摘要:

This paper reviews the approaches to multiple objective landscape planning that have developed in Swedish forestry in the 1990s. The objectives of such planning include primarily timber production and maintenance of biodiversity, but also aspects such as aesthetics and recreation. The variety of approaches and models that have emerged is caused by regional differences in land-use history, forest conditions, recreation pressure, and ownership. We distinguish three approaches: The species approach and the naturalness approach integrate conservation aspects, while the multiple aspects approach integrates several aspects (biological, social, economic, spiritual, etc.) into commercial timber-producing forestry. The species approach is exemplified by the key habitat - corridor model in which key habitats and corridors are preserved to support certain species. The natural landscape model illustrates an example of the naturalness approach, as it integrates natural forest features from a fire-disturbed landscape and gives examples of management implications at the landscape as well as at the stand level. The multiple aspects approach combines several objectives and defines important structures rather loosely. This approach was developed in areas where private nonindustrial forestry dominates. Nontimber and nonconservation aspects therefore become relevant to forest management. The supportive feature model exemplifies an application of that approach.

ISSN:0045-5067    

DOI:10.1139/x97-204

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

This study was designed to test the hypothesis that herbicide (glyphosate, active ingredient) application for conifer release would reduce species diversity (measured as richness, Simpson's index, and Shannon-Wiener index) of both plant and small mammal communities over a 5-year period in young sub-boreal spruce (Picea engelmanniiParry ex Engelm. xPicea glauca(Moench) Voss) forest. Four treated and four untreated (control) sites were studied near Prince George in central British Columbia, Canada. Crown volume index of shrub vegetation was reduced by herbicide application. Species richness of shrubs was reduced in the first year after treatment and remained lower on treated sites throughout the 5-year period. Both indices of shrub diversity, however, were not different over the 5 years. Herbicide treatment initially reduced crown volume index of herbaceous vegetation, but values quickly recovered to untreated levels by the second year after treatment. Herbaceous species diversity was not affected by herbicide treatment. Diversity of small mammal communities apparently was not affected by herbicide application. In general, diversity of plant and small mammal communities seemed to be maintained, and hence, these treatment sites may not lower overall diversity of a forested landscape. Silvicultural practices, such as conifer release with herbicides or alternative methods, may contribute to a diversity of stand structures and wildlife habitats if appropriately designed and implemented.

ISSN:0045-5067    

DOI:10.1139/x97-205

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Drainage of peatlands for forestry causes the water level to draw down, which results in subsidence of peat surface and increased peat bulk density (Db). Later on, an accelerated rate of organic matter decomposition and the pressure of the growing tree stand further compacts the peat. We measured the peatDb(0-80 cm) in 180 undrained and 209 drained (ca. 60-year-old) peatland sites representing three nutrient levels of pine fens and five macroclimatic regions from southern to northern Finland.Dbwas affected by climatic conditions, nutrient status, and the tree stand volume of the site.Dbwas significantly higher in drained than in undrained sites in all regions and site types: the mean (±SD)Dbin the whole material was 82 ± 23 kg ·m-3for the undrained sites and 133 ± 22 kg ·m-3for the drained sites. The increase inDbwas significant in all regions down to a depth of 60 cm and in southern Finland, even deeper than 80 cm. When the increase in carbon concentration was taken into consideration, the average postdrainage increase in theDbof the 0-80 cm layer equalled the amount of carbon in the 54-cm layer in average undrained peat. As the reported subsidences of peat surface in forest drainage areas in Finland are usually below this limit, the carbon storage of peat is likely to increase after drainage.

ISSN:0045-5067    

DOI:10.1139/x97-206

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

We evaluated pollen contamination, supplemental mass pollination efficacies, and natural selfing in a Douglas-fir (Pseudotsuga menziesii(Mirb.) Franco) clonal-row seed orchard using a genetic marker on the paternally inherited chloroplast (cp) genome. A primer pair for the polymerase chain reaction amplification of a variable region on the cpDNA in Douglas-fir was developed. The amplified DNA product was highly variable in size, yielding 13 different haplotype bands from 20 orchard genotypes growing in the clonal-row seed orchard. Observed band sizes ranged from 859 to 1110 base pairs (bp). To estimate variation levels in the orchard background pollen pool, 96 assayed genotypes from surrounding stands gave rise to 36 different haplotypes, ranging from 367 to 1119 bp in size, resulting in a gene diversity estimate of 0.91. Most orchard clones' haplotypes were also present in the background. After adjusting for the presence of orchard-type haplotypes in the background, contamination was found to be 40%. Natural selfing in six individual clones ranged from 0 to 19% with an average of 6%. Supplemental mass pollination efficacy was estimated to be 55%, ranging from 39 to 73%, depending on the maternal clone and flowering phenology. This DNA marker proved to be very useful in assessing seed orchard mating dynamics and orchard management efficacies for Douglas-fir.

ISSN:0045-5067    

DOI:10.1139/x97-201

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

There is concern that the conifer component of mixed conifer-deciduous forests in the Great Lakes region is on the decline, possibly the result of insufficient conifer regeneration. Limitations on conifer regeneration that occur during the first 18 months of seedling emergence and establishment were examined forAbies balsamea(L.) Mill. andPinus strobusL. in two mixed conifer-deciduous forest types in northeastern Minnesota. We hypothesized that the removal of potential barriers to regeneration, including forest floor, seed predation, and competition with understory vegetation, will enhance conifer regeneration. We also hypothesized that the importance of the above regeneration barriers, and early regeneration success of each species, will differ beneath deciduous and conifer canopy types. The study was conducted under conifer and deciduous canopy types for two sites of each forest type:Abies balsamea-Populus tremuloidesMichx. forest andThuja occidentalisL. -Betula papyriferaMarsh. Germination experiments were conducted with seeds ofA. balsameaandP. strobus. Experimental treatments included forest floor removal, caging to exclude seed predators and herbivory, and weeding to study the effects of understory competition.Abies balsameaandP. strobusresponded differently to experimental treatments at different developmental stages. The best conditions for early regeneration of bothA. balsameaandP. strobusincluded reduction of seed predation (p< 0.0001) and competition with understory vegetation (p<= 0.001).Abies balsameaadditionally benefited from a conifer overstory (p< 0.0001) and a reduction in thickness of the forest floor (p< 0.01).

ISSN:0045-5067    

DOI:10.1139/x97-196

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Black spruce (Picea mariana(Mill.) BSP) seedlings were exponentially nutrient loaded by applying 3 or 6 times more fertilizer than recommended for conventional seedling production in the nursery. Loaded seedlings were similar in height and biomass to nonloaded seedlings after nursery culture, but their tissue N, P, and K content was almost twice as much as that of nonloaded seedlings. The seedlings were transplanted on intact potted substrates (bioassays) retrieved with natural vegetation from two boreal mixedwood sites and grown for one season in a greenhouse to study early- and late-season growth and nutrient dynamics, and nutrient loading and herbicide effects on N retranslocation processes. After transplanting, height and biomass growth of loaded seedlings were, respectively, 9-14% and 24-49% more than nonloaded seedlings in herbicide-treated plots, and 14-32% and 42-85% more in untreated plots, resulting in 32-39% biomass reduction in natural vegetation. The effect of nutrient loading on growth was attributed to earlier and greater biomass and N partitioning to current needles and roots that promoted N uptake (up to 20.9 ± 1.7 mg) compared with nonloaded seedlings (up to 11.8 ± 1.2 mg). Although both loading and herbicide treatments stimulated seedling growth and N uptake, N retranslocation from older to actively growing tissues was promoted by loading but reduced by herbicide treatment. The results demonstrate the high dependence of seedlings on internal nutrient reserves when planted in competitive environments, and that nutrient retranslocation is mainly driven by current growth, nutrient uptake, and internal nutrient reserves.

ISSN:0045-5067    

DOI:10.1139/x97-207

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Studies on tree allometry have often focused on the average tree of a representative stand across an age gradient. Another dimension of change in tree form is the variation caused by differences in competitive status, evident between trees of one stand or between stands of comparable age but different stocking densities. This study compares the structural relationships of dominant Scots pine (Pinus sylvestrisL.) trees over a wide age range with those in young trees of similar age but different competitive status. Allometric relationships are developed between biomass components and diameter, and crown structure is analysed in terms of crown allometry, pipe model relationships, and foliage density. The differences in allometry seem to be largely due to the rise of the crown base, which is positively correlated with size in the age series and negatively correlated with size in the cross-sectional data. The allometric relationships of the crown are less variable, but differences are found in the crown size to foliage biomass ratios between the two data sets. In the age series, foliage biomass is proportional to crown surface area, while in the cross-sectional data, it is proportional to crown volume. It is concluded that the reaction to competition for light is twofold: (1) to allocate new foliage higher up and, consequently, to lift the crown base, and (2) to grow sparser crowns.

ISSN:0045-5067    

DOI:10.1139/x97-199

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The possibility that uneven within-tree feeding patterns by jack pine budworm (Choristoneura pinus pinusFreeman) larvae could be related to underlying variation in host jack pine (Pinus banksianaLamb.) foliar water, nutrient, and monoterpene contents was considered.Choristoneura pinus pinusfeeds disproportionately in the upper portion of the canopy and almost exclusively on the basal portions of needles. Within needles, the distribution of water, several nutrients, and monoterpenes varied significantly between the distal and basal sections. Water, nitrogen, sulfur, manganese, and zinc levels occurred in higher concentrations in the distal section of the needle, which would not be predicted based onC. pinus pinusfeeding patterns. Phosphorus, potassium, calcium, iron, and copper were significantly higher in the basal section. Although the latter differences might be predicted based onC. pinus pinusfeeding patterns, they were not strong (ranging from 7.8% to 36.4% relative differences, as compared with 10.7%-50.0% relative differences in the former group). By contrast, concentrations of foliar monoterpenes were more strongly associated with known feeding patterns ofC. pinus pinus.These relative differences ranged from myrcene (26.8%) to limonene (44.79%). Thus, foliar differences affecting within-needle feeding selection appear more associated with allelochemicals than nutrients or water. In contrast with the within-needle associations between larval feeding and foliar chemistry, no associations between upper and lower canopy foliage were observed. Water, nutrients, and monoterpenes were evenly distributed across the upper and lower canopy locations. Thus, differential feeding between canopy locations cannot be explained by foliar constituents. Rather, it is more likely explained by other environmental factors, such as proximity to and density of reproductive and vegetative shoots.

ISSN:0045-5067    

DOI:10.1139/x97-174

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

When suitable site trees are lacking in a stand, indirect methods are often used to predict site index. One such indirect method is to convert the site index of one species (the present one) into the site index of another species (the missing one) through a site index conversion equation. To develop a site index conversion equation, it is required that site index estimates must be obtained from those stands with both species present. Because of interspecific interactions, this requirement intrinsically violates assumptions behind the site index concept. To solve this problem, an ecologically based model was proposed in this study. Based on data obtained from the Sub-boreal Spruce zone of British Columbia, pure or single species dominated stands of lodgepole pine (Pinus contortaDougl. ex Loud.) and white spruce (Picea glauca(Moench) Voss) were matched within each of the three studied subzones by using the concept of ecologically equivalent sites. The method of reduced major axis (RMA) was used to develop site index conversion equations between the two species. The resulting equation was then compared with the soil-site studies and the site index comparison study on the same two species conducted in the same region. By applying the ecologically based model, site index conversion equations can be developed for any possible pair of species existing in a study area, thus making site index conversion among species operationally feasible based on forest inventory data.

ISSN:0045-5067    

DOI:10.1139/x97-214

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Intertemporal timber supply models typically assume perfect capital markets and perfectly inelastic supplies of land. Using a dynamic model of U.S. timber and agriculture markets, we examine (i) borrowing limits or capital constraints, in which investment in forest management on nonindustrial private ownerships is restricted, and (ii) a nonzero elasticity of land supply. Results suggest that alternative treatments of supply conditions for these factors influence the flexibility of the simulated market system to adapt to changes over time and across policy scenarios. Supply restrictions limit adjustment options in management activities and force greater change in other endogenous elements such as price and consumption. Implications drawn from any policy analyses also differ with input supply assumptions. Policy impacts were found to be largely transitory in the cases without investment limits and essentially permanent when limits exist. Recognizing a price-sensitive land supply, at least as this process is represented in the present model, partially compensates for the imposition of borrowing restrictions, moving projections closer to behavior observed in the perfect capital market cases. Access to additional land as potential afforestation investments provides additional private investment flexibility. Typically, however, this linkage is neither explicit nor endogenous in forest sector models.

ISSN:0045-5067    

DOI:10.1139/x97-209

出版商:NRC Research Press    

年代:1998

数据来源: NRC