摘要:

The chronology of spruce budworm (Choristoneurafumiferana(Clem.)) oubreaks for the past 200 years has been reconstructed by dendrochronological analysis of balsam fir (Abiesbalsamea(L.) Mill.) and white spruce (Piceaglauca(Moench) Voss) samples from virgin forests, unaffected by insecticide spraying programs and recently protected against fires in the north and northwest of Lac Saint-Jean. Outbreaks began around 1974, 1944, 1909, and possibly, 1832. They are closely linked with those described in the Laurentide wildlife reserve. The frequency, duration and severity of growth rings suppression associated with outbreaks are similar to those registered during outbreaks in the southern forests, except for the 1974 outbreak, which was shorter and less severe. Other outbreaks registered in southern regions, where the proportion of balsam fir is higher, have reached this region where balsam fir populations are marginal. These results underline the importance of these ecological disturbances in the population dynamics of the host trees of the region.

ISSN:0045-5067    

DOI:10.1139/x90-001

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Diploid and haploid embryogenesis was induced in twoLarixspecies (L.deciduaandL.leptolepis) and their reciprocal hybrids. Diploid embryogenic tissue was initiated in immature zygotic embryos isolated with the micropylar half of the megagametophyte left attached. These were placed either on modified LM or MSG medium supplemented with the growth regulators 2,4-D and 6-benzyladenine. MSG medium was solidified with either gellan gum or agar. There was no appreciable difference in response between the two. Haploid embryogenesis was induced in isolated megagametophytes placed on modified LM medium supplemented with 2,4-D and 6-benzyladenine. Diploid embryogenic tissue was subcultured on medium with growth regulators, but haploid embryogenic tissue grew well on medium without growth regulators. There were few morphological differences between the diploid and haploid embryogenic tissue. In all species and hybrids, haploid cultures contained more coenocytic long cells. Binucleate cells were most common, but tetranucleate and octanucleate cells were also present. Haploid cultures showed poorer organization than the diploid ones, with only a few cultures having well-developed embryoids. Haploid tissue originated from expanded cells of the megagametophyte. Diploid tissue originated from the suspensor region of the zygotic embryo; it proliferated from isolated clusters of meristematic cells in early embryoids. Diploid and haploid cultures differed not only from the outset, but also in the mature embryoids they produced.

ISSN:0045-5067    

DOI:10.1139/x90-002

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Optimal any-aged management problems for mixed-species stands have been solved for the first time. Problem formulation calls for periodic planting and harvesting controls to be applied without constraints on the stand age or size structure over time; classical definitions of both even- and uneven-aged management are, thus, subsets of this general any-aged management definition. The solution technique is a derivative-free, coordinate-search process called the method of Hooke and Jeeves. The optimizer incorporates without modification the Stand Prognosis Model, a single-tree simulator that is used extensively in the western United States. This paper focuses on sensitivity analysis and performance of the optimizer on problems with both short and long time horizons and with different definitions of the harvest controls. Superior harvest regimes are found by defining harvest controls with relatively wide diameter-class boundaries and with broad species groups. In all cases examined, there is variability in present value and harvest pattern associated with the choice of the starting point for the optimizer. The cause of these multiple optima is a nonconvex and discontinuous response surface produced by the single-tree simulator. This points out the need to examine the results from several random starts before making conclusions about optimal timber harvesting.

ISSN:0045-5067    

DOI:10.1139/x90-003

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A method is described for rapidly determining the extent of cold injury to Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) seedling root systems. It is based upon pressure:volume theory but short-cuts the tedious pressure:volume method. Injured root systems were brought to full hydration, then weighed and placed into a pressure chamber. A pressure of 1.5 MPa was applied for a 5-min period, then the root system was removed from the chamber and reweighed. The percent weight loss was then calculated. Percent weight loss was closely related to degree of low temperature exposure in Douglas-fir seedling roots. Percent weight loss values were near 5 in uninjured controls, whereas freeze-injured seedlings had percent weight loss values of 7 or greater. Percent weight loss values measured on seedlings just before planting were closely correlated with seedling vigor and mortality 3 months following planting in both a field test and a greenhouse pot trial.

ISSN:0045-5067    

DOI:10.1139/x90-004

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

In two separate experiments in the field, healthy 80-year-old lodgepole pine (PinuscontortaDougl. var.latifoliaEngelm.) were inoculated with four blue-stain fungi that are associated with mountain pine beetle (DendroctonusponderosaeHopk.) and beetle-attacked trees. Inocula ofOphiostomaclavigerum(Robins.-Jeff. & Davids.) Harrington,O,huntii(Robins.-Jeff.) de Hoog & Scheffer,O.montium(Rumb.) von Arx, andO.minus(Hedge.) H. & P. Sydow were prepared on sawdust media. Inoculum was placed under the bark in two areas (8 × 5 cm each), one above the other, separated by a 15-cm space in which heat pulse velocity (HPV) sensors were installed. HPVs in the inoculated trees were monitored daily for 4 weeks. In sections inoculated withO.clavigerum, HPVs were significantly reduced 10 to 13 days after inoculation in both experiments. Sapwood under the inoculated area was visibly altered and colonized by the fungus. The other three fungi did not significantly reduce HPVs. These results proved the capability ofO.clavigerumto colonize functional sapwood and stop sap flow within a short period of time and reconfirmed the importance of this fungus in the mortality of trees attacked by mountain pine beetle.

ISSN:0045-5067    

DOI:10.1139/x90-005

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Trees of rooted cutting and seedling origins of yellow cypress (Chamaecyparisnootkatensis(D. Don) Spach) were compared for survival and growth in two field experiments at 9 and 11 years after establishment. Experiment 1 evaluated seedlings and rooted cuttings from 1-, 3-, and 7-year-old donors. Experiment 2 compared rooted cuttings from 2-year-old donors and seedlings from the same 10 open-pollinated families. Survival was high in both experiments, with no significant differences between propagule types. In experiment 1, trees of rooted cutting origin from 1-year-old donors were significantly taller than trees of rooted cutting origin from 3- and 7-year-old donors, but there was no significant difference between trees of seedling and rooted cutting origin from any of the donor age groups. Experiment 2 found no significant differences between trees of rooted cutting and seedling origin in height or diameter, and no significant differences between families. However, in this experiment, rooted cuttings had significantly fewer multiple tops than seedlings. It is concluded that the use of rooted cuttings is a viable alternative to seedlings in reforestation of yellow cypress.

ISSN:0045-5067    

DOI:10.1139/x90-006

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Biological species of theArmillariacomplex present in declining sugar maple stands in southeastern Quebec were identified by pairing monosporous isolates with known tester strains.Armillariaostoyae(I),A.gemina(II),A.calvescens(III), andA.sinapina(V) were collected.Armillariacalvescenswas the most frequent species and was found in almost all the stands sampled. The presence of variousArmillariaspecies was not correlated with either the severity of decline of the stands or the health of the hosts with which they were associated, suggesting that none of the species present in sugar maple stands is particularly responsible for their decline. However, the role ofA.calvescensand the factors that favor its development warrant further investigations because this species appears to be found almost exclusively on maple trees.

ISSN:0045-5067    

DOI:10.1139/x90-007

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Stem maintenance respiration was linearly related to live-cell volume for lodgepole pine (Pinuscontortavar.latifoliaEngelm.) from 4 to 36 cm dbh and for Engelmann spruce (PiceaengelmanniiParry) from 0 to 20 cm dbh. Sapwood contained greater than 80% of the total live-cell volume in stems. Bole surface area, commonly used to estimate tree respiration costs, poorly estimated stem maintenance respiration. At 15 °C, maintenance costs for lodgepole pine were 6.6 × 10−5 kg C•(kg C sapwood)−1•d−1. Stem respiration during the growing season, both corrected and uncorrected for maintenance, correlated well with annual stemwood growth. Annual stem maintenance respiration for trees and stands can be estimated using sapwood volume, sapwood temperature, and knowledge of respiratory behavior. Total respiration (construction plus maintenance) estimated using stem growth and a model of maintenance respiration was compared with actual respiration measurements integrated over a 100-d growing season. Estimated respiration agreed with the integrated measurements for Engelmann spruce, but overestimated the integrated measurements by 73% in lodgepole pine. These results suggest that estimates of stem respiration made during the growing season may be affected by transpiration.

ISSN:0045-5067    

DOI:10.1139/x90-008

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Seedlings of red spruce (PicearubensSarg.) were exposed repeatedly, either in the field or in the greenhouse, to sulfuric acid mist, nitric acid mist (with or without ammonium ions), or a combination of sulfuric and nitric acid mist (with or without ammonium ions) for 10 to 39% of the time over periods of 6 to 19 weeks. Sulfuric acid mist produced visible foliar injury after repeated overnight exposures to pH 3 or less. Foliar symptoms were significantly less or absent after exposures to nitric acid or combined sulphuric–nitric acid mist at the same pH values. Abscission of needles during the subsequent winter also was increased by sulfuric acid mist. Intermittent exposures that contained fewer hours of treatment with acidic mist and longer drying periods than continuous exposures caused greater amounts of foliar injury. Wind during the drying periods enhanced foliar injury, especially with sulfuric acid mist. Significant reductions in shoot elongation occurred with sulfuric acid mist in those experiments where seedlings continued to grow throughout the treatment period. Different provenances responded similarly to acidic mist. The results indicate that red spruce is particularly vulnerable to injury from acidic mist when sulfate concentrations are high and when mist exposures are intermittent with repeated periods of drying of liquid on foliage.

ISSN:0045-5067    

DOI:10.1139/x90-009

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The effects of self-, cross-, and no pollination on cone size, filled seed, pollination efficiency, ovule development, and seed efficiency were tested on rooted ramets of six western red cedar (ThujaplicataDonn) clones. To fully develop, ovules must be pollinated with viable pollen and cones must have a minimum of one developing seed. The seed potential was constant among clones and not affected by pollination. The greatest loss of potential seed resulted from a failure of ovules to be pollinated, followed closely by the low percent viability of pollen. Unpollinated ovules aborted at the megaspore or free-nuclear stages. Pollinated ovules may abort at any stage of development, but it was most common during the long free nuclear stage. Selfing had a limited effect on postzygotic loss owing to embryo abortion or on seed set. Western red cedar is well adapted for a high degree of selfing. Clonal differences occurred in seed efficiency and stages at wich seed losses were most commun. Seed set in western red cedar may be increased if cones on female parents having a history of high seed efficiency are pollinated several times within a 1 week peak pollination period with abundant pollen of known high percent viability. Potential seed losses are discussed with reference to pollination and ovule development.

ISSN:0045-5067    

DOI:10.1139/x90-010

出版商:NRC Research Press    

年代:1990

数据来源: NRC