ALBERT

Beschreibung: The effects of fertilization and thinning of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) on the distribution of area increment along the bole were assessed using radial growth measurements 6 and 9 years after treatment. Within treatments, the average area increment per tree was linearly related to diameter at breast height, and this relationship was used to evaluate the effects of treatment on growth rate. Fertilization had the greatest effect on average area increment, and for a particular fertilization regime, thinning increased the response. Thinning modified the distribution of growth over the bole of all trees and increased butt flare, especially in smaller trees. The effect declined from the 4- to 6-year measurement period to the 7-to 9-year measurement period. Fertilization had no consistent effect on growth distribution. The regression methods used in this study provided a more sensitive measure of form changes than previous methods, were independent of size distribution, and facilitated extrapolations and evaluation of temporal trend.

Beschreibung: Organic content of the forest floor decreases for several years after clear-cutting, and then slowly recovers. Thickness, bulk density, organic matter, and nitrogen content of forest floors were measured for 13 northern hardwood stands in the White Mountains of New Hampshire. Stands ranged from 1 to about 100 years in age. Forest-floor thickness varied significantly with stand age, but bulk density, organic fraction, and nitrogen fraction were independent of age. Total organic content of the forest floor agreed very well with data from Covington's (W. W. Covington 1981. Ecology, 62: 41–48) study of the same area. Both studies indicated that mature forest floors have about 80 Mg organic matter•ha−1 and 1.9 Mg nitrogen•ha−1. Within 10 or 15 years after cutting, the organic matter content of the floor decreases to 50 Mg•ha−1, and its nitrogen content to 1.1 Mg•ha−1. The question whether the decrease is rapid and the minimum broad and flat, or if the decrease is gradual and the minimum sharp, cannot be answered. The subsequent increase to levels reached in mature forest requires about 50 years. Some of the initial decrease in organic matter and nitrogen content of the forest floor may be caused by organic decomposition and nitrogen leaching, but mechanical and chemical mixing of floor into mineral soil, during and after the harvest operation, may also be important. The difference is vital with respect to maintenance of long-term productivity.

Beschreibung: The relationships between foliage area and sapwood area between trees and within the crowns of 20 Piceasitchensis (Bong.) Carr., provenance Queen Charlotte Island, British Columbia (10 in a control plot and 10 in a plot fertilized with potassium and phosphorus 8 years before harvest) and 10 Pinuscontorta Dougl., provenance Ladysmith trees were examined using a physiological analysis based on Darcy's law. Foliage area index on the fertilized P. sitchensis plot was higher than on the control. The variation of foliage area density with depth in the canopies followed a normal distribution. Relationships between foliage area and sapwood basal area were linear but the slopes were different for the two species. There was no significant difference between the control and fertilized P. sitchensis trees. The relationship between foliage area and the product of sapwood area and permeability was linear and data from the three plots fell on the same line. Sapwood area, permeability, and their product decreased with depth through the crowns of the trees. Within the crowns, relationships between cumulative foliage area and sapwood area, and between cumulative foliage area and the product of sapwood area × permeability were different with species and treatment. A single linear relationship resulted when the product of cumulative foliage area above an internode × the internode length was plotted against sapwood area × permeability for the internode. This suggests that it is the drop in potential across a node and internode rather than the gradient of potential across the internode that is related to the flux of water through tree crowns. The data support the hypothesis that the relationship between foliage area and sapwood area depends on permeability of the sapwood and the local climate through its influence on transpiration rate, particularly via average water vapour pressure deficit of the air and stomatal conductance.

Beschreibung: The effects of two sources of nitrogen fertilizer applied at rates of 224 and 448 kg N/ha on growth of a thinned and unthinned 24-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand were studied. Ammonium nitrate yielded higher growth of diameter and volume than did urea over a 9-year period, particularly with thinning. Height growth was not affected by nitrogen source. The efficiency of nitrogen fertilization in terms of stem volume response per kilogram of nitrogen applied was greatest with ammonium nitrate in thinned plots. Tree mortality increased substantially with level of fertilization for both sources, and decreased markedly with thinning.

Beschreibung: Cambial electrical resistance (CER) was related to the number of cells per radial file of vascular cambium in dominant and codominant balsam fir (Abiesbalsamea (L.) Mill.) trees sampled during the growing season. Scanning electron microscopy (SEM) was used to examine the vascular cambial zone (VCZ) of balsam fir during the growing and dormant seasons. Trees selected for SEM were categorized as having growing season CER  12 kΩ. The two growing trees with CER  12 kΩ. Trees of either growing season category had dormant season CER 〉 12 kΩ and four cells per radial file of VCZ. The relationship between CER and the number of cells per radial file of VCZ supports the hypothesis relating CER to periodic growth rate in balsam fir.

Beschreibung: Natural inbreeding and relatedness among neighboring trees were studied in several central New Brunswick populations of white spruce (Piceaglauca (Moench) Voss). Coefficients of relationship (r) were estimated by comparing the self-, neighbor-, open-, and unrelated-pollination effects on percent full seed. The estimates were 0.29 and 0.28 for neighbor and open pollinations, respectively. The effects of natural inbreeding on juvenile traits, e.g., germination and early growth, were slight while the effect on height growth increased with age at least to age 7 years. Neighboring white spruce trees growing in natural stands appear to be related at about the half-sib level (r = 0.25). Based on percent full seed, open-pollination approximates a level of inbreeding expected from trees related at a level well above that of half-sibs. Differential selection at the pre-embryo to early seedling stages results in progenies again related at the half-sib level. It is suggested that an inbreeding equilibrium exists in natural stands of white spruce and that this equilibrium approximates that expected from half-sib matings (F = 0.125). The inbreeding equilibrium is controlled, at least in part, by the frequency of lethal genes in the populations.

Beschreibung: Light-saturated net photosynthetic rates per unit leaf area were 1.6–2.1 times greater for the photosynthetically mature leaves of plants of two hybrid Populus clones (NC-5260, 'Tristis No.1' (Populustristis Fisch. × P. balsamifera L.); NC-5326, 'eugenei' (P. deltoides Bartr. ex Marsh. × P. nigra L.)) grown in pots in the field than in comparable plants from a controlled environment growth room and a winter greenhouse. Stomatal resistances to CO2 in the field trees were only 0.4–0.6 of those in growth room and greenhouse trees. Mesophyll (residual) resistances to CO2 in field trees were 0.4–0.8 of those in growth room and greenhouse trees. Field plants had specific leaf weights 1.5–1.8 times higher than growth room and greenhouse plants, likely primarily owing to the greater average photosynthetic photon flux density in the field (835, 225, and 142 μE m−2 s−1 for field, growth room, and greenhouse conditions, respectively). When net photosynthetic rates (Ps) were corrected for the differences in specific leaf weights to derive net photosynthetic rate per unit leaf dry weight, the values were similar for plants from the three environments (Ps in field trees was 0.9–1.2 times Ps in growth room and greenhouse trees); gross photosynthetic rates per unit leaf weight were even more similar. Internal leaf CO2 concentrations, and photorespiration and dark respiration rates per unit leaf area were not related to growth environment. However, photorespiration rate as a percentage of net photosynthetic rate was lower in the field trees (12–16% in field trees, 19–24% in growth room trees, and 23–39% in greenhouse trees). Net photosynthetic rate was shown to be under strong genetic control in these clones. The effects of growth environment on variables of carbon exchange are sensitive to the basis of expression of those variables.

Beschreibung: Effects of mycorrhizae and solution pH on ammonium uptake and fluxes of hydrogen, calcium, and potassium in solution culture were determined using three Northwest coniferous species: Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), Sitka spruce (Piceasitchensis (Bong.) Carr.), and western hemlock (Tsugaheterophylla (Raf.) Sarg.). The ectomycorrhizal fungus was Hebelomacrustuliniforme (Bull, ex St. Amans) Quel. Ammonium uptake rates decreased with decreasing pH and were accompanied by decreasing H+ release to the external solution. The mycorrhizal fungus H. crustuliniforme enhanced ammonium uptake and generally released fewer hydrogen ions per ammonium ion taken up than did nonmycorrhizal roots. This altered stoichiometry in mycorrhizal seedlings could mediate pH changes in the rhizosphere of soil-grown plants. During ammonium uptake, calcium ions were released at low pH and taken up at higher pH. Potassium efflux occurred at all hydrogen levels, with less efflux at higher pH. The mycorrhizal association generally increased calcium uptake or decreased calcium and potassium efflux rates compared with nonmycorrhizal seedlings. This research demonstrates that the ectomycorrhizal fungus Hebelomacrustuliniforme can significantly improve ammonium acquisition, a major growth-limiting nutrient in most Pacific Northwest forests, and that pH strongly affects ammonium uptake.

Beschreibung: Fraser fir (Abiesfraseri (Pursh) Poir.) seed germinated under moist conditions at 5 °C. Daily illumination in combination with an initial benomyl treatment resulted in earlier commencement of germination (16 weeks) compared with nontreated seeds maintained in darkness (23 weeks). Germination was greatly enhanced by exposing seeds four times daily to 15 min. illumination from cool-white fluorescent lights.

Beschreibung: Using 3-year heights, the tallest 49 provenances were selected in a nursery test of 110 black spruce (Piceamariana (Mill.) B.S.P.) provenances. A field test of the selected provenances was planted in Wisconsin; two tests of 108 provenances, both in Minnesota. Characteristics evaluated in the nursery included heights after two, three, and five growing seasons, and growth initiation and cessation in the second and third growing season. Heights were measured in the field tests. Separate statistical analyses, ANOVA and simple correlation, were used for the full complement of provenances and for those that were selected. All nursery characteristics varied significantly; the correlations between latitude and height decreased with age, and were not significant after five season's growth. Differences among provenances in free growth may explain this. Selection at age 3 years was not effective; too many selection errors were evident in the test of the full complement of provenances. Early selection on the basis of heights and phenological characteristics is not an effective way of reducing large range-wide provenance tests to breeding populations.