Effect of Chronic Nitrogen Additions on Soil Nitrogen Fractions in Red Spruce Stands

The responses of temperate and boreal forest ecosystems to increased nitrogen (N) inputs have been varied, and the responses of soil N pools have been difficult to measure. In this study, fractions and pool sizes of N were determined in the forest floor of red spruce stands at four sites in the northeastern U.S. to evaluate the effect of increased N inputs on forest floor N. Two of the stands received 100 kg N ha^-1 yr^-1 for three years, one stand received 34 kg N ha^-1 yr^-1 for six years, and the remaining stand received only ambient N inputs. No differences in total N content or N fractions were measured in samples of the Oie and Oa horizons between treated and control plots in the three sites that received N amendments. The predominant N fraction in these samples was amino acid N (31-45% of total N), followed by hydrolyzable unidentified N (16-31% of total N), acid-soluble N (18-22% of total N), and NH₄ ⁺ (9^-13% of total N). Rates of atmospheric deposition varied greatly among the four stands. Ammonium N and amino acid N concentrations in the Oie horizon were positively related to wet N deposition, with respective r2 values of 0.92 and 0.94 (n = 4, p < 0.05). These relationships were somewhat stronger than that observed between atmospheric wet N deposition and total N content of the forest floor, suggesting that these pools retain atmospherically deposited N. The NH₄ ⁺ pool may represent atmospherically deposited N that is incorporated into organic matter, whereas the amino acid N pool could result from microbial immobilization of atmospheric N inputs. The response of forest floor N pools to applications of N may be masked, possibly by the large soil N pool, which has been increased by the long-term input of N from atmospheric deposition, thereby overwhelming the short-term treatments.     

Critically examining the knowledge base required to mechanistically project climate impacts: A case study of Europe's fish and shellfish

An amalgam of empirical data from laboratory and field studies is needed to build robust, theoretical models of climate impacts that can provide science‐based advice for sustainable management of fish and shellfish resources. Using a semi‐systematic literature review, Gap Analysis and multilevel meta‐analysis, we assessed the status of empirical knowledge on the direct effects of climate change on 37 high‐value species targeted by European fisheries and aquaculture sectors operating in marine and freshwater regions. Knowledge on potential climate change‐related drivers (single or combined) on several responses (vital rates) across four categories (exploitation sector, region, life stage, species), was considerably unbalanced as well as biased, including a low number of studies (a) examining the interaction of abiotic factors, (b) offering opportunities to assess local adaptation, (c) targeting lower‐value species. The meta‐analysis revealed that projected warming would increase mean growth rates in fish and mollusks and significantly elevate metabolic rates in fish. Decreased levels of dissolved oxygen depressed rates of growth and metabolism across coherent species groups (e.g., small pelagics, etc.) while expected declines in pH reduced growth in most species groups and increased mortality in bivalves. The meta‐analytical results were influenced by the study design and moderators (e.g., life stage, season). Although meta‐analytic tools have become increasingly popular, when performed on the limited available data, these analyses cannot grasp relevant population effects, even in species with a long history of study. We recommend actions to overcome these shortcomings and improve mechanistic (cause‐and‐effect) projections of climate impacts on fish and shellfish.     

Inflammatory bowel disease characterized by multisystemic eosinophilic epitheliotropic disease (MEED) in a horse in Saskatchewan,Canada

A 3-year-old Quarter Horse gelding was evaluated for chronic weight loss, diarrhea, and pruritus. Physical examination revealed several ulcerative lesions on the skin and mucosal membranes. Diagnostic imaging findings were consistent with enteritis, typhlitis, and colitis. Multisystemic eosinophilic epitheliotropic disease (MEED) was diagnosed upon necropsy. This disease may be considered a form of equine inflammatory bowel disease complex which can be challenging to diagnose, requiring histological assessment, and in some cases, the use of immunohistochemical markers.Key clinical message:Multisystemic eosinophilic epitheliotropic disease is challenging to diagnose but should be considered in horses with chronic weight loss that fail to respond to conventional treatment for concurrent diarrhea and skin lesions.     

Linking weed patterns with soil properties: a long-term case study

Precision Agriculture - The spatial distribution and density of different weed species were monitored during a long-term survey over a period of 9&nbsp;years on a 5.8&nbsp;ha arable field...     

Distribution of the timber quality attribute ‘knot surface’ in logs of Fagus sylvatica L. from pure and mixed forest stands

European Journal of Forest Research - Research on mixed forests has mostly focused on tree growth and productivity, or resistance and resilience in changing climate conditions, but only rarely on...     

Effect of <Emphasis Type="Italic">Meloidogyne ethiopica</Emphasis> parasitism on water management and physiological stress in tomato

Root-knot nematodes (RKN) are obligate endoparasites that severely damage the host root system. Nutrient and water uptake are substantially reduced in infested plants, resulting into altered physiological processes and reduced plant growth. The effect of nematode infestation on the morphological changes of roots and subsequent physiological plant responses of infested tomatoes with the RKN Meloidogyne ethiopica was studied in a pot experiment. Plants were infested with two inoculum densities (10 or 50 eggs per cm³ substrate) and its effect was evaluated 74 and 102 days post inoculation (DPI). Morphological changes and root growth was determined by analysing scanned images of the whole root system. Nematode infestation reduced the portion of fine roots and increased that of coarse roots due to gall formation. Fine roots of non-infested control plants represented around 51% of the area of the whole root system at 74 and 102 DPI. In comparison to controls, plants inoculated with low and high nematode density had 2.1 and 3.2-times lower surface area of fine roots at 102 DPI. Root analyses revealed that plants had a very limited ability to mitigate the effects of the root-knot nematodes infestation by altering root growth. Root galls had a major influence on the hydraulic conductivity of the root system, which was significantly reduced. The low leaf water potential of infested plants coincided with decreased stomatal conductivity, transpiration and photosynthesis. The latter two were reduced by 60–70% when compared to non-infested control plants.     

Identification of the Cdc48•20S proteasome as an ancient AAA+ proteolytic machine

Proteasomes are the major energy-dependent proteolytic machines in the eukaryotic and archaeal domains of life. To execute protein degradation, the 20S core peptidase combines with the AAA+ ring of the 19S regulatory particle in eukarya or with the AAA+ proteasome-activating nucleotidase ring in some archaea. Here, we find that Cdc48 and 20S from the archaeon Thermoplasma acidophilum interact to form a functional proteasome. Cdc48 is an abundant and essential double-ring AAA+ molecular machine ubiquitously present in archaea, where its function has been uncertain, and in eukarya where Cdc48 participates by largely unknown mechanisms in diverse cellular processes, including multiple proteolytic pathways. Thus, proteolysis in collaboration with the 20S peptidase may represent an ancestral function of the Cdc48 family.