Water Relations of Sitka Spruce Seedlings After Root Damage

Sitka spruce[Picea sitchensis(Bong.) Carr] seedlings were subjectedto varying degrees of root damage in a growth room, rangingfrom careful transplanting to exposure of the root system toair for up to 3 h. After replanting, transpiration (E), leafwater potential (₁) and growth of the shoot and root were measuredand observations made on plant survival. Some plants in the root exposure treatments died 20–85days after planting. In plants which eventually died, E wasdepressed directly after treatment, but ₁ showed a variableresponse. In some plants ₁ decreased from —8·0x 10⁵ to —30 x 10⁵ Pa after only 10 days but in othersthere was little change in ₁ for 50 days. In spite of the maintenanceof a high water potential in some of the latter plants for longperiods, no root or shoot growth occurred. In plants which lived, the root damage reduced root and shootgrowth relative to untreated controls, and most treatments stronglydepressed E but had little or no effect on ₁. The changes of E and ₁ in treated plants suggest that the suppressionof E was often independent of ₁ although water stress eventuallydeveloped in some of the severely treated plants. Sitka spruce, Picea sitchensis (Bong.)Carr, water relations, root damage, transpiration, leaf water potential     

The Influence of Pine on the Form of Sitka Spruce Fine Roots

The form of fine roots of Sitka spruce (Picea sitchensis Bong.Carr.) when grown in immediate proximity to roots of Scots pine(Pinus sylvestris L.) and when grown separately was comparedusing split-root systems. When spruce roots were intimatelymixed with pine roots the mean length of individual spruce lateralswas significantly greater, while the length: weight ratio andnumber of root tips: weight ratio were smaller than when grownalone. A similar alteration in growth strategy was achievedby direct addition of mineral nitrogen. Key words: Fine root form, pine-spruce interactions     

Timing of root dormancy and tolerance to root waterlogging in clonal Sitka spruce

 Actively growing root tips of Picea sitchensis (Bong.) Carr. plants are highly susceptible to damage if waterlogged, but they are known to have some tolerance after they stop growing in the autumn. This paper describes the selection of clones on the basis of root dormancy timing and the corresponding responses of their roots to over-winter waterlogging. Sitka spruce transplants of Alaska, Queen Charlotte Islands (QCI), and Washington provenances were screened for early or late root dormancy over 2 successive years. Cuttings were propagated from the selected plants and after growing on for 2 years, they were planted in transparent acrylic tubes within outdoor ‘root observation chambers’. Extension of main roots and the timing of onset of root dormancy was recorded on the clonal plants. The tubes were flooded in November and maintained with a water table 280 mm below the soil surface until March of the next year. Waterlogging caused most main root tips to die back, but within 2 months of draining regeneration occurred on the main roots below the waterlogging level. This regeneration was most commonly the growth of existing lateral tips or production of new lateral roots. Roots of early-dormant Washington plants died back on average 129 mm less than late-dormant Washington plants, and early-dormant Alaska plants had 173 mm less dieback than late-dormant Alaska plants. Differences between the clones of the QCI provenance were not significant. The 40% and 52% increases in survival depth of roots in early-dormant Washington and Alaska clones respectively indicates a potential for improving the rooting depth of Sitka spruce on seasonally waterlogged soils by planting clones selected on the basis of root dormancy. Received: 14 July 1997 / Accepted: 15 September 1997     

Rooting of Sitka spruce cuttings from hedges,and after chilling

Summary Four clones of Sitka spruce (Picea sitchensis (Bong.) Carr.) were established from cuttings of two and four-year old material in 1968. Within each clone half the trees were randomly hedged at 1 m in 1977. Cuttings from hedges rooted more freely than cuttings from the lower crown which, in turn, rooted more readily than upper crown cuttings. Rooting occurred most readily during January and early February. Concentrations of sugars in stems and foliage showed little correlation with rooting.Chilling must be completed for most rapid rooting of dormant Sitka spruce cuttings and this requirement can be satisfied by 10 weeks at 2°C.     

A diallel cross in Sitka spruce assessment of first year characters in an early glasshouse test

Summary The successful pollination of a complete diallel cross among six Sitka spruce (Picea sitchensis (Bong.) Carr.) trees is described, together with the assessment of a range of characters in the first growing-season of an early progeny-test in a glasshouse. Those characters chiefly concerned with tree form were found to be inherited in a predominantly additive fashion, whilst those characters reflecting various aspects of tree vigour were found to be under additive, dominance and maternal control. The results are discussed in the light of selection criteria and current techniques in Sitka spruce breeding.     

The effect of applied heat on graft union formation in dormant Picea sitchensis (Bong.) Carr

The effect of application of heat on the development of graftunions in dormant Picea sitchensis (Bong.) Carr (Sitka spruce)was observed at monthly intervals from October to March. Noadvantage over controls was gained in terms of final graft successrates. It is suggested that this may have been a result of themild winter conditions during the course of the experiment,which enabled callus formation to occur in unheated controls.On the other hand, scions of grafts which had been heated for3 weeks, and then returned to ambient conditions showed considerablygreater growth than unheated controls during the following springand summer. The amount of extension depended on how late inthe winter the graft had been prepared and heated, with leastgrowth by grafts made in October, and most by grafts made inMarch. Microscopical examination showed that callus formationwas more rapid in heated grafts than in controls, although callusformation occurred in all control grafts examined. Heat alsoinduced cambial reactivation and tracheid formation, particularlyin the vicinity of needle or bud traces in the scion. In keepingwith this, it was found that the presence of needles and budswas essential for cambial reactivation in normal dormant stemsand that reactivation was restricted to the heated region. Key words: Grafting, Sitka spruce, callus, dormancy, differentiation     

Annual Variations in Competition Symmetry in Even-aged Sitka Spruce

Understanding of the temporal development of competition symmetry,size hierarchy and the role of episodically supplied resourcesin forest stands is limited. Because of intrinsic differencesin the symmetry of competition for light and below-ground resources,it is hypothesized that the overall expression of competitionvaries as a consequence of variations in water availability.Historical growth and precipitation data from an unthinned standof Sitka spruce (Picea sitchensis(Bong.) Carr.) in Denmark areanalysed with respect to the effects of precipitation on competitionsymmetry. The shape and linearity of the size-increment relationshipare analysed, and the temporal development of diameter distributionand size hierarchy is modelled. The test value of lack of linearfit through the origin for the diameter/increment relationshipplotted against precipitation in the growth period forms a triangularenvelope, indicating a more curvilinear relationship for yearswith high water availability. This indicates that dominant treesapparently benefit more from increased precipitation than suppressedtrees—which is also shown in the analysis of the temporaldevelopment of the diameter distribution—and as a consequencethe size hierarchy increases. Finally, it is proposed that temporaland spatial variations in the availability of water and otherbelow-ground resources may have similar effects on competitionsymmetry. Copyright 2001 Annals of Botany Company Competition symmetry, size hierarchy, precipitation, temporal development, Picea sitchensis     

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...     

The role of planted forests in the provision of habitat: an Irish perspective

The continued decline of natural forests globally has increased interest in the potential of planted forests to support biodiversity. Here, we examine the potential conservation benefits of plantation forests from an Irish perspective, a country where remaining natural forests are fragmented and degraded, and the majority of the forest area is comprised of non-native Sitka spruce (Picea sitchensis (Bong.) Carr.) and Norway spruce (Picea abies (L.) Karst.) plantations. We examine the true value of Irish plantation forests to native biodiversity, relative to remaining natural forest fragments, and to prior and alternative land use to afforestation. We find that plantation forests provide a suitable surrogate habitat primarily for generalist species, as well as providing habitat for certain species of conservation concern. However, we find that plantation forests provide poor habitat for native forest specialists, and examine potential management strategies which may be employed to improve habitat provision services for this group.     

Expression of the gus A gene in embryogenic cell lines of Sitka spruce following Agrobacterium-mediated transformation

Transformation of Picea sitchensis (Bong) Carr. was investigatedby incubating embryogenic cell lines, initiated from immatureand mature zygotic embryos, with a supervirulent strain of Agrobacteriumtumefaciens. The latter carried a gus A-intron gene. Transientgene expression was determined histochemically by recordingthe number of distinct areas of ß-glucuronidase (GUS)activity. Maximum expression of the gus gene was achieved witha bacterial suspension with an OD₆₀₀ of 0.8–1.1 dilutedwith an equal volume of MPM medium, Inoculation of cells withbacteria for 30 mm, 72 h co-cultivation period and exposureof Agrobacterium and plant cells to 50 µM acetosyrmngone.These results are discussed in relation to Agrobacterium-mediatedgene delivery for the stable transformation of Sitka spruceand other conifers. Key words: Sitka spruce, Agrobacterium, transformation, embryonal suspensor masses, GUS activity     

Negative stain in wax tubes from the surface of Sitka spruce leaves

Summary Carbon replicas and scanning electron micrographs of wax outgrowths on some leaf surfaces have not shown conclusively whether the outgrowths are tubes or solid rods. Some workers have suggested that they are solid rods. We find that negative stains will penetrate into a cavity in the centre of wax outgrowths on leaves of Sitka spruce (Picea sitchensis Bong. Carr) and Tulipa kaufmanniana Elliot. Thus these outgrowths appear to be tubes.     

Quantum Requirements of Photosynthetic Electron Transport In Sitka Spruce from Different Light Environments

Quantum requirements of photosynthetic electron transport have been measured in shoots of Picea sitchensis (Bong.) Carr. (Sitka spruce) from different levels in a forest canopy and in shoots from plants grown in contrasting light environments in controlled environment chambers. Neutral density filters were used to obtain very low photon flux densities. The light absorbed by the chloroplast suspensions was calculated from measurements of the transmittance of the suspensions. The shoots from the top of the forest canopy (“sun” shoots) had lower quantum requirements for photosystems I and II than the shoots from the bottom of the forest canopy (“shade” shoots). High light grown plants and “sun” shoots had higher rates of electron transport at light saturation than low light grown plants and “shade” shoots. Thus a higher potential for electron transport was found to exist in “sun” shoots than in “shade” shoots at both high and low photon flux densities.     

Do vascular plants and bryophytes respond differently to coniferous invasion of coastal heathlands?

Invasion by non-native conifers may pose a threat to local biodiversity, but knowledge about introduced conifer effects on Northern Hemisphere ecosystems is scarce. The coastal heathlands of north-west Europe are threatened by invasion of native and introduced tree species. We assess how spread of the introduced conifer Sitka spruce (Picea sitchensis (Bong.) Carr.) into European coastal heathlands affect two major functional groups; vascular plants and bryophytes, and how these effects relate to the environmental changes imposed by the developing tree canopies. We compared the impact of introduced Sitka spruce and native Scots pine (Pinus sylvestris L.) by analysing effects on species richness and turnover of vascular plants and bryophytes along fine-scale transects from individual tree stems into open heathland vegetation. Environmental impacts were assessed by measured environmental variables, and the responses of the two species groups were assessed by calculating changes in their respective mean Ellenberg indicator values. Species richness decreased beneath both conifers, related to decreased light and increased nitrogen and pH. Whereas vascular plants responded negatively to poor light conditions beneath dense and low Sitka spruce canopies, bryophytes were more negatively affected by the warmer and drier microclimates beneath Scots pine. Introduced Sitka spruce impacts the sub-canopy environment differently from the native Scots pine, and the two functional plant groups responded differently to these impacts. This suggests that future forests are likely to differ in species richness and composition, depending on whether succession is based on native or introduced coniferous trees.     

Photosynthetic Electron Transport in Plants of Sitka Spruce Subjected to Differing Light Environments during Growth

Seedlings of Picea sitchensis (Bong.) Carr. (Sitka spruce) have been grown in four different light regimes in growth chambers. Chloroplast fragments have been isolated from the needles and Photosystem I and Photosystem II activities measured. Measurements were made at eight photon flux densities giving light response curves for photosystem activity in needles grown in the four different light regimes. Chlorophyll concentration was higher in needles from the low cultivation light environments than in those from the high light environments. Photosystem activity was higher in needles from the high cultivation light environments. Evidence that Photosystem I was limiting photosynthesis in needles grown in the high light environments was obtained.     

Studies of Growth and Flowering in Picea sitchensis (Bong.) Carr. 2. Initiation and Development of Male, Female and Vegetative Buds

Vegetative shoots from the base of the crown, and from partsof the tree likely to form male or female buds, were collectedfrom 40–years–old trees of Picea sitchensis (Bong.)Carr. throughout the 1973–4 annual growth cycle. The morphologyand growth rates of the terminal buds on these shoots were assessed. Bud scale primordia were formed most quickly in the female position,at an intermediate rate in the male position and most slowlyin the basal vegetative position during April, May and June.In July and early August the apical meristems swelled to formdomes and continued to grow at the same relative rates in themale, female and basal vegetative positions. Reproductive budswere first morphologically distinct in late August and sporangiaappeared in October. Dormancy, defined by the pause in apicalvolume increase, extended from mid-October to mid–March.Young strobili grew much faster than basal vegetative shootsof the same age between mid–March and bud burst in lateApril. Throughout the growth cycle, external changes in budsize reflected changes in size of the apical meristem, youngstrobihis or young vegetative shoot inside the bud. It is proposed that the rate of growth of an apical meristemmay be causally related to the type of bud which subsequentlydevelops from it. Sitka spruce, Picea sitchensis, bud development, morphology, growth of apical dome, flowering     

Effects of Growth Hormone Application on the Secondary Growth of Roots and Stems in Picea sitchensis (Bong.) Carr

Indol-3-ylacetic acid (IAA), gibberellin A3 (GA) and 6 benzylaminopurine(BAP) were applied factorially each at 3x10^–2 M in lanolinto the roots and stems of Sitka spruce seedlings and the activityof the two secondary meristems, the vascular cambium and phellogen,and of the parenchymatous tissues between them, was examined.All the treatments, with the exception of GA produced a localizedstimulation of radial growth at the point of application andthere was a similarity in the response of the various tissuesin both the root and stem. Radial growth of the xylem was notsignificantly affected in the roots whereas in the stems BAPand IAA stimulated growth. In the phloem BAP produced significantstimulation in both roots and stems and IAA stimulated growthin the roots. Growth of the parenchyma and periderm externalto the phloem was also strongly stimulated by both BAP, andIAA in roots and stems. In roots and stems the application of BAP altered the derivativesproduced by the vascular cambium, resulting in the productionof large multiseriate rays in the xylem, and giving rise toan overall increase in the proportion of ray tissue. Picea sitchensis (Bong.) Carr, Sitka spruce, secondary growth, xylem, phloem, periderm, wood rays, Indol-3-ylacetic acid, gibberellin A3, 6 benzylaminopurine, growth hormones     

Effects of enhanced atmospheric CO2 and nutrient supply on the quality and subsequent decomposition of fine roots of Betula pendula Roth. and Picea sitchensis (Bong.) Carr.

Fine root litter derived from birch (Betula pendula Roth.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) plants grown under two CO₂ atmospheric concentrations (350 ppm and 600 ppm) and two nutrient regimes was used for decomposition studies in laboratory microcosms. Although there were interactions between litter type, CO₂/fertiliser treatments and decomposition rates, in general, an increase in the C/N ratio of the root tissue was observed for roots of both species grown under elevated CO₂ in unfertilized soil. Both weight loss and respiration of decomposing birch roots were significantly reduced in materials derived from enriched CO₂, whilst the decomposition of spruce roots showed no such effect. A parallel experiment was performed using Betula pendula root litter grown under different N regimes, in order to test the relationship between C/N ratio of litter and root decomposition rate. A highly significant (p<0.001) negative correlation between C/N ratio and root litter respiration was found, with an r²=0.97. The results suggest that the increased C/N ratio of plant tissues induced by elevated CO₂ can result in a reduction of decomposition rate, with a resulting increase in forest soil C stores.     

A comparison of rooting environments in containers of different sizes

Experiments on plants are often carried out in growth chambers or greenhouses which necessitate the use of an artificial rooting environment, though this is seldom characterized in detail. Measurements were made to compare the rooting environment in large boxes (0.25 m³) with that in small pots (0.19, 0.55 and 1.90 dm³) in naturally lit chambers. Diurnal temperature fluctuations of 14.6, 11.6 and 7.7°C occurred in the post compared with only 1.9°C in the boxes. Soil drying to a matric potential of-50 kPa was approximately 25 times faster in the pots. The mean heights of 2 year old Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings grown throughout their second growing season in the three sizes of pots were 38, 62 and 92% of the mean height of those grown in the boxes. Soil solution nutrient concentrations in the boxes were considerably increased by soil drying, an aspect which seems to have received little attention in experiments involving artificially imposed drought. An alternative system of constraining the roots of individual plants within nylon fabric bags, embedded in larger volumes of soil, to facilitate harvesting of complete root systems is described. The importance of the rooting environment in determining the outcome of physiological experiments is also briefly discussed.     

Effect of P supply upon seasonal growth and internal cycling of P in Sitka spruce (Picea sitchensis(Bong.)Carr.) seedlings

The availability of phosphorus in many UK forest soils limits growth of Sitka spruce (Picea sitchensis (Bong.) Carr.). Efficient cycling of P within such systems is therefore necessary for sustained tree growth. Internal cycling of P is an important component of the overall P cycle in forests and the current work aims to quantify the impact of P nutrition on internal cycling and seasonal growth of Sitka spruce.Two-year old seedlings of Sitka spruce were grown in sand culture in the glasshouse for one year. Two treatments were imposed in which trees received either a complete nutrient solution from which P was excluded (-P) or one in which P was applied as labelled ³²P (+P). Internal cycling of P was measured directly in plants which had received no P and by difference in those which received ³²P.The contrasting P treatments produced an eight-fold difference in P content and a three-fold difference in tree growth between May and October. Root:shoot ratios increased during the growing season from 0.29 to 0.38 and from 0.29 to 0.52 in +P and-P treatments, respectively. In both treatments P was translocated from old shoots to support new shoot growth. P supply did not affect the amount of P remobilised but there was evidence that the rate of remobilisation may have been affected. The partition of remobilised P was affected by current P supply and differed from the partition of current P uptake.Results are compared to those from studies of growth and internal cycling of nitrogen in Sitka spruce.     

Intraspecific variation of DNA per cell between Picea sitchensis (Bong.) Carr. provenances

Quantitative intraspecific variation of DNA per cell was established by means of biochemical, double wavelength microspectrophotometry and micro-densitometric analyses of root tips from 7 seed sources of Picea sitchensis (Bong.) Carr. Northern seed sources possessed more DNA per cell than southern provenances. This, perhaps, is an indication of DNA adaptability through plasticity resulting from changing environmental stress over the natural range.