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Silvicultural management in maintaining biodiversity and resistance of forests in Europe-temperate zone.

In Europe temperate forests play a prominent role in timber production, nature protection, water conservation, erosion control and recreation. For centuries temperate forests in Europe have been affected by forest devastation and soil degradation. Applying great efforts to eliminate the severe wood shortage of those days, countermeasures were taken during the last 150 years by regenerating and tending highly productive forests. High growth rates and an increasing growing stock of these forests indicate that formerly stated goals have been successfully achieved. Coniferous species were often favoured because they were easy to establish and manage, and gave reason for high volume growth expectations. Today coniferous forests expand far beyond the limits of their natural ranges. These changes have been accompanied by a loss of biodiversity, a shift to nonsite adapted tree species and reduce the resistance against storms, snow, ice, droughts, insects and fungi. Some of these hazards were further intensified by the increasing average stand age, as well as in some areas by severe air pollution. Climatic fluctuations, especially changes in the frequency and intensity of extreme warm and dry climatic conditions and of heavy storms, had considerable impact on forest ecosystems. The changing demands of today require a widened scope of forest management. Society is asking for sustainable forestry emphasizing biodiversity and naturalistic forest management. It is of great economic and ecological relevance to know on which sites today's forests are most susceptible to climatic and other environmental changes and hazards. In those areas adjustments of management through a conversion the prevailing forests towards more site adapted mixed forests needs to be considered with priority. The high diversity in site conditions, ownership, economic and socio-cultural conditions require strategies adapted to the local and regional needs. Higher resistance of forests will increase economic and social benefits of forests and reduce the risks by maintaining sustainable forestry.

Climate↗

The intake and digestion of a range of temperate forages by sheep and fibre-producing goats.

The voluntary intake, digestibility and mean retention time of six temperate forages differing in their chemical composition by 12 adult castrated male Scottish blackface sheep, aged 15 months, and fibre-producing castrated male goats, aged 27 months, and of similar live weight, 40kg, were described. The creation of a range of chemical compositions was effected through the use of barley straw, and a low- and high-digestibility hay, and the use of ammonia treatment of these forages. A wide range of voluntary intakes (42-78gDM/kgW(0.75)/day), digestibility of dry matter (0.46-0.60) and mean retention times of undigested residues (36-72h) was achieved through feeding the six forages. Across all the forages fibre-producing goats had higher voluntary intakes, expressed on a metabolic live weight basis, and lower digestibility values than sheep, whereas the mean retention time of the undigested residues was similar for the two species. Within forages goats selected a diet of potentially higher nutritive value, as predicted from chemical composition, with a smaller particle size than sheep. It was concluded that the differences in intake and digestion of temperate forages between sheep and fibre-producing goats are broadly similar to those observed in other experiments between sheep and goats ingesting tropical forages.

Journal Article↗

Comparison of the variable loop regions of myosin heavy chain genes from Antarctic and temperate isopods.

The evolutionary adaptations of functional genes to life at low temperatures are not well characterised in marine and fresh water invertebrates. Temperature has been shown to affect the functional characteristics of fish muscles, with changes in the velocity of shortening and ATPase activity being associated with myosin heavy chain (MyHC) isoform composition and the structure of the surface loop regions. Two PCR products spanning loops 1 and 2 of a MyHC gene from an Antarctic isopod (Glyptonotus antarcticus) were sequenced and compared with those of a temperate isopod (Idotea resecata), slow and fast fibres from lobster (Homarus gammarus) and a cold water amphipod (Eulimnogammarus verrucosus), revealing specific differences between the species, possibly related to fibre type and habitat temperature. The loop 2 region from G. antarcticus myosin was cloned and used for Northern analysis of total RNA from the other species. The cloned myosin cDNA hybridised specifically to a 6.6-kb transcript, in G. antarcticus muscle. In contrast, cDNA probes for lobster slow myosin and actin hybridised to muscle RNA from all species, demonstrating that a distinct MyHC isoform is expressed in the Antarctic isopod, as opposed to the temperate species. The inter- and intra-specific sequence differences in loop 2 region suggest that this may be a site for muscle adaptation to enable function at the low temperatures found in the Southern Ocean.

Actins↗

Lipid radical generation in polar (Laternula elliptica) and temperate (Mya arenaria) bivalves.

Lipid peroxidation in Laternula elliptica was assessed by detecting lipid radicals by electronic paramagnetic resonance. The values were compared with data from the temperate mud clam Mya arenaria. Lipid radical content was higher in the Antarctic bivalve than in the temperate mud clam, even within the range of its habitat temperature. The rate of generation of lipid radicals was affected by the iron content in the samples. The iron content in individual samples of digestive glands in L. elliptica ranged from 3 to 6 nmol g(-1) fresh weight (fwt) and in M. arenaria from 0.6 to 2.7 nmol g(-1) fwt. Arrhenius plots, developed from the rates obtained in the presence of 25 microM iron, showed no significant differences between the activation energy calculated for digestive glands of L. elliptica and M. arenaria. The Fe3+ reduction rate in L. elliptica was higher than in M. arenaria (4.7 +/- 0.9 vs. 1.8 +/- 0.4 nmol mg(-1) protein min(-1), respectively). L. elliptica had a higher content of alpha-tocopherol and beta-carotene than M. arenaria. Our data suggest that increased lipid radical content in the membranes of cold-adapted organisms could be related to iron content.

Animals↗

Phenotypic plasticity of sternopleural bristle number in temperate and tropical populations of Drosophila melanogaster.

We investigated the phenotypic plasticity of sternopleural bristle (SB) number as a function of growth temperature in isofemale lines from temperate (France) and tropical (Congo) populations of Drosophila melanogaster. We found concave reaction norms with a maximum in the middle of the thermal range, except in four African lines which exhibited a regularly decreasing response curve. Genetic variability (intraclass correlation) and evolvability (genetic CV, coefficient of variation) were independent properties and did not change with temperature. Residual, within-line variability was, however, strongly influenced by growth temperature, showing a U-shaped response curve and a minimum CV of 9% at 21.5 degrees C. As expected from a previously known latitudinal cline, maximum values (MV) were higher in temperate than in tropical flies. The temperature of maximum value (TMV) was observed at a higher temperature in the tropical population, in agreement with similar adaptive trends already observed for other quantitative traits. Significant negative correlations within each population were observed between a plasticity curvature parameter and MV or TMV. No difference in curvature was, however, observed between populations, in spite of their very different MVs.

Animals↗

Airborne fungal colonisation of coarse woody debris in North Temperate Picea abies forest: impact of season and local spatial scale.

Coarse woody debris is important for mycodiversity in forest ecosystems, but its availability in managed stands is reduced. Leaving dead wood during felling is suggested as an option to sustain and restore the diversity. However, little is known what fungi would colonise freshly cut wood left on managed sites, and how the colonisation process is influenced by ecological factors. During summer and autumn, 120 freshly cut Picea abies stem sections over 8 cm in diameter were placed upright in mapped locations over two discrete plots separated by 100 m in a north-temperate forest. After seven weeks the sections were collected, and isolation and identification of fungi was done from their upper surfaces. In all 943 fungal strains were isolated, representing 97 species. Species richness in the summer survey was 42.5% higher than during the autumn survey. Low species similarity characterized the different seasons (Sorensen indices: S(S) = 0.36 and S(N) = 0.34) and for 21 species (22%) observation frequency was significantly affected by season. As a result, community structures in summer and autumn differed notably (z-test; P < 0.001). Species richness between the two plots differed by less than 10%, but there were 64 species (66%) found only in one of them, thus qualitative similarity was low (S(S) = 0.49). Quantitative similarity was higher (S(N) = 0.63), indicating that the dominant species colonised wood to a similar extent in both areas. Fungal community structure differed significantly among the two plots (z-test; P < 0.001). Our data showed that freshly cut CWD contributed to mycodiversity in managed north-temperate forest, providing habitats for numerous individuals from over 100 species. The fungal community within a single stand differed markedly both across small distances and over the seasons. In order to sustain and enhance mycodiversity in managed stands. coarse wood should always be left during harvesting. This study also demonstrates the importance of molecular identification and ITS sequence databases for exploring fungal diversity in natural communities.

Air Microbiology↗

Environmental factors affecting productivity, indican content, and indigo yield in Polygonum tinctorium Ait., a subtropical crop grown under temperate conditions.

Polygonum tinctorium Ait. is a herbaceous subtropical annual plant, belonging to the family Polygonaceae. Within the cells of its leaves P. tinctorium accumulates large amounts of a colorless glycoside, indican (indoxyl beta-d-glucoside), from which the blue dye indigo is synthesized. P. tinctorium is well-known in Japan, where it had been cultivated to produce natural indigo for textile dyeing, whereas it represents a potentially interesting new crop in Europe. To better understand the effects of environmental parameters on P. tinctorium crop production and indigo yield, field experiments were carried out in central Italy under temperate climate. Three lines were tested during the 2001 and 2002 growing seasons, and plant/leaf yields as well as indican contents were evaluated. The results showed that P. tinctorium grown in temperate climate conditions can be harvested three times a year. Yields of 82 and 120 t ha(-1) of fresh plant yield were obtained in 2001 and 2002, respectively. The contrasting weather conditions between the two years significantly affected biomass production, which was higher in the 2002 season, characterized by wet weather conditions. The cycle length from sowing to the last harvest was accomplished in 229-238 days when plants had accumulated 2017-2018 degrees C. Green leaves accounted for 40-45% by weight of fresh plant tissue and contained 11-20 g kg(-1) indican. The three lines did not significantly differ in the main productive parameters or in fresh leaf indican content (14.1 g kg(-1) mean value). Photosynthetic active radiation influences indican leaf production according to the model y = 0.0004x + 8.566 (P < 0.01, correlation coefficient = 0.818). Indican content ranged from 12 to 25 g kg(-1) of fresh leaves with PAR daily values from 10000 to 40000 mEinstein m(-2) (recorded in May and at the end of July-beginning of August, respectively). The results indicate that in nonlimiting rainfall conditions a very high indican content and a potentially high indigo yield can be obtained by cultivating P. tinctorium in this pioneer geographical area.

Climate↗

On the efficiency of exchange in parallel tempering monte carlo simulations.

We introduce the concept of effective fraction, defined as the expected probability that a configuration from the lowest index replica successfully reaches the highest index replica during a replica exchange Monte Carlo simulation. We then argue that the effective fraction represents an adequate measure of the quality of the sampling technique, as far as swapping is concerned. Under the hypothesis that the correlation between successive exchanges is negligible, we propose a technique for the computation of the effective fraction, a technique that relies solely on the values of the acceptance probabilities obtained at the end of the simulation. The effective fraction is then utilized for the study of the efficiency of a popular swapping scheme in the context of parallel tempering in the canonical ensemble. For large dimensional oscillators, we show that the swapping probability that minimizes the computational effort is 38.74%. By studying the parallel tempering swapping efficiency for a 13-atom Lennard-Jones cluster, we argue that the value of 38.74% remains roughly the optimal probability for most systems with continuous distributions that are likely to be encountered in practice.

Journal Article↗

On the convergence of parallel tempering Monte Carlo simulations of LJ38.

The convergence of parallel tempering Monte Carlo simulations of the 38-atom Lennard-Jones cluster starting from the Oh global minimum and from the C(5v) second-lowest-energy minimum is investigated. It is found that achieving convergence is appreciably more difficult, particularly at temperatures in the vicinity of the Oh --> C(5v) transformation when starting from the C(5v) structure. A strategy combining the Tsallis generalized ensemble and the parallel tempering algorithm is implemented and used to improve the convergence of the simulations in the vicinity of the Oh --> C(5v) transformation.

Journal Article↗

Soil pathogens and spatial patterns of seedling mortality in a temperate tree.

The Janzen-Connell hypothesis proposes that host-specific, distance- and/or density-dependent predators and herbivores maintain high tree diversity in tropical forests. Negative feedback between plant and soil communities could be a more effective mechanism promoting species coexistence because soil pathogens can increase rapidly in the presence of their host, causing conditions unfavourable for local conspecific recruitment. Here we show that a soil pathogen leads to patterns of seedling mortality in a temperate tree (Prunus serotina) as predicted by the Janzen-Connell hypothesis. In the field, the mean distance to parent of seedling cohorts shifted away from maternal trees over a period of 3 years. Seedlings were grown in soil collected 0-5 m or 25-30 m from Prunus trees. Sterilization of soil collected beneath trees improved seedling survival relative to unsterilized soil, whereas sterilization of distant soil did not affect survival. Pythium spp., isolated from roots of dying seedlings and used to inoculate healthy seedlings, decreased survival by 65% relative to controls. Our results provide the most complete evidence that native pathogens influence tree distributions, as predicted by the Janzen-Connell hypothesis, and suggest that similar ecological mechanisms operate in tropical and temperate forests.

Biological Evolution↗

Large-scale processes and the Asian bias in species diversity of temperate plants.

An important issue in the study of biodiversity is the extent to which global patterns of species richness reflect large-scale processes and historical contingencies. Ecological interactions in local assemblages may constrain the number of species that can coexist, but differences in diversity in similar habitats within different regions (diversity anomalies) suggest that this limit is not firm. Variation in rate of species production could influence regional and perhaps local diversity independently of the ecological capacity of an area to support coexisting species, thereby creating diversity anomalies. Temperate Zone genera of plants that are disjunct between similar environments in eastern Asia and eastern North America (EAS-ENA) have twice as many species in Asia as in North America. Because lineages of these genera in Asia and North America are mostly sister pairs, they share a common history of adaptation and ecological relationship before disjunction. Thus, the diversity anomaly in EAS-ENA genera is not an artefact of taxon or habitat sampling but reflects differences in the net diversification (speciation-extinction) of the lineages in each of the continents. Here we propose that the most probable cause of the EAS-ENA anomaly in diversity is the extreme physiographical heterogeneity of temperate eastern Asia, especially compared with eastern North America, which in conjunction with climate and sea-level change has provided abundant opportunities for evolutionary radiation through allopatric speciation.

Asia↗

Human body-fluid distribution during exercise in hot, temperate and cool environments.

Using a simultaneous-dilution technique, we investigated body-fluid volume changes during exercise in seven males, during 50 min of cycling (50% maximal work rate) in hot (36.2 degrees C), temperate (22.0 degrees C) and cool conditions (14.4 degrees C). Total body water (TBW), extracellular fluid (ECFV), plasma (PV) and erythrocyte volumes (RCV) were measured, while blood volume (BV), interstitial fluid volume (IFV), extracellular water (ECW) and intracellular water volumes (ICW) were derived. During the initial 10 min of cycling, BV decreased in all environments (P .01), primarily because of a PV reduction (P = 0.01), while IFV, ECFV and ICW were not significantly changed. By 30 min, BV recovered in the temperate and cool conditions, despite mass losses of 563 and 520 mL (respectively), but remained depleted in the hot condition (P = 0.01). The 50-min volume changes revealed that, throughout exercise, body-fluid losses appeared to be drawn primarily from the extracellular space, regardless of air temperature. In the hot condition, the PV change represented 63% of the TBW loss, with the ICW contributing 23%. It was concluded that, during cycling, progressive dehydration mainly affected the extracellular space, with the intravascular and intracellular spaces being defended in less stressful conditions.

Adult↗

An improved plaque assay for poor plaque-producing temperate lactococcal bacteriophages.

This report summarizes the results from an effort to optimize the double-agar plate assay for visualization of the plaques made by six temperate bacteriophages induced from industrial strains of Lactococcus lactis. Among the several parameters found to influence the plaque assay, the effect of incorporating glycine into the growth medium was most striking, resulting in extensive increase in the plaque size of all of the 13 phage-host pairs tested. Notable effects on the plaque size of other factors such as the procedure for sterilization of the agar medium, the volume and softness of the top and bottom layers, and the number and growth stage of the bacterial cells added to the lawn, were also observed. By exploiting these findings in an optimized procedure for plaque assaying, several indicator strains were identified which were unable to support the development of plaques on standard double-agar plates. Since bacterial hosts usually are identified by their ability to support the development of plaques, this observation suggests that the severe difficulty experienced in identifying lactococcal starter strains that are sensitive towards a temperate phage, partly is a problem of methodology.

Bacteriophages↗

Generalized simulated tempering realized on expanded ensembles of non-Boltzmann weights.

A generalized version of the simulated tempering operated in the expanded ensembles of non-Boltzmann weights has been proposed to mitigate a quasiergodicity problem occurring in simulations of rough energy landscapes. In contrast to conventional simulated tempering employing the Boltzmann weight, our method utilizes a parametrized, generalized distribution as a workhorse for stochastic exchanges of configurations and subensembles transitions, which allows a considerable enhancement for the rate of convergence of Monte Carlo and molecular dynamics simulations using delocalized weights. A feature of our method is that the exploration of the parameter space encouraging subensembles transitions is greatly accelerated using the dynamic update scheme for the weight via the average guide specific to the energy distribution. The performance and characteristic feature of our method have been validated in the liquid-solid transition of Lennard-Jones clusters and the conformational sampling of alanine dipeptide by taking two types of Tsallis [C. Tsallis, J. Stat. Phys. 52, 479 (1988)] expanded ensembles associated with different parametrization schemes.

Computer Simulation↗

All-exchanges parallel tempering.

An alternative exchange strategy for parallel tempering simulations is introduced. Instead of attempting to swap configurations between two randomly chosen but adjacent replicas, the acceptance probabilities of all possible swap moves are calculated a priori. One specific swap move is then selected according to its probability and enforced. The efficiency of the method is illustrated first on the case of two Lennard-Jones (LJ) clusters containing 13 and 31 atoms, respectively. The convergence of the caloric curve is seen to be at least twice as fast as in conventional parallel tempering simulations, especially for the difficult case of LJ31. Further evidence for an improved efficiency is reported on the ergodic measure introduced by Mountain and Thirumalai [J. Phys. Chem. 93, 6975 (1989)], calculated here for LJ13 close to the melting point. Finally, tests on two simple spin systems indicate that the method should be particularly useful when a limited number of replicas are available.

Journal Article↗

Optimized parallel tempering simulations of proteins.

We apply a recently developed adaptive algorithm that systematically improves the efficiency of parallel tempering or replica exchange methods in the numerical simulation of small proteins. Feedback iterations allow us to identify an optimal set of temperatures/replicas which are found to concentrate at the bottlenecks of the simulations. A measure of convergence for the equilibration of the parallel tempering algorithm is discussed. We test our algorithm by simulating the 36-residue villin headpiece subdomain HP-36 where we find a lowest-energy configuration with a root-mean-square deviation of less than 4 A to the experimentally determined structure.

Algorithms↗

Reducing relative humidity is a practical way to control dust mites and their allergens in homes in temperate climates.

BACKGROUND: Maintaining a relative humidity (RH) of less than 50% is one recommendation for reducing numbers of house dust mites and their allergens in homes. OBJECTIVE: The purpose of this study was to determine whether, in a humid temperate climate, indoor RH could be sufficiently lowered to control dust mites and their allergens. METHODS: During a period spanning 2 humid summers (May 1998 to October 1999), dust mite and allergen densities were determined in 3 groups of homes. One group (low RH group, n = 23) maintained an RH of less than 51%. Most of these homes used a high-efficiency dehumidifier and air conditioning. A second group of homes (group A) used air conditioning only (n = 19) or air conditioning and dehumidification (n = 5) but did not maintain an RH of less than 51%. A third group of homes (group C, n = 24) controlled climate by opening windows and had an RH of greater than 51%. Normal housecleaning was maintained in all homes during the study. RESULTS: The low RH group homes started in June with a mean +/- SE of 401 +/- 124 live mites and 17 +/- 3 microg of total Der 1 allergen per gram of dust. After 17 months of maintaining an RH of less than 51%, these declined significantly to 8 +/- 3 live mites per gram (P =. 004) and 4 +/- 1 microg of Der 1 per gram of dust (P <.001). In contrast, group A and C homes exhibited seasonal peaks of 500 to 1000 mites and 40 to 70 microg of Der 1 per gram of dust. At all time points after the baseline sample, the low RH group homes had significantly less (P <.001) allergen than the group A and C homes. After 17 months, allergen levels were more than 10 times lower in low RH homes compared with humid homes. CONCLUSION: This study showed that it is practical to maintain an indoor RH of less than 51% during the humid summer season in a temperate climate, and this resulted in significant reductions in mite and allergen levels.

Air Pollution, Indoor↗

Mechanical characteristics of various tempers of as-received cobalt-chromium archwires.

The mechanical characteristics of 24 of the 36 wire cross-sectional configurations were investigated in the as-received state from among the 4 tempers of a cobalt-chromium product. After engineering mechanics were used to validate the efficacy of the span combinations, each wire was measured in flexure to determine its elastic modulus and in tension to determine its yield strength, ultimate tensile strength, and ductility. Other combined characteristics were evaluated, including flexibility, resilience, and the yield strength criterion. In these as-received materials the formability sometimes followed expectations, but the flexibility and resilience characteristics were variable and independent of temper. And although the elastic modulus was independent of testing parameters, it was affected by the loss of material at the corners of rectangular wires. Overall, the stiffnesses of cobalt-chromium wires in round configurations were comparable to those of multi- and single-stranded stainless steel wires but were 3 and 6 times greater than the stiffnesses of beta-titanium and nickel-titanium wires, respectively. In the final analysis, these as-received wires do not meet their potential as a variably formable and variably resilient alternative to stainless steel. Perhaps this is why cobalt-chromium wires have never had the impact on the profession that was expected from them several years ago.

Algorithms↗