Acidic precipitation and forest vegetation

Effects of acidic precipitation on forest vegetation may be classified as being either direct or indirect. Among the most important direct effects are damage to protective cuticular layers, interference with normal functioning of guard cells, poisoning of plant cells after diffusion of acidic substances through stomata or cuticle and interference with reproductive processes. Indirect effects include accelerated leaching of substances from foliar organs, increased susceptibility to drought and other environmental stress factors, and alteration of symbiotic associations and host-parasite interactions. The potential importance of nutrient take up through foliage and the need to understand atmosphere-plant-soil interactions are stressed.     

Thymocyte growth factor: A progression growth factor for cycling immature cortical thymocytes

A growth factor for cultured guinea pig thymocytes was isolated from an extract of calf thymus. This thymocyte growth factor (TGF) was purified to apparent homogeneity employing reverse phase high performance liquid chromatography as the final step. TGF was characterized as an N-terminal blocked hydrophilic peptide with an apparent M_r of 1600. The amino acid composition revealed a high content of acidic amino acids but no apparent relationship with previously defined growth factors and thymic differentiation hormones. TGF was active in nanomolar concentration and stimulated the DNA synthesis and mitotic activity specifically in a subpopulation of thymocytes with immature cortical phenotype. The responsive thymocytes were recruited from G₁ into S phase within 2 h after addition of TGF. In the absence of the growth factor, the target cells were blocked at a putative restriction point in G₁, prior to the onset of the S phase. It is proposed that TGF is a progression growth factor participating in the regulation of the intense proliferation of immature thymocytes in the thymus cortex in vivo.     

Antigenic analysis of Peptococcus indolicus by crossed immunoelectrophoresis

Quantitative immunoelectrophoretic methods have been used to study the antigenic mosaic of Peptococcus indolicus, an anaerobic coccus frequently isolated from udder secretions from heifers and dry cows with mastitis. Three antigenic components of liquid cultures of this bacterium were analyzed, compared and characterized, namely concentrated culture filtrate containing extracellular antigens, a cytoplasmic antigen fraction obtained by freeze-press disruption of bacterial cells and Triton X-100-soluble antigens from cell wall-membrane fractions. The extracellular antigens were further investigated because they proved to be particularly useful in preliminary studies on the antibody response of cows to P. indolicus. The possible cross-reactivity of peptococcal antigens with extracellular antigens from other bacteria causing, or associated with, mastitis was investigated. The contribution of medium components to the immunoprecipitate profile, the heat-stability of antigens and the relationship of serotypic antigens to those in the standard extracellular concentrate were established using co-immunoelectrophoresis, crossed-line immuno-electrophoresis and crossed immunoelectrophoresis with intermediate gel. Attempts to identify enzyme-active immunoprecipitates with histochemical enzyme staining methods revealed only glutamate dehydrogenase.     

Fibrin sealant as a treatment for canine aural haematoma: a case history

Aural haematomas occur commonly in dogs in which predisposing factors include trauma to the pinna, a history of violent head shaking, and acute or chronic otitis externa. Treatment usually involves invasive surgery performed under general anaesthesia but these techniques can create wounds requiring intensive aftercare. Furthermore, certain breeds of dog and/or older animals are often at greater risk due to complications arising from the use of anaesthetics. Therefore, a need exists for a less invasive procedure which can be performed easily in general practice and with minimal reliance on anaesthetics. Fibrin sealants fulfil these criteria and have been used successfully to treat aural haematomas in humans. This is the first known report on the use of fibrin sealant to treat a canine aural haematoma. In the present case, the haematoma recurred shortly after removal of the protective collar, and was subsequently treated by conventional surgery. Possible reasons for initial success of the fibrin sealant and then later recurrence of the haematoma (e.g. premature removal of the collar) are discussed.     

Short feeding migration associated with a lower mean size of whitefish in the River Tornionjoki,northern Baltic Sea

The size of anadromous whitefish caught with dip nets in the River Tornionjoki in the northern part of the Gulf of Bothnia has decreased during recent decades. To find an explanation for this trend, ascending whitefish were sampled in the lower part of the river in August 2016, and they were divided into two groups according to fish length. The length of the SMALL group was ≤ 32 cm (n = 32) and that of the LARGE group ≥ 33 cm (n = 65). The elemental analysis of otoliths revealed that the barium concentration was clearly higher in otoliths from the SMALL group compared to the LARGE group. This indicates that the fish in the LARGE group had migrated to feed further south in the Gulf of Bothnia, with a higher salinity, than the fish in the SMALL group. Because of this migration difference, and a decline in the gillnet effort, especially in the feeding areas near the river mouth, it is assumed that proportionally more fish in the SMALL group are able to ascend the river to spawn than previously, thus decreasing the mean size. At the same time, the heavy gillnet fishery in the south removes fish from the LARGE group.     

Liming in Sweden

Air-borne pollutants have acidified 90,000 km of running water and at least 18,000 of Sweden's 90,000 lakes. In 1977 a national liming program to mitigate the effects of acidification in surface waters started with governmental support. Governmental subsidies usually amount to 85 % of the total liming cost but can in rare cases be extended to 100 % when waters of great national interest are threatened. The main liming agent is limestone of the size 0 to 0,2 mm. In lakes lime is spread by pontoon boats, helicopters and other vehicles. In running waters dosers and diversion wells are used. By 1985, the national liming program has been able to lime approximately 3,000 lakes and 100 streams.     

Simulating site-specific nitrogen mineralization dynamics in a Swedish arable field

Abstract

The objective of this work was to test whether a dynamic soil C and N model using site-specific information improved estimates of apparent net N mineralization compared with regressions only based on static soil properties. This comparison was made using data from a 34-point sampling grid within a Swedish arable field during two growing seasons, using a simple carbon balance and nitrogen mineralization model (ICBM/N) for the dynamic approach. Three free model parameters were simultaneously optimized using non-linear regression to obtain the best model fit to the data from all grid points and both years. Calculated annual mean net mineralization (Nm_sim) matched the measured Nm mean exactly, and was 44 and 71 kg N ha^?1 for the two growing seasons 1999 and 2000, respectively. However, the variability in calculated Nm_sim values among the 34 grid points was smaller than that measured, and only a small proportion of the variation within a single year was explained by the model. Despite this, the model explained 56% of the total variation in Nm during the two growing seasons, mainly due to the good fit to the seasonal overall difference. Significant factors influencing net mineralization included the soil environment controlling mineralization, total N in soil organic matter and N in crop residues. Uncertainties in estimation of θ _fc and θ _wp (soil water content at saturation and wilting point) and the possible influence of unknown horizontal and vertical water flows made high-precision calculations of soil water content difficult. The precision and general applicability of the actual measurements thus set limits for estimating critical parameters, and the limitations of both the experimental design and the model are discussed. It is concluded that improvements in precision in sampling and analysis of data from the grid points are needed for more critical hypothesis testing.     

Earthworms influenced by reduced tillage,conventional tillage and energy forest in Swedish agricultural field experiments

Abstract

We compared earthworm density, depth distribution and species composition in three soil cultivation experiments including the treatments ploughless tillage and mouldboard ploughing. Sampling was done in September 2005 and for one experiment also in 1994. By yearly sampling 1995–2005, earthworms in an energy forest of Salix viminalis were compared with those in an adjacent arable field. Sampling method was digging of soil blocks and hand sorting and formalin sampling in one cultivation experiment. Both methods were used in the energy forest and arable land comparison.

In two soil cultivation experiments, highest abundances or biomass were found in ploughless tillage. Earthworm density was higher in the upper 10 cm, especially in the ploughless tillage. Earthworm density was significantly higher in the energy forest than in the arable field. Formalin sampling revealed c. 36% of the earthworm numbers found by digging in the energy forest and gave almost no earthworms in the arable field. In all treatments with soil cultivation, species living and feeding in the rhizosphere and soil dominated. One such species, Allolobophora chlorotica, was more abundant under mouldboard ploughing than ploughless tillage. Lumbricus terrestris, browsing on the surface and producing deep vertical burrows, was more common in the ploughless tillage. Species living and feeding close to the soil surface were almost only found in the energy forest, which had not been soil cultivated since 1984.

The findings support earlier studies pointing out possibilities to encourage earthworms by reduced soil cultivation. This is one of the first published studies that followed earthworm populations in an energy forest plantation during several years. Explanation of earthworm reactions to management and environmental impacts should be done with consideration of the ecology of species or species groups. Earthworm sampling by formalin must always be interpreted with caution and calibrated by digging and hand-sorting sampling.     

Root biomass dynamics in a semi-natural grassland exposed to elevated atmospheric CO2 for five years

The effects of elevated atmospheric CO₂ on root dynamics were studied in a semi-natural grassland in central Sweden during five consecutive summer seasons. Open-top chambers were used for ambient and elevated (+350 μmol mol^?1) concentrations of CO₂, and chamberless rings were used for control. Root dynamics were observed in situ with minirhizotrons during the five summers and root biomass production was measured with root in growth cores during the last two years, from which total root biomass was estimated for each of the five years. The elevated CO₂ treatment showed both a greater increase in root numbers during the early summer and a greater decline in root numbers during autumn and winter than the ambient CO₂ treatment. Mean root production under elevated CO₂ was 50% greater than ambient CO₂ during the five years, and the difference increased from +25% in the first year to +80% in the last two years. Conversely, during the same period, the elevated to ambient CO₂ difference in shoot biomass decreased from +50% to +5%. This resulted in a dramatic change in root to shoot ratios in elevated CO₂ compared with the ambient treatment, which increased from ?15% in 1996 to +70% in 2000. Similar differences were seen between elevated CO₂ and the chamberless grown control plants, where root to shoot ratios increased steadily from ?47% in 1996 to +27% in 2000. Less dynamically, the root to shoot ratios of ambient CO₂ grown plants compared with the chamberless control plants were consistently ?29%±6% during the experimental period. In conclusion, during the 5 years this grassland was studied, there was a clear shift in plant biomass partitioning from above to below ground for plants exposed to elevated CO₂.