Intraspecific variation in Heterobasidion annosum for growth in sapwood of Picea abies and Pinus sylvestris

Two greenhouse experiments were conducted to study intraspecific variation in growth of the root rot fungus Heterobasidion annosum in living host sapwood. In experiment 1, Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings were inoculated with H. annosum isolates, 14 each of the S-and P-intersterility groups, collected from various parts of Sweden. In pine, the P-group isolates were more virulent than the S-group isolates both in terms of infection frequency, induced mortality rate (p < 0.05), and fungal growth in sapwood (p < 0.05). In spruce, the P-group isolates were also more virulent on average, but the difference was not statistically significant. Both S and P isolates had a higher infection frequency and a significantly longer sapwood growth on spruce than on pine. The P-group caused higher mortality on pine than on spruce. The length of the lesion in the inner bark was strongly correlated with fungal growth in spruce, but not in pine where the lesions were short or absent. In experiment 2, ten Norway spruce clones were inoculated with 18 S-isolates, originating from nine live-decayed trees and from nine spore-infected stumps in a single Norway spruce stand. The objective was to test whether any selection for growth rate in sapwood was detectable among individuals of H. annosum originating either from stumps or trees. The results gave no support for such selection since no difference in sapwood growth between the two groups of isolates was found.     

Growth rates of Heterobasidion annosum s.s. and H. parviporum in functional sapwood of Pinus sylvestris and Picea abies

Growth rates of H. annosum s.s. and H. parviporum were investigated in the functional sapwood of young Pinus sylvestris and Picea abies plants as an indicator of the relative susceptibilities of the hosts to these pathogens. The stems of 520 five‐year‐old P. abies and 321 four‐year‐old P. sylvestris plants were inoculated and the extent of infection determined 16 weeks later. H. annosum s.s. grew further than H. parviporum in P. sylvestris sapwood, while in P. abies, no differences between the two Heterobasidion spp. were found. Both H. annosum s.s. and H. parviporum spread faster in the sapwood of P. abies than in P. sylvestris. There was high within‐host species variation in growth rates for both P. sylvestris and P. abies suggesting it may be possible to identify tree genotypes with lower susceptibility.     

Stilbenes and resin acids in relation to the penetration of Heterobasidion annosum through the bark of Picea abies

Concentrations of the stilbene glucosides astringin and isorhapontin, which ranged from 5 to 50 mg/g fresh weight in Picea abies bark, decreased in response to in vivo infection with the root-rot fungus Heterobasidion annosum. The initial concentration of the stilbene astringin was negatively correlated with the depth of hyphal penetration. Resin acid contents increased following infec-tion, but were not correlated with the depth of hyphal penetration. The spatial distribution of stilbene glucosides in spruce stem, root collar and root bark, and the seasonal variations in con-centration, were estimated.     

Root growth capacity and field performance of Pinus sylvestris and Picea abies seedlings

Correlations between root growth capacity (RGC), at the time of planting, and field performance were studied for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings. Before planting a gradient in seedling viability was generated through exposure to low root temperatures and different winter storage regimes. The hypothesis that high RGC values would improve field performance was to some extent verified for pine seedlings while no correlations could be registered for spruce. Reasons for these results are discussed.     

Variation in growth of Heterobasidion annosum among clones of Picea abies incubated for different periods of time

Thirty‐seven 4‐year‐old clones of Picea abies were inoculated with one isolate of the S intersterility group of Heterobasidion annosum in a greenhouse. The dehardened cuttings were organized in three different groups with four to six ramets in each group. All groups were inoculated on the same day shortly after shoot elongation. The groups were sampled for H. annosum growth after 34 (group 1), 83 (group 2) and 182 days (group 3), respectively. Measured parameters were cutting height and diameter, vigour index of the cuttings, infection incidence, mortality rate and fungal growth in the stem. The height of the cuttings was almost constant during the 6 months of incubation, whereas the diameter increased by about 10% during the same period. The proportion of living cuttings containing H. annosum decreased with time (99.5, 93 and 67% infection in groups 1, 2 and 3, respectively) and differed significantly among clones in group 3. Mortality rate increased with time (0.5, 22 and 37% mortality in groups 1, 2 and 3, respectively) and differed significantly among clones in groups 2 and 3; the same clones being most susceptible for both times. Mean fungal growth into the wood was significantly different among groups and among clones within each group. The ranking position for fungal growth was similar in the three groups. The results indicate that frequency of infection success, mortality rate and fungal growth are clone‐dependent factors. Broad sense heritability varied between 0.08 and 0.25 for fungal growth and lesion length at the three incubation periods. Infection success frequency was initially not different among clones but in the longer incubation periods there were significant differences among clones, indicating differences in resistance. Fungal growth in wood differed among separate host clones irrespectively of the length of inoculation period. The vigour of the cuttings seem to influence the length of fungal extension only in the initial stage of the infection.     

Root-associated fungi of healthy-looking Pinus sylvestris and Picea abies seedlings in Swedish forest nurseries

The aim of this study was to assess fungal communities in roots of healthy-looking Pinus sylvestris L. and Picea abies (L.) Karst. seedlings in nine forest nurseries in Sweden using a combination of traditional culturing and direct sequencing of internal transcribed spacer of fungal ribosomal RNA (ITS rRNA) from the roots. Culturing from 1800 surface-sterilised root segments resulted in 2387 fungal cultures representing 42 different taxa. Direct sequencing from 180 root segments resulted in 119 ITS rRNA sequences representing 25 different taxa. In total, 55 different fungal taxa were detected using both methods. Although direct sequencing was more efficient than culturing in detecting different fungal taxa, both methods provided complementary information about fungal communities in roots since each detected rather different groups of fungi. The most dominant taxa detected by culturing were Trichoderma viride Pers. (19.5%), Phoma mucivora Davey & Currah (19.1%), Phialocephala fortinii Wang & Wilcox (17.4%) and Meliniomyces variabilis Hambl. & Sigler (10.2%), while Thelephora terrestris Ehrh. (26.1%), Unidentified sp. NS126 (25.2%) and Heliotales sp. C20 (10.1%) were most commonly detected by direct sequencing. In conclusion, results showed that forest nurseries in Sweden harbour diverse communities of fungi associated with the roots of healthy-looking P. sylvestris and P. abies seedlings. Although fungal communities were often dominated by saprotrophs and endophytes, several facultative pathogens were also detected indicating that under suitable conditions they may be a potential threat to the plants.     

Effects of site preparation on soil properties and on morphology of Pinus sylvestris and Picea abies seedlings sown at different dates

The aims of the study are to find out the effects of site preparation on soil properties and on the morphology of three-year-old Pinus sylvestris L. and Picea abies (L.) Karst. seedlings sown at different dates along a slope with variation in soil texture, water, and fertility. Based on the hypothesis that soil texture affects soil water content, water retention capacity, and nutrient content, we studied site preparation of varying intensities: exposed C horizon, mounds (broken O/E/B horizons piled over undisturbed ground), and exposed E/B horizon. Though the growing time difference between sowings was about one month, after three growing seasons, spring-sown seedlings were larger than summer-sown seedlings. P. sylvestris seedlings were largest with mounds and smallest with exposed C horizon, but site preparation did not affect the morphology of P. abies seedlings.     

Incidence of Gremmeniella abietina in planted seedlings of Picea abies and Pinus sylvestris in northern Finland

The ascomycete Gremmeniella abietina causes a disease (scleroderris canker) on conifers. The pathogen kills terminal shoots and branches of Pinus sylvestris and Picea abies, sporulates on host shoots and causes leader changes (i.e. dieback). Damage caused by G. abietina was investigated in young P. abies and P. sylvestris plantations in northern Finland. Side branches from seedlings of both species and the main stems of P. sylvestris were collected from three sites in two locations (Poksa 1 and 2, Kivalo) in northern Finland. The number of cankers and leader changes was counted in branches of each age (i.e. year) in a total of ca. 6300 shoots of P. abies and 1200 shoots of P. sylvestris. Cankers were common on both P. abies and P. sylvestris in Poksa 1 (2002–2008) and on P. abies in Poksa 2 (1998–2001). In Kivalo, cankers occurred only sporadically on P. sylvestris. Leader changes were most frequent in 1999–2009 in Poksa 1, in 2001–2009 in Poksa 2 and in 2003 in Kivalo. Cankers and other symptoms of infection were more obscure on P. abies than on P. sylvestris. According to both conidial morphology and molecular analysis, the strain of G. abietina infecting both P. abies and P. sylvestris was small‐tree type (STT). This is the first report of G. abietina, STT or B type, injuring P. abies in plantations.     

Canopy density in stands of Picea abies and Pinus sylvestris after different thinning methods

Altogether 82 plots (261 estimations) of Picea abies (L.) Karst, and 193 plots (360 estimations) of Pinus sylvestris (L.) stands were estimated by a vertical tube. The “crown free projection”, CFP, of stands thinned in three methods with different thinning grades was measured: unthinned, heavily and very heavily thinned, heavily thinned delayed first thinning, extra heavily thinned and thinned from the top. Basal area (m²ha^?1) density (stems ha^?1) and diameter sum (m ha^?1) were plotted against CFP. Basal area was the best practical measure of stand in this study. Generally Scots pine stands have higher CFP and the curves are steeper than in Norway spruce stands. Depending on the grade of thinning, heavily and very heavily thinned spruce stands, delayed first thinning included, have CFP values of 10–15% and stands thinned from the top, 20–40%, compared with 30–80% and 30–60% respectively in pine stands. Extra heavily thinned stands have the highest CFP, 20–80% in spruce and 50–90% in pine stands. The CFP levels after thinning are too high in pine stands for avoidance of sucker and sprout production of aspen and birch. In dense Norway spruce stands thinned from the top or heavily and very heavily thinned, the CFP values are low enough (≤30%) to diminish the production of suckers.     

Application of growth regulators in aqueous media and organic solvents to seeds of Picea abies and Pinus sylvestris

Incubation with acetone and dichloromethane had little effect on the germination of different lots of Norway spruce seeds. This was not the case with Scots pine where almost half the seed lots tested were adversely affected by acetone and dichloromethane. The auxins indole‐3‐acetic acid (IAA) and indole‐3‐butyric acid (IBA) were applied to Scots pine seeds in acetone, dichloromethane and phosphate‐citrate buffer. The uptake of the two compounds was most rapid from acetone. Although the uptake from dichloromethane was slower than from acetone it reached the same level after 6 h. Uptake of the growth regulators from buffer was significantly lower than from the organic solvents. The accumulation of IAA and IBA into the seeds from both acetone and dichloromethane was linear between 0.5 and 10 mM, and between 0.5 and 15 mM from buffer. IAA and IBA levels in infused seeds declined over a 5‐day germination period, the former more rapidly than the latter. The metabolic activity of the IAA degradation system was as effective in seeds after immersion in the organic solvents as seeds immersed in buffer.     

Aluminium concentration versus the base cation to aluminium ratio as predictors for aluminium toxicity in Pinus sylvestris and Picea abies seedlings

Aluminium (Al) toxicity is considered an important factor in forest deterioration caused by soil acidification. A ratio of base cations (BC) to Al in the soil solution lower than 1 is widely used as an indicator for potentially adverse effects on tree health. In our view, the validity of the assumptions underlying the use of the BC:Al ratio as an indicator for Al toxicity in trees has never been evaluated properly.Here, we evaluate the importance of the base cations Ca and Mg in counteracting Al toxicity. Pinus sylvestris and Picea abies seedlings were grown on nutrient solution with a range of Al (0–0.25–0.5–1–2 mM) and base cation (0.25–0.5–2 mM) concentrations, giving BC:Al ratios of 1 at different levels of Al. Increasing concentrations of Al in solution caused growth reductions, which could not be counteracted by increasing concentrations of BC in solution with P. sylvestris and only partly counteracted with P. abies. Increased concentrations of Al in solution decreased the concentrations in shoot and root of both Ca and Mg, while increased concentrations of BC in solution increased tissue concentrations of BC. Growth reductions were, however, not a result of BC deficiencies, as growth reduction already occurred in tree seedlings that maintained adequate concentrations of Ca and Mg.All growth and uptake variables measured showed a higher or equal correlation with the absolute concentrations of Al or Al+BC in solution than with the BC:Al ratio. We conclude that Al toxicity is determined solely by the concentration of Al in solution. Shoot growth decreased significantly as dissolved Al increased at a constant BC:Al ratio of 1. In P. abies, but not in P. sylvestris, dissolved BC can positively affect uptake of BC and growth, which might partly alleviate the toxic effects of Al. Our results show that the mechanistic explanation for the effect of the BC:Al ratio is insufficient to describe Al toxicity. Care should be taken when using models based on the BC:Al ratio to predict the effect of Al on tree growth.     

Ectomycorrhiza formation and growth of Picea abies seedlings inoculated with alginate-bead fungal inoculum in peat and bark compost substrates

Sphagnum peat (peat), spruce bark compost (compost), peat +perlite (1 : 1, v : v) and compost + perlite (1 : 1, v : v)substrates were inoculated with vegetative alginate-bead inoculumof Hebeloma crustuliniforme, Hygrophorus agathosmus or Paxillusinvolutus or left uninoculated prior to the addition of Norwayspruce seed. Growth and percentage of mycorrhization of barerootseedlings cultivated in a greenhouse were evaluated after thefirst growing season. Seedlings grown in peat-based substrateshad significantly larger aboveground and total dry weight, butsignificantly lower mycorrhization percentage than those grownin compost-based substrates. There were no significant differencesbetween fungal treatments (including control) for both the percentageof mycorrhization and growth of seedlings. The artificiallyintroduced fungi were not efficient in mycorrhizal formation– naturally occurring fungi were common in all treatments.However, a significant interaction between substrate and fungustreatments in root dry weight was detected. Hebeloma-inoculatedseedlings grown in peat showed the highest value of root dryweight. This fact indicates other possible effects of the fungion root growth independent of mycorrhization. Growth parameterswere negatively correlated with the extent of mycorrhization,indicating allocation of host photosynthates to the fungi. Tothe best of our knowledge, operational inoculation of Norwayspruce seedlings with the test fungi has not been reported previously.     

Snow-packing as a potential harmful factor on Picea abies,Pinus sylvestris and Betula pubescens at high altitude in northern Finland

Snow-packing, a combination of ice, hoarfrost and snow on trees, and the subsequent tree damage by snow, were estimated on Norway spruce (Picea abies), Scots pine (Pinus sylvestris), and pubescent birch (Betula pubescens) in the winter of 1993-94 in southern Lapland, northern Finland, near the local alpine timberline around 400 m a.s.l. Snow-packing on each fully sized tree increased from a few hundred kilograms at 150–250 m a.s.l. to a maximum of 3290 kg at 300–350 m a.s.l. At 300 m a.s.l., snow-packing per metre of stem increased from 30 to 50 kg on trees < 5 m in height up to 180–200 kg on 20-m trees. There was 300 000-480 000 kg/ha of snow accumulated on tree crowns. No stem breakage by snow-packing occurred at or below 250 m a.s.l., whereas at 290–350 m a.s.l., 0-46%, 39-100%, and 0–33% of the spruce, pine and birch trees, respectively, had broken tops. Birch appeared to be the most resistant and pine the most susceptible to snow breakage.     

Stomatal conductance alone does not explain the decline in foliar photosynthetic rates with increasing tree age and size in Picea abies and Pinus sylvestris

Foliar light-saturated net assimilation rates (A) generally decrease with increasing tree height (H) and tree age (Y), but it is unclear whether the decline in A is attributable to size- and age-related modifications in foliage morphology (needle dry mass per unit projected area; M(A)), nitrogen concentration, stomatal conductance to water vapor (G), or biochemical foliage potentials for photosynthesis (maximum carboxylase activity of Rubisco; V(cmax)). I studied the influences of H and Y on foliage structure and function in a data set consisting of 114 published studies reporting observations on more than 200 specimens of various height and age of Picea abies (L.) Karst. and Pinus sylvestris L. In this data set, foliar nitrogen concentrations were independent of H and Y, but net assimilation rates per unit needle dry mass (A(M)) decreased strongly with increasing H and Y. Although M(A) scaled positively with H and Y, net assimilation rates per unit area (A(A) = M(A) x A(M)) were strongly and negatively related to H, indicating that the structural adjustment of needles did not compensate for the decline in mass-based needle photosynthetic rates. A relevant determinant of tree height- and age-dependent modifications of A was the decrease in G. This led to lower needle intercellular CO2 concentrations and thereby to lower efficiency with which the biochemical photosynthetic apparatus functioned. However, V(cmax) per unit needle dry mass and area strongly decreased with increasing H, indicating that foliar photosynthetic potentials were lower in larger trees at a common intercellular CO2 concentration. Given the constancy of foliar nitrogen concentrations, but the large decline in apparent V(cmax) with tree size and age, I hypothesize that the decline in Vcmax results from increasing diffusive resistances between the needle intercellular air space and carboxylation sites in chloroplasts. Increased diffusive limitations may be the inevitable consequence of morphological adaptation (changes in M(A) and needle density) to greater water stress in needles of larger trees. Foliage structural and physiological variables were nonlinearly related to H and Y, possibly because of hyperbolic decreases in shoot hydraulic conductances with increasing tree height and age. Although H and Y were correlated, foliar characteristics were generally more strongly related to H than to Y, suggesting that increases in height rather than age are responsible for declines in foliar net assimilation capacities.     

Mycelial growth and exclusion of Heterobasidion parviporum inoculated in branches of 15‐year‐old Picea abies clones

Twigs of 22 clones of 15‐year‐old Picea abies grafts were inoculated with Heterobasidion parviporum in July and in September 2003. Fungal growth varied between clones and exclusion of the pathogen varied significantly among clones inoculated in July. The results indicate that twigs exhibit the same infection pattern as cuttings when inoculated with H. parviporum and that exclusion of the pathogen in twigs is a clone‐dependent character that occurs during the vegetation period.     

Current growth differences of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and birch (Betula pendula and Betula pubescens) in different regions in Sweden

Abstract

The choice of species in forestry is important, and a real issue as large areas of wind-damaged forest land in southern Sweden need to be regenerated. To compare the growth potential between the most common tree species in Sweden, ratios between site quality derived from site index values determined with site properties were used. A regression function to determine site index for birch from site properties was used to complement the known relationships between site properties and site index for spruce and pine. In large regions of Sweden the distribution of site quality classes was calculated to compare the special characteristics and demands of the three species. On average, the growth difference for pine compared to spruce was about 60% in southern Sweden and 95% in northern Sweden. Corresponding figures between birch and spruce were 40% and 60%. Birch was expected to produce around 60% of pine in northern Sweden and about 70% in southern Sweden. However, it must be stressed that the comparison is based on survey data encompassing mainly naturally regenerated birch, whereas spruce and pine are mainly planted.     

磷肥诱导下层植被伴生的辐射松苗生长、磷素营养和土壤有效磷变化

通过在温室条件下施加不同剂量的重过磷酸钙(0,50和100mg·kg-1P),对典型水铝英石土壤(Orthic Allophanic Soil)的土壤植物有效磷、磷素营养和伴生有金雀花(Cytisus scoparius)或黑麦草(Lolium multiflorum)的辐射松苗木生长变化情况进行了研究。结果表明,施加磷肥增强了辐射松根际和磷素匮乏土体的有效磷。与辐射松苗伴生的金雀花、黑麦草根际土壤有效磷也增加。辐射松新枝和老枝松针、茎和根系中磷含量随施加重过磷酸钙剂量的增加而增加;但是金雀花、黑麦草对辐射松苗磷素营养的影响依赖于土壤磷状态。未施肥处理下,与金雀花伴生的辐射松新枝和老村松针、茎和根系中磷含量要高于与黑麦草伴生的辐射松苗,而施肥处理下,结果相反。这可能与金雀花生长大量消耗土壤中有效磷有关。因为,在两个施肥剂量(50mg·kg-1P和100mg·kg-1P)上,与金雀花伴生的辐射松根际土壤中Bray-2磷含量始终低于与黑麦草伴生的辐射松根际土壤。此外,在施肥浓度100mg·kg-1下,与金雀花伴生的辐射松苗干特质量低于黑麦草伴生的辐射松。说明在中、高施肥水平,辐射松苗与黑麦草伴生生长好于与金雀花伴...     

Growth response of broom (<Emphasis Type="Italic">Cytisus scoparius</Emphasis>) growing with and without radiata pine (<Emphasis Type="Italic">Pinus radiata</Emphasis>) seedlings to different P levels in soils

A study was carried out to test the effects of three rates of TSP (triple superphosphate) (0, 50, and 100 mg·kg -1 P) on growth of broom with and without radiata pine seedlings and to determine the rela- tionships between P concentrations in the broom shoot and dry matter yields with soil plant-available P (Bray-2 P). A bulk sample of soil was collected from Kaweka forest at soil depth of 0 10 cm, in New Zealand on March 11, 2001. The forest area was not supplied with fertiliser at least 30 years. The results show that TSP application increased P avail- ability in the soil. The P availability concentration in soil of broom with radiata pine seedlings was higher than that in soil of broom alone. Bray-2 P concentrations had a significant logarithmic relationship with P con- centrations of broom shoot and an exponential relationship with dry matter weight of whole broom plant.     

Characterization of juvenile wood to mature wood transition age in black spruce (Picea mariana (Mill.) B.S.P.) at different stand densities and sampling heights

The radial pattern of both maximum ring density and ring area of 36 black spruce trees were used to determine the transition age from juvenile wood to mature wood. The data were obtained by X-ray densitometry and both segmented linear and polynomial regressions were used to point out the age of the juvenile wood boundary. Three stand densities (1,790, 2,700 and 3,400 stems/ha) and three sampling heights (2.4, 5.1 and 7.8 m) were studied. Although maximum ring density and ring area presented similar radial patterns, they gave two significantly different results of transition ages. The maximum ring density over-estimated the transition age (17.6 years) in contrast to ring area (14 years). The results show that the transition from juvenile wood to mature wood occurred after 12 years at 7.8 m (versus 13.1 years at a height of 5.1 m, and 17.6 years at 2.4 m). Although transition age occurred later in the high stand density group (21 years), the difference was not significant between the three stand density groups. Nevertheless, transition age remains difficult to determine since no standard definition exists. The transition occurs over years, and most probably a transition wood exists between juvenile wood and mature wood. Estimation of the juvenile wood proportion in volume shows that it remains constant along the stem and it increases with stand density.