摘要:

Growth and survival from age 1 to 13 years, stem straightness, and resistance toDioryctria splendidellaHerr. Schaff. were assessed in 154 families belonging to interprovenance hybrids of maritime pine (Pinus pinasterAit.). The hybrids were part of a full 10 × 10 diallel mating scheme. The 10 parental provenances belonging to the three major geographic groups of maritime pine (Atlantic, Mediterranean, and North African) were also included in the experiment as controls. The variance among families within an interprovenance hybrid combination represented only a minor part of the total variance, except for height and survival from age 1 to 3 and resistance toDioryctria. General combining abilities were more important than specific combining abilities for all traits except for survival during the juvenile stages. General reciprocal effects were only significant for height at age 1 and stem straightness at age 8. A few hybrids between Atlantic and Mediterranean or North African provenances combined the good growth of the former provenance with the excellent stem straightness of the latter ones, suggesting new alternatives for tree improvement

ISSN:0045-5067    

DOI:10.1139/x99-178

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Maritime pine (Pinus pinasterAit.) is a species characterized by a discontinuous natural range with populations as a rule of small size and growing in heterogeneous environments. Ten provenances belonging to the three biosystematic groups of the species (Atlantic, Mediterranean, and North African) were crossed using a diallel scheme. Parental provenances and their hybrids were tested and measured for height growth at age 1, 2, 3, 8 and 13, as well as for insect resistance and stem crookedness in a trial in southwestern France. The results show a decrease in the variance of heterosis for height growth with age. Heterosis measured as the relative superiority of the hybrid to the midparent varies from -10% to 42% at age 1 and between 2 and 20% at age 13. There is no age effect on the mean value of heterosis, which amounts to 9.7% at age 1 and 8.4% at age 13. The value of heterosis was then compared with the genetic distance of parental provenances measured with various traits and markers (phenotypic traits, terpenes, isozymes, denaturated proteins). There was a weak but significant positive correlation between genetic divergence based on markers and heterosis for height at all ages. These relations were confirmed when the level of heterosis was compared for hybrids clustered according to the subdivision of the species in three major groups. The results are in agreement with theoretical analysis of heterosis and suggest that there is a disequilibrium between loci controlling height growth and neutral loci at the between population level. No significant relationship between levels of heterosis and stem crookedness or insect resistance was detected.

ISSN:0045-5067    

DOI:10.1139/x99-179

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A detailed analysis of diameter-height relationships was applied to an old-growthPseudotsuga menziesii(Mirb.) Franco var.menziesii-Tsuga heterophylla(Raf.) Sarg. forest in southwestern Washington State, U.S.A., to predict future development of vertical stratification among tree species. Differences among species in relative abundance and size structure resulted in diameter-height regressions of varying certainty and stability. Damage and shading had negative impacts on predicted heights and estimates of maximum attainable height (Hmax) in all species. However, species varied as to the main causes and size dependency of damage in relation to tree height. Current height-growth rates of the upper canopy species declined with increasing tree height, reaching minimum values near the predictedHmax. The future development of the forest canopy would involve a slow invasion of the upper canopy byTsuga heterophyllaandThuja plicataDonn ex D. Don, asP. menziesiiare near their maximum attainable height, andAbies amabilisDougl. ex Forbes andTaxus brevifoliaNutt. are restricted to the middle to lower canopy. However, if current height-growth rates continue,P. menziesiishould maintain its dominant status in the upper canopy for at least another century.

ISSN:0045-5067    

DOI:10.1139/x99-180

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We experimentally examined the influences of within-gap environmental heterogeneity on regeneration patterns ofNothofagus pumilio(Poepp. & Endl.) Krasser near the xeric limit of its distribution in northern Patagonia, Argentina. Results from this xeric old-growth forest are compared with patterns previously described for the same species in mesic forests. Survival ofN. pumilioseedlings beneath tree-fall gaps in this relatively xeric forest appears to be strongly influenced by moisture availability. Seedlings and saplings that have survived this demographic bottleneck are found at microsites where soil water potentials are higher, such as in the shady northern edges of tree-fall gaps (Ψ = -0.46 MPa compared with less than -0.6 MPa in other gap positions) and on coarse woody debris (Ψ = -0.29 MPa, compared with -0.51 MPa on the forest floor). Although gap creation in this dryN. pumilioforest is favorable to tree regeneration by releasing light resources, decreased water resources may switch the system from a light- to a water-limited system in some positions of the gap. This may explain the lack of regeneration ofN. pumiliooften observed after creation of large gaps towards the xeric end of its range and needs to be considered in the management of this important timber species.

ISSN:0045-5067    

DOI:10.1139/x99-181

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The LANDIS model simulates ecological dynamics, including forest succession, disturbance, seed dispersal and establishment, fire and wind disturbance, and their interactions. We describe the addition to LANDIS of capabilities to simulate forest vegetation management, including harvest. Stands (groups of cells) are prioritized for harvest using one of four ranking algorithms that use criteria related to forest management objectives. Cells within a selected stand are harvested according to the species and age cohort removal rules specified in a prescription. These flexible removal rules allow simulation of a wide range of prescriptions such as prescribed burning, thinning, single-tree selection, and clear-cutting. We present a case study of the application of LANDIS to a managed watershed in the Missouri (U.S.A.) Ozark Mountains to illustrate the utility of this approach to simulate succession as a response to forest management and other disturbance. The different cutting practices produced differences in species and size-class composition, average patch sizes (for patches defined by forest type or by size class), and amount of forest edge across the landscape. The capabilities of LANDIS provide a modeling tool to investigate questions of how timber management changes forest composition and spatial pattern, providing insight into ecological response to forest management.

ISSN:0045-5067    

DOI:10.1139/x99-188

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A system for rating the susceptibility of lodgepole pine (Pinus contortaDougl. var.latifoliaEngelm.) stands to the mountain pine beetle (Dendroctonus ponderosaeHopkins) was field tested in 38 stands in the Cariboo forest region of British Columbia in a retrospective study. A linear relationship was defined between the percentage of basal area killed by the mountain pine beetle and the susceptibility indices for the sample stands. The system was further tested using an independent data set of 41 stands from across southern British Columbia. Forty of the 41 stands fell within the 95% prediction interval of the original model data for stand susceptibility. This study provides validation for a susceptibility rating model described in 1992. The regression model and associated confidence interval also provide a useful tool for landscape level loss predictions due to the mountain pine beetle.

ISSN:0045-5067    

DOI:10.1139/x99-182

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Co-baiting to contain and concentrate the spruce beetle,Dendroctonus rufipennis(Kirby), and the western balsam bark beetle,Dryocoetes confususSwaine, was investigated at four locations in British Columbia. Two 9-ha areas were established at each location; one was baited and the other left as a control. Single "interior firs,"Abies bifoliaA. Murray ×Abies lasiocarpa(Hook.) Nutt., or groups of two or three trees, were baited with (±)-exo-brevicomin released at 1.0 mg/24 h. "Interior spruces,"Picea engelmanniiEngelm. ex Parry ×Picea glauca(Moench) Voss, were baited with frontalin released at 0.1, 0.6, or 2.5 mg/24 h, or at 0.6 mg/24 h with alpha-pinene, ethanol, or ethyl crotonate. Another experiment investigated possible interspecific interference betweenD. confususandD. rufipennisbaits. Ratios of currently attacked "green" trees to previously attacked "red" trees for both insects were significantly higher in baited than in control areas, indicating that populations were contained. Baiting, however, did not attract either insect from a zone surrounding each baited area. There was a significant increase inD. confususattack when two trees instead of one were baited per centre, no increase inD. rufipennisattack when frontalin was released alone or with the potential adjuvants, no effect of frontalin release rates on the percentage of trees attacked byD. rufipennis, and no indication of cross-repellency between bait

ISSN:0045-5067    

DOI:10.1139/x99-184

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Regeneration of first-cut strips in a two-cut system of strip clear-cutting was compared to that of large clear-cutting in four different areas representative of the black spruce (Picea mariana(Mill.) BSP) stands of the boreal forest of Quebec. Seedlings were more evenly distributed in clearcut strips than in large clearcuts. Differences of about 10 000 black spruce seedlings per hectare and 20% of stocking were observed in favour of clearcut strips compared to large clearcuts. Black spruce stocking was about 14% larger on lowland than on upland sites but height growth was better on upland sites. A regeneration problem similar to that of large clearcuts was observed when the second strips were cut. One year after cutting these second strips, winter harvesting resulted in a 23% gain in black spruce stocking as compared to summer harvesting. Even if black spruce stocking marginally increased during the years following winter harvesting, the height advantage of the preserved advance growth justifies the application of this harvesting method. The strip clear-cutting system effectively improved the stocking of former black spruce stands but if the stocking level of advance growth is adequate, careful harvesting to preserve advance regeneration should be the preferred method since it would be more cost-efficient.

ISSN:0045-5067    

DOI:10.1139/x99-189

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We described a general pattern of cohort development following two types of even-aged reproduction methods in northern hardwoods. Three clearcut sites initially had divergent numbers of stems, because of variable amounts of advance regeneration. By 10 years, total stem densities became quite similar across sites. Three sites treated by shelterwood seed cutting lacked advance regeneration. Compared with the clearcuts, seedlings became established at much higher stem densities there, and even early cohort development followed a consistent pattern. By 20-25 years, both the clearcut and shelterwood sites supported 7600-8900 total stems/ha. Stems >=2.54 cm diameter at breast height peaked at about 6000, but by age 15 following clear-cutting, and not until age 20 after shelterwood seed cutting. The time lag likely reflects initial differences in advance regeneration, and possibly other factors between sites. Basal area at the clearcut sites reached 26 m2/ha within about 25 years. At the shelterwood sites it reached 22 m2/ha by age 25. The quadratic stand diameter increased consistently across sites and treatments. Regression models describe changes in numbers of total stems, numbers of saplings, stand basal area, and quadratic stand diameter for each treatment.

ISSN:0045-5067    

DOI:10.1139/x99-190

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A chronosequence of three species of logs (Pinus sylvestrisL.,Picea abies(L.) Karst, andBetula pendulaRoth.) from northwestern Russia was resampled to develop a new method to estimate rates of biomass, volume, and density loss. We call this resampling of a chronosequence the decomposition-vector method, and it represents a hybrid between the chronosequence and time-series approaches. The decomposition-vector method with a 3-year resampling interval gave decomposition rates statistically similar to those of the one-time chronosequence method. This indicated that, for most cases, a negative exponential pattern of biomass, volume, and density loss occurred. In the case of biomass loss ofP.sylvestris, however, polynomial regression indicated decomposition rates were initially low, then increased, and then decreased as biomass was lost. This strongly suggests three distinct phases: the first when decomposers colonized the woody detritus, a second period of rapid exponential mass loss, and a third period of slow decomposition. The consequences for this complex pattern of decomposition were explored at the ecosystem level using a simple model. We found that a single rate constant can be used if inputs vary within a factor of 10, but that this approach is problematical if inputs are more variable.

ISSN:0045-5067    

DOI:10.1139/x99-187

出版商:NRC Research Press    

年代:2000

数据来源: NRC