摘要:

This study compares snowmelt models and determines the relative importance of the meteorological parameters affecting snowmelt during the 1985, 1986, and 1987 melt seasons in a dense balsam fir stand in Laurentide forest, 80 km north of the city of Québec. Net all-wave radiation, air temperature, wind speed, relative humidity, and rainfall were correlated with meltwater that reached the base of the snow cover as measured with a 20-m2snow lysimeter. The estimation of energy balance components of the snow cover during the snowmelt period showed that while solar radiation absorption dominated, turbulent transfers as well as heat exchanges with ground and rain were negligible. The temperature index modelSNOW-17 yielded predictions of snow cover outflow as accurately as the energy balance model, both explaining 64% of hourly outflow variation and more than 85% of daily outflow variation. Single meteorological parameters usually explained less than 25% of the hourly melt because of the meltwater transmission lag through the snowpack. On a daily basis, the relationships using air temperature or net all-wave radiation as sole index both explained nearly 70% of snowmelt outflow for the same period. Combining these two parameters with rainfall in the same equation increased the explained variance to 85%.

ISSN:0045-5067    

DOI:10.1139/x91-001

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A genetic improvement project for black spruce (Piceamariana(Mill.) B.S.P.) was initiated in Minnesota in 1974, with an objective of improving the inherent growth rate of the local population. This study reports some field results from the initial phase of the project. Study objectives were to (i) estimate genetic and environmental variance components of early (age 10 years) tree height, (ii) estimate expected genetic gains from various selection methods in three seedling seed orchards and a clonal seed orchard, and (iii) evaluate the effect that these selection methods have on inbreeding levels in the rogued seedling orchards. Additive genetic variance accounted for 15 to 22% of the phenotypic variance in three wind-pollinated family tests and 10% of the phenotypic variance across the tests. Expected gains from combined-index (family and individual) selection in the family test - seed orchards (selection of 22 to 27%) ranged from 4.6 to 6.1%. Family + within-family selection and individual selection were 18 and 32% less efficient, respectively. Index selection resulted in the highest estimated levels of inbreeding in the rogued orchards. However, the largest difference between the various selection methods resulted in a difference in the average inbreeding coefficient of less than 0.15%. Based on this small difference, index selection could be used in roguing similarly designed seedling seed orchards with minimal risk of elevated inbreeding levels.

ISSN:0045-5067    

DOI:10.1139/x91-002

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Juvenile lodgepole pine (PinuscontortaDougl. var.latifoliaEngelm.) were excavated at three sites near Hinton, Alberta. In all cases in whichArmillariaostoyae(Romagn.) Herink had become established in the root collar or taproot, it was also able to colonize lateral roots. In cases in which only lateral roots were infected, subsequent colonization generally was primarily distal to the point of infection. Rhizomorphs were associated with 89% of 21 infected roots, whereas only 19% of 70 roots with no associated rhizomorphs were infected. Stumps, roots, and debris from the previous generation of trees were the inoculum sources for 78% of 36 infected juvenile trees, and infected regeneration served as the inoculum source for the remaining trees. Rhizomorphs occasionally were attached to the roots or rhizomes of plants other than pine, especially fireweed (EpilobiumangustifoliumL.). There was no spatial relationship between stumps and symptomatic trees. Nearest neighbor analysis indicated that the likelihood of an individual tree developing symptoms was dependent on whether trees within 0.15 m were dead or dying but independent of the apparent health of trees at greater distances.

ISSN:0045-5067    

DOI:10.1139/x91-003

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Roots of 5-year-old Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco var.menziesii) on three Oregon sites were excavated with explosives and analyzed for the effects of competition on root biomass and for planting-induced root deformities. The plantations were in Nelder designs with graduated spacing from 300 to 15 250 cm2per tree. Competition treatments consisted of weed-free intraspecific competition, grass cover seeded after 1 year of seedling growth, and red alder (AlnusrubraBong.) interplanted 1:1 among the Douglas-fir. All plantations were kept at low water stress in year 1. The ratio of standing aboveground to belowground biomass was the same for each competitor type. Shoot:root ratios averaged about 4:1, except in severely suppressed trees, where ratios dropped toward 1:1 in those near death. Neither shoot:root ratio nor tree size was affected by planting-induced root deformities such as J- or L-rooting. It appears that after 5 years all root systems have fully compensated for planting deformities and future growth and stability have not been jeopardized.

ISSN:0045-5067    

DOI:10.1139/x91-004

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A vacuum extractor was used to examine the effects of increased SO42−deposition on net S retention and cation leaching in three Maine Spodosols (Berkshire, Dixfield, and Rawsonville series) and an Illinois Alfisol. Columns (leached daily for 30 days with either a simulated throughfall solution containing 80 μequiv. SO42−•L−1(pH = 4.77) or a simulated throughfall solution plus 200 μequiv. H2SO4•L−1(pH = 3.66)) were constructed using O horizons over upper B (Bh or Bhs) and lower B (Bhs or BC) horizons for the Spodosols and two depth increments of bulked soil (0–12 and 12–25 cm) for the Alfisol. Leachate concentrations of base cations were dominated by Ca2+and were generally greater in the Alfisol than in the Spodosol leachates. Declining concentrations of base cations and NH4+with time led to an increase in Al3+concentrations and a decrease in pH for some of the Spodosol leachates (e.g., leachate Al3+increased from 19 μequiv. Al3+•L−1(day 2) to 194 μtequiv. Al3+•L−1(day 30), and pH decreased from 5.53 to 4.41, respectively, for the Dixfield high-S treatment). Columns that received the high-S treatment retained a greater percentage of the added S than those that received the low-S treatment because of increased SO42−adsorption in the former. High rates of net organic S mineralization were found for all soil types (e.g., 169 μg organic S•g−1over 30 days for the Rawsonville Bhl horizon, 15% of the total S); no treatment effects were found for the amount of S mineralized. Trends in net S retention across soil type (within the same treatment) reflected increases in soil SO42−from adsorption, as well as decreases in organic S from mineralization. When net S mineralization was removed from leaching losses of S, trends in net S retention closely reflected SO42−adsorption differences (50, 23, 8, and 1% of the added S retained by the Rawsonville, Dixfield, and Berkshire series, and the Alfisol, respectively, for the high-S treatment). Because of the low SO42−adsorption capacity of the Alfisol relative to the Spodosols, organic processes were more important in affecting net S retention for the Alfisol. Inorganic processes of S retention were more important for the three Spodosols studied.

ISSN:0045-5067    

DOI:10.1139/x91-005

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The susceptibility of white spruce,Piceaglauca(Moench) Voss, leaders to damage by the spruce bud moth,ZeirapheracanadensisMut. & Free., was assessed for 72 half-sib families at four half-sib family test sites and in one seedling seed orchard in New Brunswick. Trees of intermediate height (1.5–3.75 m) were the most damaged, and damage in one year was positively correlated to damage in the next. During 2 consecutive years, half-sib family explained only 1% of the variation in damage when all four test sites were analysed together. However, half-sib family explained between 2.9 and 7.9% of the variation in damage at individual sites. At the four test sites, mean growth reductions of trees in the two most susceptible families were estimated to be approximately 30% higher than those of trees in the two least susceptible families. When all 72 families were ranked with respect to height, trees in the most susceptible and least susceptible families were ranked very poorly and highly, respectively. This suggested that trees in more susceptible families were smaller because of damage by the spruce bud moth. However, this pattern was observed at all sites, including one where bud moth damage was negligible. Thus even in the absence of damage by the spruce bud moth, trees in these least susceptible families had a greater growth rate, in terms of height, than trees in the most susceptible families. This indicates that selection for plant traits reducing susceptibility to bud moth may be compatible with breeding programs attempting to improve height growth. Implications of these results for tree improvement programs are discussed.

ISSN:0045-5067    

DOI:10.1139/x91-006

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The modulus of elasticity and the tensile strength were determined for a sample of live Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) roots collected in the Oregon Coast Range. Most of the roots displayed both a "form" modulus of elasticity and a "material" modulus of elasticity. The form modulus occurred as a tortuous root straightened out, whereas the material modulus developed following this initial straightening as the wood fibers within the root directly resisted elongation. The average form and material moduli of elasticity were, respectively, 185 and 503 MPa, whereas the average tensile strength was 17 MPa.

ISSN:0045-5067    

DOI:10.1139/x91-007

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Reversible changes in cell wall water content, elasticity, and osmotic adjustment are all important drought tolerance mechanisms. Pressure chambers have been used extensively to generate water-release curves from which these basic water relations parameters are derived. Major limitations of this technique include the considerable time required to generate water-release curves and the difficulty in avoiding damage to tissue during the process. A simple and practical technique is descried that overcomes these limitations and allows the routine and rapid generation of water-release curves. Needles were removed from hydrated black spruce (Piceamariana(Mill.) B.S.P.) shoots, weighed on a precision balance, and suspended above unsaturated salt solutions of known molality in sealed test tubes held at 5 °C. Eighteen solutions were used with water potentials ranging from −0.09 to −4.67 MPa. Once needles had equilibrated with air above the salt solution (8–30 h depending on needle age), they were weighed and oven-dried. Water-release curves were obtained by plotting paired values of needle relative water content and solution water potential. Typically, 35 curves were generated over 3 days compared with 7 curves generated using a pressure chamber over the same period. There was excellent agreement between methods in estimates of elastic modulus, osmotic potential, and apoplastic water content.

ISSN:0045-5067    

DOI:10.1139/x91-008

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Chi-square (χ2) tests are analytic procedures that are often used to test the hypothesis that animals use a particular food item or habitat in proportion to its availability. Unfortunately, several sources of error are common to the use of χ2analysis in studies of resource utilization. Both the goodness-of-fit and homogeneity tests have been incorrectly used interchangeably when resource availabilities are estimated or knownapriori. An empirical comparison of the two methods demonstrates that the χ2test of homogeneity may generate results contrary to the χ2goodness-of-fit test. Failure to recognize the conservative nature of the χ2homogeneity test, when "expected" values are knownapriori, may lead to erroneous conclusions owing to the increased possibility of committing a type II error. Conversely, proper use of the goodness-of-fit method is predicated on the availability of accurate maps of resource abundance, or on estimates of resource availability based on very large sample sizes. Where resource availabilities have been estimated from small sample sizes, the use of the χ2goodness-of-fit test may lead to type I errors beyond the nominal level of α. Both tests require adherence to specific critical assumptions that often have been violated, and accordingly, these assumptions are reviewed here. Alternatives to the Pearson χ2statistic are also discussed.

ISSN:0045-5067    

DOI:10.1139/x91-009

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

This study investigates the impact of postulated greenhouse warming on the severity of the forest fire season in Canada. Using CO2levels that are double those of the present (2 × CO2), simulation results from three general circulation models (Geophysical Fluid Dynamics Laboratory, Goddard Institute for Space Studies, and Oregon State University) were used to calculate the seasonal severity ratings for six stations across Canada. Monthly anomalies from the 2 × CO2simulation results were superimposed over historical sequences of daily weather. Then, seasonal severity ratings of the present were compared with those for 2 × CO2using five variations involving temperature, precipitation, and relative humidity. The relationship between seasonal severity rating and annual provincial area burned by wildfire was explored. The results suggest a 46% increase in seasonal severity rating, with a possible similar increase in area burned, in a 2 × CO2climate.

ISSN:0045-5067    

DOI:10.1139/x91-010

出版商:NRC Research Press    

年代:1991

数据来源: NRC