摘要:

Much of the research in forest inventory has focussed on the generation of estimates of forest attributes at particular times and estimating how these attributes change over time. In descriptions of this work in recent decades, the terms forest growth and forest change have been used interchangeably. In this paper, the distinction between growth and change is defined and an example is given illustrating the differences between the two. Unbiased estimators of both processes are presented, and a simulation study with an artificial population is used to illustrate their properties. The results of the simulation study indicate that estimates of forest growth tend to be slightly more efficient than estimates of forest change.

ISSN:0045-5067    

DOI:10.1139/x98-086

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In the Finnish compartmentwise inventory systems, growing stock is described with means and sums of tree characteristics, such as mean height and basal area, by tree species. In the calculations, growing stock is described in a treewise manner using a diameter distribution predicted from stand variables. The treewise description is needed for several reasons, e.g., for predicting log volumes or stand growth and for analyzing the forest structure. In this study, methods for predicting the basal area diameter distribution based on thek-nearest neighbor (k-nn) regression are compared with methods based on parametric distributions. In thek-nn method, the predicted values for interesting variables are obtained as weighted averages of the values of neighboring observations. Usingk-nn based methods, the basal area diameter distribution of a stand is predicted with a weighted average of the distributions ofk-nearest neighbors. The methods tested in this study include weighted averages of (i)Weibull distributions ofk-nearest neighbors, (ii)distributions ofk-nearest neighbors smoothed with the kernel method, and (iii)empirical distributions of thek-nearest neighbors. These methods are compared for the accuracy of stand volume estimation, stand structure description, and stand growth prediction. Methods based on thek-nn regression proved to give a more accurate description of the stand than the parametric methods.

ISSN:0045-5067    

DOI:10.1139/x98-085

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

We investigated above- and below-ground biomass allocation and allometric relationships of canopy dominant and suppressed loblolly pine (Pinus taedaL.) trees from a range of diameters at breast height (DBH = 3.5-35.6cm) to determine if shifts in allocation may influence the growth and persistence of suppressed trees in the understory. Using mass and volume conversions from harvested trees (15 dominant and 15 suppressed), we developed regressions to predict total and component biomass from DBH. Bole, branch, needle, and total mass differed between dominance categories (ANCOVA,P< 0.10). For a representative size (15cm DBH), dominant trees allocated 63.4, 13.2, 11.3, and 12.0% of biomass to bole, branch, needle, and root tissue compared with 75.9, 6.7, 5.6, and 11.7% for suppressed trees. At any given DBH, suppressed trees were also taller than dominant trees and had a greater porportion of heterotrophic (bole plus branch plus root mass) to autotrophic (needle mass) tissue. Percent carbon and nitrogen of tissues did not differ between dominance categories. Unlike the increased investment in leaf area observed for seedlings and saplings of shade-tolerant species, suppressed loblolly pine increased allocation to bole mass and height growth. An increase in height for this shade-intolerant species may enable some suppressed individuals to escape competition for light. However, increased allocation to heterotrophic versus autotrophic tissue in suppressed trees may confer a cumulative disadvantage over time because of increased respiratory load.

ISSN:0045-5067    

DOI:10.1139/x98-083

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Green oak (Quercus ilexL.) is the most common forest species growing under Mediterranean climate. Because of important past anthropic perturbations, green oak old-growth forests are very unfrequent and constitute, for that reason, a most interesting domain where to analyze the natural evolution of green oak stands. Such forests exist in Corsica and this study deals with vegetation successions as they occur in naturally occuring gaps. Because of the taxonomic poorness (32 species), two statistical tools (canonical correspondence analysis and random permutations) were used to take into account vegetation spatial structure according to types (herbaceous, shrubby, or arborescent). These statistical analyses show that plant succession does not really exist in gaps of green oak old-growth forests but rather a structural organization of common species found in the maquis. Results support the hypothesis about the internal dynamics of these forests going through a maquis phase.

ISSN:0045-5067    

DOI:10.1139/x98-070

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Genetic diversity of allozymes at 24 loci was studied in 23 populations of longleaf pine (Pinus palustrisMill.), including three seed orchard populations and an old-growth stand. Overall, the mean number of alleles per polymorphic locus was 2.9, the percentage of polymorphic loci was 92%, and the mean expected heterozygosity was 0.105. These values are comparable with diversity measures found in a similar loblolly pine (Pinus taedaL.) study. Diversity measures of the seed orchard sources and the old-growth stand were similar to those in the other natural seed sources.Fstatistics indicate very little inbreeding overall (FIS= -0.002) and low differentiation among populations (FST= 0.041). All measures of genetic diversity were significantly related to longitude; western sources tended to have more allozyme diversity. Since growth or survival are not related to longitude, and no important climatic variables are related to longitude within the natural range of longleaf, it is proposed that the east-west variation in longleaf pine is a result of migration from a single refugium in the west (south Texas or northeastern Mexico) after the Pleistocene.

ISSN:0045-5067    

DOI:10.1139/x98-102

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The reproductive development from pollination until seed maturity for Pacific silver fir (amabilis fir;Abies amabilis(Dougl. ex Loud.) Dougl. ex J. Forbes) was studied at two sites in British Columbia. Ten trees growing at varying elevations at each site were flagged and two or more cones were collected from each tree every 1 or 2 weeks. Following size measurements, cones were dissected and 20 ovules from each cone were sampled, fixed, embedded in paraffin, sectioned, and stained for anatomical study. Ovule, megagametophyte, and embryo size was measured and stage of ovule or seed and embryo was determined. At both sites the phenology and details of development were similar. The major causes of cone loss were frost at pollination and insect damage following pollination. The seed potential per cone was 359-408, but the filled seeds per cone based on cutting tests and X-raying was only 18-22%. The major causes of seed loss were insect damage (32-39%) during ovule and seed development and failure of ovules to be pollinated (26-31%). Although the amount of insect damage was similar at both sites, damage at Site 1 was primarily caused byMegastigmussp. larvae in the seeds whereas at Site 2, damage was to seeds, scales, and the cone axis and due toEaromyia abietumlarvae. Megagametophyte and embryo development is described and the time and causes of the seed loss are related to development. Anomalous types of development are described and possible causes discussed.

ISSN:0045-5067    

DOI:10.1139/x98-089

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Relationships between tree traits and tree value for lumber production were investigated. For the purposes of estimating relative economic weights for use in multitrait selection in coastal Douglas-fir(Pseudotsuga menziesii(Mirb.) Franco var.menziesii), tree height, diameter at breast height, and branch diameter were measured on 164 trees (ages 36-66 years). Increment cores from a subsample (92) of these trees were assayed by X-ray densitometry to determine wood density. Bole volume was derived by summing the log volumes of all logs from each tree. Value of lumber recovered from each tree was determined in a separate mill study using both visual and machine stress rated (MSR) grading rules. Multiple linear regression was used to relate tree value to the growth and wood quality traits. Stem volume and branch diameter significantly influenced tree value under visual grading, with relative economic weights of 0.06dm3and -5.22cm, respectively. Wood density significantly influenced tree value under MSR grading (relative economic weights: 0.06dm3, -6.69cm, and 0.06kg/mdm3, respectively), where lumber strength is measured more accurately. These regression coefficients can be used directly as economic weights in selection indices.

ISSN:0045-5067    

DOI:10.1139/x98-084

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The slenderness coefficients of trees, defined as the ratio of total height to diameter at 1.3m above ground, have been widely used as an index of the resistance of trees to windthrow. For many European coniferous species, slenderness coefficients have been intensively studied, but very little information is available for the tree species in boreal mixedwoods of Canada. By applying correlation analysis and graphical approaches to permanent sample plots data from Alberta, the relationships between slenderness coefficients and tree or stand variables were investigated for the five major species in boreal mixedwoods. Tree slenderness coefficients were found to be negatively correlated with tree diameter at breast height (DBH), height, crown length and age, but positively correlated with stand density level, species composition, and site index values. For three coniferous species, the results were consistent with those found for European coniferous species in literature. However, for the two deciduous species, no similar studies were found for comparison. The graphical results indicated that about 50% of the sampled stands of the data had a slenderness coefficient over 100 and may be at high-risk for windthrow. Models were also developed to predict slenderness coefficient values from (i) DBH only and (ii) DBH and stand variables combined. The negative decay function was found to be the best for this prediction purpose. Potential applications of these models include selecting windfirm residual trees in a partial cutting and developing windthrow hazard rating systems.

ISSN:0045-5067    

DOI:10.1139/x98-092

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The objective of this study was to determine if acidic deposition predisposes oaks to decline after drought. Associations were evaluated between oak decline and mortality after drought and (1)pre-drought growth; (2)tree size, age, and competitive status; (3)attack by twolined chestnut borer (TLCB); (4)acidic deposition; and (5)soil acidity. This study was conducted in the Ohio River region of the United States. White oak (Quercus albaL.), black oak (Quercus velutinaLam.), and the locally dominant oak (chestnut oak (Quercus prinusL.) or post oak (Quercus stellataWangenh.)) were studied at six similar sites along an acidic deposition gradient during the period 1988-1992. Prevalence of severe branch dieback and mortality was low ( < 10%) at all sites, but fewer oaks in Illinois were in the 0-10% dieback class than in other states. Also, fewer oaks in Illinois than Ohio exhibited immediate recovery after the 1988 drought. Prevalence of TLCB attack was similar across all sites; >85% of dead trees had been attacked, but <10% of living trees were damaged. Most dead oaks had lower pre-drought radial growth than survivors of the same species. Branch dieback, growth decline, and mortality were more prevalent in the black oak population than the other oak species. There was no evidence that acidic deposition predisposed oaks to post-drought decline.

ISSN:0045-5067    

DOI:10.1139/x98-098

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Poor performance of Douglas-fir (Pseudotsuga menziesii(Mirb.) Franco) plantations established in 1987 has occurred in southwestern British Columbia. Affected sites were planted with 1-year-old container stock that exhibited some root dieback in the nursery. A study was initiated in 1991 to assessCylindrocarponandFusariumroot infection in planted and naturally regenerating (natural) Douglas-fir seedlings from seven affected plantations. Percentages of seedlings harboringCylindrocarponspp.and percent root colonization were significantly greater for planted seedlings compared with natural seedlings. A significant linear trend inCylindrocarponroot colonization was observed for planted seedlings with colonization levels being highest for roots closest to the remnants of the root plug and decreasing at distances greater than 10cm from that region. This trend inCylindrocarponcolonization was not observed for natural seedlings.Cylindrocarpon destructans(Zins.) Scholten var.destructansandC.cylindroidesWollenw. var.cylindroideswere the only species isolated from planted and natural conifer seedlings. For most sites, percentage of seedlings harboringFusariumspp.and percentFusariumroot colonization were less than forCylindrocarpon.Recovery ofFusariumspp.from seedlings and root colonization levels were not significantly different for planted and natural seedlings from all sites.

ISSN:0045-5067    

DOI:10.1139/x98-080

出版商:NRC Research Press    

年代:1998

数据来源: NRC