摘要:

Branches on mature red spruce trees (PicearubensSarg.) were fumigated with SO2in late summer of 1990 and 1991. There were four SO2treatment levels (0, 0.1, 0.2, and 0.4 ppm) and 12 fumigation chambers. Each treatment was replicated on three neighboring trees. Net photosynthesis and stomatal conductance of current-year foliage were determined with a Li-Cor photosynthesis system. Rates of foliar SO2absorption were estimated using regression models, with leaf temperature, relative humidity, atmospheric CO2concentrations, and photosynthetically active radiation as predictors. Fumigation effects became visible in terms of needle yellowing and browning after a few weeks of treatment. Effects on net photosynthesis and stomatal conductance were generally negative and in direct proportion with cumulative foliar SO2absorption. It was found that, in shade-adapted foliage, visible symptoms were delayed, and stomatal conductance was slightly stimulated at low SO2levels. In other foliage, leaf yellowing and browning occurred earlier, and stomatal conductance was depressed. Net photosynthesis was depressed at about the same rate regardless of branch position. Foliage subjected to high SO2concentration treatments did not recover from SO2damage 1 year after treatment: needles had fallen off the twigs, and needle and twig length of new foliage was reduced.

ISSN:0045-5067    

DOI:10.1139/x94-189

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Sequential and double sampling plans calibrated for estimating point density (mean number of seedlings per quadrat) at a specified level of precision (ratio of the standard error of the mean to the mean) within mixed black spruce (Piceamariana(Mill.) B.S.R)–balsam fir (Abiesbalsamea(L.) Mill.) seedling populations were compared using sampling simulations. Specifically, plans employing a precision level of 0.25 and 10.1-m2quadrat size were assessed on the following criteria: (i) total number of samples required; (ii) bias in the resultant point density estimates; and (iii) bias in precision levels attained (i.e., difference between the precision level specified in the plans and the actual levels obtained during sampling). The data base consisted of three population clusters derived from forty-three 0.121-ha sample plots situated on recently disturbed sites throughout central insular Newfoundland. Variation in stocking level and spatial pattern heterogeneity characterized differences between clusters: low stocking levels and highly aggregated spatial patterns (cluster A), moderate stocking levels and aggregated spatial patterns (cluster B), and high stocking levels and slightly aggregated spatial patterns (cluster C). Results indicated that the sequential plan required fewer samples than the double sampling plan irrespective of cluster conditions. The percentage of point density estimates within ±25% of their population cluster means obtained from sequential sampling was 63, 71, and 68% for clusters A, B, and C, respectively. Corresponding values for double sampling were 68, 75, and 73% for clusters A, B, and C, respectively. The percentage of sequential simulations in which the specified precision was attained or exceeded was 34, 64, and 61% for clusters A, B, and C, respectively. Corresponding values for double sampling were 51, 77, and 71% for clusters A, B, and C, respectively. Although these results suggest that double sampling may be a practical alternative to sequential sampling, further research into the economic consequences of increased sample sizes coupled with decreased survey distances at various scales is required before the operational utility of the plan is fully ascertained.

ISSN:0045-5067    

DOI:10.1139/x94-190

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Open-pollinated progeny trials of Fraser fir (Abiesfraseri(Pursh) Poir.) assessed at 8 years provided genetic parameter estimates for growth, Christmas tree quality traits, and wholesale value at harvest age. Significant variation was found between and within nine different seed sources. Estimated individual tree heritabilities of important traits ranged from a low of 0.13 for USDA Christmas tree grade to a moderate value of 0.33 for crown diameter. Heritabilities within the better performing seed sources tended to be higher. Of the two traits that determine wholesale value, USDA grade and height class, the latter proved to have the greater influence, both phenotypically and genetically. Genetic correlations of early age height growth with 8-year total height, height class, USDA Christmas tree grade, and individual tree wholesale value proved favorable and strong (range of 0.57–0.96). In combination with moderate heritabilities for early growth traits, such correlations provide potential for effective early age selections in Fraser fir Christmas trees.

ISSN:0045-5067    

DOI:10.1139/x94-191

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Selection methods forAbiesfraseri(Pursh) Poir. for Christmas tree wholesale value were evaluated based on parameters from the species' first genetic field test. For single-trait individual selection, combined individual plus family selection at half rotation age (4 years) on total height (HT4) gave the greatest estimated full rotation (8-year) retail value (VALUE) gain of 24.3%. The best 8-year trait, crown diameter, resulted in a gain of only 22.4%. Incorporation of family mean information together with individual values in the selection process was important in maximizing gains. Only 8-year stem straightness (STR8) had unfavorable genetic and phenotypic correlations with other traits. With multitrait combined optimum index selection, use of Kempthorne restrictions to prevent adverse change in this trait seriously limited gains in other 8-year traits. Severity of this limitation increased for younger age indices, and for those with fewer traits. Unrestricted combined optimum indices offered substantial VALUE gain advantages and only small decreases in STR8. Initial selection among seed sources also increased VALUE gain, despite decreasing the effective additive genetic variation. VALUE gains through initial source selection exceeded gain reductions from the genetic variation decreases. The optimum selection strategy, with 30.5% VALUE gain, involved initial source selection followed by unrestricted combined optimum index selection on HT4, and 4-year density. Though slightly below the maximum, this strategy would provide substantial economic and technical advantage in conducting field tests.

ISSN:0045-5067    

DOI:10.1139/x94-192

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The tissue water relations ofPinusponderosaDougl. ex Laws, (ponderosa pine) andArctostaphylospatulaGreene (greenleaf manzanita) seedlings subjected to three levels of soil moisture availability were monitored over a 6-month period. Throughout the study, osmotic potentials at full turgor and at the turgor loss point were approximately 0.5 MPa greater for pine than for manzanita. Osmotic adjustment occurred for both species as evidenced by declines in osmotic potentials at full turgor and at the turgor loss point of 0.5–0.6 MPa over the study period. Pine maintained higher bulk tissue elasticity and lower water content at the turgor loss point relative to manzanita. Moisture regime had little effect on the measured parameters except for apoplasmic water content which increased at moderate and high stress levels for both species. Results suggest that osmotic adjustment occurred, at least partially, as a result of factors other than moisture availability. The lower tissue elasticity and higher water content at the turgor loss point for manzanita suggest that the shrub species is more dependent upon high foliar water content for the maintenance of turgor compared with the conifer.

ISSN:0045-5067    

DOI:10.1139/x94-193

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Timber harvesting operations often employ continuous landings on or along truck road right-of-ways. During the harvest-unit design process forest engineers describe the spatial distribution of turns with respect to a proposed landing by distribution parameters such as average yarding distance and average yarding slope. In this two-part paper these parameters and others are derived for a continuous landing model. In this first paper, parameters are derived and applied to a continuous landing located on or along a road center-line tangent. In the second paper, a similar development is applied to a continuous landing located on or along the circular curve of a road.

ISSN:0045-5067    

DOI:10.1139/x94-194

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Timber harvesting operations often employ continuous landings on or along truck road right-of-ways. During the harvest-unit design process forest engineers describe the spatial distribution of turns with respect to a proposed landing by distribution parameters such as average yarding distance and average yarding slope. In this two-part paper these parameters and others are derived for a continuous landing model. In the first paper, parameters were derived and applied to a continuous landing located on or along a road center-line tangent. In this second paper, a similar development is applied to a continuous landing located on or along the circular curve of a road.

ISSN:0045-5067    

DOI:10.1139/x94-195

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The objectives of our study were to determine the effects of commercial thinning and broadcast burning on sporocarp production of hypogeous ectomycorrhizal (HEM) fungi. At two sites in northeastern California, Jennie Springs (JS) and Swain Mountain (SM), we compared HEM sporocarp production among units that had been heavily thinned, moderately thinned, and unthinned. At one of those sites, JS, we also compared sporocarp production between units that had been broadcast burned and units left unburned. Sporocarps were sampled in 1992, 10 years after thinning and 9 years after burning occurred at JS, and 17 years after thinning occurred at SM. Total relative frequency and biomass of sporocarps did not differ significantly among thin levels at either site, or between burn levels at JS. There was, however, significant association between thin level and frequencies of the most common genera at JS, suggesting that thinning significantly affected the composition of HEM fungi. The association between burn level and frequencies of the most common genera was also significant, but less pronounced than the association between thin level and the frequencies of common genera.

ISSN:0045-5067    

DOI:10.1139/x94-196

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A simple device for assisting in the recovery of a jammed increment borer from a tree or log is described. The low-cost parts are readily obtained.

ISSN:0045-5067    

DOI:10.1139/x94-197

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

not available

ISSN:0045-5067    

DOI:10.1139/x94-198

出版商:NRC Research Press    

年代:1994

数据来源: NRC