摘要:

The pattern of vertical stratification in mixed Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) and western hemlock (Tsugaheterophylla(Raf.) Sarg.) stands was documented by observing tree interaction patterns on temporary plots in stands between 35 and 80 years old. It was found that Douglas-fir predictably dominated the hemlock. Several possible causes of the stratification were studied. They were differences in ages between species, differences in mortality patterns, and differences in growth rates. Increment borings of trees on sample plots in the 35- to 80-year stands with the observed stratification revealed the overtopping Douglas-firs and suppressed hemlocks to be essentially of the same age. Searches for dead or dying Douglas-fir in groups of mixed stands of 35 to 80 years, 22 to 35 years, and less than 12 years revealed very little Douglas-fir mortality by suppression. Therefore, the possibility of death of intermediate and suppressed Douglas-firs was not an important factor leading to Douglas-firs being found primarily in the upper crown positions. Height and diameter growth patterns of closely growing codominant Douglas-firs, co-dominant hemlocks, and suppressed hemlocks were documented by stem analyses. Douglas-fir became significantly taller than the hemlocks after about 20 years and suppressed competing hemlocks. The possibility of stratification in mixed planted stands is less certain, since only young planted stands were available for study. Management of such mixed stands appears to improve the yield and quantity of wood and reduce or eliminate costly precommercial thinnings.

ISSN:0045-5067    

DOI:10.1139/x79-001

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Projected levels of nitrogen availability resulting from seven different harvesting regimes in northern hardwoods were used as inputs to a forest growth model. Results were analysed in terms of differences in net production and total yield by treatment. Production was highest under long (90-year) rotations and was reduced under short (45- and 30-year) rotations. Intensive harvesting (whole tree and complete forest cutting) removed a greater percentage of net production than clear-cutting. Complete forest utilization on a 90-year rotation produced the greatest total yield assuming that all harvesting treatments had the same effect on rates of regeneration and successional changes in litter input to the forest floor.

ISSN:0045-5067    

DOI:10.1139/x79-002

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Respiration rates of 3-year-old red pine (PinusresinosaAit.) and 3-year-old white spruce (PiceaglaucaMoench. (Voss)) were measured in sealed containers at 4.5 °C. Increase in CO2concentration was measured using an infrared gas analyser (IRGA). Respiration continued steadily, at 0.025–0.046 mg CO2 g−1dry matter h−1up to CO2concentrations of 2%, which are similar to those encountered in storage bags. Respiration rate of white spruce tended to be higher than that of red pine at 4.5 °C, and measurements of dry matter loss over 49 and 107 days confirmed that both species decrease in dry weight by about 4% in 100 days of storage at this temperature.

ISSN:0045-5067    

DOI:10.1139/x79-003

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Values for the various fluxes of nitrogen through the tree–soil system were calculated using models derived from measurements of rates of input, accumulation, and transfer in plots of 11-m-tallPinusnigravar.maritima(Ait.) Melv. that were showing growth responses to varying rates of nitrogen fertilizer. As the result of continuing immobilization in trees and humus, growth of the unfertilized trees was declining and the trees were having to sacrifice older tissues to mobilize sufficient nitrogen for new growth. In the fertilized trees, there was similar mobilization but of excess nitrogen stored during the period that fertilizers were applied. Models of the flux of nitrogen, phosphorus, calcium, and magnesium at optimum growth showed that tight cycling and low rates of immobilization, coupled with effective retention of relatively high atmospheric inputs, probably represents the adaptive mechanism that enables trees to thrive on soils low in potassium and magnesium. However, high rates of immobilization and low rates of atmospheric input relative to tree uptake mean that despite the maintenance of tight cycles, the trees continued to make significant demands on soil reserves of nitrogen, phosphorus, and calcium throughout their life cycle.

ISSN:0045-5067    

DOI:10.1139/x79-004

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

White ash (FraxinusamericanusL.) collected from a total of 36 geographic areas (in New Brunswick, Ontario, Quebec, and 18 areas of the United States) were outplanted in New Brunswick. The seven hundred and eighty-three 3-year-old seedlings showed a height range from 76 to 25 cm; the height was correlated with latitude (positive) and persistence of the apical bud (negative). Material from more southerly states (Illinois, Tennessee, and Kentucky) survived but suffered the most heavy apical damage of all the material outplanted in New Brunswick. It is suggested that white ash from the northeast of the continent, especially that from New Brunswick, is more resistant to winter damage and local indigenous material is therefore recommended for planting. More southerly material showed purple discoloration of the foliage and crinkled leaf edges. There was little correlation between height of seedlings and elevation of the original populations.

ISSN:0045-5067    

DOI:10.1139/x79-005

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Phellinuspinivar.cancriformans, newly described, is a causal agent of cankers and limited stem decay in white firs in southern Oregon and northern California. Merchantable losses attributed to the effect of this fungus are estimated to be 13% of the standing volume. Sixteen percent of the trees surveyed had large visible cankers.

ISSN:0045-5067    

DOI:10.1139/x79-006

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Gases extracted from wetwood of unwounded black cottonwood (PopulustrichocarpaTorrey and Gray) trunks near Vancouver, B.C., throughout 1974 contained less than 0.10% O2for periods of 5 to 19 weeks during the summer, and an average of approximately 2.5% O2in winter. CO2ranged from an average of about 8.5% in summer to about 6% in winter. Decay tests using surface and completely sterilized cottonwood sapwood and wetwood blocks showed no significant weight loss (average 0.2%) after 10 weeks under near-anaerobic conditions (O2at 0.08%), while parallel tests under aerobic conditions resulted in 42% average weight loss. Both test fungi (PolyporusdelectansPeck andGanodermaapplanatum(Pers.) Pat.) survived 10 weeks under near-anaerobic conditions, but resumption of decay following this period was considerably delayed. It is suggested that in black cottonwood, wetwood is not necessarily a deleterious phenomenon but rather a condition that imparts considerable decay resistance to the inner wood of unwounded trees.

ISSN:0045-5067    

DOI:10.1139/x79-007

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A stepwise discriminant function analysis, based on soil chemical properties at the growing site, was used to differentiate conifers with root decay caused byArmillariellamellea(Vahl. ex Fr.) Karst. from conifers withoutA.melleadecay. Discriminant functions developed for Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) and grand fir (Abiesgrandis(Doug.) Lindl.) were significant. Low soil nitrogen and pH were associated with decayed Douglas-fir; low soil calcium and phosphorus and high soil potassium were associated with decayed grand fir.

ISSN:0045-5067    

DOI:10.1139/x79-008

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The timing and pattern of starch storage and the timing of radial root growth in sugar maple,Acersaccharum, were observed with micro- and histo-chemical techniques from May to December. Results of initial monthly observations showed that starch deposits were very low or depleted in May shortly after budbreak but were fairly heavy by mid-July. A starchless ring of xylem was evident on some roots in mid-July and all roots in mid-August but was not visible in early November. Data from weekly observations indicated that the starchless xylem resulted from new tissue development that began in early July after substantial starch storage. The major portion of growth occurred by early September. The new xylem had no visible starch until mid-August. Initially, starch deposits developed in new xylem cells nearest to the previous annual ring. Starch appeared first in the ray parenchyma, next in the xylem fibers adjacent to vessels, and then in xylem fibers more distant from the vessels. By late September, the outer ring of xylem was no longer distinctly different from the older tissue. In contrast with the stem, where radial growth precedes or coincides with carbohydrate storage, substantial storage of carbohydrates preceded radial growth in the roots.

ISSN:0045-5067    

DOI:10.1139/x79-009

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Effects of SO2pollution on stomatal aperture and sulfur uptake varied with SO2dosage and plant species. Fumigation ofUlmusamericanaL. seedlings with 1 ppm SO2for 8 h inhibited stomatal closure and fumigation with 2 ppm SO2for 12 h induced stomatal closure. Sulfur uptake of fumigatedUlmusamericanaseedlings depended on stomatal aperture and was much higher in the light than in the dark. Fumigation of water-stressedGinkgobilobaL. seedlings with 2 ppm SO2for 6.5 h tended to prevent stomatal closure. However, the effects of SO2on stomatal aperture were modulated and often overridden by environmental stresses such as low light intensity and drought.

ISSN:0045-5067    

DOI:10.1139/x79-010

出版商:NRC Research Press    

年代:1979

数据来源: NRC