摘要:

Exploratory studies were initiated at two high-elevation red spruce (PicearubensSarg.) stands in the Great Smoky Mountains of western North Carolina to document the magnitude and physiological basis of differences in tree growth at the two sites. Increment core data indicate that conditions have become relatively less favorable for mature trees at the upper site during the past 20 years and that annual height growth of sapling trees has been 40% less at that site compared with a similar site at an elevation 215 m lower. Seasonal measurements of net photosynthesis and dark respiration rates of saplings indicated that differences in sapling growth rates at the upper site were associated with increases in dark respiration and less favorable net photosynthesis:dark respiration ratios. Basal diameter increment was most closely associated with differences in current net photosynthesis rates among trees at the upper site, whereas height and diameter growth of the upper canopy related most closely to the net photosynthesis rate among lower-elevation trees. Reduced foliar calcium and magnesium, reduced foliar chlorophyll, increased foliar aluminum, and low ratios of calcium:aluminum were found at the upper site. Tissue and soil aluminum levels that are in the range of those associated with aluminum toxicity to red spruce provide a preliminary indication that current high atmospheric inputs of the strong anions SO4and NO3to acidic soils may be adversely affecting growth and physiology of trees at the high-elevation site.

ISSN:0045-5067    

DOI:10.1139/x90-064

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The computed estimate of basal area was the focus of this investigation into the accuracy of tree diameter measurements. Diameter at breast height was measured on 101 trees, the breast height disc was removed from the stem, and each disc outline was then digitized to determine its actual area. Actual areas were compared with the basal areas computed with the field measurements of diameter by expressing the deviations as a proportion of the actual areas. These relative errors averaged 3.1% when basal area was computed with a taped diameter at breast height, and they averaged −2.5% when the mean of two calipered, perpendicular diameter at breast height measurements were used. Noncircularity accounted for about 2.6% of the bias, on average, in basal areas from taped diameters. Root mean square error of relative basal area errors ranged from 7.3 to 7.9% among these methods. The difference between basal areas computed with a taped diameter at breast height and with calipered diameter at breast height was computed and expressed as a proportion of the actual basal area. On average, a difference of 5% was observed. Interval estimates for these differences are presented.

ISSN:0045-5067    

DOI:10.1139/x90-065

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Growth of northern red oak (QuercusrubraL.), white ash (FraxinusamericanaL.), and white pine (PinusstrobusL.) seedlings was evaluated for 2 years after germination in 12 environments that consisted of four levels of herbaceous interference (fern, fern free, grass, grass free) crossed with three levels of light intensity (100, 45, and 20% full sun), at two clear-cuts in central Pennsylvania. Grass and fern interference reduced soil moisture content and reduced height or diameter growth of all species. Shading ameliorated soil moisture, reduced herbaceous growth, generally reduced growth of all tree species in interference-free environments, and had no effect on growth of any tree species in fern and grass environments. Reduction in growth due to herbaceous interference was lower for northern red oak and white pine than for white ash, while shading had similar effects on growth of all species. Results suggest that stresses induced by shading alone have little short-term effect on the establishment of these species under conditions of heavy herbaceous interference.

ISSN:0045-5067    

DOI:10.1139/x90-066

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Tree wood tissue was sampled in 169 forest stands, which represented five forest types, across the states of Minnesota, Wisconsin, and Michigan. The molar ratio of elemental sulfur to nitrogen for 3 decades of wood growth (1956 to 1985) was related to (i) location, as defined by five sampling zones, (ii) the molar ratio of elemental sulfur to nitrogen in soils, and (iii) wet sulfate deposition. There were also differences in molar ratios of sulfur to nitrogen among tree species and no significant interactions between species and zone. The sulfur to nitrogen ratios of both soil and wood increased from west to east across the sulfate deposition gradient. This trend is consistent with growing evidence that sulfate and other sulfur ions deposited through air pollution are accumulating in various compartments of forest ecosystems in the north central United States. These results also support studies that indicate that more sulfur is being taken up by trees than needed for nutrition.

ISSN:0045-5067    

DOI:10.1139/x90-067

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

In a field experiment in central Sweden, current shoots representing one-fifth of the needle biomass were removed from Scots pine (PinussylvestrisL.) by hand pruning young and old trees and by inducingTomicuspiniperda(L.) (Coleoptera: Scolytidae) attacks on caged young trees. Branches in the uppermost whorls were pruned in later summer, early summer, or both. Starch and nitrogen concentrations in needles were monitored for two growing seasons. After four seasons the trees were felled and effects on growth were recorded. Starch and nitrogen concentrations in needles of pruned branches decreased and increased, respectively, compared with the controls. In old trees, but not in young ones, the raised nitrogen level persisted for 3 years after pruning. Starch and nitrogen concentrations in unpruned branches of pruned whorls did not change compared with the control until these branches became pruned, i.e., each branch acted as a semiautonomous integrated physiological unit. At felling, pruned trees were short of a portion of needle biomass equal to that removed, while at the same time, the needle biomass grown out above the pruned whorls was larger than the corresponding part of the controls. Stem volume losses in old hand-pruned trees were larger than and lasted longer than in young ones and were not yet completed four growing seasons after treatment. In a stepwise linear regression analysis, final needle biomass explained most of the total variation in volume growth of young hand-pruned trees, whereas for old trees, intertree competition was more important. Responses of beetle-pruned trees were similar to those of young hand-pruned trees. Differences in response to pruning and defoliation and in recovery between young and old trees are discussed in terms of source and sink theory and of compensatory mechanisms and carbohydrate limitation, respectively.

ISSN:0045-5067    

DOI:10.1139/x90-068

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Repeated measures data occur in a wide variety of experimental situations and are often analyzed without full consideration of the statistical issues involved. In this paper, a discussion of model construction, univariate versus multivariate solutions, and statistical assumptions is motivated by examples from a tree physiology experiment. In addition, several examples from the forestry literature are reviewed. It is hoped that this discussion will help scientists with little statistical training to become aware of the different analyses available and perhaps to recognize the associated models in their own research. The examples range from a simple repeated measures design with one within-subject factor and no between-subjects factors to a more complex design involving multiple within-subject and between-subjects factors. The modelling approach used here permits a straightforward comparison between the univariate and multivariate solutions. Although no single approach is consistently best, the multivariate approach is always appropriate and provides the same interpretations as the univariate approach. However, when appropriate assumptions such as sphericity are met, power considerations tend to favor the more traditional univariate analysis.

ISSN:0045-5067    

DOI:10.1139/x90-069

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Tree height of jack pine full-sib families, originating from all possible combinations of three parental provenances and growing on three sites, was analyzed with 1 classical model and 11 nearest-neighbour spatial process models. Extension of the classical linear model with spatial interaction terms was deemed necessary in light of significant neighbourhood correlations among effect-free observations (residuals) on two of the three sites. The strength and extent of spatial and temporal correlations are demonstrated in both visual and tabular form. Only 4 of the 11 spatial models provided a substantial reduction (5–20%) in the significant difference between two estimates of full-sib family tree height. Spatial adjustments averaged 1–3% at the family level, with few families adjusted by more than 10%. The cumulative (temporal) effect of spatial covariance was demonstrated in rank correlations between adjusted and observed family means. No simple trends were obtained when adjusted variance components and heritabilities were compared with their unadjusted counter-parts, but most models tended to deflate genetic effects and reduce heritabilities. It is concluded that although spatial analyses provide an attractive tool for the experimenter, the lack of a cause and effect hypothesis in forest genetic trials necessitates model searching without the guarantee of true treatment effects. Spatial analysis provides good indicators of the need to collect additional site information for more powerful analyses. Careful planning and intensive site preparation may greatly reduce spatial covariances and the need for spatial analyses.

ISSN:0045-5067    

DOI:10.1139/x90-070

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

In the summer of 1988, a vegetation survey of the Siberian taiga was conducted in a discontinuous permafrost zone of northern China where a destructive fire had occurred in the spring of 1987. The dominant forest cover of this area was larch, with spruce forests occurring in wet valleys and pine forests on steep, dry slopes. The vertical structure of forests showed that the spruce forests were preceded by larch forests; however, most of the larch forests were self-renewable probably because their habitats were too dry for spruce trees to compete. In larch forests, the 1987 fire seriously damaged perennial herbs; in spruce forests, however, most of the herbaceous plants were protected by wet conditions of their habitats, except feather mosses, which could not survive in the habitat opened by fire. Many plants of the burnt habitats recovered vegetatively; in particular, the burnt stems of birch trees frequently sprouted many shoots and consequently appeared to be contributing to the rapid reestablishment of larch, which is generally preceded by birch trees in ecological succession. Pine forests were not self-renewable; however, they seemed independent of the normal course of succession by dominating dry habitats where their competitors were not successful.

ISSN:0045-5067    

DOI:10.1139/x90-071

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A per acre property tax model is proposed for taxing plantation-grown timber in western Washington State. The taxable assets consist of the bare land value plus the reforestation investment necessary to establish the timber stand. Under this system, an annual ad valorem property tax, or a harvest yield tax that substitutes for all, or part, of the annual ad valorem tax is levied on the full value of the tax base. Thus, unlike the traditional case where an annual property tax is levied on modified bare land and timber values to reduce the deferred yield bias associated with long-lived timber crops, the tax base under the proposed system requires no comparable modification. A variety of input scenarios are used to compare the numerical consequences of applying the proposed tax system with those of a land only, a land plus timber, and a harvest yield tax system; all levied at full value. Further comparisons with Washington's existing forest tax system, which is composed of an annual ad valorem property tax on a legislatively mandated statutory bare land value and a 5% harvest yield tax imposed in lieu of an annual ad valorem property tax on maturing timber, demonstrates how highly modified Washington's current system has become to accommodate forest owners and temper the deferred yield bias the property tax theoretically fosters.

ISSN:0045-5067    

DOI:10.1139/x90-072

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Interior spruce (Piceaglaucaengelmanniicomplex), lodgepole pine (PinuscontortaDougl.), Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco), and western hemlock (Tsugaheterophylla(Raf.) Sarg.) were grown from seed for 20 weeks in containers, with 18-h photoperiods. Fortnightly, over a 12-week acclimation period (September 7 – December 1) outdoors at Vernon, B.C., samples were taken for (i) foliage frost hardiness measurement, (ii) poststorage root growth capacity, and (iii) outplanting on forest sites. In all species, frost hardiness and root growth capacity increased with weeks of acclimation. Frost hardiness and root growth capacity were correlated with each other in western hemlock, lodgepole pine, and Douglas-fir, and with field performance (survival or growth) in interior spruce, lodgepole pine, and Douglas-fir.

ISSN:0045-5067    

DOI:10.1139/x90-073

出版商:NRC Research Press    

年代:1990

数据来源: NRC