Whole-plant frost hardiness of mycorrhizal (Hebeloma sp. or Suillus luteus) and non-mycorrhizal Scots pine seedlings.

Ectomycorrhizal trees are common in the cold regions of the world, yet the role of the mycorrhizal symbiosis in plant cold tolerance is poorly known. Moreover, the standard methods for testing plant frost hardiness may not be adequate for roots and mycorrhizas. The aims of this study were to compare the frost hardiness of mycorrhizal and non-mycorrhizal Scots pine (Pinus sylvestris L.) seedlings and to test the use of reverse-flow root hydraulic conductance (Kr) measurement for root frost hardiness determination. Mycorrhizal (Hebeloma sp. or Suillus luteus) and non-mycorrhizal seedlings were grown in controlled-environment chambers for 13 weeks. After this, half of the plants were allotted to a non-hardening treatment (long day and high temperature, same as during the preceding growing season) and the other half to a hardening (short day and low temperature) 'autumn' treatment for 4 weeks. The intact seedlings were exposed to whole-plant freezing tests and the needle frost hardiness was measured by relative electrolyte leakage (REL) method. The seedlings were grown for three more weeks for visual damage assessment and Kr measurements using a high-pressure flow meter (HPFM). Mycorrhizas did not affect the frost hardiness of seedlings in either hardening treatment. The effect of the hardening treatment on frost hardiness was shown by REL and visual assessment of the aboveground parts as well as Kr of roots. Non-mycorrhizal plants were larger than mycorrhizal ones while nitrogen and phosphorus contents (per unit dry mass) were similar in all mycorrhiza treatments. In plants with no frost exposure, the non-mycorrhizal treatment had higher Kr. There was no mycorrhizal effect on plant frost hardiness when nutritional effects were excluded. Further studies are needed on the role of mycorrhizas especially in the recovery of growth and nutrient uptake in cold soils in the spring. The HPFM is useful novel method for assessment of root damage.

Photosynthesis, nutrient accumulation and growth of two Betula species exposed to waterlogging in late dormancy and in the early growing season.

Increased risk of soil waterlogging in winter and spring at northern latitudes will potentially affect forest production in the future. We studied gas exchange, chlorophyll content index, chlorophyll fluorescence, nutrient concentration and biomass accumulation in 1-year-old silver (Betula pendula Roth) and pubescent birch (Betula pubescens Ehrh.) seedlings. We hypothesized that B. pubescens has different physiological mechanisms that make it tolerate waterlogging better than B. pendula. The treatments were: (i) no waterlogging throughout the experiment; (ii) 4-week waterlogging during dormancy (dormancy waterlogging 'DW'); (iii) 4-week waterlogging during the early growing season (growth waterlogging 'GW'); and (iv) 4-week DW followed by 4-week GW during the early growing season ('DWGW'). Stomatal conductance and light-saturated net assimilation rate were reduced by GW in both species, and in B. pubescens also by DW. However, recovery was seen during the follow-up growing season. In B. pendula, DW, GW and DWGW temporarily resulted in reduced stem biomass, and GW and DWGW caused reduced leaf biomass. In B. pubescens, the stem biomass was decreased in GW and DWGW. Leaf nitrogen (N) and phosphorus (P) concentrations were generally low, and increased by GW, while potassium, calcium, magnesium and to some extent, boron and zinc concentrations decreased in both species and additionally manganese in B. pendula. The increases in N and P are mostly due to a concentration effect due to smaller leaf biomass, yet suggest that their uptake was not impaired. The decreases in cation concentrations are likely to be connected to impaired root functioning, which was not yet fully recovered from GW. We conclude that morphological acclimation to waterlogging of the leaves and roots rather than photosynthesis explains why B. pubescens is able to grow better in wetter areas than B. pendula.

Current food chain information provides insufficient information for modern meat inspection of pigs.

Meat inspection now incorporates a more risk-based approach for protecting human health against meat-borne biological hazards. Official post-mortem meat inspection of pigs has shifted to visual meat inspection. The official veterinarian decides on additional post-mortem inspection procedures, such as incisions and palpations. The decision is based on declarations in the food chain information (FCI), ante-mortem inspection and post-mortem inspection. However, a smooth slaughter and inspection process is essential. Therefore, one should be able to assess prior to slaughter which pigs are suitable for visual meat inspection only, and which need more profound inspection procedures. This study evaluates the usability of the FCI provided by pig producers and considered the possibility for risk ranking of incoming slaughter batches according to the previous meat inspection data and the current FCI. Eighty-five slaughter batches comprising 8954 fattening pigs were randomly selected at a slaughterhouse that receives animals from across Finland. The mortality rate, the FCI and the meat inspection results for each batch were obtained. The current FCI alone provided insufficient and inaccurate information for risk ranking purposes for meat inspection. The partial condemnation rate for a batch was best predicted by the partial condemnation rate calculated for all the pigs sent for slaughter from the same holding in the previous year (p<0.001) and by prior information on cough declared in the current FCI (p=0.02) statement. Training and information to producers are needed to make the FCI reporting procedures more accurate. Historical meat inspection data on pigs slaughtered from the same holdings and well-chosen symptoms/signs for reporting, should be included in the FCI to facilitate the allocation of pigs for visual inspection. The introduced simple scoring system can be easily used for additional information for directing batches to appropriate meat inspection procedures. To control the main biological public health hazards related to pork, serological surveillance should be done and the information obtained from analyses should be used as part of the FCI.

Waterlogging in late dormancy and the early growth phase affected root and leaf morphology in Betula pendula and Betula pubescens seedlings.

The warmer winters of the future will increase snow-melt frequency and rainfall, thereby increasing the risk of soil waterlogging and its effects on trees in winter and spring at northern latitudes. We studied the morphology of roots and leaves of 1-year-old silver birch (Betula pendula Roth) and pubescent birch (Betula pubescens Ehrh.) seedlings exposed to waterlogging during dormancy or at the beginning of the growing season in a growth-chamber experiment. The experiment included 4-week dormancy (Weeks 1-4), a 4-week early growing season (Weeks 5-8) and a 4-week late growing season (Weeks 9-12). The treatments were: (i) no waterlogging, throughout the experiment ('NW'); (ii) 4-week waterlogging during dormancy (dormancy waterlogging 'DW'); (iii) 4-week waterlogging during the early growing season (growth waterlogging 'GW'); and (iv) 4-week DW followed by 4-week GW during the early growing season ('DWGW'). Dormancy waterlogging affected the roots of silver birch and GW the roots and leaf characteristics of both species. Leaf area was reduced in both species by GW and DWGW. In pubescent birch, temporarily increased formation of thin roots was seen in root systems of GW seedlings, which suggests an adaptive mechanism with respect to excess soil water. Additionally, the high density of non-glandular trichomes and their increase in DWGW leaves were considered possible morphological adaptations to excess water in the soil, as was the constant density of stem lenticels during stem-diameter growth. The higher density in glandular trichomes of DWGW silver birch suggests morphological acclimation in that species. The naturally low density of non-glandular trichomes, low density of stem lenticels in waterlogged seedlings and decrease in root growth seen in DWGW and DW silver birch seedlings explain, at least partly, why silver birch grows more poorly relative to pubescent birch in wet soils.

Needle metabolome, freezing tolerance and gas exchange in Norway spruce seedlings exposed to elevated temperature and ozone concentration.

Northern forests are currently experiencing increasing mean temperatures, especially during autumn and spring. Consequently, alterations in carbon sequestration, leaf biochemical quality and freezing tolerance (FT) are likely to occur. The interactive effects of elevated temperature and ozone (O(3)), the most harmful phytotoxic air pollutant, on Norway spruce (Picea abies (L.) Karst.) seedlings were studied by analysing phenology, metabolite concentrations in the needles, FT and gas exchange. Sampling was performed in September and May. The seedlings were exposed to a year-round elevated temperature (+1.3 °C), and to 1.4× ambient O(3) concentration during the growing season in the field. Elevated temperature increased the concentrations of amino acids, organic acids of the citric acid cycle and some carbohydrates, and reduced the concentrations of phenolic compounds, some organic acids of the shikimic acid pathway, sucrose, cyclitols and steroids, depending on the timing of the sampling. Although growth onset occurred earlier at elevated temperature, the temperature of 50% lethality (LT(50)) was similar in the treatments. Photosynthesis and the ratio of photosynthesis to dark respiration were reduced by elevated temperature. Elevated concentrations of O(3) reduced the total concentration of soluble sugars, and tended to reduce LT(50) of the needles in September. These results show that alterations in needle chemical quality can be expected at elevated temperatures, but the seedlings' sensitivity to autumn and spring frosts is not altered. Elevated O(3) has the potential to disturb cold hardening of Norway spruce seedlings in autumn, and to alter the water balance of the seedling through changes in stomatal conductance (g(s)), while elevated temperature is likely to reduce g(s) and consequently reduce the O(3)-flux inside the leaves.

The ectomycorrhizal fungus Tricholoma matsutake is a facultative saprotroph in vitro.

Tricholoma matsutake is an economically important ectomycorrhizal fungus of coniferous woodlands. Mycologists suspect that this fungus is also capable of saprotrophic feeding. In order to evaluate this hypothesis, enzyme and chemical assays were performed in the field and laboratory. From a natural population of T. matsutake in southern Finland, samples of soil-mycelium aggregate (shiro) were taken from sites of sporocarp formation and nearby control (PCR-negative) spots. Soil organic carbon and activity rates of hemicellulolytic enzymes were measured. The productivity of T. matsutake was related to the amount of utilizable organic carbon in the shiro, where the activity of xylosidase was significantly higher than in the control sample. In the laboratory, sterile pieces of bark from the roots of Scots pine were inoculated with T. matsutake and the activity rates of two hemicellulolytic enzymes (xylosidase and glucuronidase) were assayed. Furthermore, a liquid culture system showed how T. matsutake can utilize hemicellulose as its sole carbon source. Results linked and quantified the general relationship between enzymes secreted by T. matsutake and the degradation of hemicellulose. Our findings suggest that T. matsutake lives mainly as an ectomycorrhizal symbiont but can also feed as a saprotroph. A flexible trophic ecology confers T. matsutake with a clear advantage in a heterogeneous environment and during sporocarp formation.

Extensive tree health monitoring networks are useful in revealing the impacts of widespread biotic damage in boreal forests.

We surveyed the regional distribution of conifer defoliation in Finland with an extensive monitoring network during 1995-2006 (EU Forest Focus Level I). The average defoliation in the whole Finland was 10.3% in pine and 19.9% in spruce. The sharp changes were often related to abiotic and biotic factors. The mean age of the stand explained more than one half of the between-plot variance in defoliation. In a variance component analysis, the main effect of years was negligible, while most of the random variation was due to plot main effect and plot x year interaction. About one fifth of the defoliation could be attributed to abiotic or biotic damage, and there were strong local correlations, e.g., between the changes in defoliation and degree of pine sawfly (Diprionidae) damage. There were clear temporal and spatial patterns in the incidence of the most important causes [Scots pine: Scleroderris canker (Gremmeniella abietina), pine shoot beetles (Tomicus sp.), and pine sawflies (Diprion pini, Neodiprion sertifer); Norway spruce: rust fungi (primarily Chrysomyxa ledi)]. Our results suggest that extensive monitoring networks can reveal useful information about the widespread outbreaks of pest organisms (insects and fungi) already in their increase phases, giving some time for management decisions. In a changing climate, large-scale, regular monitoring of tree health, including abiotic and biotic causes, is more important than ever before.

Temperature sum accumulation effects on within-population variation and long-term trends in date of bud burst of European white birch (Betula pendula).

Within-population variation in phenology of boreal trees indicates their adaptability to climatic variations. Although interannual variations in date of bud burst have been widely discussed, little is known about within-population variation, the key determinants for this variation and the effects of this variation on estimates of trends in bud burst date. Over a period of nine years, we monitored timing of bud burst daily in 30 mature white birch (Betula pendula Roth) trees in a naturally regenerated stand. Our results revealed not only large interannual variation but also considerable intraannual variation among individual trees in date of bud burst, the maximum within-population variation being four weeks. Bud burst can be accurately predicted by the date when a threshold value of temperature sum in spring is reached (base temperature +5 degrees C). Based on this temperature sum and past temperature records, we estimated the trend in date of bud burst. The linear trend estimate based on the years 1926-2005 is an advancement of 1.2 days per decade (95% confidence interval, +/- 0.7 days), which is much less than that predicted by time series based on coarser time intervals. We conclude that, because of large interannual differences, and large annual within-population variations in bud burst, estimates of bud burst date based on measurements made over a period of only a few decades are unreliable.

Ontogeny and environment as determinants of the secondary chemistry of three species of white birch.

This study investigates variation in the secondary chemistry of the bark of three closely related, winter-dormant species of white birch (Betula resinifera, B. pendula, and B. platyphylla) at different ontogenetic stages by using different plant parts (top and base). The experimental birches were grown for 4 years in two growing conditions (pot and field) at different nutrient levels. There was considerable species-specific quantitative and qualitative variation in the secondary chemicals in bark, but this was also affected by fertilization and the age of the plant. In general, there was greater chemical diversity in saplings than in seedlings. The study revealed three new components, secoisolariciresinol 9-O-beta-glucopyranoside and two of its derivatives, that have not been reported previously for the bark of white birches. Principal component analysis showed that the species studied had a similar chemical composition at the juvenile stage, but as the plants grew, they became more clearly differentiated, which indicates that the species of older plants can be identified by chemotaxonomy. Evidently, the secondary chemistry of birches is under genetic control, but it is affected by properties of growing conditions and ontogeny.

Variation in birch (Betula pendula) shoot secondary chemistry due to genotype, environment, and ontogeny.

Plant secondary chemistry is determined by both genetic and environmental factors, and large intraspecific variation in secondary chemistry has frequently been reported. The heritability of specific tree secondary metabolites is, however, mostly unknown. We tested the effect of plant genotype, environment, and ontogeny on the variation in shoot secondary chemistry of juvenile and mature European white birches (Betula pendula). Phenolic compounds and triterpenoids were analyzed in 30 naturally regenerated 20-year-old parental trees and micropropagated plantlets that originated from 14 of those same parental trees, planted at four growing sites. Most of the variation for phenolic compounds was explained by differences between parental trees, whereas triterpenoids had a high variation both between parental trees and within the canopy of individual tree. The effect of ontogeny was strong for some individual compounds. In mature trees, the amount of triterpenoids was less than 1 mg/g (DW), whereas the concentration in juvenile plantlets was up to 64 mg/g (DW). Clonal plantlets and parental trees were generally quite similar in their phenolic contents, but there were significant differences for all analyzed compounds among clones. Environment had no significant effect on the accumulation of some compounds, whereas for others, a significant environmental effect and/or significant genotype by environment interaction was found. These results suggest that birch shoot secondary chemistry is under strong genetic control and that the environmental effects depend on the studied chemical trait.