Growth and visible responses of Scots pine (Pinus sylvestris L.) seedlings to simulated summer frost

Scots pine seedlings, 20–30 days old, were exposed to simulated summer frost in controlled environment growth chambers. The responses observed showed extreme variation between individual seedlings; seedlings suffering from needle-necrosis, healthy-looking, and dead seedlings were found in the same treatment. Four days exposure to temperatures below –4.5°C caused multiple-leaders maximally in 7.7 % of the pine seedlings and resulted in decreased shoot and root dry weight and shoot length.     

Improved recruitment and early growth of Scots pine (Pinus sylvestris L.) seedlings after fire and soil scarification

The success of seedling recruitment of Scots pine (Pinus sylvestris L.) is strongly dependent on soil surface properties, such as humus depth and moisture content. In an undisturbed forest floor, seedlings are seldom able to become established due to the high incidence of desiccation in the organic soil layer. Methods that remove the organic soil layer are often necessary to improve the availability for radicles to reach the more stable moisture regime in the mineral soil. In this study we investigated pine-seedling establishment after mechanical soil scarification, burning of litter (O_L) and burning of litter and humus (O_L and O_FH) in two mature pine stands in Germany. The herbaceous layer of the first stand was dominated by grasses (Molinia caerulea L. and Deschampsia flexuosa L.), whereas the herbaceous layer of the second stand was dominated by blueberry (Vaccinium myrtillus L.). Pine seeds were placed in experimental plots, and seedling numbers and heights were recorded at regular intervals. All treatments that removed organic soil resulted in higher seedling counts than did the undisturbed forest floor. The highest seedling counts were found on scarified and severely burnt plots, whereas seedling counts were lower on lightly burnt plots. Seedlings were significantly taller on burnt plots. This study shows that pine regeneration is stimulated by fire, not only in boreal forests, but also under central European conditions. With the expectation of higher fire frequency in the near future due to climatic changes, natural regeneration and succession on burnt sites should receive more focus in forest management and research.     

Spatial structure of semi-natural and plantation stands of Scots pine (Pinus sylvestris L.) in northern Scotland

The success of current initiatives to maintain and enhance thearea of and the special habitats provided by the remnant semi-naturalpinewoods of northern Scotland will depend upon foresters' abilityto foster more natural structures in even-aged plantations throughstand manipulation. However, there is little information onthe structures and spatial patterns that can be found in Scottishpinewoods; such knowledge could be used to design appropriatesilvicultural regimes. A study was carried out to compare spatialstructure in three 0.8–1.0 ha plots in the CairngormsNational Park; one plot was a 78-year-old plantation stand,the other two were semi-natural stands with trees up to 300years old. Basic mensurational data showed that the semi-naturalstands were characterized by a wider range of tree sizes andmore large (>50 cm d.b.h.) trees. Spatial structure was evaluatedwith a range of different indices: the aggregation index ofClark–Evans (CE), the uniform angle and diameter differentiationindices, Ripley's L function of tree spatial distribution, pairand mark correlation functions and experimental variograms oftree diameter. The CE revealed a regular distribution in theplantation with the semi-natural stands having a random pattern.Further analysis of the latter stands indicated that, in eachcase, the older trees in the stand were regularly distributedwhile the younger ones were clustered. There was little differencein uniform angle values between the stands while the diameterdifferentiation distributions suggested greater variety in diameterwithin the semi-natural stands than in the plantation. The Ripley'sL function showed that trees in the plantation were regularlydistributed at close distances but clustered over wider distances.There were differences in pattern between the semi-natural stands;in one, trees were clustered because the positions of the youngertrees were influenced by past regeneration trials, whereas inthe other stand a random pattern was observed. Similarly, thevariogram indicated widespread homogeneity in diameter withinthe plantation, while the semi-natural stands showed high variationat close spacing because of competition followed by spatialautocorrelation up to 20 m distance. Thereafter, one of thesestands had a very different pattern because of a more intensiveregeneration history. All the indices, apart from uniform angle,were able to discriminate between the plantation and the twosemi-natural stands, but only the more detailed spatial indiceswere capable of identifying differences within the latter. Theimplications of these results for management strategies in plantationsare discussed.     

Stand structure and dynamics of four native Scots pine (Pinus sylvestris L.) woodlands in northern Scotland

Stands in four native pinewoods (Glenmore, Black Wood of Rannoch,Glen Garry and Glen Affric) dominated by Scots pine (Pinus sylvestrisL.) with contrasting management histories and climates wereassessed for differences in age, structure and dynamics. Treeage, height, diameter at breast height (d.b.h.), basal area,stem density and x, y coordinates were used to compare the recruitmentof trees (>1.3 m height, >7 cm d.b.h.), saplings (>1.3m height, <7 cm d.b.h.) and seedlings (<1.3 m) followingdisturbance events and protection from browsing. There was a20-year lag between localized intensive cultivation and treerecruitment on sites that were protected from deer browsing(Glenmore and Glen Garry). Recruitment was low in sites withdisturbance but no protection (Black Wood of Rannoch). The oldestpopulation, Glen Affric, showed signs of initial intense recruitmentfollowed by a long period of nil recruitment. Abundant standingdead trees were recorded only in Glen Affric, and prolific birchand rowan only in Glen Garry. Managers should consider localizedintense cultivation in conjunction with a complete reductionin browsing pressure for rapid seedling recruitment and increasedstructural diversity.     

Estimating sapling vitality for Scots pine (Pinus sylvestris L.) in Russian Karelia

A new method is proposed for estimating vitality or growth potential for saplings of Scots pine (Pinus sylvestris L.), based on height, diameter and height increment. A two-stage process was used to establish the vitality index. The logarithms of height, diameter and height increment were regressed against age, to adjust for the wide range of ages present in our data (c. 10,000 saplings with ages spanning 4–50 years). Then principal component analysis was used to obtain coefficients, which were, in turn, standardized on each axis to provide a vitality index scaled in standard deviations. This standardized scale allows the rank of an individual in the population to be assessed, and draws attention to possible outliers. The use of age-adjusted residuals ensured that the estimator was independent of age, and stable over a wide age range. The first principal component indicates if a sapling is relatively tall (weight = 0.5), thick (w = 0.5) or fast-growing (w = 0.7) for its age. Most of the information is contained in the first principal component, but the second component, which explains about 10% of the variance, appears to offer some utility as an indicator of ‘acceleration’ due to changing conditions. The resulting measures of vitality have been useful for research and management in the dry lichen-moss pine forest in Russian Karelia, but are specific to this species, locality and ecotype. Further research and site-specific data are necessary to adapt the system to other situations.     

Development and transferability of two multiplexes nSSR in Scots pine (Pinus sylvestris L.)

Single sequence repeat(SSR) multiplexing is a semi high-throughput PCR methodology for the analysis of multiple SSRs.We developed two SSR multiplexes selected from SSR loci previously reported in the pine literature and tested the transferability of both SSR multiplexes in nine other pine species.We tested 234 nuclear SSR loci(n SSRs) previously described in the pine literature and selected ten n SSRs following the simple criteria of interpretability and reproducibility.Selected nuclear loci were divided into two n SSRs multiplex sets and their amplification was optimized for three different multiplex PCR methods based on:(a) a custom PCR protocol,(b) a custom protocol with hotstart taq polymerase,and(c) a commercially available kit for SSR multiplexing.To validate their performance,the level of genetic diversity was assessed in three Scots pine natural populations(Hungary,northern Sweden and southern Sweden).In addition,we also tested the transferability of these multiplexes in nine other pine species.We have developed two n SSRs multiplexes of five loci each that will contribute to reduce the costs of n SSR scoring,while increasing the capacity of n SSR loci analysis.Amplification was successful in all three populations(94 % success) and the level of polymorphism(7.1 alleles/marker) was similar to that previously reported for other Scots pine natural populations.Transferability of both multiplexes was successful for those pine species closely related to Scots pine.     

Effects of low night temperature and light on chlorophyll fluorescence of field-grown seedlings of Scots pine (Pinus sylvestris L.)

In vivo chlorophyll fluorescence kinetics was observed in naturally regenerated and planted Scots pine (Pinus sylvestris L.) seedlings growing at two adjacent sites in northern Sweden. Some seedlings were shaded from direct solar radiation and some were protected from frost at night. Air temperature and solar radiation were monitored. In vivo chlorophyll fluorescence kinetics of current-year needles was measured at both room temperature and 77 K. On clear days during August, variable fluorescence of photosystem II of needles from exposed, naturally regenerated seedlings was reduced by night frosts, whereas frost caused little change in fluorescence of needles from shaded seedlings. Overnight frost-protection reduced the inhibition of photosystem II by direct sunlight. Recovery from photoinhibitory damage occurred on cloudy days. In September, the decline of variable fluorescence of photosystem II was more pronounced in unshaded than in shaded seedlings, and coincided with frosts at night. In addition, the reduction in variable fluorescence was larger for planted seedlings than for naturally regenerated seedlings. It is suggested that the inhibition of photosystem II activity was caused by an interaction between low temperatures and light. Natural night frosts are proposed to increase the susceptibility to photoinhibition in the following day(s).     

Stand structure, competition and growth of Scots pine (Pinus sylvestris L.) in a Mediterranean mountainous environment

The relationship between competition and tree growth was studied in four stands of Pinus sylvestris L. occurring in a continental Mediterranean mountain area (in the Guadarrama range, Spain), i.e., an uneven-aged stand, a stand with oak (Quercus pyrenaica Willd.) understorey, a plantation, and a mature even-aged stand. Competition was measured by a simple size-ratio distance-independent index and was negatively associated with tree diameter. This negative association was stronger in the uneven-aged, plantation and mature even-aged stands than in the stand with oak understorey. Competition was also negatively associated with current diameter increment. This relationship was moderately strong in the mature even-aged stand and weak in the uneven-aged stand and the plantation. In the uneven-aged and the mature even-aged stands, a weakly significant relationship was found between diameter growth and tree size, whereas these parameters were not associated in the stand with oak understorey. The competition index provided a better prediction of growth rate than the alternative use of diameter. Both diameter and basal area growth were greater in the uneven-aged than in the even-aged stands.     

Comparison of terrestrial laser scanning and X-ray scanning in measuring Scots pine (Pinus sylvestris L.) branch structure

While X-ray scanning is increasingly used to measure the interior quality of logs, terrestrial laser scanning (TLS) could be used to collect information on external tree characteristics. As branches are one key indicator of wood quality, we compared TLS and X-ray scanning data in deriving whorl locations and each whorl’s maximum branch and knot diameters for 162 Scots pine (Pinus sylvestris L.) log sections. The mean number of identified whorls per tree was 37.25 and 22.93 using X-ray and TLS data, respectively. The lowest TLS-derived whorl in each sample tree was an average 5.56?m higher than that of the X-ray data. Whorl-to-whorl mean distances and the means of the maximum branch and knot diameters in a whorl measured for each sample tree using TLS and X-ray data had mean differences of ?0.12?m and ?6.5?mm, respectively. One of the most utilized wood quality indicators, tree-specific maximum knot diameter measured by X-ray, had no statistically significant difference to the tree-specific maximum branch diameter measured from the TLS point cloud. It appears challenging to directly derive comparative branch structure information using TLS and X-ray. However, some features that are extractable from TLS point clouds are potential wood quality indicators.     

Correlations between needle and shoot growth characteristics in Scots pine (Pinus sylvestris L.) stands

Shoot, needle and bud growth in three stands of different ages(9, 20, and 60 years) of Scots pine were studied in order toreveal relations between these variables. Within the growingseason the sizes of buds and needles developed in parallel.Significant regressions between number of short shoots and eitheraverage needle length or total needle length of the parent shootwere found. The strongest regressions were found in the twoyoungest stands as well as in the top of the canopy.     

Influence of high-temperature convective flow on viability of Scots pine needles(Pinus sylvestris L.)

During a forest fire, plants are affected by high temperatures causing stress. At the time of burning, it is difficult to record temperature changes in tree crowns and the associated effects on photosynthesis. This paper presents the results of modelling a high-temperature effect simulating a convective flow from a ground fire. Evaluation of the response was carried out by the parameters of rapid fluorescence(Fv/Fm, ETR), the state of the pigment complex, and the relative water content in the needles. To characterize the degree of heat endurance and short-term effects concerning thermal damage, saplings of Scots pine(Pinus sylvestris L.) were used at different times during the growing season(June, July, August, September). Experimental heating at 55 ℃ lasted for 5 and 10 min. There were different levels of heat resistance by the needles. Data in June show that heating of the saplings significantly suppressed photosynthesis. In July, August, and September, the photochemical quantum yield(Fv/Fm) was restored to 75% and 60% from the initial level after 5-and 10-min heating, respectively. The electron transport rate(ETR) for saplings in September was restored to their initial level within 3 days after a short heat exposure.Restoration of the photosynthetic activity in needles was observed after a 5-min impact, but by the end of the study period, restoration had not reached control values. A longer heating of 10 min resulted in an irreversible suppression of photosynthesis and destruction of the photosynthetic apparatus, as evidenced by the decrease in the number of photosynthetic pigments.     

Exploratory study on the impregnation of Scots pine sapwood (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) with different hot melting waxes

Scots pine sapwood (Pinus sylvestris L.) and beech (Fagus sylvatica L.) were impregnated with five waxes. The experiments indicate deep penetration into pine sapwood. Besides the viscosity, an influence of the wax polarity is presumed. Wax penetrates pine wood deeply via the cross-section, but not sufficiently enough to impregnate longer construction elements. However, the radial wax uptake exceeds the uptake via the tangential orientation and guarantees complete soaking of the sapwood tissue. The lateral wax penetration within beech is quite low and irregular. In addition to the temperature, a prolonged process procedure is decisive for an increasing wax uptake. As such, beech wood vessel elements seem to be fully impregnable via the longitudinal surface after a longer process procedure.     

Modelling mortality of Scots pine (Pinus sylvestris L.) plantations in the northwest of Spain

Mortality is an important element of growth and yield models, especially if only low intensity silvicultural treatments are carried out. The objective of the present study was to develop a model for predicting tree number decline in planted even-aged stands of Scots pine (Pinus sylvestris L.) in Galicia (northwestern Spain). The model was constructed using data from two inventories of a trial network involving 68 permanent plots located in unthinned stands, or stands thinned lightly from below. Two alternatives were tested. In one alternative, a two-step modelling strategy was applied. First, a binary response function predicting the survival probability of all the trees in the stand was constructed, and an equation for reduction in tree number was developed, using only data where death had occurred over the period analyzed. Three different approaches were then used to compare the application of the above-mentioned functions together. In the other alternative, a mortality function for directly predicting the reduction in tree number was fitted, including all plots (with and without occurrence of mortality). Both alternatives provided similar results, showed logical behavior, and performed satisfactorily in evaluation tests. However, in choosing the best strategy for inclusion in a stand-level simulator, the use of the second alternative is recommended because it possesses the path invariance property required in a mortality model.     

Evolutionary history and phylogeography of Scots pine(Pinus sylvestris L.) in Europe based on molecular markers

In this review we summarized recent historical records and molecular studies on evolutionary history and phylogeography of Scots pine with focus on the European highly fragmented distribution area of the species. Fossilized pollen, plant micro-and macrofossil records provided evidences on the large-scale species' range shifts and demographic changes during the Quaternary. Populations of Scots pine were documented both in the glacial(incl.full glaciation) and interglacial periods. Recolonization of Europe after the glaciation originated from the(Sub)Mediterranean areas like the Balkan Peninsula but also from around the Eastern Alps and the surroundings of the Danube plain. Fennoscandia and northern European Baltic regions were most probably colonized from two main directions, from Western Europe and from the Russian Plain. Modern history of Scots pine was hardly affected by anthropogenic activities that started to strengthen in the Bronze and Iron Age. Along with the fossil records,molecular genetic tools were used to infer the origin and putative history including migration, differentiation and demography of the species. In this paper we compiled the major publications(30) of molecular genetic studies of the past 20 years derived from distinctly inherited organelle genomes(mitochondrial, chloroplast, nuclear) revealed by different marker systems(mt DNA-cox1,-nad1,-nad3,-nad7, ISSR, cp SSR, n SSR, B-SAP, SNP). It is important to consider that different phylogeographic patterns can be drawn by the analysis of different DNA marker types.Accordingly the use of more than one marker simultaneously outlines the most sophisticated phylogeographical pattern on the genetic lineages and can reveal high differentiation of the European distribution. Combined marker systems and markers derived from coding sequences have also been used to detect species' phylogeographic patterns,but these were rarely applied to Scots pine. Although new molecular techniques can provide higher resolution data for populations, the reviewed results can shape the direction of further studies.     

Crookedness of pedunculate oak (Quercus robur L.) growing under a canopy of Scots pine (Pinus sylvestris L.)

Natural regeneration of pedunculate oak growing under a canopy of Scots may be used for conversion into a mixed or predominantly broadleaved forest. From an economic perspective it is desirable that the oaks have straight stems. In this paper we present a case study for analysing oak stem curvature and its causes. The study was conducted in a mature pine stand with understorey oaks of age ca. 60 years in Poland. The oaks were classified into two main groups as either straight or crooked. The following variables were measured or assessed for the oaks: (1) stem curvature (crookedness), total tree height, diameter at breast height (DBH) and some tree crown characteristics, (2) the growth of DBH and height in each year of the life of each tree and (3) the competitive pressure of surrounding trees. Durable stem curvatures were formed at the culmination of the height increment. The first 20 years of the life of the oak were crucial in terms of stem quality. The annual height increment was larger in the years when the curvature was formed than in adjacent years. The factors that caused crooked stems were the same for straight and crooked oaks, but the magnitude of the response was different. When planning the conversion of Scots pine into oak, full overhead light should be provided as early as possible, but not later than 20 years since the establishment of the regeneration.     

Modelling silvicultural and economic alternatives for Scots pine (Pinus sylvestris L.) plantations in north-western Spain

Two silvicultural alternatives for Scots pine (Pinus sylvestrisL.) plantations in north-western Spain were simulated and compared.One corresponded to the current management practice appliedin the region and the other was an intensive silvicultural regime.Both alternatives were described by a specific combination ofplantation density, precommercial treatments, thinning patternand rotation age. Stand development of each silvicultural alternativewas generated using a regional growth and yield model implementedin a simulator called GesMO, for three site qualities that representedpoorest, intermediate and best sites found in the region. Differenttimber grades associated with each alternative were predicted,and estimates of costs and selling prices were used to predicta cash flow pattern for each of the simulated alternatives.The alternatives were ranked using the criterion of net presentvalue of an infinite series of rotations. Sensitivity analysis,in terms of basic prices, discount rate and rotation length,was also carried out. In addition, the effects of risk of fireon net revenues were evaluated. For the present regional marketconditions the results showed that the currently applied alternativeis not the best one if the main aim is profit maximization.For very poor quality sites the proposed schedules are uneconomicalfor all silvicultural alternatives.     

Water sorption in coated Scots pine (Pinus sylvestris L.) logs and influence of incipient decay

Abstract

Scots pine log specimens were given three different surface treatments and two different orientations of large cracks, and subjected to cyclic wetting and drying. Individual fitting of a mechanistic growth model was used to study the shape of absorption and accumulation curves and the final drying curve. Two parameters from this model (increase/decrease rate and maximum/minimum weight gain) were used for statistical analysis. The results indicate that wood tar results in less accumulated moisture over time than solvent-borne or water-borne coating or no treatment at all. An incipient attack by a white-rot fungus on parts of the material during storage affected water uptake greatly, often overriding surface treatment.     

Influence of gibberellic acid and stock plant irradiance on carbohydrate content and rooting in cuttings of Scots pine seedlings (Pinus sylvestris L.)

Seedlings of Pinus sylvestris L. were grown at three different irradiances (12, 30, or 60 W m(-2)) under a 17 h photoperiod. After six weeks, cuttings were excised and rooted at 30 W m(-2). Gibberellic acid (GA(3), 5 microl of 2 x 10(-4) or 2 x 10(-3) M) was applied to each cutting immediately after excision. Cuttings from stock plants grown at the low irradiance rooted most quickly, whereas the highest number of roots per cutting was obtained in cuttings from stock plants grown at 30 W m(-2). Gibberellic acid delayed rooting and reduced the number of roots in cuttings from stock plants grown at 12, 30, or 60 W m(-2). The initial carbohydrate content of cuttings increased with stock plant irradiance. For all carbohydrates, except myoinositol and an unknown inositol derivative, the content per cutting increased during the first 28 days of rooting. The GA(3) treatment significantly reduced the starch content of cuttings during the rooting period, but did not significantly change the content of ethanol soluble carbohydrates.     

Determination of elements removal in different harvesting scenarios of Scots pine (Pinus sylvestris L.) stands

Increasing demand for renewable energy and limiting CO₂ emissions have stimulated much interest in wood-based biofuels. Unfortunately, expanding the utilization of forest biomass may cause nutrient depletion in forested environments. This study investigates the element content from various parts of the tree. Comparisons were made between different harvesting scenarios and their impact on the amount of nutrients removed from the forest environment. The harvesting scenarios were: stem-only harvesting (SOH), branch and stem harvesting (BSH), and two variants of whole-tree harvesting (WTH). The elements taken into account were: carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), sulphur (S), copper (Cu), iron (Fe), nickel (Ni), manganese (Mn), zinc (Zn), cadmium (Cd), chromium (Cr) and lead (Pb). To make the results comparable, the same amount of removed biomass was taken into calculation. The differences between harvesting scenarios were significant. The amounts of removed elements formed similar pattern: the lowest level was found in SOH, average in BSH, and highest in both variants of WTH. This confirms that the application of WTH is connected with increased risk of nutrient depletion, even when the volume of harvest would be equal to other variants.     

Regulation of organic and inorganic nitrogen uptake in Scots pine (Pinus sylvestris) seedlings

Plants possess regulatory mechanisms that enhance nitrogen (N) uptake under conditions of spatial and temporal variation in N availability. Study of regulatory mechanisms has focused almost exclusively on the uptake of inorganic N sources (i.e., ammonium (NH4+), nitrate (NO3-). Several lines of evidence, however, suggest that amino acids may constitute a potential source of N for a number of plant species, including conifers. In the present study, we investigated the uptake of amino acids and inorganic N in Scots pine (Pinus sylvestris L.) seedlings grown at different N concentrations. We compared the uptake rate of the individual N sources using U-[13C2], [15N]-glycine, U-[13C6], [15N4]-arginine, 15NH4, or 15NO3, and tested the short-term effect of N supply on the uptake rate of glycine, arginine and in field-grown Scots pine seedlings. Our data indicate that Scots pine seedlings can absorb substantial amounts of N in the form of intact arginine and glycine molecules. The data also suggest that Scots pine seedlings down-regulate their uptake of NH4+-N and arginine-N, but not of glycine-N in response to increased endogenous N concentrations.