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1.
Green spruce aphid Elatobium abietinum (Walker) is a major defoliator of Sitka spruce (Picea sitchensis (Bong.) Carr.) in north-west Europe and other parts of the world that have a mild and wet maritime climate. Periods of cold weather during the winter currently limit E. abietinum populations and the amount of damage, but as mean winter temperatures rise in response to global climate change, overwinter survival of the aphid is likely to improve and the risk of severe and more widespread defoliation will increase. Populations of E. abietinum are also influenced by mortality caused by generalist invertebrate predators, although the extent to which predation might modify the response of E. abietinum to climate change is unclear. In this study, the response of generalist predators to changes in environmental conditions and potential increases in E. abietinum populations was evaluated by sampling invertebrate predators in the canopy of Sitka spruce along an altitudinal gradient from 310 m to 610 m above sea-level. Variation in predator abundance was related to local climate and aphid numbers. Population densities of E. abietinum differed widely between altitudes, and showed different patterns in different years, but mean densities over the 3-year study were highest at mid altitudes. In contrast, the majority of invertebrate predators (coccinellid and cantharid beetles, syrphid larvae, brown lacewings, spiders and harvestmen) were most abundant at low altitudes. Their abundance was not correlated with E. abietinum densities, but coincided with the more favourable climatic conditions at low altitudes and the availability of alternative prey. The association of low population densities of E. abietinum with greater general abundance of invertebrate predators at low altitudes, where higher temperatures would have been expected to promote higher aphid populations, suggests that above a certain temperature regime generalist predators have the capacity to prevent E. abietinum responding to further increases in environmental temperatures and eventually cause mean population densities to decline. Consequently, increases in the activity and abundance of natural enemies need to be considered when predicting how E. abietinum might respond to climate change.  相似文献   

2.
Light availability and infestation by the green spruce aphid (Elatobium abietinum) are key factors affecting the growth of Sitka spruce (Picea sitchensis) seedlings under a mature tree canopy, but their combined effect on seedling growth has not previously been quantified. A controlled outdoor experiment in which light levels (high light (HL): 100%, intermediate light (IL): 24%) and aphid infestation (absence/presence) were manipulated was conducted over 2 years to look at the effects on seedling growth and biomass distribution patterns. Aphid population assessments showed a significantly increased population density under IL, with three to four times higher cumulative aphid densities than that under HL. Defoliation rates of infested seedlings were directly related to aphid density. Total seedling biomass was strongly reduced in IL, and aphid infestation caused additional reductions in the biomass of particular components of the seedlings. Dry weight (DW) of older (≥1-year-old) needles in infested trees was significantly decreased in both years. Total root DW at the end of the second year was significantly affected by aphid infestation, and the reduction (14-18%) was similar in IL and HL treatments despite large differences in aphid density. Biomass distribution patterns in infested trees were similar to that of uninfested trees within each light treatment, indicating that the relative decreases in root biomass were accompanied by similar reductions in distribution to the above-ground parts of the seedlings. Leader extension growth of infested seedlings was reduced by 15-17% compared with uninfested seedlings under IL, whereas only a 2-3% reduction in leader extension of infested seedlings under HL was observed. The results showed that the response of seedlings to E. abietinum were primarily dependent on the light environment. The significant reduction caused by aphids on the total DW of older needles and roots, and on leader extension growth, does suggest the potential for effects to accumulate over time.  相似文献   

3.
Damage caused by Elatobium abietinum was estimated as needle loss in a progeny trial of Sitka spruce in Denmark in 1990 and 1992. The parents of the progeny had been selected for putative aphid resistance during a massive attack of aphids in 1957. Needle loss was significantly less in the progeny than in a standard provenance. Family heritability was estimated as 0.72 (P>0.0001). Aphid damage had an impact on growth and vigour of trees following warm winters in 1989 and since, but no correlation could be found between growth parameters and damage of different families. Due to high heritability and large variation, high gains are expected by breeding. Practical and theoretical consequences of including aphid resistance in breeding programmes of Sitka spruce are discussed.  相似文献   

4.
SEABY  D. A.; MOWAT  D. J. 《Forestry》1993,66(4):371-379
Following a severe attack by Elatobium abietinum (Walker) in1979–80, annual observations were made for 5 years on320 pole-size Sitka spruce in a nitrogen and phosphate experimentlaid out on oligotrophic blanket bog. Leader length was reduced by 25.5 per cent in 1980–81compared with the 3 previous years. This reduction was highlycorrelated with defoliation, being 39.4 per cent for trees thatlost all 1977–79 needles and 8.4 per cent in trees thatlost no needles. There were strong interactions with fertilizertreatment. Defoliated trees continued to grow less well duringthe 5 years of observations and were more likely to go intogrowth check. Early flushing trees suffered significantly less growth reductionfollowing defoliation. The same trees consistently broke budearly over 4 years of observations. Early bud burst was notcorrelated with height, girth or defoliation. No reattack by aphids was observed in the experiment until 1985–86and in this minor infestation the trees previously colonizedwere found to be significantly more likely to be recolonized. A novel measuring-rod for tree height is described.  相似文献   

5.
Norway spruce trees in the subalpine forests of the European Alps are frequently attacked by the needle rust Chrysomyxa rhododendri. The obligate parasite undergoes a complex life cycle with a host shift between rhododendrons (Rhododendron sp.) and Norway spruce [Picea abies (L.) Karsten] and causes a yellowing and defoliation of the current-year needles in summer. Infected trees show several anatomical, morphological and physiological modifications, including a decrease in pigment content and net photosynthesis of infected needles, lower biomass production and reduced radial and height growth. The consequences are diminished timber yield and cripple growth. Because of repeated heavy infections in recent years, forest managers report increasing difficulties in both natural regeneration and afforestation at high elevation sites, where rhododendrons occur. This review gives a summary of the present knowledge about the effects of C. rhododendri infections on Norway spruce, including so far unpublished findings and with particular attention to the phenomena of resistant trees. Implications for subalpine forests and counter strategies are discussed.  相似文献   

6.
PARRY  W. H. 《Forestry》1969,42(1):69-82
A correlation between the size of the surviving overwinteringpopulation of Elatobium abietinum and the size of the succeedingsummer population peak is shown. It is also demonstrated thatthe loss of the needles from Sitka spruce is, in turn, relatedto the size of the summer population of aphids. After applyingmalathion in early April at the end of the overwintering periodonly small summer populations of aphids occurred, with consequentretention of needles. It is shown that predators, parasites,and alate migration have little effect on the population build-upand are not responsible for the breakdown of summer populationlevels. A diminishing rate of increase of the populations isdemonstrated from April to July in all plots where no chemicalcontrol had been attempted. It is suggested that this may bedue to a density-independent change in the quality of the phloemsap resulting in a drop in aphid numbers where population densitiesare low, and to this factor plus a density-dependent loss offeeeding sites where population densities are high.  相似文献   

7.
The research site, Wingst Compartment 123B, is a 68-year-old Norway spruce (Picea abies (Karst.)) stand located in the coastal area of northern Germany. This area receives high atmospheric inputs of ammonium and also has relatively high ozone concentrations (0.061 mg m−3).Ten trees were categorized as healthy to slightly damaged (3–29% needle loss) or severely damaged (49–71% needle loss). Apparent net photosynthetic rates were measured on detached branches at light saturation (1000 μE m−2 s−1). Needles were analyzed for chlorophyll, N, C, Ca, Mg, K, Zn, Mn and Fe.When compared to the healthy-to-slightly-damaged trees, the severely damaged trees tended to have higher rates of net apparent photosynthesis in the 1 and 2-year-old needles and similar rates in the current-year needles. All three needle ages from the severely damaged trees had higher average stomatal conductances to water vapor (gs. Although the damaged trees had significantly less total chlorophyll in all needle ages sampled, there was no statistically significant difference in the chlorophyll a:b ratio between the healthy and severely damaged trees.Nitrogen contents of the current-year needles were slightly lower in the severely damaged trees. Carbon and calcium levels did not significantly differ between the damage classes, although the average Ca content of all younger needles was generally under the recommended sufficiency levels. The current-year needles of the severely damaged trees had significantly less magnesium (0.42–0.46 mg Mg g−1) than those of the healthy trees, and all trees had Mg values in the deficiency range (< 0.7 mg g−1). The severely damaged trees also had lower average potassium levels in the older needles.The annual volume increment per unit crown surface area declined with increasing crown damage. Trees with a 50% needle loss showed a 62% loss of volume increment.Soil investigations revealed conditions of high soil acidity and poor nutrient capacity. The low pH values (pH < 3.8) in 64% of all samples indicated a high risk of acid toxicity for plant roots in the investigated area.The significance of these results relative to the current ideas concerning forest decline is discussed.  相似文献   

8.
HAYES  A. J.; SHIPP  V. M. 《Forestry》1983,56(2):195-205
Differences were observed in the intensities of infestationof E. nanana on crops of Norway and Sitka spruce of differentages at Redesdale Forest, Northumberland. Attacks were moreserious in stands on northerly aspects. Norway spruce was moreintensely infested than was Sitka spruce, attacks being moresevere in older stands. Attacks occurred more frequently onsuppressed and subdominant trees. The intensity of infestationincreased progressively with increasing height of foliage upto 3.5 m above ground level. Attack occurred preferentiallyon current and 1-year-old needles. Continental experience withthis pest suggests that the risk of cumulative long-term damageis slight.  相似文献   

9.
Litterfall was investigated in three even-aged Norway spruce (Picea abies), sitka spruce (Picea sitchensis) and beech (Fagus sylvatica) stands on a nutrient poor-soil in Southern Denmark. Dry weights and N, P, K, S, Mg, Ca, Na, Al, and Fe concentrations and fluxes were examined in litterfall fractions. Foliage litter amounted to 90% of total litterfall. The tree stands showed a similar mean annual litterfall. In the spruce stands, annual litterfall was correlated negatively with the current year increment and positively with the previous year increment. Annual litterfall in beech was constant during the 6 study years whereas Norway spruce and sitka spruce showed large fluctuations between years caused by drought, spruce aphid infestations and probably sea salt stress. Norway spruce responded with a long lasting elevated needle loss. Sitka spruce responded to infestations with premature needle loss during short periods. The presence of a large syrphid (Coccinellidae) population was important in regulating aphid (Elatobium abietinum) population density. The between-year variation in element concentrations of litterfall was small whereas variations during the year were large. Interspecific levels were recognized: Norway spruce>beech>sitka spruce. High concentrations in Norway spruce were ascribed to a combination of drought, sea salt stress and elevated transpiration. In sitka spruce, aphid infestations reduced the litterfall N content. Sitka spruce showed the smallest amount of base cation fluxes with litterfall. In contrast, spruce and beech exhibited even litterfall element fluxes. Litterfall studies revealed reduced vitality in the non-native spruce stands and underlined the perception of a healthy stand of native beech.  相似文献   

10.
Forests of the Kenai Peninsula, Alaska experienced widespread spruce (Picea spp.) mortality during a massive spruce beetle (Dendroctonus rufipennis) infestation over a 15-year period. In 1987, and again in 2000, the U.S. Forest Service, Pacific Northwest Research Station, Forest Inventory and Analysis Program conducted initial and remeasurement inventories of forest vegetation to assess the broad-scale impacts of this infestation. Analysis of vegetation composition was conducted with indirect gradient analysis using nonmetric multidimensional scaling to determine the overall pattern of vegetation change resulting from the infestation and to evaluate the effect of vegetation change on forest regeneration. For the latter we specifically assessed the impact of the grass bluejoint (Calamagrostis canadensis) on white spruce (Picea glauca) and paper birch (Betula papyrifera) regeneration. Changes in vegetation composition varied both in magnitude and direction among geographic regions of the Kenai Peninsula. Forests of the southern Kenai Lowland showed the most marked change in composition indicated by relatively large distances between 1987 and 2000 measurements in ordination space. Specific changes included high white spruce mortality (87% reduction in basal area of white spruce >12.7 cm diameter-at-breast height (dbh)) and increased cover of early successional species such as bluejoint and fireweed (Chamerion angustifolium). Forests of the Kenai Mountains showed a different directional change in composition characterized by moderate white spruce mortality (46% reduction) and increased cover of late-successional mountain hemlock (Tsuga mertensiana). Forests of the Gulf Coast and northern Kenai Lowland had lower levels of spruce mortality (22% reduction of Sitka spruce (Picea sitchensis) and 28% reduction of white spruce, respectively) and did not show consistent directional changes in vegetation composition. Bluejoint increased by ≥10% in cover on 12 of 33 vegetation plots on the southern Kenai Lowland but did not increase by these amounts on the 82 plots sampled elsewhere on the Kenai Peninsula. Across the Kenai Lowland, however, regeneration of white spruce and paper birch did not change in response to the outbreak or related increases in bluejoint cover from 1987 to 2000. Although some infested areas will be slow to reforest owing to few trees and no seedlings, we found no evidence of widespread reductions in regeneration following the massive spruce beetle infestation.  相似文献   

11.
The susceptibility of Sitka spruce (Picea sitchensis) and grand fir (Abies grandis) to decay by Heterobasidion annosum was compared on a site with a previous history of serious disease. The incidence of decay 15–16 years after planting was 1.5% in grand fir, compared with 34.8% in Sitka spruce. These results are broadly similar to those reported from other trials. More information is required for older trees in Britain but the evidence so far available suggests that grand fir is more resistant to H. annosum than Sitka spruce. Planting grand fir on severely infested sites may therefore significantly reduce the serious losses that could be expected with Sitka spruce. In 14 out of 271 decayed Sitka spruce H. annosum was absent from the middle or base of the decay column but present at the top. Approximately 3% of infected spruce showed features suggesting some degree of resistance. Resin bleeding was observed at the base of 23.2% of the infected spruce, and the mean height of the decay column in these trees was significantly greater (0.96 m) than in those without this feature (0.66 m). The inoculum for infection was provided by stumps of the previous crop, and the genets of H. annosum that were present in some infected trees were also identified in stumps. The majority of infected trees contained only a single genet but three trees contained two genets. In this young crop individual genets were smaller than those found elsewhere; the largest extended to include six trees.  相似文献   

12.
Hemlock looper (Lambdina fiscellaria fiscellaria (Guen.)) is an economically damaging defoliator that undergoes periodic outbreaks in Newfoundland, Canada. It defoliates and causes extensive tree mortality to its primary host, balsam fir (Abies balsamea [L.] Mill.). We quantified tree survival using data from permanent sample plots (PSPs) and growth reduction or release using dendrochronology, and related these impacts to defoliation severity determined from annual aerial defoliation survey data. Such impact relationships are necessary as a fundamental input to a Decision Support System. Growth and survival of balsam fir, black spruce (Picea mariana (Mill.) B.S.P.) and white birch (Betula papyrifera Marsh.) were assessed from 1996 to 2008 in 48 Newfoundland Forest Service PSPs, selected based on four classes of defoliation severity. Two years of severe (71-100%) defoliation resulted in almost complete mortality for balsam fir, 10 years after defoliation, whereas survival was 70-80% for black spruce and white birch. Lower defoliation severity (1-2 years of moderate (31-70%) or 1 year of severe) resulted in approximately 60% survival for balsam fir and no reduction in survival for black spruce and white birch. Maximum growth reduction of balsam fir was 10-15% with 1 year of moderate-severe defoliation, 35-40% with 2 years of moderate defoliation, and about 50% with 2 years of severe defoliation. Growth recovered to pre-defoliation rates 5 years after defoliation ceased in all severity classes. Growth reduction and recovery of black spruce were more variable and lower than for balsam fir, and white birch exhibited only minor (<10%) growth reduction during the defoliation year or 1 year after defoliation. Control measures should focus on avoiding severe defoliation for two consecutive years.  相似文献   

13.
Both drought and root pruning (RP) increased the number of cones induced when black spruce (Picea mariana (Mill.) B.S.P.) grafts were injected with gibberellins A(4/7) (GA), but their effects on predawn shoot water potential and current-year needle development differed. Drought decreased predawn shoot water potential (Psi(pd)), but only during the period when irrigation was withheld, and it had no effect on the growth or gas exchange properties of current-year needles. Conversely, root pruning had little effect on Psi(pd), but it resulted in trees with smaller current-year needles that had lower nitrogen and chlorophyll concentrations and reduced rates of gas exchange up to the later stages of shoot elongation compared with needles of control trees. These findings are discussed in relation to potential effects on the development of induced cones in the following growth cycle.  相似文献   

14.
Chrysomyxa rhododendri (DC.) De Bary is a needle rust with a host shift between Rhododendron sp. and Norway spruce (Picea abies (L.) Karst.), penetrating only the new developing flushes of the conifer. Because little is known about its effects on trees, we investigated several parameters related to photosynthesis in artificially infected 3-year-old Norway spruce seedlings. The potential efficiency of photosystem II (PSII; derived from chlorophyll fluorescence measurements) was reduced in infected current-year needles as soon as disease symptoms were visible, about three weeks after inoculation. Two weeks later, photosynthetic O(2) evolution (P(max)) of infected needles was less than 20% of control needles, whereas respiratory O(2) uptake (R(D)) was about three times higher than that of control needles. Nonstructural carbohydrate concentrations were about 60% of control values in all parts of the shoots of infected trees. Photosynthetic inhibition was associated with marked decreases in chlorophyll concentration and chlorophyll a/b ratio but only a small reduction in carotenoid concentration. In infected trees, P(max) of noninfected 1-year-old and 2-year-old needles was 50 and 80% higher than in the corresponding age class of needles of control trees. Estimation of potential daily net dry mass production, based on P(max), R(D), specific leaf area, carbon content and needle biomass, indicated that seedlings infected once were able to produce 60%, and those infected twice only 25%, of the dry mass of controls. We conclude that afforestation and regeneration of Norway spruce is seriously impaired in regions where seedlings are frequently attacked by Chrysomyxa.  相似文献   

15.
Seasonal retranslocation in white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss) was examined in response to silvicultural treatments (scarification, annual fertilization application, and annual control of competing vegetation with herbicide) that changed both environmental conditions and the growth rate of the trees. Four years after plantation establishment and initial treatment, nutrient accumulation in current-year needles of white pine and retranslocation from 1-year-old needles were increased following the vegetation control treatment, which increased resource availability (nutrients, water and light) and, hence, growth rate. Nutrient accumulation also increased in current-year white spruce needles following the same treatment, whereas retranslocation decreased in 1-year-old white spruce needles. Correlations of retranslocation (N, P and K) with growth rate (shoot biomass increment) showed a strong positive relationship for white pine and a negative relationship for white spruce. Retranslocation of K was correlated with foliar and soil K concentrations; the availability of this nutrient was also significantly reduced by vegetation control. A general theory for the control of nutrient retranslocation in conifers, which is not based exclusively on either sink strength or soil nutrient availability, is proposed. We conclude that retranslocation response is species specific and related to the potential phenotypic growth response to changing environmental conditions and to short-term imbalance in the supply versus the demand for nutrients.  相似文献   

16.
PINDER  P. S.; HAYES  A. J. 《Forestry》1986,59(1):97-106
Highly significant differences were observed in the intensityof defoliation on Sitka spruce of different heights at CarronValley Forest, Central Region. Most severe defoliation occurredon the smallest trees. Significant differences also occurredbetween degree of defoliation and foliar potassium and phosphorusconcentrations. Winter and summer rainfall patterns immediatelyprior to the outbreak showed higher than average winter andlower than average summer rainfall compared with the 30-yearmean. Experience with this pest suggests that it will continueto have local nuisance value.  相似文献   

17.
We investigated effects of nutrient addition on several physiological characteristics of 60-cm-tall black spruce (Picea mariana Mill. B.S.P.) layers (i.e., rooted branches of overstory trees) and 20-cm-tall planted seedlings on a clear-cut, N-limited boreal site. After two growing seasons, current-year and one-year-old needles of fertilized trees (layers and seedlings combined) had higher net photosynthetic rates (A(n)) and maximum capacity of Rubisco for CO(2) fixation (V(max)) than unfertilized trees. One-year-old needles of fertilized trees had higher stomatal conductance (g(s)), higher water-use efficiency, and lower intercellular to ambient CO(2) ratio than unfertilized trees. Additionally, fertilized trees had higher predawn and midday shoot water potentials than unfertilized trees. Stomatal conductance of 1-year-old needles was 23% higher in seedlings than in layers, but there were no significant differences in g(s) of current-year needles between the regeneration types. For both needle age-classes, A(n) and V(max) of layers were 25 and 40% higher, respectively, than the corresponding values for seedlings. The higher values of A(n), V(max) and foliar N concentration of layers compared with seedlings after two growing seasons may be associated with the larger root systems of the layers compared with the transplanted seedlings.  相似文献   

18.
Current-year needles of Sitka spruce (Picea sitchensis) can be injured by frost after hardening of stem and buds in the autumn, and in Scotland trees of southern provenances are most susceptible to damage. In October 1993 a frost of −5°C caused needle damage to clonal plants of Alaskan, Queen Charlotte Islands, and Washington provenances of Sitka spruce that had been selected for variation in the onset of root dormancy. Visual damage assessment revealed significant differences among clones in the severity of damage, and this damage was positively correlated with the lateness of root dormancy. Measurement of electrolyte leakage from shoot samples confirmed the observed differences between clones. The large clonal differences in frost hardiness found in this study demonstrate a potential for selecting frost tolerant trees from within southern provenances of Sitka spruce.  相似文献   

19.

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.  相似文献   

20.
Effects of magnesium deficiency and variation in nitrate to ammonium ratio on needle histology and chlorophyll concentration were investigated in current-year and one-year-old needles of clonal Norway spruce trees (Picea abies (L.) Karst.). Six-year-old trees were grown for one year in sand culture with circulating nutrient solutions containing a sufficient (0.2 mM) or a limiting (0.04 mM) concentration of Mg. The nitrogen concentration was not varied (5 mM), but the NO(3) (-)/NH(4) (+)-ratio was adjusted to 0.76 in Mg-sufficient and to 1.86, 0.76 or 0.035 in Mg-limited plants. Visible symptoms of Mg deficiency occurred only in current-year needles, indicating adequate Mg nutrition before the experiment. Under conditions of Mg limitation, chlorophyll and Mg concentrations were lowest in needles of trees supplied with NH(4) (+) as the major nitrogen source and highest in needles of trees supplied with NO(3) (-) as the major nitrogen source. In current-year and one-year-old needles, starch accumulation induced by Mg deficiency was increased when NH(4) (+) was the major nitrogen source. The accumulation of tannin spherules in current-year needles, which occurred in response to Mg deficiency, also increased with decreasing NO(3) (-)/NH(4) (+)-ratios. Deficient Mg supply caused premature aging in tissues of the vascular bundle, as indicated by modifications of the cambium and increased amounts of collapsed sieve cells. The number of collapsed sieve cells was slightly lower in needles grown in a NH(4) (+)-dominated nutrient regime than in needles grown in a NO(3) (-)-dominated nutrient regime. We conclude that was not directly toxic to Norway spruce trees at the applied concentrations. However, effects of Mg deficiency were considerably greater in an NH(4) (+)-dominated nutrient regime than in a NO(3) (-)-dominated nutrient regime.  相似文献   

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