摘要:

Light-saturated photosynthesis following artificial frosts was monitored for black spruce (Picea mariana(Mill.) BSP), jack pine (Pinus banksianaLamb.), and trembling aspen (Populus tremuloidesMichx.). None of the species exposed to -9°C in May or to -6 and -9°C in August recovered within the 23- and 14-day monitoring periods, respectively. Black spruce and jack pine treated at -6°C in May recovered within 5 and 23 days, respectively. Black spruce treated at -3°C in August recovered within 10 days. Frosts were applied to the upper and lower canopies of mature black spruce and jack pine in June and to mature trembling aspen in July. For black spruce, the lower canopy did not recover whereas the upper canopy partially recovered over the 10-day monitoring period. For jack pine and trembling aspen, there were no differences in recovery between canopy levels. Jack pine treated at -5.5°C recovered within the 10-day monitoring period whereas at -8.5°C, it only partially recovered. Although recovery period varied with species, phenological state, and frost temperature, gradual recovery of photosynthesis over 5-21 days seems a reasonable modelling algorithm for boreal tree species when growing season frosts lower than -3°C occur. However, cooling rates in our experiments were greater than those that normally occur in nature.

ISSN:0045-5067    

DOI:10.1139/x97-184

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Altogether 15 root systems, five at each of three plots (north- and south-facing slopes and plateau), of 40-year-oldPicea abies(L.) Karst. trees with different symptoms of forest decline were excavated down to a root diameter of 0.5 cm. The object was to investigate the variability of root morphology and to assess the influence of environmental variation on the architecture of the woody root system. For each tree, total height, diameter at breast height, and needle and twig biomasses were determined, and for each root system, biomass, growth, length, cross-sectional area, number and initial direction of branches, and branching forms were determined. The differences in many of the wood parameters within and between the plots were relatively few, so that forest decline symptoms determined at the crown could not be sufficiently related to the root system architecture. The results suggest a small influence of microsite conditions on the structural root systems, an influence of stand density on root distribution and soil exploitation, and a functional difference between horizontal and vertical roots that points out the importance of extensive long vertical roots, which insure a sufficient water and nutrient uptake.

ISSN:0045-5067    

DOI:10.1139/x97-181

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

To consider the regional scale effects of forest management requires complete and consistent data over large areas. We used Landsat Thematic Mapper and Multispectral Scanner (TM and MSS) imagery to map forest cover and detect major disturbances between 1975 and 1992 for a 4.2 x 106ha area of interior British Columbia. Forested pixels were mapped into closed conifer, semiopen conifer, deciduous, and mixed forest classes, with further subdivision of the closed conifer type into three age-classes. The image-based estimate of harvested area was similar to an independent estimate from forest inventory data. Changes in landscape pattern from 1975 to 1992 were examined by calculating indices that describe overall landscape pattern and that of conifer and harvested patches in each biogeoclimatic zone. Harvesting affected 8.4% of the forest area outside provincial parks during the 17-year period. Harvested areas were consistently much smaller than conifer patches in all biogeoclimatic zones and had a lower percentage of interior area and perimeter/area ratio. Conifer patch-shape complexity varied between zones; harvested patches had simpler shapes and were similar in all zones. Results indicate that this landscape is only in the early stages of fragmentation, but a similar harvest pattern has been imposed on differing ecological zones.

ISSN:0045-5067    

DOI:10.1139/x97-186

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

An improved model for estimating nutrient contents of the commercial portion of tree boles was developed for four boreal tree species (Populus tremuloidesMichx.,Betula papyriferaMarsh.,Picea glauca(Moench) Voss, andAbies balsamea(L.) Mill.). This model considers the spatial pattern of variation of nutrient concentrations inside the bole and its relationships with tree size. For all species-nutrient combinations, no significant pattern was found for vertical variations in nutrient concentrations, while two types of nonlinear models, using distance from the tree periphery as the independent variable, fit the pattern of horizontal (or radial) variations. These patterns of variability were used to estimate the global nutrient concentration of the bole by using mathematical integration. The values obtained with this method were generally lower, especially for large stems, than values obtained with traditional methods that do not consider the variability of nutrient concentrations inside the bole. This improved model would permit better estimates of the amounts of nutrients lost in biomass upon forest harvesting, as well as internal cycling of nutrients within the bole.

ISSN:0045-5067    

DOI:10.1139/x97-176

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Seedlings of four geographically diverse paper birch (Betula papyriferaMarsh.) populations native to British Columbia were grown under low and high levels of water and nitrogen in a greenhouse for 3 months to examine the relative sensitivity of each population to water and nutrient availability. Nine sequential measurements on height and basal diameter growth were made, and then the seedlings were harvested for final biomass measurements. Under optimal conditions the highest elevation population ceased height growth, while the low-elevation coastal population continued to increase in height under all treatment conditions. Plants of all populations grown under high N conditions grew faster and had larger total biomass and lower root/shoot ratios than plants grown under low N conditions. Relative growth rate was significantly correlated with shoot and foliage biomass, leaf area, and root weight ratio. All populations generally responded more to low N level than to low moisture level in terms of height growth, relative growth rate, total biomass, and root/shoot ratio. This suggests that the populations observed in this study are better adapted to drought than poor soil nutrient availability. Therefore, consideration of site quality, which includes soil moisture regime and soil nutrient regime, should be a primary concern when allocating birch seed lots in a planting program.

ISSN:0045-5067    

DOI:10.1139/x97-191

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The main hypothesis tested in this paper is whether heavy thinnings affect the correlations among ring width, wood density, and mean tracheid length. Within-tree correlations were calculated between time series of yearly measurements. Among-tree correlations were computed (1) between averages over a growing period and (2) year by year. Correlations were analyzed on 20 fast-grown and 20 slow-grown Norway spruces (Picea abies(L.) Karst.) from an even-aged, plantation-grown stand near Rendeux, Belgian Ardennes. In the within-tree approach, fast-grown spruces showed a stronger negative correlation between ring width and fiber length. In among-tree approach 1, the widely held negative correlation between ring width and wood density vanished when the spruce growth rate was above 2.2 cm/year in circumference. Among-tree approach 2 demonstrated that the magnitude and sign of the correlations also depended on the year; a few years showed a significant correlation between ring width and wood density for the fast-grown Norway spruces, whereas the correlation was systematically negative and significant on many years for the slow-grown spruces. This study may explain part of the contradictory results reported in the literature concerning hypotheses similar to ours.

ISSN:0045-5067    

DOI:10.1139/x97-189

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Rooted cuttings and seedlings of loblolly pine (Pinus taedaL.) were established in a central Alabama field trial. Five, full-sib families, with an average number of six clones per family, were evaluated. Mean cutting/seedling height ratios revealed that despite initial differences in size, relative growth rates of both propagule types stabilized and were equal by age 7 years. Through age 10 years, results show virtually no difference in height, diameter at breast height, volume, or stem taper between the rooted cuttings and seedlings.

ISSN:0045-5067    

DOI:10.1139/x97-193

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Test plantations were established in western Washington and Oregon to compare tree growth at six initial planting densities ranging from 300 to 2960 trees/ha (120 to 1200/acre). A size-density relation was visually apparent 3 to 4 years after planting. Inventory data from the oldest 11 trials (5 or 6 years after planting) showed that initial spacing strongly influenced early growth of coast Douglas-fir (Pseudotsuga menziesii(Mirb.) Franco var.menziesii). Average height and diameter at breast height were progressively larger as planting density increased; at the widest spacing (lowest stand density), average height was 75% and average diameter at breast height was 67% of that at the closest spacing. We have no firm explanation for the early faster tree growth at close spacings. Trees planted at 2960 trees/ha (1200 trees/acre) attained breast height (1.3 m) 2 years earlier than trees planted at a density of 300/ha (120/acre). This finding has practical significance to current efforts to achieve early establishment of plantations.

ISSN:0045-5067    

DOI:10.1139/x97-190

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Transformed pollen could be used in crossings to provide a new approach for producing transgenic seedlings of gymnosperms recalcitrant to tissue culture. The aim of this study was to investigate different pollination techniques in Norway spruce (Picea abies(L.) Karst.) and in Scots pine (Pinus sylvestrisL.) using both natural pollen and pollen bombarded with DNA-coated microprojectiles. Cone and seed set after liquid pollinations with natural and bombarded pollen was compared with conventional crossings in which dried natural pollen was used. Liquid pollination proved inferior to conventional crossings. In Norway spruce, the percentages of mature cones and full seeds were lower with liquid pollination than with the conventional method; and in Scots pine, the number of conelets was lower than in pollinations in which dried pollen was used. With bombarded pollen, the results were even lower. To improve possibilities to obtain transgenic progenies, a method was developed that allows the use of bombarded pollen in conventional crossings. This technique is based on dehydration of pollen suspensions and storage at -20°C, which results in a slight decrease in the germination ability of pollen but leads to a high level of the beta -glucuronidase reporter gene expression. This is the first report on transient foreign gene expression in plant material stored in a metabolically inactive form for 1 month before gene expression was assayed.

ISSN:0045-5067    

DOI:10.1139/x97-194

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Leaf samples ofCryptomeria japonicaD. Don (and some other conifers) taken from various locations in Japan were analyzed for differences in the amount and elemental composition of their epicuticular wax. InC. japonicathe amount of wax per unit leaf mass was lower, and the C content of the wax relatively higher, than those of other species. The properties of the wax (amount, C and O contents) varied according to natural environmental factors such as altitude and exposure to volcanic acidic gases such as H2S, as well as branch height and leaf age within the tree. The amount of wax increased with leaf age (during the growing phase), altitude, branch height, and exposure to the gases, while the C content of wax decreased and the O content increased, except in the case of altitude, where they showed an opposite change. These findings suggest different alterations in wax properties under the effects of water stress (on high branches and at locations with a low rain factor), exposure to noxious gases, and strong UV radiation at high altitude.

ISSN:0045-5067    

DOI:10.1139/x97-167

出版商:NRC Research Press    

年代:1998

数据来源: NRC