摘要:

Weed control and 2nd-year survival and growth of newly planted Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) and noble fir (AbiesproceraRehd.) seedlings were measured after application of herbicide and fertilizer in a replicated complete factorial experiment with four levels of simazine (0, 2.2, 4.4, 8.8 kg/ha), three levels of nitrogen (0, 110, 220 kg/ha), two types of nitrogen (urea prill; urea + trimamino-s-triazine (TST) prill), and two kinds of formulations (cogranular prill of simazine + nitrogen; nitrogen prill followed by liquid simazine). For the first growing season, total weed and grass control increased with increasing simazine rates. Total weed control was better when urea + TST, rather than urea alone, was applied in conjunction with simazine. Formulation and nitrogen rate were not significant. After plot treatment with 1.1 kg/ha of liquid hexazinone at the beginning of the second growing season, Douglas-fir survival decreased as rate of urea alone increased; survival decreased with little or no weed control and remained constant or increased with good weed control as rate of urea + TST increased. Noble fir height and diameter and Douglas-fir diameter declined with poor weed control but increased at least to the levels of untreated seedlings with good weed control. Noble fir diameter responded positively to added nitrogen. Although simazine may be toxic to 1st-year conifers, this study suggests that more complete weed control in conjunction with fertilization may benefit young conifer plantations.

ISSN:0045-5067    

DOI:10.1139/x90-224

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Duration of branch radial growth and longevity were summarized for 2153 branches immediately below the current live crown of Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) trees in southwestern Oregon. Branch longevity averaged 24 years with a range of 4 to 72 years. The number of years without perceptible (13 × hand lens) annual branch radial growth averaged 8 years with a range of 0 to 49 years. Expressed as a percentage of branch longevity, the period lacking perceptible radial growth ranged from 0 to 93% with an average of 34%. As would be expected, greater longevity implied survival deeper into the crown; average percentage of longevity without radial growth also decreased with increasing depth into crown. The implications of branch growth patterns to stem growth and wood quality are discussed.

ISSN:0045-5067    

DOI:10.1139/x90-225

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The sensitivity of seedling morphological attributes to changing competition levels was evaluated on 4-year-old black spruce (Piceamariana(Mill.) B.S.P.) and jack pine (PinusbanksianaLamb.) seedlings to determine the most appropriate response variables to be used in the assessment of early plantation performance. A total of 720 seedlings (360 per species) were sampled between 1987 and 1989, covering a range of stock types, soil textures, and competition levels. A competition index, derived from hemispherical photographs, provided an estimate of incident radiation received by each sampled seedling. Seedling stem volume at time of planting was used as a covariate in the regression analyses. Stratification by plantation was done to account for variations in site quality. The results from this study demonstrated that total height or current height increment were not reliable for quantifying individual seedling response to inter specific competition for 4-year-old black spruce or jack pine plantations. Overall, the most consistent response variable was total seedling dry weight. Coefficients of determination ranged from 0.116 to 0.534 for black spruce and from 0.601 to 0.810 for jack pine across the range of sites and stock types. If it is inappropriate to determine total seedling dry weight, root collar diameter would be the best substitute. Correlation coefficients between these two variables were 0.897 for black spruce and 0.912 for jack pine.

ISSN:0045-5067    

DOI:10.1139/x90-226

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Open-grown jack pine (PinusbanksianaLamb.) in northern Ontario, ranging in age from 9–20 years, bore an average of 311 receptive seed cones, with the greatest number in the upper midcrown. Generally, counts of receptive seed cones varied more among trees than among directions; most of the variation among trees occurred in the mid to upper crown. The expressionF(H) = Hb+1[b + 2 − (b + 1)H], withb = 3.12 (P < 0.001,R2 = 0.94), described the cumulative proportion of receptive seed cones occurring up to relative crown height,H. Significant directional differences in the parameter estimates forbshowed that the open-grown jack pines initiated seed cones at slightly lower heights on the south side than on the other sides. For monitoring the crop, a procedure for randomly selecting receptive seed cones with respect to their vertical distribution in the crown was developed. The construction of simple, cost-effective sampling plans for estimating yields of receptive seed cones in jack pine seed orchards is explained. This involves determining the cost of conducting the sampling necessary to achieve a desired precision of estimation. It also involves determining the precision attainable with limited resources to conduct the sampling. With this focus, simple random sampling and two types of stratified random sampling were compared. Stratified random sampling based on relative crown height with equal stratum widths was cost-effective and should be relatively easy to implement operationally.

ISSN:0045-5067    

DOI:10.1139/x90-227

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Newly germimated pitch pine (PinusrigidaMill.) seedlings inoculated with a mycorrhizal fungus (Pisolithustinctorius(Pers.) Coker & Couch) were grown for 13 weeks in sand irrigated with nutrient solution (pH 4.0) containing 0, 12.5, 25, 50, or 100 mg/L of aluminum (Al) in growth chambers fumigated with 0, 50, 100, or 200 ppb ozone. Increasing the concentration of ozone or Al caused increasing reductions in needle length, seedling height, and biomass of needles, stems, and roots. Significant ozone × Al interactions indicated that ozone and Al were interacting synergistically in reducing growth. Effect of treatments on the root/shoot ratio demonstrated that shoot growth was more sensitive to Al than root growth, whereas root growth was more sensitive to ozone. The concentration of most mineral elements (P, K, Ca, Mg, Mn, Cu, Zn) in needles was reduced by ozone or Al. Iron was the only element that increased with increasing concentrations of ozone or Al.

ISSN:0045-5067    

DOI:10.1139/x90-228

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Size hierarchy development is a commonly observed structural feature within naturally regenerating forest tree populations. The objective of this study was to describe initial size hierarchy development within second-growth black spruce (Piceamariana(Mill.) B.S.P.) stands. Three dense black spruce stands that developed naturally following conventional cut and skid harvesting, conducted in 1970, were selected for analysis within insular Newfoundland. Employing historical stand reconstruction techniques within 13 temporary sample plots of variable size, temporal and spatial establishment patterns, structural development patterns, and competitive relationships were described. Size inequality peaked during the period in which 87.5% of the population became established (degree of inequality within the height and volume frequency distributions as measured by the Gini coefficient). Subsequently, size inequality and asymmetry decreased (degree of asymmetry within the volume frequency distribution as measured by the skewness coefficient and Shapiro–Wilk'sWstatistic). The rate of decline in size inequality and asymmetry was inversely proportional to stand density. Temporal declines in individual-tree vigour across size classes were approximately proportional (vigour as measured by relative volume production rate). These patterns suggested competition was symmetric (individuals share the finite environmental resources equally or in direct proportion to their relative sizes). However, variation in individual-tree vigour, possibly due to temporal and spatial establishment pattern heterogeneity, negated the conclusive acceptance of the resource depletion hypothesis. Based on these observations, a size hierarchy developmental pattern is proposed for second-growth black spruce stands.

ISSN:0045-5067    

DOI:10.1139/x90-229

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A model was developed to estimate total leaf dry weight of individual standing trees ofEucalyptusregnansF. Muell. in even-aged, monoculture stands aged 8–20 years. Tree biomass data were collected for a sample of 42 trees from four plots at three sites in Victoria and Tasmania. One plot had been heavily thinned 10 years prior to sampling. The model was based on the pipe model theory,L(x) = as(x)p(x), whereL(x) is leaf dry weight above some height (x),s(x) andp(x) are, respectively, stem sapwood area and permeability atx, and a is a parameter. Permeability is known to vary with site and tree conditions, and an empirical model was developed that replacedap(x) in the pipe model theory with a function in terms of tree age, diameter at breast height over bark, and distance along the stem from the tip of the tree. The resulting model to predict leaf weight appeared to be unbiased across sites, among trees within sites, and with respect to thinning treatment. It was found that given a prediction from the model of total leaf dry weight of one tree, it could be assumed with 95% confidence that the true value of leaf weight fell within an interval bounded by values of −60 to +76% of the estimate. When the model was used to predict stand leaf weight by summing estimates from many individual trees, the interval was bounded by minimum values of −3 to +19% of the stand estimate. These errors of estimate were probably conservative. It appeared that errors of similar magnitude may apply to other published models of this type.

ISSN:0045-5067    

DOI:10.1139/x90-230

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The importance of provenance and fungal species effects on mycorrhiza formation inPiceamarianawas determined. Seed was collected from two sites near Chapleau, Ontario. One provenance was collected from an upland site with sandy soil, the second from a lowland site with peaty soil. Seedlings were grown under aseptic conditions in test tubes. Two experiments were performed: in the first, seedlings were inoculated withHebelomacylindrosporum,Laccarialaccata, orPaxillusinvolutus, whereas in the second, seedlings were inoculated withLaccariabicolor,Laccarialaccata,Laccariaproximoor noninoculated agar plugs. Counts of ectomycorrhiza and lateral root formation were analyzed for significance with two-way factorialANOVAS. When inoculated withL.laccata, seedlings from the lowland seed source had significantly more mycorrhizal second order lateral roots than seedlings from the upland seed source. Lowland seedlings also had greater shoot dry weight and foliage length values. However, overall differences between provenances were small. In contrast, differences between fungal treatments were pronounced. BothL.laccataandL.bicolorinitiated good ectomycorrhiza formation and increased seedling growth.

ISSN:0045-5067    

DOI:10.1139/x90-231

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The effects of both seed source and fungal species on the formation of beads in roots ofPiceamariana(Mill.) B.S.P. were examined. Seed was collected from two sites near Chapleau, Ontario. One provenance was an upland site with sandy soil, the second a lowland site with peaty soil. Seedlings were grown under aseptic conditions in test tubes and inoculated with eitherLaccariabicolor(Maire),Laccarialaccata(Scop, ex Fr.),Laccariaproximo(Boud.) Pat., or agar plugs. Each constriction or striation on the root was counted as a single bead. These constricted regions were associated with the accumulation of a darkly stained substance and the absence of a Hartig net. Bead formation on first order lateral roots from each treatment was assessed and the data were analyzed for significance with a two-way factorialANOVA. There was a significant interaction between seed source and fungal species on the numbers of beads formed. Bead formation was significantly more common on the lowland seed source in theL.laccatatreatment only.L.laccatainoculation resulted in the greatest number of beads on first order lateral roots followed by control andL.proximotreatments. Colonization of seedlings withL.bicolorresulted in the formation of significantly fewer beads than in the control or any other treatment.

ISSN:0045-5067    

DOI:10.1139/x90-232

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

This paper presents a model of the recent dynamics of a boreal fir population (Abiesbalsamea(L.) Mill.) exposed to a major disturbance, taking a blowdown as an example. The blowdown was precisely dated with the use of reaction wood. Age structures and growth curves were used to reveal the population history and to follow the evolution of the regeneration. The blowdown occurred in 1947. The majority of the firs of the actual population were established before the event. Their age structure conforms to the normal distribution. The original population, which was blown down, was replaced by a similar population in terms of the species' relative proportion. The blowdown is associated with a spruce budworm (Choristoneurafumiferana(Clem.)) outbreak which began around 1944. The population growth curve shows a distinct growth release following these two disturbances. The regeneration mechanisms of this site could serve as a model applicable to more complex but just as devastating disturbances, such as spruce budworm outbreaks.

ISSN:0045-5067    

DOI:10.1139/x90-233

出版商:NRC Research Press    

年代:1990

数据来源: NRC