Tree,stand and site characteristics affecting the occurrence of lammas growth and multiple tops in field-grown Norway spruce

New Forests - In the Nordic-Baltic region, there has been a growing concern about an increasing occurrence of multiple tops in young stands of Norway spruce. There is however a lack of...     

Photoperiod in recirculation aquaculture systems and timing of seawater transfer affect seawater growth performance of Atlantic salmon (Salmo salar)

Production of Atlantic salmon smolts in recirculation aquaculture systems (RAS) is growing, and novel production protocols using continuous light in RAS are being implemented in the industry. In the present study, Atlantic Salmon parr were exposed to either a traditional protocol (short-day winter signal [12:12 L:D] for 6 weeks) or to continuous light. Both photoperiods were applied in freshwater (FW) and brackish water RAS. Salmon from all treatments were transferred to seawater pens at 200 and 600 g and grown until slaughter size. A control group was smoltified with a 6-week short-day winter signal and kept in FW until sea transfer at 100 g. Continuous light gave a higher growth rate in RAS but reduced feed intake and growth and increased feed conversion ratio during the first 8 weeks in seawater. However, at slaughter, fish exposed to continuous light was bigger than fish given a winter signal because of the higher growth rate in RAS. Slaughter weight was lowest in fish transferred to sea at 600 g, despite having the highest day-degree sum during their life span. The best performing group was the control group transferred at 100 g. All treatments handled transfer to seawater and survival and maturation were not affected by the treatments in RAS. The immune status was examined with a multigene expression assay on BioMark HD platform from parr stage to 5–7 months after seawater transfer. Overall, there was no significant effect of photoperiod or salinity on the expression of the selected immune genes. In sum, the results from this study indicate that using continuous light in RAS may have negative effects on performance shortly after transfer in fish transferred to sea at 200 g, whereas at 600 g, all treatments had reduced growth after transfer irrespective of treatment in RAS.     

Abbau von Huminstoffen durch Bodenmikroorganismen — eine Übersicht

Degradation of humic substances by soil microorganisms — a review Humic substances which represent differently extractable fractions of the soil organic matter exert multifarious effects on soil as a site for plant growth and a part of terrestrial environments. Among them especially humic acids and fulvic acids are subject to degradation and/or transformation by soil microorganisms. Several authors demonstrated the participation of different species of fungi, actinomycetes and also of non-mycelial aerobic or anaerobic bacteria in those processes under laboratory conditions. Indications exist that humic substances irrespective of their structure undergo degradation on cell surfaces due to the activity of exoenzymes. In this respect microbial phenoloxidases play an extraordinarily important role. The degradation rate of humic substances can be followed by optical, gravimetric and chemoanalytical methods as well as using biochemical and microbiological procedures (CO₂ release, microbial growth, biomass formation). An objective evaluation, however, can be hindered by the adsorption of humic substances on microbial biomass and sometimes also by formation of novel humic-like microbial metabolites. Therefore it is necessary to apply a multifactorial approach in the study of the degradation of humic substances which includes both quantitative and qualitative parameters. To better elucidate how these processes may occur under natural conditions, mixed populations of soil microorganisms should be predominantly involved in future studies.     

Growth, feed and nutrient utilisation and gastrointestinal evacuation time in Atlantic salmon (Salmo salar L.): the effect of dietary fish meal particle size and protein concentration

Growth, nutrient utilisation and gastrointestinal evacuation time using different fish meal particle sizes and dietary protein concentration was examined in Atlantic salmon. Salmon were given micro, standard or coarse grounded fish meals at two dietary protein concentrations (30 or 45%) in isolipid diets. Gastric evacuation time was influenced by fish meal particle size. Coarse ground fish meal gave a slower gastric evacuation time compared to finer ground fish meal. Specific growth rate was not influenced by the protein concentration, but there was an adverse effect of coarse ground particles. This effect may be explained by the reduced feed intake of fish fed diets containing coarse ground fish meal. Feed conversion ratio (FCR) or energy conversion ratio (ECR) was reduced with increasing dietary protein concentration. This effect was mainly caused by different energy levels in the diets and not protein/carbohydrate levels. Standard coarse fish meal gave a reduction in ECR, but there was no effect of fish meal particle size on FCR. A protein sparing effect of starch was demonstrated. Productive protein value (PPV) and productive energy value (PEV) was not affected by dietary protein concentration or fish meal particle size. Dietary protein concentration had no effect on nitrogen or fat digestibility but there was a reduction in fat digestibility when coarse ground fishmeal was used in the diets. There were only minor effects on the dressing out percentage, condition factor and fat in cutlet.     

Release and mobility of polycyclic aromatic hydrocarbons and iron‐cyanide complexes in contaminated soil

Export of organic and inorganic pollutants from the unsaturated zone of manufactured gas plant (MGP) sites may endanger groundwater quality. The release and mobility of polycyclic aromatic hydrocarbons (PAH) and iron‐cyanide complexes (FeCN) in soils from a former MGP site were studied in column and batch experiments. The unsaturated column experiment involved two parts. (1) The development of steady‐state effluent concentrations was studied under constant irrigation. (2) Rate‐limited contaminant release was studied by the system's response to flow interruption. Transport data were supplemented by a sequential batch‐desorption experiment. During constant irrigation the initial concentrations of total PAH and FeCN, but also the concentration of dissolved organic carbon (DOC) were higher than the steady state level, indicating that a specific fraction of the DOC and the contaminants was readily mobilized. Cyanide reached a constant effluent concentration after seven pore volumes (pvs), whereas equilibration of effluent PAH took 20 pvs. After flow interruption, rate‐limited release of DOC, PAH, and FeCN was observed by increased effluent concentrations. Comparison of FeCN levels with theoretical equilibrium concentrations indicated that in addition to the dissolution of iron(II)ferrocyanide (Berlin Blue), Fe₄[Fe(CN)₆]₃, other cyanide‐species may control the release and such the mobility of FeCN. This was confirmed by decreasing FeCN concentrations during sequential batch extractions. Due to rate‐limited release, seepage water concentrations of DOC, PAH, and FeCN in alkaline MGP soils are influenced by the flow regime. Experiments performed at continuous irrigation may therefore severely underestimate the release of PAH and FeCN under field conditions. The effect of DOC on the release and mobility of PAH and FeCN under transient conditions has to be further investigated.     

The paramount influence of nitrate in increasing apoplastic pH of young sunflower leaves to induce Fe deficiency chlorosis,and the re-greening effect brought about by acidic foliar sprays

The main objective of the present work was to clarify the causal relationship between leaf apoplastic pH increase and Fe chlorosis under alkaline growth conditions. It has been shown that nitrate supply in contrast to ammonium supply induced a pH increase in the apoplast of young green leaves of Helianthus annuus which was followed within 12 hours by leaf yellowing. Hence nitrate nutrition is the primary cause of a high leaf apoplastic pH which induces Fe deficiency chlorosis and not the impaired provision of ATP for plasmalemma H⁺ pumps in yellow leaves. Supply of bicarbonate in physiological concentrations had virtually no influence on leaf apoplastic pH. Spraying leaves with diluted acids (citric acid, sulphuric acid) resulted in a decrease of apoplastic pH followed by leaf re-greening. Interestingly, the Fe concentrations remained the same in the yellow control leaves and in the sprayed green leaves. From this it follows that Fe efficiency in leaves is mainly related to the Fe distribution between apoplast and symplast. It was demonstrated that Fe chlorosis induced by nitrate nutrition begins from the base of the youngest leaves, presumably from growing interveinal microsites showing high nitrate uptake rates. Leaf yellowing spread gradually from the leaf base to the tip and after seven days of nitrate supply the leaf was almost completely yellow (98%). Leaf yellowing was measured by means of a video imaging technique. Leaf apoplastic pH recordings were conducted after loading the fluorescent dye FITC-Dextran (4000 D) into the leaf apoplast of intact plants thus simulating in vivo conditions. It was also shown using the new loading technique that the fluorescent dye did not penetrate the leaf symplast.     

奥地利两块基因资源保育林内英国紫杉生态条件与保护现状比较

在奥地利及其他多数欧洲国家英国紫杉濒临灭绝,被列为濒危树种.基于不同地理位置的自然群落的比较,调查了奥地利两块基因资源保育林内英国紫杉的空间结构、更新状况及可采取的保育方法等.每块样地圆杆材分布变化较大.林地Stiwollgraben内紫杉单位面积植株总数,平均胸径和平均株高分别为492 n·hm-2, 8.8 cm and 6.3 m;Leininger Riese仅为45 n·hm-2, 16.3 cm and 7.6 m.Stiwollgraben群落紫杉长势较好,健康植株79%以上,而Leininger Riese群落的健康植株低于49%.两块样地内紫杉更新模式差异较大,与其各自的树龄动态分布相一致.1年龄幼树相比较,Stiwollgraben林地内紫杉密度为13019株/公顷,而Leininger Riese仅为1368株/公顷.Leininger Riese林地内未发现树高51-150cm的幼树,而Stiwollgraben林地内树高30-150cm的幼树鲜能见到.这种情况下,英国紫杉林的保育需要管理完善的保护区、采伐期间采取长期轮伐,同时还要防止牲畜啃食和减轻种间竞争,以此来增强红豆杉的生存能力.图4表4参41.     

Long-term base cation mass balances for Swedish forests and the concept of sustainability

Data from the Swedish Forest Inventory was used to calculate mass balances for base cations Ca, Mg and K for Swedish forests. Using lysimeter and forest survey soil analyses to estimate present base cation leaching from the root zone reveals that weathering plus base cation deposition is not sufficient to support both, the present base cation leaching rate and the present rate of uptake caused by stem growth. Calculations suggest that 96% of the productive forested area may have higher rates of removal than supply for one or more base cation. Under a best-case scenario, assuming less pollution, the present growth rate and 100% efficiency in uptake of available nutrients, the area with more removal than supply would still be at least 30% of the total area. Forest soils are being depleted at a rate where the exchangeable reservoirs have high risk of being severely depleted in the next few decades in central and southern Sweden. During 1983–1985 the depletion rate is calculated to be, on the average, 0.33 keq ha⁻¹ year⁻¹. The weathering rate and present base cation deposition can sustain growth at a level where (80–85)×10⁶m³ stemwood year⁻¹ can be harvested. Any harvested growth beyond this volume must be sustained by artificial means.

For whole-tree harvesting without base cation return, the calculations indicate that it would significantly increase the base saturation depletion rate to an average of 0.62 keq ha⁻¹ year⁻¹, and risk depletion of the soil in less than one-to-two rotation periods almost anywhere in Sweden.

The calculations stress the importance that sustainable forest management must include the management of nutrient fluxes and reservoirs.