摘要:

Radial growth patterns, canopy recruitment characteristics, and disturbance histories were examined in a shade-tolerant species,NyssasylvaticaMarsh., and a shade-intolerant species,LiriodendrontulipiferaL., to determine the influence of canopy gaps in species with contrasting life histories. Tree cores of these co-occurring species were taken from three mixed-Quercusforests in northern Virginia. MostN.sylvaticaindividuals became established prior to 1850 and experienced multiple release and suppression periods coinciding with logging during the late 1800s and early 1900s. ManyL.tulipiferabecame established during the early 1900s following logging, and only a few individuals experienced prolonged suppression periods. Regardless of site,L.tulipiferagrew faster thanN.sylvatica(average radial growth >1.70 mm/year forL.tulipiferavs. <0.82 mm/year forN.sylvatica.).Liriodendrontulipiferaalso exhibited longer periods of mean yearly growth >2 mm (15–37 years forL.tulipiferavs. <5 years forNsylvatica). Consecutive growth <0.5 mm/year ranged from 43 to 66 years inN.sylvaticavs. 2–11 years inL.tulipifera. Ring width patterns indicate that both species used different strategies following disturbance that enabled them to coexist in these forests.Nyssasylvaticapersisted in subcanopy positions for extended periods of time but was capable of responding to release even after 170 years (i.e., gap facultative). In contrast,L.tulipiferaappeared to rely on a strategy of rapid height and radial growth for canopy accession following large disturbances (i.e., gap obligate). The results of this study indicate the importance of using dendroecological techniques in the study of forest dynamics and species' growth strategies.

ISSN:0045-5067    

DOI:10.1139/x94-276

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

We examined the genetic variation of ecophysiological traits within and among 40 red alder (AlnusrubraBong.) provenances (two families per provenance) in a common-garden experiment in the summer of 1993. The provenances were representative of the entire species range in British Columbia, Canada. We found significant genetic variation among provenances (P < 0.001) in photosynthetic rate (A), mesophyll conductance (gm), transpiration rate (E), stomatal conductance (gsw), stomatal sensitivity to water vapour pressure deficit (SENSVPD), intercellular to ambient CO2concentration ratio (Ci/Ca), and midday xylem water potential (ψ). Photosynthetic water-use efficiency, however, did not differ significantly among provenances. There were no significant differences between families within provenance for any of these variables. A weak but significant geographic trend was detected in ecophysiological traits: ψ,A,gm, andEincreased, and SENSVPDdecreased, from southeast to northwest. Photosynthetic rate,E,gm,gswand ψ were positively related to each other, but negatively correlated with SENSVPD.Ci/Cawas negatively correlated withgsw. These correlations indicate that red alder might have undergone genetic differentiation in drought resistance.

ISSN:0045-5067    

DOI:10.1139/x94-277

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Production of hypogeous fungi (truffles) in high-elevation, 180-year-old mature forest fragments ofPseudotsugamenziesii(Mirb.) Franco was compared with surrounding regenerated clearcuts ranging from 4 to 27 years since harvest at two study areas. Thirty pairs of plots, one of each pair in soil, the other in brown-cubical-rotted coarse woody debris (CWD), were searched for truffles in each stand during four periods; August and November 1990, and February and May 1991. Overall analysis of presence/absence of truffles using log-linear models revealed that CWD and mature forest status of stands each significantly influence truffle occurrence. Mature forest fragments had greater percent frequency of occurrence and truffle number and dry weight than did plantations. Truffle numbers and dry weight were 30 and 20 times greater, respectively, in mature forests than in plantations. The plantations did not differ significantly among each other for any parameter. CWD yielded higher numbers and biomass of truffles than soil in the mature forest, but production in plantations did not differ between substrates. The total dry weight of truffles in CWD exceeded that in soil by more than 10 times in mature forests. Of 21 truffle species found, 13 were only in the mature forest and 8 only under coarse woody debris. Forest practices that emphasize the retention of mature trees and coarse woody debris promote the abundance and diversity of truffles, which are integral and functionally important members of forest ecosystems.

ISSN:0045-5067    

DOI:10.1139/x94-278

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A framework has been developed to predict growth of Sitka spruce (Piceasitchensis(Bong.) Carr.) at a regional scale throughout Scotland based on an analysis of yield, site, and climatic factors. Using the general yield class (GYC) system for predicting forest production (m3•ha−1•year−1), the statistical model was integrated with a geographic information system to predict tree growth at a resolution of 1 km2. Site factor data from 487 sample sites were analysed along with the associated climate data derived from monthly 30-year means recorded at meteorological stations throughout the country. Multiple regression was used to develop and validate the model, which accounted for 59% of the variation in observed GYC. Standard errors of prediction were determined by analysis of variance to provide confidence limits for the 1-km2GYC predictions. The distribution of these estimates of production was plotted in the form of a digital map for Scotland, housed within the geographic information system and providing a facility to readily analyse and summarise regional information.

ISSN:0045-5067    

DOI:10.1139/x94-279

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Radial and height growth are characterized for saplings of 10 dominant tree species in a transition oak–northern hardwoods forest in southern New England. Growth of saplings in the field is regressed against measures of whole-season light availability, soil moisture, and sapling size. Statistical tests show strong effects of light availability on growth, but no significant effects of soil moisture. Comparison of the light-dependent growth functions for the 10 species revealed three apparent interspecific trade-offs. (i) Species growing quickly at high light tended to grow slowly at low light and vice versa. The order of species from fast growing at high light to fast growing at low light did not correspond to traditional classifications of shade tolerance, and variation along this axis was approximately continuous. (ii) There was substantial variation off the species continuum defined ini. At any point along the continuum from fast growth at high light to fast growth at low light, some species grew faster than others, and these faster growing species had lower survivorship during periods of suppression than the slower growing species. (iii) Height growth at high light was inversely related to survivorship when suppressed. This variation was again continuous (species did not cluster into discrete categories), but the order of the species did correspond closely to a traditional ordering of shade tolerance. There was little correspondence between our estimated growth functions and the growth functions assumed in theJABOWA–FORETclass of forest simulation models. These results raise serious concerns about the current practice of assigning growth functions to species in simulation models using traditional classifications of shade tolerance.

ISSN:0045-5067    

DOI:10.1139/x94-280

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A combination of antiaggregation and aggregation pheromones was tested for protecting stands of Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) at high risk for infestation by the Douglas-fir beetle (DendroctonuspseudotsugaeHopkins). The antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), was applied in a bubble capsule formulation to the perimeter of 1-ha circular plots at a rate of 60 g/plot. Treated plots also had three or four clusters of four Lindgren funnel traps baited with frontalin, seudenol, 1-methylcyclohex-2-en-1-ol, and ethanol located outside of the plot but within 160 m of the boundary. Mean (±SE) accumulated catches in all traps per plot were 73 658 ± 19 721 Douglas-fir beetles and 12 892 ± 2 513Thanasimusundatulus(Say), a predator of the Douglas-fir beetle. The mean percentage of Douglas-fir trees ≥20 cm DBH that were mass attacked was reduced by 80% within the treated plots compared with the untreated plots. However, there was an eightfold increase in the percentage of trees mass attacked in the area outside the treated plots in the vicinity of the funnel traps. The net effect of the treatment was to concentrate mass-attacked trees within a limited area outside of the protected stand. Our results indicate that Douglas-fir beetle antiaggregation and aggregation pheromones can be used effectively to reduce the probability of infestation in small, high-value stands.

ISSN:0045-5067    

DOI:10.1139/x94-281

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Four species of boreal conifer seedlings used for reforestation in eastern Canada were tested for their tolerance to the microbially produced herbicide bialaphos under controlled conditions. The tolerance levels of white spruce (Piceaglauca(Moench) Voss), black spruce (Piceamariana(Mill.) B.S.R), Norway spruce (Piceaabies(L.) Karst.), and red pine (PinusresinosaAit.) were studied over two consecutive growing seasons using different morphological and growth criteria. Application rates were the equivalent of 0, 1.0, 1.5, 2.0, 2.5, and 3.0 kg active ingredient (bialaphos) per hectare in a 1400-L solution and were applied in July, August, or September. Survival rates were a linear function of the dose of bialaphos, but were greater than 95% for all treatments. Results indicated that there was no significant correlation between visible foliar injury and the amount of epicuticular wax on needles. There was also no significant correlation between visible foliar injury and initial seedling height. However, a significant negative correlation was observed between the degree of foliar injury and the relative growth rate following treatment. No additional foliar injury occurred during the second growing season. Doses of bialaphos that did not exceed the equivalent of 2.0 kg active ingredient per hectare had no effect on subsequent growth. Tolerance was greatest when the herbicide was applied in August and least when applied in July. These results, combined with the lower tolerance previously demonstrated for several species that compete with planted conifers in eastern Canada, suggest that bialaphos has a strong potential as an alternative to chemically synthesized herbicides for vegetation management in conifer plantations.

ISSN:0045-5067    

DOI:10.1139/x94-282

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The effect of the microbially produced herbicide bialaphos on ammonium accumulation and photosynthesis of white spruce (Piceaglauca(Moench) Voss) and red pine (PinusresinosaAit.) seedlings was studied under controlled environmental conditions. Ammonium accumulation increased markedly during the first 48 h for seedlings treated in June and was greater in red pine than in white spruce. Ammonium accumulation also increased with higher doses of bialaphos. In contrast, the accumulation of ammonium following bialaphos application in August was minimal for both species and for doses up to an equivalent of 3.0 kg active ingredient (bialaphos) per hectare. Continuous measurements of photosynthesis for the first 12 h following bialaphos application showed a slight negative effect of the herbicide on photosynthetic activity within 2 h of treatment. The decrease was greater for red pine than for white spruce. Photosynthesis measurements taken under three different levels of photosynthetic photon flux density 24 h after bialaphos application showed a greater decline with increasing photosynthetic photon flux density and with higher doses of bialaphos. Furthermore, the decline was greater in red pine than it was in white spruce. When photosynthesis was followed over a 7-day period, a large decrease was observed during the first 24 h, after which time photosynthesis stayed relatively constant. The decrease was greater with higher doses and was greater for red pine than for white spruce. There was a strong negative correlation between photosynthetic rate at day 7 and both the dose of bialaphos and the development of chlorotic foliage. These results help provide a physiological basis for understanding previously reported morphological and growth responses.

ISSN:0045-5067    

DOI:10.1139/x94-283

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The growth efficiencies (E; stemwood growth per unit leaf area) of balsam fir (Abiesbalsamea(L.) Mill.) trees from 20 stands were reconstructed over the 30-year period from 1960 to 1989 in order to determine ifEcould be used to predict tree mortality occurring during and after an epidemic of eastern spruce budworm (Choristoneurafumiferana(Clem.)). Growth efficiencies were reconstructed based on the relationship between age and the number of annual growth rings in the cross-sectional area of heartwood at breast height (R2 = 0.97) and on the previously demonstrated relationship between sapwood area and leaf area of balsam fir across a wide geographic area. Profile and logistic regression analyses demonstrated that apparentE(i.e., the historically reconstructedE) of surviving trees was greater than that of dead trees for every year of the 30-year analysis period. For trees in the 25- to 35-year age-class in 1960, apparentEwas the only variable measured prior to the epidemic that was significantly related to balsam fir mortality. For all trees (aged 11 to 46 years in 1960), both tree age and apparentEwere significant factors prior to the epidemic. During and following the epidemic, several of the more standard mensurational variables (e.g., diameter and basal area growth) were also significantly associated with balsam fir mortality, but apparentEhad the highest levels of significance. Using logistical regression, criticalEvalues below which trees would be predicted to die were calculated as 5-year running averages for the period prior to the epidemic (1960–1968). These were stable at around 0.17 × 10−4 m2basal area growth•(m2leaf area)−1•year−1. Following the epidemic, criticalEvalues were again stable but at a lower level of around 0.07. There was a negative exponential relationship between apparentEand leaf area. Furthermore, for the same level of leaf area, surviving trees had a higher apparentEthan trees that died, up to approximately 30 m2of leaf area. These results suggest that growth efficiency should be considered as part of standard forest inventories in the balsam fir zone because of its ease of measure and its apparent ability to provide a sensitive, physiologically based index of forest health. Furthermore, the technique of historically reconstructingEdemonstrated in this study may be of interest for other types of dendrochronological research.

ISSN:0045-5067    

DOI:10.1139/x94-284

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The daytime pattern of mitotic index (MI) (percent of apical cells undergoing mitosis) in the shoot apex ofPiceaglauca(Moench) Voss (white spruce) containerized seedlings was examined and compared for five cultural treatments. From sowing in March until mid-July, all seedlings were grown under an extended, 23-h photoperiod in a common nursery culture. In mid-July, an array of photoperiod treatments was created, ranging from ambient photoperiod and temperature to different levels of short day length and ambient or controlled, constant temperature. Consistency of MI comparisons among the treatments at different specimen collection times was emphasized rather than treatment effects on MI. Specimens were collected four times a day on two dates: when most seedlings in all treatments were initiating bud scales and when most seedlings were initiating leaf primordia. Patterns of MI were different on each of these dates. It is shown that conclusions about treatment effects on MI can be influenced by the sampling protocol and analytical approach. End of the growing season studies of white spruce andP.glauca × Piceasitchensis(Bong.) Carr. (white × Sitka spruce hybrid) seedlings grown in a greenhouse culture showed that MI below 1% was well correlated with low (<25%) foliage damage, reasonably correlated with stem tissue damage, and not correlated with bud damage resulting from controlled freezer tests to −18 °C. It is concluded that the MI technique could be useful in lifting-date determination, but different MI thresholds must be established for southern, northern, or coastal seed sources. Monitoring MI was not a good alternative to using days to bud break (testing under forcing conditions) to determine bud dormancy status. However, mitotic reactivation of the apical meristem in seedlings overwintering in a nursery bed occurred earlier in the spring than visible signs of growth reactivation (bud swelling and bud break). Studies of growth resumption of western red cedar (ThujaplicataDonn) seedlings in winter revealed that this species would be considered quiescent if tested under a long photoperiod, while under a short photoperiod growth resumption was much slower in early than in mid- and late winter.

ISSN:0045-5067    

DOI:10.1139/x94-285

出版商:NRC Research Press    

年代:1994

数据来源: NRC