传统温室和塑料大棚之间.建造这座温室的地方,坡度达到了10%,科拉沃公司对此进行了专门的设计.     

In Vivo Transfection of Adult Eastern Oysters Crassostrea virginica

The eastern oyster Crassostrea virginica provides a commercially valuable industry along the eastern and Gulf coasts of the United States. Recently this industry has been damaged by disease problems, creating an interest in the use of gene transfer (transfection) to improve disease resistance. We transfected adult oysters with two genes, red-shifted green fluorescent protein ( rsGFP ), commonly used as a reporter gene, and the lytic peptide cecropin B ( cepB ), known to have antimicrobial properties. Oysters were transfected by injecting DNA mixed with SuperFect™ reagent (Qiagen Inc.) into the adductor muscle sinus. Oysters were assigned to three groups of 15: the first was injected with rsGFP complexed with transfecting reagent: the second was injected with cepB complexed with transfectlng reagent; and the third was injected with saline (control group). Hemolymph was collected at 4 and 10 d after injection. DNA was extracted for analysis by polymerase chain reaction (PCR), and hemocytes were examined by flow cytometry and fluorescence microscopy for detection of green fluorescence due to rsGFP expression. The rsGFP gene was detected by PCR in hemocytes from 14 of 15 oysters at day 4, and in 15 of 15 oysters at day 10. The cepB gene was detected by PCR in 12 of 15 oysters at day 4 and in 14 of 15 oysters at day 10. No oysters from the control group were positive for either gene at days 4 or 10. Green fluorescence was detected by flow cytometry at significantly higher levels ( P < 0.05) in oysters injected with rsGFP than in other oysters at day 4, but not at day 10. This report indicates the ability to introduce DNA into adult eastern oysters with subsequent gene expression. Future work will involve developing these techniques for enhanced disease resistance in oysters.