摘要:

Effects of diameter distribution on the growth of simulated uneven-aged sugar maple (AcersaccharumMarsh.) stands are described using output from a computer simulation model. Results indicate that the combination ofqratio (a constant ratio between the numbers of trees present in adjacent diameters over the entire range of size classes present), maximum tree size, and basal area should vary depending on management objectives and cutting cycle length. A ratio of 1.2 appears best for describing a diameter distribution to maximize growth of large sawtimber, but largerqratios are needed in the sapling and pole size classes to insure sufficient numbers of trees to sustain the distribution through the end of a cutting cycle. Retaining trees larger than a 40 cm diameter at breast height offers no advantage when objectives stress maximum volume production. A 50 cm maximum tree size appears better suited for maximizing large sawtimber volume and value growth, but a 40 cm maximum will yield a better compound rate of return on initial stand value. Under all options, longer cutting cycles require lower initial basal area levels.

ISSN:0045-5067    

DOI:10.1139/x87-001

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

In many central hardwood stands, forest managers should be concerned about maintaining or improving the potential quality of future crop trees as well as increasing growth. Thinning practices have been shown to increase diameter and volume growth but there have been few studies on the effects of thinning on product potential. The effect of thinning to various basal area levels on the limb-related defect development of 80-year-old white oak (QuercusalbaL.) is analyzed by Markov Chain analysis. The transition probabilities from the Markov Chain analysis were used to predict the expected number of limb-related defects by 5-year intervals for 40 years after treatment. At this age, the average tree in the untreated plots and the standard thinning had a probability of 0.81 of attaining grade 1. The average tree in the heavy and severe thinning had only a probability of about 0.25 of attaining grade 1. Generally, severe thinnings may result in a decrease of tree quality, particularly in white oak. Managers must balance this with increased growth potential and the inherent quality potential of the stand before making decisions.

ISSN:0045-5067    

DOI:10.1139/x87-002

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Crown ratio was incorporated into four Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) total-stem cubic volume equations as a nonlinear multiplier. Two of the equations are traditional linear equations, one is nonlinear, and one is a new component approach that divides stem volume into that above and that below breast height. These equations, with and without crown ratio terms, were fitted to a modeling data set, and the statistical significance of the crown ratio terms was examined. All equations were then applied to a validation data set for comparison of their predictive abilities. The crown ratio term proved to be highly significant in the component approach, and component equations that included crown ratio had the smallest bias and the greatest prediction precision of all equations examined. That form was therefore selected as the most accurate characterization of Douglas-fir stem volume.

ISSN:0045-5067    

DOI:10.1139/x87-003

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Seedlings ofPinustaedaL. were planted in 1982 on a clear-cut site in the northeastern Piedmont of North Carolina. Two intensities of site preparation (chopping and shear–pile–disk) were applied in the previous year, and seedlings were maintained under three intensities of cultural practice (no treatment, application of herbicides, and hand weeding) for control of successional vegetation regrowth. Both site preparation and cultural practice significantly affected pine performance (relative growth rate) and predawn leaf water potentials. Soil water potentials showed no significant treatment effects, even during a severe drought in the summer of 1983. An index of moisture strain for the pine seedlings was developed by regressing predawn leaf water potentials of individual pines against the mean leaf water potentials of all pines using data collected on 5 days in the summer of 1983. This index accounted for 55% of the variation in pine performance. The predictive value of the index resulted from its integration of a variety of stress factors and was probably enhanced by its application during a dry growing season.

ISSN:0045-5067    

DOI:10.1139/x87-004

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Greenhouse-grown black spruce and jack pine container seedlings were fertilized weekly with a 20–8–20 fertilizer at four concentrations during the fall. Seedlings were sampled when 23 weeks old towards the end of the greenhouse cultural period to determine the effect of fertilization on the free amino acid concentrations. All amino acids, except tryptophan, showed significant increases in concentration with higher levels of fertilizer; the concentration of tryptophan decreased with increasing fertilizer concentration. Amino acids with the highest concentrations in black spruce were arginine, glutamic acid, and proline, while in jack pine, besides these three, aspartic acid and glutamine were also found in high concentrations. Black spruce had significantly higher amino acid concentrations than jack pine. The concentrations of certain free amino acids may be more sensitive indicators of seedling nitrogen status than total foliar nitrogen.

ISSN:0045-5067    

DOI:10.1139/x87-005

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Eight isolates ofPisolithustinctorius(Pers.) Coker and Couch (three each from Georgia and northern California and one each from Oregon and Washington) were comparedinvitrofor growth rate, for alkaline and acid phosphatase and nitrate reductase activities, for acid phosphatase isozyme patterns, and for cytokinin, indoleacetic acid, and gibberellin production. Significant differences appeared between isolates for each parameter examined. All isolates showed relatively low phosphatase and nitrate reductase activities. Isolate S-359 from northern California grew the slowest in culture and produced significantly more indoleacetic acid than all other isolates and more cytokinin than six of the other seven isolates; this isolate was also the only one of the eight that did not share at least one acid phosphatase allele with the others in the isozyme analysis.

ISSN:0045-5067    

DOI:10.1139/x87-006

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Containerized black oak seedlings in which the growth medium was inoculated withPisolithustinctorius(Pers.) Coker Couch or left uninoculated were grown for 16 weeks with or without a polyacrylic starch containing 1000 μg indolebutyric acid per gram mixed throughout the growth medium. Seedlings treated with indolebutyric acid developed more than twice as many lateral roots as control seedlings which did not receive indolebutyric acid. Indolebutyric acid reduced the percentage of primary laterals colonized byP.tinctorius; however, the total number of colonized lateral roots was not affected. The combination of ectomycorrhizal inoculation with the indolebutyric acid treatment significantly increased the growth and development of black oak seedlings.

ISSN:0045-5067    

DOI:10.1139/x87-007

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Bareroot 2-0 Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) and ponderosa pine (PinusponderosaDougl. ex Laws.) seedlings were subjected to five undercutting treatments, which varied by number and depth of undercut and seedling phenology at time of treatment, so that morphological characteristics at lifting and field performance 4 years after planting on droughty south slopes in southwest Oregon could be evaluated. All undercutting treatments significantly reduced seedling top growth, but changes in root system morphology depended upon treatment severity and species. Treatment effects were generally more pronounced in ponderosa pine than Douglas-fir. Multivariate analysis of variance showed significant treatment effects for both species based on seedling morphology at lifting, but discriminant analyses revealed that these differences existed primarily between undercut seedlings, regardless of undercutting treatment, and controls. In Douglas-fir this separation was largely due to differences in seedling height and in ponderosa pine it was due to differences in tap root biomass. However, no treatment effects were detectable 4 years after outplanting for either species despite record high air temperatures during the first growing season, suggesting that morphological differences at lifting were probably not of sufficient magnitude to affect field performance.

ISSN:0045-5067    

DOI:10.1139/x87-008

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Containerized aspen (PopulustremuloidesMichx.) seedlings were planted at high-elevation sites in southern (May 1982) and northern (July 1983) New Mexico. Each plantation compared fall cultivation (20 cm depth), prior to planting the following spring or summer, with cultivation at the time of planting. Subtreatments of the tests included applications of the postemergent herbicide dalapon and the preemergents linuron, trifluralin, or simazine applied 2 to 3 weeks before planting. First season survival exceeded 75% for the best treatment at each site. Cultivation, in general, effectively reduced weed cover and improved seedling success. Fall cultivation, in particular, improved seedling survival and growth only at the relatively dry southern site. Except for spring-cultivated plots in the south, some herbicide applications improved weed control and seedling performance over cultivation alone. The combination of fall cultivation plus trifluralin is considered the best site preparatory treatment tested.

ISSN:0045-5067    

DOI:10.1139/x87-009

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Three species of 11-year-old pine trees were inoculated withBursaphelenchusxylophilusin the field. Four branches in single whorls on red, Scots, and jack pine trees were wounded and inoculated with 10 000 nematodes each or with water extracts fromBotrytiscinereacultures. Prior to field inoculations, the pathogenicity of the nematode isolate was confirmed on seedlings in the greenhouse. Fourteen weeks after inoculation, 27 of 80 and 13 of 52 branches were dead or dying on Scots and jack pine trees, respectively. No symptoms were observed on red pine trees inoculated withB.xylophilusor on any controls. Branch death was attributed to the formation of girdling cankers resulting from inoculation. An average of 9.14, 10.39, and 0.02 nematodes were extracted per gram of wood from branch samples collected from Scots, jack, and red pine trees at 14 weeks, respectively, and at 58 weeks an average of 13.82, 1.01, and 0.05 nematodes per gram of wood sampled were recovered. Proportions of branch samples with nematodes declined from 14 to 58 weeks after inoculation. Although limited mortality of branches occurred, the pine wood nematode was not found to cause tree death following inoculation.

ISSN:0045-5067    

DOI:10.1139/x87-010

出版商:NRC Research Press    

年代:1987

数据来源: NRC