Microsatellites as DNA markers in Sitka spruce

Nine microsatellite loci were found by screening a genomic DNA library of Sitka spruce (Picea sitchensis) with the four oligonucleotide probes (TG), (CAC), (GATA) and (AT). Pairs of flanking primers were generated for seven microsatellites. Five primer pairs were used to screen up to 58 Sitka spruce clones. The five loci SStg3a, SStg4, SStg4a, SStg4c and SSgataS were found to have 15, 13, 4, 3 and 6 different length alleles respectively, and in using a combination of them almost all 58 Sitka spruce genotypes could be identified. The five primer pairs were successful in amplifying DNA from two other spruce species (Picea albutilia and Picea smithiana), while only one primer pair could amplify DNA from the pine species, Pinus sylvestris and Pinus latifolia. The inheritance of microsatellites in Sitka spruce was co-dominant Mendelian.     

Insects associated with the Sitka spruce weevil,Pissodes Strobi [Col.: Curculionidae] on Sitka spruce,Picea sitchensis in British Columbia,Canada

BioControl - Insects associated with the Sitka spruce weevil,Pissodes strobi (Peck), on Sitka spruce,Picea sitchensis (Bong.) Carr. were sampled at 9 locations in British Columbia. Fourteen species...     

Response over two growing seasons of a Sitka spruce stand to 15N-urea fertilizer

Urea fertilizer labelled with ¹⁵N (2.5 atom %) was applied to a 20 year old Sitka spruce stand on a peaty gley at a rate equivalent to 160 kg N ha⁻¹. The application of urea resulted in increased biomass and N concentration of needles and enhanced development of the crown. Differences in N concentrations of the amended trees were also observed for new wood and bark. Analysis of ¹⁵N in tree biomass showed a continued influence of fertilizer N in the second growing season following urea application. The overall recovery of fertilizer N in the trees was estimated to be about 10%.     

Colonization of Sitka spruce stumps by decay-causing hymenomycetes in paired inoculations

Sitka spruce stumps were inoculated with decay fungi using colonized sawdust or dowel inoculum to investigate colonization in paired combinations. Estimates of domain sizes were made in the top 15 cm of stump after 13–14 or 21–23 months with sawdust or dowel inoculations, respectively. None of the co-inoculated species prevented colonization by Heterobasidion annosum; sapwood colonization by Resinicium bicolor may limit growth of H. annosum colonies out of heartwood, reducing the incidence of disease transfer at root contacts. H. annosum colonized stumps despite the presence of competing inoculum. Reduced colonization occurred in paired inoculations with R. bicolor, but not with other fungi. Co-inoculations with Stereum sanguinolentum increased colonization by H. annosum. R. bicolor largely remained in the upper 3–4 cm of stumps and reduced colonization by Melanotus proteus; growth of S. sanguinolentum was completely prevented. The results are discussed in relation to the colonization strategies of the decay fungi, their ability to colonize stumps in the presence of competitors and factors influencing development of communities of decay fungi in stumps.     

Influence of the green spruce aphid on defoliation and radial stem growth of Sitka spruce

Premature abscission of older Sitka spruce foliage on trees within forests in Northern Ireland was compared with green spruce aphid population levels 2 to 3 months earlier. Each aphid has a lower relative impact on needle loss at higher aphid population density; nevertheless, more aphids on a tree results in greater rates of needle loss. Evidence from horizontal stem increment sequences suggested that aphid feeding inhibited incremental growth, and that this inhibition might be delayed for up to two field seasons. However, the effect of aphids on stem growth in most years and on most trees seems relatively small compared with the potential of other tree-or year-specific processes.     

Within-crown distribution of male and female cones on clonal Sitka spruce trees

The within-crown distribution of cones (strobili) was mapped on 48 mature grafts of Sitka spruce [Picea schensis (Bong.) Carr.]. The total number of cones per tree was increased by a mainstem injection of 20 mg GA_4/7 and 8 mm wide bark ring. The cones and buds were classified as either lateral or terminal on each individual branch. The distribution of lateral female, terminal female, lateral male and terminal male cones, showed a general progression from the upper distal to lower proximal regions of the tree crown in all 12 clones. Evidence for preferential allocation of cones to particular branch types is presented. The region of the tree with the greates number of cones varied with treatment and reflected differences in the sex ratio of the individual trees. There is evidence for a relationship between branch length, position within the crown and the type of cone produced.     

Field measurements of the acidity of cloudwater deposited on polypropylene surfaces and Sitka spruce shoots

Summary Enhancement of the acidity of water on conifer needles, caused by evaporation even during the presence of cloud, is investigated. Field measurements of the acidity of droplets on polypropylene surfaces, shaped like needle bearing conifer shoots, and on Sitka spruce shoots, showed that surface droplet acidity varied significantly over a few hours, due to many causes. The acidity of the droplets commonly reached 800 eq/l (pH = 3.1) and occasionally 1000 eq/l (pH = 3.0). Increases in H⁺ ion concentration due to evaporation of pure water from the droplets occurred particularly around the end of cloud events. It was concluded that variation of H⁺ concentration of water on conifer needles due to evaporation during the presence of cloud is likely to be less important than that due to the other reasons. In particular the increase in H⁺ concentration from the reduction in droplet volume, due to evaporation, after the end of a cloud event is likely to be the most significant.     

Allometric analysis of Sitka spruce branches: mechanical versus hydraulic design principles

The geometry of tree branches can have considerable effect on their efficiency in terms of carbon export per unit carbon investment in structure. The purpose of this study was to evaluate different design criteria using data describing the form of Picea sitchensis branches. Allometric analysis of the data suggests that resources are distributed to favour shoots with the greatest opportunity for extension into new space, with priority to the extension of the leader. The distribution of allometric relations of links (branch elements) was tested against two models: the pipe model, based on hydraulic transport requirements, and a static load model based on the requirement of shoots to provide mechanical resistance to static loads. Static load resistance required the load parameter to be proportional to the link radius raised to the power of 4. This was shown to be true within a 95% statistical confidence limit. The pipe model would require total distal length to be proportional to link radius squared but the measured branches did not conform well to this model. The comparison suggests that the diameters of branch elements were more related to the requirements for mechanical load. The cost of following a hydraulic design principle (the pipe model) in terms of mechanical efficiency was estimated and suggested that the pipe model branch would not be mechanically compromised but would use structural resources inefficiently. Resource allocation among branch elements was found to be consistent with mechanical stability criteria but also indicated the possibility of allocation based on other criteria, such as potential light interception by shoots. The evidence suggests that whilst branch topology increments by reiteration of units of morphogenesis, the geometry follows a functional design pattern.     

Total, organic and extractable-P in humus and soil beneath Sitka spruce planted in pure stands and in mixture with Scots pine

Total, organic and extractable P were measured in the humus and underlying soil to 10 cm depth beneath Sitka spruce (SS) and mixed Sitka spruce and Scots pine (SS+SP) stands planted on upland heath. The humus beneath SS+SP contained significantly (p<0.01) greater amounts of total and organic-P than that in SS and the mixed stands had more effectively retained approximately 87 per cent of previously applied fertilizer-P, totalling 100 kg P ha^–1, compared with 70 per cent in SS. Despite the larger amounts of total-P in the mixed plots 0.01 M CaCl₂ extractable molybdate reactive phosphorus (MRP) was significantly (p<0.05) greater in SS+SP humus only during March and April. Greater concentrations of MRP were released from the humus and soil during July and August at a mean rate of 58 g P ha^–1 day^–1. This coincided with drying of the soil during the summer and the rate of release, attributed to death of fine roots and microorganisms, was 4 to 30 times greater than reported values for rates of net mineralization of P from forest soils.     

When is the structural root system determined in Sitka spruce?

Summary Growth ring analysis was carried out on root systems of Sitka spruce trees which had been planted for 8 and 34 years. Retrospective measurements were made on cross-sectional area increment near the root base. Differentiation of the main laterals into roots of widely different radial growth rates took place mainly during the first eight years, resulting in 3–11 major woody roots and a larger number of small minor ones, with some of intermediate vigour. The major roots established during the first few years constituted the main structural root system at 34 years. Many of the minor roots stopped growing in diameter after a few years, but were still alive and extending at 34 years. The differentiation into major and minor roots is discussed with reference to their origins and the local environment.     

Clonal differences in rooting ofAlnus incana leafy cuttings

Summary Green cuttings ofAlnus incana (L.) Moench, consisting of one internode and one leaf with its axillary bud, were easily rooted in aerated liquid substrate under growth-chamber conditions. In tests on material of up to 8 years-old, the age of the stock plants was shown to have no influence on rooting. Tap water or a diluted nutrient solution gave higher rooting percentages than a full strength nutrient solution. Root growth was most rapid in the diluted nutrient solution. Eight out of 9 clones ofA. incana gave a rooting percentage of 80–100% while one clone gave only 40%. Good rooting ofA. incana leafy cuttings, therefore, seems to be genetically controlled.     

Rooting and vitality of poinsettia cuttings was increased by arbuscular mycorrhiza in the donor plants

In this paper, we provide evidence that the rooting performance of cuttings can be improved by the arbuscular mycorrhizal (AM) symbiosis of donor plants. Poinsettia stock plants were inoculated with the Glomus intraradices isolate H510 and grown in three different cultivation systems (two organic and one conventional). AM colonization was not related to P availability in the substrate. Decay of the excised cuttings in response to unfavorable postharvest storage conditions was significantly reduced by AM colonization of the stock plants. In most cases, AM significantly promoted the formation of adventitious roots in the stored cuttings. The strongest effect of AM was found when donor plants were grown in a modified organic substrate; then AM-conditioned cuttings showed higher leaf sugar levels and a changed kinetic of carbohydrates during storage. Analyses of N, P, and K in cuttings did not indicate a nutritional effect. The results support the idea that an altered carbohydrate metabolism and plant hormones can contribute to improved rooting performance of cuttings excised from mycorrhizal donor plants.     

Interactions between green spruce aphid (Elatobium abietinum (Walker)) and Norway and Sitka spruce under high and low nutrient conditions

1 Green spruce aphid (Elatobium abietinum) is a serious pest of spruce (Picea spp.) in north‐west Europe, causing defoliation of one‐year‐old and older needles. 2 Relationships between population development of E. abietinum, needle loss and tree growth were compared for five pure genotypes of Sitka spruce and mixed‐genotype material of Sitka and Norway spruce, grown under high and low nutrient conditions. 3 Despite wide differences in flushing date between spruce genotypes, E. abietinum populations peaked on the same date on each genotype and on the mixed‐genotype material, irrespective of nutrient supply. 4 Larger aphid populations developed on trees grown under high nutrient conditions than under low nutrients. However, more needles were lost per aphid in the low nutrient treatment and overall defoliation rates in the two nutrient treatments were similar. 5 Total aphid numbers differed significantly between Sitka spruce genotypes within nutrient treatments, but not in relation to bud‐burst or needle terpene content. Reductions in height growth caused by infestation were greater (15–44%), and related to mean aphid densities and defoliation, in the low nutrient treatment, but were smaller (11–27%) and not related to aphid density and defoliation in the high nutrient treatment. 6 Development of E. abietinum populations was similar on Norway and Sitka spruce, but Norway spruce lost fewer needles. However, the effects of infestation on tree growth were more closely related to aphid density and were similar for Norway and Sitka spruce. 7 Infestation caused a decrease in total root dry weight of Norway and Sitka spruce in proportion to the reductions observed in above‐ground growth.     

The effect of long term CO2 enrichment on the growth,biomass partitioning and mineral nutrition of Sitka spruce (Picea sitchensis (Bong.) Carr.)

Sitka spruce [Picea sitchensis (Bong.) Carr.] seedlings were grown for 3 years in an outside control plot or in ambient (355 mol mol^-1) or elevated (ambient + 350 mol mol^-1) atmospheric CO₂ environments, within open top chambers (OTCs) at the Institute of Terrestrial Ecology, Edinburgh. Sequential harvests were carried out at the end of each growing season and throughout the 1991 growing season, five in all. Plants grown in elevated CO₂ had, (i) 35 and 10% larger root/shoot ratios at the end of the first and third season, respectively, (ii) significantly higher summer leader extension relative growth rates, which declined more rapidly in early autumn than ambient grown plants, (iii) after three growing seasons a significantly increased mean annual relative growth rate, (iv) consistently lower foliar nutrient concentrations, and (v) after two growing seasons smaller total projected needle areas. Plants grown inside OTCs were taller, heavier and had a smaller root/shoot ratio than those grown outside the chambers. There was no effect of CO₂ concentration on Sitka spruce leaf characteristics, although leaf area ratio, specific leaf area and leaf weight ratio all fell throughout the course of the 3 year experiment.     

Effects of simulated acid precipitation on the cycling of manganese under Sitka spruce (Picea sitchensis)

Simulated acid rain at pH 3.3, 4.3 and 5.3 has been applied by overheadspraying to reconstructed soil profiles and young Sitka spruce (Piceasitchensis) trees in pots to assess the effect of rainfall acidityonthe fate and recycling efficiency of Mn from ⁵⁴Mn-labelled Sitkaspruce litter. The concentration of ⁵⁴Mn in throughfall wassignificantly increased by acidification of the rain, but ⁵⁴Mnactivity in drainage water remained low and was not significantly affected. Thefact that only < 1.5% of ⁵⁴Mn was lost in drainage water suggeststhat forest ecosystems efficiently retain Mn, at least in the short term. Thebulk of ⁵⁴Mn (approximately 60 to 70%) was retained in the litterlayer. Compared with rain at pH 4.3, rain at pH 3.3 acidified L/F and H/Ahorizon soils. The amount of ⁵⁴Mn found in the different soilhorizons was only influenced significantly by rainfall acidity in the E horizonsoil, however, where ⁵⁴Mn activity was increased by the most acidtreatment. The activity of ⁵⁴Mn in Sitka spruce needles did notdiffer significantly with treatments.     

Effect of mycorrhizal inocula on the growth of Sitka spruce seedlings in different soils

Summary Different mycorrhizal fungi were tested for their effectiveness in promoting growth of Sitka spruce seedlings, in two contrasting soils, in a glasshouse pot experiment. In nursery soil,Laccaria amethystina significantly improved growth of seedlings in comparison toL. laccata. Seedlings inoculated with a forest isolate ofThelephora terrestris were significantly larger than those inoculated with a nursery isolate when grown in forest soil. The effectiveness ofComplexipes moniliformis in forest soil was poor in comparison to other mycorrhizal fungi. Strains aswell as species of mycorrhizal fungi affect seedling growth differently. These effects are further influenced by soil type.     

The mycorrhizal community in a forest chronosequence of Sitka spruce [Picea sitchensis (Bong.) Carr.] in Northern England

Demography and fungal diversity of the belowground ectomycorrhizal community in a chronosequence of Sitka spruce [Picea sitchensis (Bong.) Carr.] in Northumberland, Northern England, were analysed; mycorrhizal root samples were taken from 6-, 12-, 30- and 40-year-old stands, and fungal fruiting bodies were collected in autumn to complement the survey. Naturally germinated seedlings less than 1 year of age (taken from the 30-year-old stand) were also examined. A total of 118,000 mycorrhizal root tips were extracted from 40 soil cores (ten per age class) and from the complete root systems of 25 seedlings and separated into active and senescent root tips according to their morphology and anatomy. Active tips were distinguished according to their mycobionts which were characterised and identified microscopically. Although almost 100% of all fine roots were mycorrhizal, EM fungal diversity throughout the chronosequence was low, consisting of a total of 16 species of which three were only found as fruiting bodies. Of the six mycobionts found most regularly below ground, Tylospora fibrillosa was the most common, colonising about 70% of all root tips and more than 90% of those of seedlings and young trees. Root density and mycorrhizal diversity increased, but percentage of vital root tips decreased with increasing tree age, levelling off in the 30- and 40-year-old stand. Among the five subdominant fungal species, Dermocybe crocea was found to have its peak of distribution in the 12-year-old stand and Russula emetica, Lactarius rufus, Hymenoscyphus ericae agg. and the unidentified Piceirhiza sulfo-incrustata in the 30- and 40-year-old stands. The possible correlations between the mycorrhizal community structure and biotic and abiotic factors are discussed.