Decomposition of organic matter and nutrient mineralisation in wood ant (<Emphasis Type="Italic">Formica rufa</Emphasis> group) mounds in boreal coniferous forests of different age

Wood ants (Formica rufa group) are dominating ecosystem elements of the boreal region due to their wide and abundant occurrence. They collect and concentrate organic material from the surrounding forest floor by building large above-ground mounds. These mounds have higher temperature and lower water content than the surrounding forest floor. We studied how these peculiar environmental conditions affected mass loss and carbon (C), nitrogen (N), phosphorus (P) and potassium (K) mineralisation of organic matter in boreal Norway spruce (Picea abies L. Karst.)-dominated mixed forest stands of four different age classes (5-, 30-, 60-, and 100-year-old) situated in eastern Finland using the litter bag technique. Norway spruce needle litter was incubated in inhabited and abandoned wood ant mounds as well as on the surrounding forest floor. We expected decomposition to be extremely slow due to the dryness of the mounds. Mass losses inside inhabited mounds were lower compared to the surrounding forest floor (on average 30 vs 50% after 2 years) but not as low as we expected, which might be a result of ant and microbial activity in the mounds. Decomposition in the abandoned mounds proceeded similarly as on the forest floor. Nutrient mineralisation proceeded more slowly in the ant mounds than on the surrounding forest floor. Mineralisation occurred for all studied nutrients in the ant mounds, except for N, which net amount remained stable during the years of the experiment. When wood ant mounds are abandoned and their porous and dry structure is no longer maintained by the ants, their decomposition is accelerated, and nutrients may be available for uptake by plants, although the nutrient mineralisation seems still to remain lower compared to the surrounding forest floor. However, eventually the mound material will be decomposed and nutrients mineralised, thus providing a nutrient hot spot increasing the heterogeneity of forest floor nutrient availability.     

Road culvert restoration expands the habitat connectivity and production area of juvenile Atlantic salmon in a large subarctic river system

The effects of restoration of impassable road culverts on the distribution of juvenile Atlantic salmon, Salmo salar L., were evaluated in seven small tributaries of the subarctic River Teno system, northernmost Finland/Norway. Restoration enabled the passage of juvenile salmon through the culverts and increased the distribution area of salmon parr in the seven streams by tens or hundreds of metres, depending on the natural slope of the tributary with a total of ≈1 km new area for ascending juveniles. Areas upstream of the culverts were colonised after varying number of years, mostly 2–3, following restoration. Age‐1 and age‐2 parr were the first salmon age groups entering the new territory after removal of the migration barrier. Although the restoration measures were conducted at the downstream outlet area of the culverts only, the connectivity was improved and increased the production area accessible to juvenile salmon. Such removal of migration barriers and securing habitat connectivity by passable culverts should be taken into account in environmental management strategies of river systems safeguarding the essential habitats of salmonid fish.     

Effect of water activity on the release characteristics and oxidative stability of D-limonene encapsulated by spray drying

The stability of encapsulated D-limonene, which was prepared by spray drying, was studied in view of the release characteristics and oxidation stability. Gum arabic, soybean water-soluble polysaccharide, or modified starch, blended with maltodextrin were used as the wall materials. The powders were stored under the conditions of 23-96% relative humidity at 50 degrees C. The release rate and the oxidation rate were closely related to the relative humidity. The relationship was not simple. Initially, the release rate and the oxidation rate increased with increasing water activity, but around the glass transition temperature, the rates decreased sharply to increase again at a further increase of water activity. The results could be explained by a change in the powder structure, where a glass capsule matrix was changed into rubbery state during storage.     

Differential responses of silver birch (Betula pendula) ecotypes to short-day photoperiod and low temperature

We investigated interrelations of dormancy and freezing tolerance and the role of endogenous abscisic acid (ABA) in the development of silver birch (Betula pendula Roth) ecotypes in controlled environments. Short-day treatment induced growth cessation, bud set and dormancy development, as well as initiation of cold acclimation and an increase in freezing tolerance. Subsequent low temperature and short days (12-h photoperiod) resulted in a significant increase in freezing tolerance, whereas bud dormancy was gradually released. The concentration of ABA increased in response to short days and then remained high, but ABA concentrations fluctuated irregularly when the dormant plants were subsequently exposed to low temperature during short days. Although there was a parallel development of freezing tolerance and bud dormancy in response to short days, subsequent exposure to low temperature had opposite effects on these processes, enhancing freezing tolerance and releasing dormancy. Compared with the southern ecotype, the northern ecotype was more responsive to short days and low temperature, exhibiting earlier initiation of cold acclimation, growth cessation and an increase in ABA concentrations in short days, and higher freezing tolerance, faster dormancy release and greater alteration in ABA concentrations when subsequently exposed to low temperature during short days. The rates and extent of the increases in ABA concentration may be related to increases in freezing tolerance and dormancy development during short days, whereas the extent of the fluctuations in ABA concentration may play an important role in enhancing freezing tolerance and releasing dormancy during a subsequent exposure to low temperature during short days.     

Effects of release timing on migration behaviour and survival of hatchery‐reared Atlantic salmon smolts in a regulated river

In this study, 221 two‐year‐old hatchery‐reared salmon, Salmo salar, smolts were tagged with radio transmitters over a period of three consecutive years and released in the river in groups of 20–21 fish in various dates between late April and early June. Tagged smolts were tracked during their downstream migration in the lower 36‐km stretch of the regulated River Oulujoki, with the focus on the effects of release date, water temperature and river flow on migration behaviour and survival. The results indicate that release timing and river temperature have profound effects on the initiation of migration, swimming speed and survival of released S. salar smolts. Smolts released early in the spring in cold waters ceased migration after brief downstream movement and were vulnerable to predation, whereas the migration speed and survival rates increased markedly for smolts released later in the spring.     

Transfer of the Kosena Rfk1 gene,required in hybrid seed production,from oilseed rape to turnip rape

Radiant frost is a major abiotic stress, and one of the principal limiting factors for agricultural production worldwide, including Australia. Legumes, including field pea, faba bean, lentil and chickpea, are very sensitive to chilling and freezing temperatures, particularly at the flowering, early pod formation and seed filling stages. Radiant frost events occur when plants and soil absorb the sunlight during the day time and radiate heat during the night when the sky is clear and the air is still. Dense chilled air settles into the lowest areas of the canopy, where the most serious frost damage occurs. The cold air causes nucleation of the intracellular fluid in plant tissues and the subsequent rupturing of the plasma membrane. Among the cool season grain legume crops, chickpea, lentil and faba bean and field pea are the most susceptible to radiant frost injury during the reproductive stages. The more sensitive stages are flowering and podding. Frost at the reproductive stage results in flower abortion, poor pod set and impaired pod filling, leading to a drastic reduction in yield and quality. In contrast, in the UK and European countries, frost stress is related to the vegetative stages and, in particular, the effects of frost have been studied on cotyledon, uni/tri-foliolate leaf and seedling stages during the first few weeks of growth. Few winter genotypes have been identified as frost tolerant at vegetative stages. Vegetative frost tolerance is not related to reproductive frost tolerance, and hybrids from the vegetative frost-tolerant genotypes may not necessarily be tolerant at the reproductive stage. Tolerance to radiant frost has an inverse relationship with plant age. In the field, frost tolerance decreases from the vegetative stage to reproductive stage. Unlike wheat and barley, it is difficult to analyse and score frost damage in grain legume crops due to the presence of various phenophases on one plant at the reproductive stage. The extent of frost damage depends on the specific phenophases on a particular plant. However, current studies on genetic transformation of cold tolerant gene(s), membrane modifications, anti-freeze substances and ice nucleating or inhibiting agents provide useful information to improve our current understanding on frost damage and related mechanisms. The effects of frost damage on yield and grain quality illustrate the significance of this area of research. This review discusses the problem of radiant frost damage to cool season legumes in Australia and the associated research that has been carried out to combat this problem locally and worldwide. The available literature varies between species, specific climatic conditions and origin.     

Wild origin and enriched environment promote foraging rate and learning to forage on natural prey of captive reared Atlantic salmon parr

Abstract – After release to the wild, captive reared salmon have shown lower foraging rates on natural prey and impaired ability to avoid natural predators and thus lower survival compared with wild‐born conspecifics. Here, we examine whether captive breeding influences learning of foraging on natural prey and how enriched rearing methods may improve foraging on natural prey by Atlantic salmon (Salmo salar) parr. We reared offspring of hatchery or wild salmon of the same population in either a standard or enriched environment at production‐scale densities. The enriched environment featured submerged overhead shelter, varying water current, depth and direction and consequently alterations in food dispersion. Parr reared in the enriched environment expressed higher feeding rates, and parr of wild origin started to forage earlier on natural prey. The enriched method promoted foraging of hatchery reared parr on natural prey and is easily applicable to commercial production of salmonids for reintroduction or stock enhancement purposes.     

Application of optical coherence tomography enhances reproducibility of arthroscopic evaluation of equine joints

Background

Arthroscopy is widely used in various equine joints for diagnostic and surgical purposes. However, accuracy of defining the extent of cartilage lesions and reproducibility in grading of lesions are not optimal. Therefore, there is a need for new, more quantitative arthroscopic methods. Arthroscopic optical coherence tomography (OCT) imaging is a promising tool introduced for quantitative detection of cartilage degeneration and scoring of the severity of chondral lesions. The aim of this study was to evaluate the inter-investigator agreement and inter-method agreement in grading cartilage lesions by means of conventional arthroscopy and with OCT technique. For this aim, 41 cartilage lesions based on findings in conventional and OCT arthroscopy in 14 equine joints were imaged, blind coded and independently ICRS (International Cartilage Repair Society) scored by three surgeons and one PhD-student.

Results

The intra- and inter-investigator percentages of agreement by means of OCT (68.9% and 43.9%, respectively) were higher than those based on conventional arthroscopic imaging (56.7% and 31.7%, respectively). The intra-investigator Kappa coefficients were 0.709 and 0.565 for OCT and arthroscopy, respectively. Inter-investigator Kappa coefficients were 0.538 and 0.408 for OCT and arthroscopy, respectively.

Conclusions

OCT can enhance reproducibility of arthroscopic evaluation of equine joints.     

From mouth to macrophage: mechanisms of innate immune subversion by Mycobacterium avium subsp. paratuberculosis

Johne’s disease (JD) is a chronic enteric infection of cattle caused by Mycobacterium avium subsp. paratuberculosis (MAP). The high economic cost and potential zoonotic threat of JD have driven efforts to develop tools and approaches to effectively manage this disease within livestock herds. Efforts to control JD through traditional animal management practices are complicated by MAP’s ability to cause long-term environmental contamination as well as difficulties associated with diagnosis of JD in the pre-clinical stages. As such, there is particular emphasis on the development of an effective vaccine. This is a daunting challenge, in large part due to MAP’s ability to subvert protective host immune responses. Accordingly, there is a priority to understand MAP’s interaction with the bovine host: this may inform rational targets and approaches for therapeutic intervention. Here we review the early host defenses encountered by MAP and the strategies employed by the pathogen to avert or subvert these responses, during the critical period between ingestion and the establishment of persistent infection in macrophages.     

Monolignol oxidation by xylem peroxidase isoforms of Norway spruce (Picea abies) and silver birch (Betula pendula)

We partially purified peroxidase isoform fractions from xylem extracts of a gymnosperm, Norway spruce (Picea abies (L.) Karst.), and an angiosperm, silver birch (Betula pendula Roth.), to determine the participation of xylem-localized peroxidases in polymerization of different types of lignin in vivo. Several peroxidase fractions varying in isoelectric point values from acidic to basic were tested for their ability to catalyze the oxidation of the monolignols coniferyl alcohol, sinapyl alcohol and p-coumaryl alcohol in vitro. All of the xylem peroxidases extracted from Norway spruce and most of those from silver birch showed the highest rate of oxidation with coniferyl alcohol in the presence of hydrogen peroxide. The exception was an acidic peroxidase fraction (pI 3.60-3.65) from silver birch that exhibited higher oxidation activity for sinapyl alcohol than for coniferyl alcohol. For the xylem enzyme fractions extracted from silver birch, the ability to oxidize the artificial phenolic substrate syringaldazine coincided with high specific activity for sinapyl alcohol. Therefore, we conclude that the acidic, neutral and basic xylem peroxidases of Norway spruce all function in the synthesis of guaiacyl-type lignin, whereas in silver birch the acidic peroxidases preferentially oxidize sinapyl subunits. The latter provides a mechanism for synthesis of guaiacyl-syringyl lignin typical of tracheid cell walls in angiosperm trees.