摘要:

Difficulties were observed in the leafing of mature birch, alder, and willow species in southern Finland in the spring 1989, especially at lush growing sites. The suspected reason was freezing of the buds in the preceding autumn caused by disturbed bud dormancy. The hypothesis was tested experimentally with 1-year-oldBetulapendulaRoth seedlings, investigating the effects of partial defoliation, nitrogen nutrition, and temperature. Defoliation clearly weakened both the growth and overwintering of the seedlings, altered the carbohydrate relations in their roots, and markedly delayed leafing in the spring. The earlier in the summer the defoliation was performed, the more conspicuous were its effects, which were also emphasized by the fertilization. A short greenhouse treatment in autumn had no significant effect, however, and it is thought that the partial death of the defoliated top shoots may have been caused by frost drying. The main reason for the late leafing seems to be the delayed development of the buds as a consequence of early defoliation. On the other hand, the growth-promoting effect of nitrogen fertilization and the premature branching of the buds evidently disturbed the carbohydrate balance in the roots and thus the development of the whole seedlings.

ISSN:0045-5067    

DOI:10.1139/x94-246

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Dendroecological techniques were used to study the influence of climate on the growth of subalpine fir (Abieslasiocarpa(Hook.) Nutt.), Engelmann spruce (PiceaengelmanniiParry), and subalpine larch (LarixlyalliiParl.) in the North Cascade Mountains of Washington state. Study sites were selected on different topographic features at three points along an elevation gradient (ridgetop, valley slope, and valley floor) to characterize site influences on growth response to climate. Mixed species stands were sampled to identify possible differences in species response to climate on a common site. Species differences account for most of the variability in radial growth patterns and response to climate. The greatest differences are between subalpine fir and subalpine larch, while the greatest similarities are between subalpine fir and Engelmann spruce. After species, aspect is the most significant factor affecting growth response to climate. Spring snowpack and summer temperature are the primary climatic factors influencing growth. Spring snowpack is negatively correlated with growth for all three species, but the relationship is strongest for subalpine fir and weakest for subalpine larch. Subalpine larch growth is positively correlated with June temperature. Subalpine fir growth is positively correlated with July–August temperature. Engelmann spruce growth is positively correlated with June–August temperature, but unusually warm July–August temperatures are associated with reduced growth the following year. The response of subalpine forests in the North Cascades to future climate change will depend on winter snowpack accumulations and spring snowmelt rates. Earlier meltouts and warmer summers would benefit growth on north aspect sites, but could also increase the frequency and severity of summer drought conditions on ridges and south-aspect sites, where summer soil moisture may already be limiting.

ISSN:0045-5067    

DOI:10.1139/x94-247

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Following fire, changes in streamflow and bank stability in burned watersheds can mobilize coarse woody debris. In 1990 and 1991, I measured characteristics of coarse woody debris and standing riparian trees and snags in Jones Creek, a watershed burned in 1988, and in Crow Creek, an unburned watershed. The mean diameter of riparian trees along Jones Creek was less than that of trees along Crow Creek, but the coarse woody debris in Jones Creek was greater in mean diameter. Tagged debris in Jones Creek was three times as likely to move, and moved over four times as far as such debris in Crow Creek. In Jones Creek, the probability of movement was higher for tagged pieces that were in contact with the stream surface. Larger pieces tended to be more stable in both streams. It appears that increased flows and decreased bank stability following fire increased the transport of coarse woody debris in the burned watershed. Overall, debris transport in Rocky Mountain streams may be of greater significance than previously recognized.

ISSN:0045-5067    

DOI:10.1139/x94-248

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The frequency of canopy disturbance over the past 150 years was reconstructed on a 5-ha study area dominated by a patchy mosaic of old-growth sugar maple (AcersaccharumMarsh.) and eastern hemlock (Tsugacanadensis(L.) Carr.) forest in the Sylvania Wilderness Area in western Upper Michigan. The study area was divided into a 10-m grid system and one tree was cored near the center of each grid cell so that the spatial patterns of tree cohorts could be examined. The canopy turnover rate, averaged over all species and 150 years was 5.4% per decade, with a corresponding canopy residence time of 186 years. Canopy-residence times do not vary much between sugar maple (170 years) and hemlock (167 years), but yellow birch has a much longer canopy-residence time (232 years). Canopy-residence times calculated for individual decades over the last 150 years varied from 81 to 556 years. The spatial pattern of gaps of various ages is caused by disturbances in light intensity (2–12% canopy removal) that occur nearly every decade, each of which creates several to many small gaps scattered across the study area. As a result, the study area has a fine-grained random spatial mixture of age-classes at all distance classes from 5 m to >100 m. This mixture is stable throughout the mesic forest in the study area. None of the cohorts resulting from disturbance correspond spatially to patches dominated by either hemlock or sugar maple. Apparently, the dynamics of patch formation by gap-creating disturbances operate independently from the dynamics of the much larger mono-dominant patches. In forests such as the northern hardwood–hemlock type, where several tree lifetimes pass between any two large-scale catastrophic disturbances, spatial and temporal stability of the patch-dynamic processes (quasi equilibrium) may exist for periods of several decades in areas of <1 ha, and several thousand years for landscapes >10 000 ha in size.

ISSN:0045-5067    

DOI:10.1139/x94-249

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

From 1987–1991, conditions in 110 conventional plantings of introduced lodgepole pine (PinuscontortaDougl. ex Loud.) were investigated in northern Sweden. Severe damage byScleroderriscanker, caused by the fungusGremmeniellaabietina(Lagerb.) Morelet, was recorded at high elevations in 1987. Damage was related to a period with extreme weather conditions. The disease was initially severe in low lying areas, from where it quickly spread throughout the plantations during 1988. Temperatures above average during 1988–1990 favoured tree vigour, which in turn slowed the spread of the disease. The frequency of stem cankers increased in seriously infected areas during 1989, and new severe damage was recorded locally in 1990 and in 1992. A strong correlation was found between disease severity and the temperature sum at the site. Lodgepole pine planted on spruce sites was often severely affected. A negative correlation was found between the frequency ofG.abietinaand the abundance of birch thicket. In large areas in northern Sweden with a more favourable climate, lodgepole pine plantations were healthy and productive up to 1991. However, instability, leading to increased susceptibility to disease, has become a problem of great concern in some of these areas during the 1990s.

ISSN:0045-5067    

DOI:10.1139/x94-250

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Forty families ofSalixviminalisL. from an eight by eight factorial crossing were planted in contrasting environments to estimate genetic additive, dominance, and epistatic variances and to estimate the impact of genotype–environment interaction. From each family, 14 seed plants were vegetatively propagated. The material was planted in two contrasting soils, heavy clay soil and sandy soil, and in two contrasting nutrient availabilities, high and low. The nutrient experiment was harvested annually for 3 years. The clay–sand experiment was harvested in the 1st, 4th, and 6th year. Height, diameter, weight, and number of shoots were measured. Additive genetic variance was found, but there were large standard deviations in many of the estimates, especially in the nutrient experiment. Dominance and epistatic variances of greater significance were found for weight characters in the clay–sand experiment. Narrow-sense heritability estimates varied, with the highest estimate being 0.34. Genotype–environment interaction seems to be of greatest importance in the establishment years in the soil contrast but of increasing importance in the nutrient contrast. Breeding strategies in connection with these findings are discussed.

ISSN:0045-5067    

DOI:10.1139/x94-251

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A fuzzy surface map representation for a forested area in Quebec was developed and evaluated relative to ground truth for two forest parameters (basal area and species composition). The fuzzy surface representation was found to perform slightly better than a conventional thematic map relative to both parameters. The fuzzy surfaces were also better at estimating species composition than basal area. It is suggested that because the fuzzy surface representation has the potential to show local variations, and to show boundaries between forest types as transition zones, it is a more realistic and useful representation of "the real world" in forestry than are conventional thematic maps. With refinement, the fuzzy surface representation developed has the potential to decrease the amount of simplification required in the map construction process and store a more realistic version of a forest in a geographic information system, thereby allowing practitioners to be closer to analyzing real-world conditions than is presently possible.

ISSN:0045-5067    

DOI:10.1139/x94-252

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The leaf-spot pathogenValdensiniaheterodoxaPeyronel is reported for the first time from the United States (Idaho, Washington, and Oregon), based on the recovery of the anamorph. Scanning electron micrographs illustrate anamorphic propagules collected from economically significant ericaceous hostsGaultheriashallonPursh,VacciniumalaskaenseHowell, andVacciniummembranaceumDouglas.

ISSN:0045-5067    

DOI:10.1139/x94-253

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

MelampsoramedusaeThuem. f.sp.deltoidaewas found to be the primary cause of leaf rust in a stool bed, in Westport, Oregon, on 41 hybrid poplar clones. Each clone was represented by approximately 1000 ramets planted in a block in spring of 1992. Rust severity was rated, using the Schreiner scale (0–100), on three dates in the fall of 1992: August 28, September 18, and October 28, 1992. Of the 41 clones, 1, 12, and 21 scored 100 (i.e., maximal rust) on the three rating dates, respectively. Percent mortality the following spring was estimated for each clone on May 19. Correlation coefficients for rust severity versus mortality on the three rating dates were 0.89 (p < 0.0001), 0.85 (p < 0.0001), and 0.63 (p < 0.0001), respectively. Thus, rust severity and subsequent mortality were highly correlated, especially on the first rating date characterized by maximal infection of the most susceptible clone.

ISSN:0045-5067    

DOI:10.1139/x94-254

出版商:NRC Research Press    

年代:1994

数据来源: NRC