摘要:

A naturally occurring triploid elm hybrid was found in the American elm,UlmusamericanaL., planting on the National Mall in Washington, D.C. Chromosome examinations of mitosis in root tips and meiosis in pollen mother cells showed a chromosome complement of 2n = 3x = 42. The chromosome alignment at meiotic metaphase I was predominantly 14 bivalents and 14 univalents, indicating that one parent was an American elm, which contributed the bivalents through autosyndetic pairing. When DNA underwent restriction digestion withHindIII and probed with a 9.5-kilobase cloned ribosomal DNA fragment from pea,PisumsativumL., the triploid hybrid showed a band not found in American elms. Seed from the open-pollinated parent tree had low viability and seedlings were highly variable in height, leaf size, and shape. The small leaves of some seedlings suggest that the other parent was a species with leaves smaller than American elm. The hybrid was found to be resistant toOphiostomaulmi(Buis.) Nannf. When twig crotches were inoculated, only 14% developed wilt compared with 63% in the American elm. None of the 22 hybrid trees inoculated developed systemic wilt compared with 8 of the 18 American elms inoculated. The hybrid, which is easily propagated by softwood cuttings, has rapid growth, good crown structure, and many characteristics of the American elm.

ISSN:0045-5067    

DOI:10.1139/x94-087

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Several recent publications suggest that acid deposition produces high anion concentrations in the soil solution of high-elevation forests, causing Al-induced Ca deficiency in red spruce (PicearubensSarg.) root tips. Some authors suggest that this results in decreased growth below and above ground, decline, and ultimately in death. Accordingly, we examined soil solution Al and Ca, soil and foliar chemistry, and their relationship to red spruce decline on Whiteface Mountain, New York, where severe red spruce mortality occurred between the mid-1960s and late 1980s. Spruce mortality and crown condition are strongly related to elevation, but there is no evidence that the occurrence or degree of spruce decline is related to exchangeable Al, Mg, Ca, or their ratios in mineral or organic horizons. Foliar Ca and Mg concentrations that we measured were in the range judged to be sufficient based on field fertilization studies. Soil solution ratios of Ca:Al in mineral and organic horizons were above the threshold (1:1 molar ratio) proposed as detrimental to Ca uptake in all samples collected during three of four growing seasons, and soil-solution Al concentrations were well below levels thought to inhibit spruce root growth. If Al toxicity is a factor in red spruce decline on this mountain, it is acting in a way that is not detectable using soil and foliar analyses.

ISSN:0045-5067    

DOI:10.1139/x94-088

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

To assess the impact of atmospheric deposition on soil acidification and base cation supplies in montane spruce–fir forest soils at Whiteface Mountain, New York, base cation and proton fluxes were determined for organic and mineral horizons from measurements made at four stands (1020–1090 m above sea level) over a 4-year period. Our best estimates indicate an annual accumulation of H+and a net loss of base cations from the forest floor of about 0.71 kmolc/ha, a 2.8% per year loss of the total forest floor base cation pool. This high rate of acidification is attributable to base cation leaching by sulfate and organic anions, and uptake by living biomass. From 1986 to 1990, the annual net loss rate of forest floor Ca, the most abundant base cation, was several times greater than historical loss rates as determined by 50-year comparisons of forest floor Ca in nearly identical forests of the Adirondack High Peaks region. Published data on long-term trends in Ca deposition in the U.S. Northeast suggest that the difference between historical and current net loss rates of forest floor Ca may be due to sharply reduced atmospheric inputs of Ca after about 1970, exacerbated by sulfate leaching. In mineral horizons where the total base cation pool (mostly mineral bound) is very large, the net losses of base cations were substantially lower and in the range where losses due to leaching and uptake can be countered by mineral weathering.

ISSN:0045-5067    

DOI:10.1139/x94-089

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Forty-one seedling populations of western red cedar (ThujaplicataDonn ex D. Don) were compared in five environmentally disparate common gardens. Separate tests of 25 wind-pollinated families from a single population were conducted on two of the sites. Genetic differences among populations and families were detected for variables related to growth and winter hardiness. Statistically significant multiple regression models withR2values as high as 0.53 related genetic variation among populations to the elevation and geographic origin of the seed. The slope of the clines, however, was so gentle that populations must be separated by about 600 m in elevation or by 2° latitude before one can be reasonably certain of genetic differentiation. While genetic variation among families suggests that gains in the growth of western red cedar can be made through tree breeding, establishing evaluation trials for estimating genetic variances, breeding values, and responses to selection is problematic on sites in the interior.

ISSN:0045-5067    

DOI:10.1139/x94-090

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The biochemical bases of water-stress tolerance in a pedigree consisting of black cottonwood (PopulustrichocarpaTorr. & Gray female) and eastern cottonwood (PopulusdeltoidesBartr. male) parental clones and four hybrid progeny were investigated. Trees were grown outdoors in pots; well-watered trees (soil water potential greater than −0.03 MPa) were kept moist in trays, and stressed trees (soil water potential less than −2.0 MPa) were subjected to repeated cyclical stress of 1 or 2 days duration over the 14-week study. Analysis of the major metabolites and ions in fully expanded leaves demonstrated that the greatest degree of osmotic adjustment was displayed by male hybrid 242, theP.deltoidesmale parent, and male hybrid 239 to a lesser extent. Osmotic adjustment in leaves of both hybrid 242 and theP.deltoidesmale parent was primarily constituted by malic acid, K, sucrose, and glucose, with the same metabolites also increasing in fine roots of hybrid 242, the only clone to display osmotic adjustment in roots. Female clone 240 andP.deltoidesdisplayed organic solute-based adjustments to water stress that were offset by declines in inorganic ions, particularly Na and Mg. Given that theP.trichocarpafemale parent did not display osmotic adjustment in either tissue, the hybrids' capacity for adjustment was likely conferred by theP.deltoidesmale parent.

ISSN:0045-5067    

DOI:10.1139/x94-091

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Some physical, thermal, and chemical properties of bark of 16 tree species native to the central hardwood region were measured to determine their potential to protect the vascular cambium from damage by fire. The relationship between DBH and bark thickness for each of 16 species was determined. For purposes of monitoring seasonal trends, two species (QuercusmacrocarpaMichx. andAcersaccharinumL.) were sampled periodically during one growing season. Temperature response to bark surface heating of 11 species was monitored at the cambial layer during simulated fires conducted in the field. Bark samples were analyzed for moisture content, specific gravity, dry weight, volatile matter content, and time until ignition. Overall, during simulated fires, temperature gradients were decreased and maximum cambial temperatures were reduced as bark thickness increased. Thick-barked species had lower maximum cambial temperatures, longer times to reach peak temperatures, slower rates of heat loss, and shorter time until surface ignition.PopulusdeltoidesMarsh, was the most heat resistant among species tested, whileAcersaccharinumwas the least. Higher specific gravities were associated with higher rates at which cambial temperatures rose as well as with increased time required for surface ignition.

ISSN:0045-5067    

DOI:10.1139/x94-092

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A forest succession model has been adapted to simulate the dynamics of subarctic spruce–lichen woodland of northeastern Canada. Most adaptations concern the simulation of seed regeneration of subarctic forest communities growing on moderately to well drained sites. The yearly seed production inPiceamariana(Mill.) B.S.R stands is controlled by temperature and stand structural characteristics. In addition to the seed input, the model considers the influence of seedbed properties on the establishment of seedlings. Overall, this model simulates the entire regeneration dynamics in a more realistic way than in most other gap models where successional processes are driven by resource constraints on tree growth. The model produces realistic predictions about the pattern of early post-fire age structure, and the biomas and density dynamics of black spruce populations. Simulations under a climate-warming scenario suggest that physiognomic change in subarctic spruce–lichen woodland would be more pronounced in areas subjected to moderately frequent forest fires than in those where the fire frequency is very low.

ISSN:0045-5067    

DOI:10.1139/x94-093

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Postinoculation wetness duration, temperature, and light conditions were investigated in relation.to infection of container-grown seedlings of black spruce (Piceamariana(Mill.) B.S.P) byBotrytiscinereaPers.:Fr. Seedlings were predisposed to the pathogen by treatment at 35 ± 1 °C in darkness for 4 days immediately before inoculation, and infection was assessed indirectly by estimating sporulation incidence of the pathogen on 6-mm segments of the needles. Sporulation incidence was zero when the temperature during 32 h of the postinoculation wetness was 1, 4, and 36 °C, about 7–10% at 12 °C, 40–47% at 28 °C, and maximal (44–56%) at 20 °C. Sporulation incidence was zero at all tested temperatures when wetness duration was <8–12 h, but increased progressively when the wetness period was increased from 12 to 32 h. Light and darkness during the wetness period did not significantly affect sporulation incidence. Logistic regression models were developed that adequately described sporulation incidence, and by inference, infection incidence, as functions of the postinoculation wetness period and temperature, and were validated using sets of independent data.

ISSN:0045-5067    

DOI:10.1139/x94-094

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Open-pollinated seeds were collected from loblolly pine (PinustaedaL.) selections made in natural stands in eastern North Carolina, then planted in a short-term, closely spaced test and in a conventional genetic test. Wood density measurements from seedlings, from older trees, and from parents aged 40–75 years old were used to estimate the genetic covariance structure between juvenile and mature wood. These data were also used to determine if the genetic relationship between juvenile and mature wood varied with the estimation method used or with the fertilizer and irrigation treatments in the short-term test. Age–age relationships were moderately to highly positive and these results were corroborative using several methods: parent–offspring regression and coefficient of genetic prediction, half-sib analyses, and graphical use of type I selection mistakes. Strong age–age relationships (rg = 0.76 to 0.90) were expressed between juvenile wood in the short-term test and older-tree wood density in the genetic test. Moderate to high heritabilities (h2 = 0.55–0.76) were estimated for juvenile wood in short-term tests. The latter estimates tended to be higher than heritability estimates based on parent–offspring regression (h2 = 0.23–0.25). There was negligible family × treatment interaction due to rank change between short-term testing treatments. Height and specific gravity expressed a slight positive correlation at all ages.

ISSN:0045-5067    

DOI:10.1139/x94-095

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Genetic parameters were estimated, using the restricted maximum likelihood method, for 1112 open-pollinated progenies ofPinuscontortaDougl. ex Loud. var.latifoliaEngelm. plus trees selected from among 83 undisturbed stands in the interior of the Yukon and British Columbia, and five similar stands in Alberta. The progenies were grown in Swedish test plantations. Tree condition, height, and ramicorn whorl frequency were assessed at ages ranging between 8 and 12 years. On the harshest sites, weather and fungal damage, e.g., caused byGremmeniellaabietina(Lagerb.) Morelet, were also assessed. Categorical data were transformed into values on a normal score scale to improve the efficiency of the evaluation. The genetic coefficients of variation in tree height ranged between 8 and 17%. The heritabilities for tree height, including stand genetic variation, were estimated to range between 0.10 and 0.54. Genetic correlations between tree height and trunk leaning were usually high and positive, as were correlations between height and ramicorn whorl frequency. At one site, heritability estimates for trunk injury and (or) canker and fungal and (or) weather damage were 0.12 and 0.18, respectively.

ISSN:0045-5067    

DOI:10.1139/x94-096

出版商:NRC Research Press    

年代:1994

数据来源: NRC