摘要:

Equations needed to determine the economically optimal spacing of roads for multistage, one-way to roadside cable yarding were derived. The equations were used in a case study of optimal road spacing on four grapple yarding operations in coastal British Columbia. Two-stage yarding was cheaper and led to closer road spacing than one-stage yarding in all cases. The break-even point for two- and three-stage yarding with respect to road cost was defined as critical road cost. Three-stage yarding provided cost savings and a substantial increase in road spacing once critical road costs were exceeded. Critical road costs for three-stage yarding were within the range experienced in coastal British Columbia for the operations included in the case study. The potential for cost savings and reduced site disturbance from multistage yarding warrants serious consideration of these systems during harvest planning.

ISSN:0045-5067    

DOI:10.1139/x90-089

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The abundance and distribution of rhizomorphs ofArmillariaspp. in the soil were quantified in undisturbed stands and in stands defoliated 1 and 5 years previously by insects. Although the species ofArmillariawas not determined, similar mixed oak forests in south central Pennsylvania contain North American biological species VII (ArmillariabulbosaBarla.). Several analysis techniques were tested for sensitivity to differences in distribution of rhizomorphs. Rhizomorph distribution within the 0.04-ha study plots was uniform in the undisturbed stands, but was significantly greater near dead trees in the defoliated stands. Total rhizomorph abundance was greater on plots defoliated 5 years before sampling than on more recently defoliated plots, and it was least on undefoliated plots. Rhizomorph density near dead trees was highly correlated with overall rhizomorph density. Greater rhizomorph abundance near recently dead trees or stumps may have important implications for management decisions in the presence of gypsy moth (LymantriadisparL.) infestations.

ISSN:0045-5067    

DOI:10.1139/x90-090

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Fourteen treatments expected to promote and regulate flowering were administered to 7-year-old seedlings of Chinese pine (PinustabulaeformisCarr.), and three were administered to 11-year-old grafted propagules. The cultural treatments, including root pruning, stem girdling, polyethylene mulching, and injection of gibberellin A3(GA3) significantly increased male cone bud production of the young seedlings. For female flowering, however, only GA4injection, alone and in combination with root pruning, had a statistically significant positive effect.N6-benzyladenine (BA) injection significantly decreased both male and female cone-bud production. There was no synergistic effect between the cultural and the hormonal treatments on flowering of the seedlings. Treatments with naphthaleneacetic acid dramatically enhanced male cone bud production of the grafted propagules, but did so at the expense of female cone bud production. The hormonal treatments (GA3, GA4, and BA injection) all promoted vegetative shoot growth of the treated seedlings. The cultural treatments generally inhibited shoot length growth and had no significant effect on diameter growth.

ISSN:0045-5067    

DOI:10.1139/x90-091

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A soil-site study was conducted for inland Douglas-fir growing in northern Idaho and north western Montana. The hypothesis was that standard soil survey procedures would provide edaphic data that could predict site index in the absence of site trees. Soil profile descriptions and physical analyses were obtained on 133 plots, along with several physiographic site descriptors. Chemical analyses were performed on soil samples from a third of these plots, and moisture availability was determined on 60% of the plots. Site index was based on felled-tree stem analyses. Elevation was the strongest predictor, accounting for a third of the variation in site index. The addition of habitat type information resulted in a significant improvement (as did longitude and precipitation), but still left over half the variation unexplained. After examining numerous soil properties the standard error could only be reduced 0.3 m, a disappointing result in light of the considerable time and expense necessary for soil sampling. The causes of these low soil–site correlations could not be conclusively determined, but the most likely explanations are (i) that the number of important site factor interactions occurring in this large and complex study area far exceeded the sample size, and (ii) failure to measure the true causes of site productivity.

ISSN:0045-5067    

DOI:10.1139/x90-092

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Vegetation from 133 relevés representing a broad spectrum of peatland types from the Prince Rupert area, British Columbia was divided into six relevé groups. The 210 taxa found in these relevés were classified into six species groups. In general, the species groups are related to one another along shade and height (above water level) gradients. Chemical and physiographic gradients that correlate with the relevé distribution pattern on a detrended correspondence analysis ordination are surface water chemistry, shade, and height. In particular, the major gradient influencing the first axis of the ordination is shade. The second axis of the ordination is related to a complex chemical gradient in which hydrogen ion, calcium, and sulphate are the most important components. These chemical changes are influenced by ombrotrophy. Surface water chemistry patterns show enriched ionic conditions on Graham Island (Queen Charlotte Islands), with a decrease inland. Especially important is the decrease of sodium and chloride ion. The peatlands studied include ombrotrophic bogs and soligenous fens. Raised bogs were found in basins, whereas blanket bogs occurred on gentle slopes at the most oceanic site.PinuscontortaLoud. var.contortais most abundant on ombrotrophic sites, whereasChamaecyparisnootkatensis(Lamb.) Spach is dominant in soligenous fens. Soligenous poor fen, characterized by highSphagnumabundance in lawns and forest islands and pH of 4.4–6.6, is the peatland type most frequently encountered in the study area.

ISSN:0045-5067    

DOI:10.1139/x90-093

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A greenhouse bioassay was used to compare the growth, ectomycorrhiza formation, and foliar nutrient concentrations of Douglas-fir seedlings grown in soils collected at different distances from hardwood species. Soil nutrient concentrations and bulk densities were also determined. The soils were collected from two southwestern Oregon sites that had been clear-cut and broadcast burned 5 years previously. The sites, poorly stocked with conifer reproduction, were occupied primarily by grasses, forbs, and scattered individuals of tanoak (Lithocarpusdensiflora(Hook. & Arn.) Rehd.), Pacific madrone (ArbutusmenziesiiPursh), and canyon line oak (QuercuschrysolepisLiebm.). Five-month-old seedlings grown in media containing mineral soil collected beneath hardwood crowns had on average 60% greater height, 2.2 times greater weight (roots plus shoots), and almost 2 times more total and ectomycorrhizal short roots than seedlings grown in media containing soil collected more than 4 m from a hardwood.Rhizopogonsp. andCenococcumgeophilumdominated on seedlings grown in hardwood soils, and an unidentified brown ectomycorrhiza dominated on seedlings grown in open area soils. The effect of hardwoods did not vary among the three hardwood species or between the two sites. A study of soils collected at various distances from hardwoods indicated that the effect extended between 2 and 3 m. Average foliar nitrogen was higher for seedlings grown in hardwood area than in open area soils, but differences were not statistically significant. Differences in other foliar nutrients of seedlings grown on soils from beneath the three hardwood species were inconsistent. Differences in soil nutrient concentrations were also inconsistent; however, rates of mineralizable nitrogen (anaerobic) were from 2 to nearly 6 times higher in hardwood area than open area soils, and soil pH was higher. Results suggest that the pioneering hardwoods strongly influence soil biological activity in these clear-cuts and impose one or more soil patterns that favor establishment and growth of conifer seedlings.

ISSN:0045-5067    

DOI:10.1139/x90-094

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Growth responses of Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) seedlings to the gibberellin synthesis inhibitor paclobutrazol were examined in sand culture. Shoot and root dry weights and root lengths were reduced at 5 mg (active ingredient) of paclobutrazol per litre, in the nutrient solution, although the proportion of dry matter allocated to roots was increased by 5 mg (active ingredient) of paclobutrazol per litre. Similar effects were observed with triadimefon, although the reduction in height growth was less in triadimefon-treated seedlings than in paclobutrazol-treated seedlings. Stomatal conductance, transpiration, and needle area:weight ratio were reduced by both paclobutrazol and triadimefon treatments of 13.5-week-old seedlings, although paclobutrazol was more effective than triadimefon in reducing needle arear:weight ratio. Treatment of 1-year-old container seedlings of Douglas-fir and white spruce (Piceaglauca(Moench) Voss) by shoot dipping or plug drenching with paclobutrazol, in December or March, reduced height growth and new needle area:weight ratio after 6 weeks growth in a greenhouse. Xylem water potential of paclobutrazol-drenched seedlings was increased by 0.7 MPa above controls (−1.8 MPa) 11 weeks after planting, and stomatal conductance of drenched white spruce increased with paclobutrazol concentration.

ISSN:0045-5067    

DOI:10.1139/x90-095

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

We classified dead bole wood in an old-growth Engelmann spruce – subalpine fir (PiceaengelmanniiParry –Abieslasiocarpa(Hook.) Nutt.) forest in Rocky Mountain National Park, Colorado, into decay classes and measured dead bole surface area, volume, biomass, and nutrient content. Biomass of dead boles was 70 Mg/ha, about half as large as aboveground live biomass in these forests. Net accumulation of N, P, Ca, and Na occurred with increasing decay. The N:P ratio varied little with decay, approaching a value of 20 in the most decayed wood, typical of that found in other studies of dead boles. Loss of K during bole decay exceeded the rate of weight loss, whereas Mg loss followed weight loss. The total pools of nutrients in dead boles and in parentheses, the amount of nutrients stored in dead boles as a percentage of total above- and below-ground living, forest floor, and dead wood nutrients were 92.2 kg N/ha (7%), 4.89 kg P/ha (5%), 67.9 kg K/ha (16%), 156.6 kg Ca/ha (12%), 28.9 kg Mg/ha (17%), and 0.74 kg Na/ha (9%). Storage of relatively high amounts of Ca in dead wood of most natural forests indicates that management could have a significant effect on its availability in the long term.

ISSN:0045-5067    

DOI:10.1139/x90-096

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Time series techniques were utilized to evaluate the influence of selected climatic factors on basal area increment growth of loblolly pine (PinustaedaL.) in rural Alabama and to address the possibility of a changing growth trend. This study is unique in its application of these techniques to an important southern United States timber species. An important asset of the study is the availability of long-term weather records from a weather station only 0.5 km distant. Basal area increment from 1906 to 1986 was modelled using an autoregressive integrated moving average model. Significant predictors of annual increment are previous annual increment, average temperature in June, precipitation in May, June, and August, the annual drought index for southern pine, and the Palmer drought severity index value for August. The best predictor variable examined was the August Palmer drought severity index value. Basal area increment was examined for interventions indicating a changing growth trend. No significant (p ≤ 0.05) interventions were observed in the climatically modelled series.

ISSN:0045-5067    

DOI:10.1139/x90-097

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The red spruce (PicearubensSarg.) growth decline in the northeastern United States does not appear to be ubiquitous. Some selected tree-ring data sets are compared graphically and with two models that tend to support the notion that differences exist between stands as to the presence and degree of decline. It appears that the degree of post-1960 decline is related to the proportion of trees showing a pre-1950 growth increase, and stratifying the data into as few as two classes can improve model fit substantially. The models used in the comparisons are of interest in themselves, because they are capable of exhibiting the mathematical phenomenon of chaos.

ISSN:0045-5067    

DOI:10.1139/x90-098

出版商:NRC Research Press    

年代:1990

数据来源: NRC