Occurrence of Bursaphelenchus species in declining Pinus sylvestris in a dry Alpine valley in Switzerland

We determined the incidence of Bursaphelenchus species in declining Pinus sylvestris stands in the Swiss Alps. A total of 217 trees showing different degree of decline were sampled from various locations in Valais between 2001 and 2004. Bursaphelenchus species were only found in recently dead or dying trees with an overall incidence of 40%. There was a positive relationship between Bursaphelenchus infestation and blue stain in these trees. Five Bursaphelenchus species were identified: Bursaphelenchus vallesianus, Bursaphelenchus mucronatus, Bursaphelenchus sexdentati, Bursaphelenchus leoni and Bursaphelenchus silvestris. The most frequent species were B. vallesianus detected in 75% and B. mucronatus in 20% of all Bursaphelenchus‐positive trees. Bursaphelenchus vallesianus is a recently described species within the B. sexdentati group, and could be a contributing factor in the observed pine decline in Valais.     

Effects of artificial environmental conditions on anatomical and physiological ripening of Pinus sylvestris L. seeds

To determine suitable conditions for artificial ripening of Scots pine seeds, cones collected on seven occasions between August 6 and November 26, 1990, in northern Sweden, were subjected to artificial ripening at different temperatures (+5°–+15°C) and cone moisture contents for 3–9 weeks. Complete physiological ripening and improved seed vigour were attained after artificial ripening if collection occurred no earlier than the beginning of September. The highest germination percentage after artificial ripening, ca 90%, was achieved for seeds collected after the anatomical ripening in nature had ceased and was at least as high as for seeds ripened in nature. Temperature did not influence ripening, whereas a low cone moisture content impaired ripening of those seeds collected earliest. The germination percentage was not influenced by 2–6 months of cone storage subsequent to artificial ripening, but seed vigour was impaired. Anatomical ripening during artificial ripening was very limited.     

Induction of hairy and normal roots on Picea abies,Pinus sylvestris and Pinus cortorta by agrobacterium rhizogenes

Two‐ to three‐week‐old seedlings of Picea abies, Pinus sylvestris and Pinus contorta were inoculated with the supervirulent strain Agrobacterium rhizogenes R1600 2cm above the base of the hypocotyl; other treatments included inoculation with Agrobacterium tumefaciens strain A281 (pTVK291) or mock inoculation. Hairy or highly branched roots formed on 2–3% of seedlings of all 3 species that were infected by R1600 but on none of the other seedlings. Normal adventitious roots were also induced on 5–10% of Agrobacterium‐treated seedlings but none appeared on the other seedlings. Opine assays and growth rates of hairy and normal roots indicated that only roots with the hairy morphology were transformed.     

Blue‐stain infections in roots,stems and branches of declining Pinus sylvestris trees in a dry inner alpine valley in Switzerland

Increased mortality rates in Scots pine (Pinus sylvestris) forests have recently been observed in the inner alpine Swiss Rhone valley. Drought, in combination with stand competition, mistletoe infections as well as nematode and insect infestations, appears to be the main factor for the decline. In focus of this study was the occurrence and role of fungal pathogens in the decline dynamics. Branches, stems and roots of 208 trees in five different crown transparency classes were collected and inspected for blue stain and fungal infections. Neither Armillaria species nor Heterobasidon annosum s. str. were detected, but blue stain was commonly observed. Visible blue stain increased with increasing crown transparency. Among the recently dead trees, 80% showed visible blue stain in the branches, 90% in the roots and 100% in the stems. In the crown transparency classes 2 and 3 (25–60% crown transparency), five of the 103 trees showed visible blue stain in the roots, one of 130 trees in the stem but none in the branches. Blue‐stain fungi were isolated from all parts of the trees and from all crown transparency classes. Overall incidence of blue stain was highest in the roots and lowest in the branches. In class 2, roots of 60% of the trees were visibly blue‐stained or developed blue stain in culture, but stems of only 24% and branches of 14% of the trees. In the roots Leptographium species, mostly L. serpens, dominated. From stems and branches, mainly Ophiostoma species were isolated. The positive relationship between the incidence of blue stain and crown transparency, in combination with the high infection levels of roots of fairly vigorous Scots pines, indicates the pathogenic potential of the blue‐stain fungi. Hence, these fungi together with their insect vectors may well act as an important contributing factor involved in pine decline.     

Somatic embryogenesis of Pinus sylvestris

Embryogenic cultures (EC) of Scots pine (Pinus sylvestris L.) were initiated from immature embryos. Whole ovules were used as expiants. The responsive period for initiation began just after fertilization and remained throughout the development of first stages of early embryos. The main part of the embryogenic cultures were initiated by the time of cleavage polyembryony. Strong correlation was obtained between degree days and the responsive period. During subsequent years the experiments were repeated in Finland and Sweden. In all cases the responsive period for initiating embryogenic cultures was the same, about two weeks after fertilization.

In 1991–1993, a total of 138 clones of elite pine trees were tested for their ability to initiate embryogenic cultures. Of these, 33% were responsive under our experimental conditions. Based on about 300 ovules per clone the number of embryogenic lines induced by the responding clones varied from 0.2% to 9.0% of the expiants.

Several nutrient media were found to be suitable for initiation and proliferation of ECs. About half of the cell lines responded to abscisic acid by producing maturing embryos. The embryos reached full maturity in cultures of only a few cell lines. Some of the embryos that produced roots were planted in soil and transferred to a greenhouse.     

Predicting anatomical maturity of Pinus sylvestris L. Seeds in northern Fennoscandia

The hypothesis tested was that it should be possible to predict maximum attainable level of anatomical maturity of Pinus sylvestris L. seeds, and thus the germination capacity, using only one x‐ray based sample value of anatomical potential (Ap) in combination with a time function. This sample should be taken after commencement and before cessation of embryo growth. Since this predictive model should be independent of temperature, it was validated by repeatedly collecting seeds from several localities with presumably different temperatures during ripening. Although the temperature sums differed between localities, the rate of increase in Ap was almost identical in August. According to multiple linear regression analysis, the highest coefficient of determination (0.81) was achieved if Ap values from collections made in August were used in the regression. The average absolute deviation for the different localities between actual and predicted maximum Ap was 2%, and the highest deviation 7.2%. Thus, it should be possible to make a good prediction of the maximum germination capacity as early as in August. The practical consequence of this is that cone collection and possible artificial ripening could be started very close to the optimal time. Furthermore, soil scarification could be done in seed tree stands before seedfall when high seed quality is predicted.     

Seed yield from polluted stands of Pinus sylvestris L.

The number of seed scales, filled andempty seeds were evaluated for two populations growingin polluted environments in southern Poland and oneclean population growing in northeastern Poland. Thenumber of filled seeds ranged from 23 to 25 per conefrom both polluted and clean pine stands. Thevariation of investigated characters was higher amongyears than between polluted populations and the cleanone. This could be due to protection by the plant ofthe traits of generative propagation against poisonousimpact of industrial contaminants.     

Predicting knottiness of Pinus sylvestris for use in tree bucking procedures

Abstract

The quality and accompanying value of Scots pine (Pinus sylvestris L.) lumber varies markedly in the Nordic countries. Consequently, tree bucking has a great impact on the economic result. The objectives of this study were (1) to analyse which knot characteristics usually reduce pine lumber sawn from the butt-logs to the next quality grade, (2) to determine the most appropriate characteristics that could be used in predicting lumber quality, and (3) to develop models that could be used in practice for predicting the probability of certain quality grades. The study was based on field experiments and test sawing data on 100 Scots pine stems from south-western Finland. Since the results showed that the maximum dead knot is the most crucial knot characteristic when the first cross-cutting point is determined, models were created that predict the height of the first dead knot that lowers grade A to B (B-grade dead knot). Both early growth rate and dead branch height should be measured to predict pine butt-log quality. Early growth rate seems to be appropriate in predicting between-stand variation, while dead branch height is appropriate for predicting within-stand variation.     

Analysis of microtubule and microfilament distribution in Pinus sylvestris roots following infection by Heterobasidion species

Cytoskeletal dynamics play a crucial role in pathogen recognition and cell defence during the initial interactions between an invader and plant host. The aim of the work reported here was to characterize how Heterobasidion annosum s.s., Heterobasidion parviporum, and Heterobasidion abietinum affect the microtubules and microfilaments of Pinus sylvestris root cells 12‐, 24‐, 48‐, and 96‐h post‐inoculation. Inoculation of P. sylvestris with H. parviporum or H. abietinum, which have a lower specificity for P. sylvestris than H. annosum s.s, resulted in greater reorganization of host microtubules during the early stages of interaction than inoculation with the more specific H. annosum s.s. In some infected cells, spots of actin aggregates were observed. Disruption of cytoskeletal components by the application of specific cytoskeletal inhibitors facilitated the entry of the H. parviporum and H. abietinum into roots. These results suggest that the P. sylvestris cytoskeleton plays a role in the host response in the initial stages of the host–pathogen interaction.     

Gains from selecting Pinus sylvestris in southern Sweden for volume per hectare

Abstract

An overall objective of the Swedish Scots pine (Pinus sylvestris L.) tree breeding programme is to increase volume production. Selection is based on height at young age as an indicator of future volume production. This study examined the relationship between height at young age and volume production in block-plots at older ages, and the sustainability of increased growth in volume per unit area using parent breeding values. The study included five trials with controlled pollinated progenies from 71 phenotypically selected plus-trees. Height and diameter were measured in the trials at ages ranging from 7 to 36 years. The genetic correlation between height at 9 years and volume growth per unit area at 30 years of age was 0.8. The additive genetic coefficient of variation for growth per area unit was 17% at the age of 30 years, i.e. first thinning. Based on the estimated parameters, selection of the best 25% genetic entries according to their height at age 9 years resulted in 13% volume gain at age of 30 years, while selection of the 10% best resulted in 18% volume gain. The plus-tree progenies had 12% higher volume growth per unit area than the unimproved commercial check lots, and this difference needs to be added to obtain the total gains. This means that selection of the 25% best parents gave a gain of 25% in volume per hectare compared with unimproved check lots.     

Age and spatial structure of natural Pinus sylvestris stands in Latvia

Abstract

The age and spatial structure of six natural old growth Pinus sylvestris stands in Latvia were investigated, to attempt to identify retrospectively the past features of development. In each stand, one or two plots of size 200–900 m² were established. Tree locations were mapped, stem diameter was measured, and tree age was determined from cores or by counting branch whorls. Tree distribution was assessed by Ripley's K function. A clumped spatial pattern was shown for P. sylvestris younger than 100 years. The temporal patterns of establishment could be partly linked to favourable climatic periods. The major disturbance affecting pine stands along the coast was windblown sand, which partly buried some stems and probably affected the patterns of seedling recruitment and mortality. Disturbance caused by fire had a major role in determining the past regimens of mortality and establishment in dry stands located inland. The successful invasion during the last century of spruce in more mesic plots with a pine overstorey may be due to fire suppression.     

Survival and strobili production in topgrafted scions from young Pinus sylvestris seedlings

Abstract

Reducing the generation turnover increases the genetic gain in a breeding programme. Topgrafting, new genetic material being grafted into the crown of ramets of reproductive mature trees, can deliver this aim since it is able to induce strobili production in young material of conifers. To this end, I studied the effect of scion age (seedlings of 4–6 years from seed) on topgraft vitality/survival, and female and male strobili production in Pinus sylvestris (L.) over 5 years. The seedlings' growing environment prior to topgrafting had a significant impact on topgraft vitality, with more vital topgrafts obtained from potted seedlings than from seedlings grown in raised nursery beds. However, the growth environment had no clear effect on female or male strobili production. In the second year, after grafting up to 76% of the topgrafted seedlings had female strobili. Vitality increased with age of the seedling from which the scions were collected, but differences in both female and male strobili production were only marginal. The position of the topgraft within the interstock crown influenced both vitality and strobili production, with higher vitality and greater male strobili production in low positions and greater female strobili production in high positions. Based on these results, breeders should perform topgrafting as soon as the seedlings have enough scions for planned crossing activities.     

敖汉旗沙地樟子松造林试验

为探讨樟子松在敖汉旗沙地的适生能力，进行了樟子松沙地造林试验，结果表明，24年生的樟子松林，表现基本稳定，生长较快，年平均树高生长量达0．22－0．38m，胸径生长量达0．34－0．59cm，比油松和小叶杨的生长量大。调查研究发现，影响樟子松林生长的主要因素是，当地的降水量较低，在干旱年分林分出现水分亏缺；部分地区的土壤下层有白土间层，水分和养分的含量低；有些林分密度偏大，林分出现枯死现象。     

Timber quality after thinning from above and below in stands of Pinus sylvestris

Timber quality and logging damage after different thinning types in Scots pine (Pinus sylvestris L.) stands were studied in a field experiment in north Sweden. Thinning operations were mechanized and carried out according to normal Swedish practise. The treatments were thinning from below and thinning from above. The quality of the residual stand was evaluated using variables such as diameter of the thickest branch, stem taper, annual ring width, straightness and lean of trees. The only variables showing differences between treatments were lean of tree and stem straightness. No difference in the frequency of trees with logging damage was found. The conclusion of this study is that differences between thinning types in first thinning may be evened out when carried out as in commercial forestry due to extraction of strip road and damaged trees. Consequently, differences in timber quality and logging damage in the residual stand may be small.     

One-hundred-year foliage comparison of Pinus ponderosa and Pinus sylvestris under dry growing conditions in Brandenburg,Germany

Abstract

The dynamics of six different needle parameters of Pinus sylvestris L. and Pinus ponderosa Dougl. ex P. & C. Laws. were examined retrospectively for a 112-year-old mixed stand in Brandenburg, Germany, using the needle trace method. Similarities were found in needle production, needle loss and needle density. However, needle age, needle retention and total number of needles revealed significant differences between the tree species, with higher values for P. ponderosa. Pinus ponderosa yielded approximately twice as much mean whole-crown needle dry mass as P. sylvestris. Furthermore, different branching systems could be detected between the species, with both pines following “Corner's rule”. The results suggest that under identical growing conditions, P. ponderosa exhibits more efficient water use and can therefore maintain a bigger crown (as the basis for increased growth) than P. sylvestris.     

Seedling shoot,needle and bud development in three provenances of Pinus sylvestris and Pinus contorta cultivated in northern Sweden

The patterns of current‐year shoot, needle and terminal bud elongation in seedlings of three Scots pine (Pinus sylvestris L.) and three lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) provenances were compared during the third and fourth growing seasons after planting. Lodgepole pine produced longer shoots and buds than did Scots pine, mainly because lodgepole pine formed more stem units and elongated at a faster rate. Stem unit length and the duration of shoot and bud elongation differed relatively little between species and provenances. Lammas or polycyclic growth occurred in some lodgepole pine provenances, but not in any Scots pine provenance, and was associated with enhanced shoot elongation. Needle elongation commenced earlier, proceeded at a faster rate, and was greater in lodgepole pine than in Scots pine, but ceased about the same time in all species and provenances. The heat sum required to attain 50% of final length was lower for shoots and needles in lodgepole pine than in Scots pine, and for shoots in northern provenances than in southern ones. Mitotic activity in the apical meristem of the terminal bud, which occurred less than one week after the seedlings were free from snow, started and ceased about the same time in each species, but was higher in lodgepole pine than in Scots pine early in the shoot elongation period.     

Autumn frost hardiness of Pinus sylvestris offspring from seed orchard grafts of different ages

Autumn frost hardiness of offspring from clones (originating from 66.0–68.8° N) in six southern (62° N) and one northern (66.5° N) Pinus sylvestris seed orchards in Finland, was evaluated. One‐year‐old seedlings derived from open pollinated grafts of young, intermediate, and fairly mature age, and natural stand seedlings, were artificially freeze tested. The northerly located orchard produced the least injured offspring. There were no significant systematic differences between age classes. Neither were there any indications of decreased freezing injury with later age classes. The family variance was significant in four orchards. The estimated injury levels of orchard offspring were, in general, closer to those of natural stands in the neighbourhood of the orchard than natural stands at the place of clonal origin. It is suggested that not only differences in mother clone hardiness but also clonal differences in pollen contamination rate caused the observed family variation.     

Timing and intensity of precommercial thinning in Pinus sylvestris stands

The effects of timing and intensity of precommercial thinning were studied in three Scots pine artificially regenerated stands on Vaccinium forest sites in southern Finland. A two-level factorial design (3×3) was used in each stand: thinning at dominant height of 3, 6 and 9 m to 1000, 1600 and 2200 stems ha^?1. The effects of the treatments were analysed after a period of 23–25 yrs when the dominant height was 14–15 m. Early thinning resulted in the highest standing volume and amount of merchantable wood, and also in slightly accelerated height development. Thinning to 1000 stems ha^?1 caused a considerable production loss, but there were no differences between the densities of 1600 and 2200 stems ha^?1. Branches became thicker after early thinning, but the differences between the treatments were negligible for crop trees. Crown ratio was lowest as the result of early or moderate thinning (2200 stems ha^?1).     

Optimizing thinning and rotation in a stand of Pinus sylvestris on a drained peatland site

A non‐linear programming algorithm was combined with a stand simulator consisting of individual‐tree, distance‐dependent diameter growth, mortality and thinning models, and a distance‐independent height growth model. The Hooke and Jeeves’ direct search method was used for determining the optimum thinning schedule and rotation length. The optimum solutions for both deterministic and stochastic optimization, with stochastic growth predictions, were calculated. In the optimization, stand density was regarded as a function of the distance to ditch. On the rather infertile site, it was most profitable to keep the stand about twice as dense near ditches and the extraction road, which was placed midway between two adjacent ditches. Stochasticity did not affect the optimum regimes markedly nor did it increase the expected returns of the optimum regimes.     

Pathogenicity of canadian isolates of the Bursaphelenchus xylophilus (pinewood nematode) to provenances of Pinus sylvestris and Pinus contorta as grown in Finland: A greenhouse study

Seedlings of Scots pine (Pinus sylvestris L.) and lodgepole pine (P. contorta Dougl.) provenances, as grown in Finland, were inoculated with “m”; and “r”; “forms”; of the pinewood nematode (Bursaphelenchus xylophilus) from Canada, an m form isolate from France and an r form isolate from Missouri, USA. Scots pine was highly susceptible to an Alberta r form and a British Columbia m form isolate and moderately susceptible to two Quebec m form isolates. Lodgepole pine was higly susceptible to the two r form (Alberta and Missouri) isolates and moderately susceptible to the British Columbia m form and the two Quebec m form isolates. Mortality of both pines after inoculation with the French isolate was inconsistent. Mortality of both pines occurred more rapidly following inoculation with r form than with m form nematodes. Large numbers of nematodes were generally found in the tissues of both pines. Our results with seedlings need to be corroborated by inoculating larger field‐grown trees.