摘要:

The distribution of coarse woody debris in a fifth-order Cascade Range (Oregon) stream system was examined from a geomorphic point of view. The number, volume, location, orientation, decay class, and pool formation roles of coarse woody debris were investigated. The processes of coarse woody debris production, transport, and storage, which vary with channel and valley floor geomorphology, are responsible for the pattern of coarse woody debris distribution on valley floors. Channel width and sinuosity are the main factors that control production, storage sites, and hydrologic effects of coarse woody debris. The amount of coarse woody debris and the number of pool-forming pieces are relatively high in wide, sinuous reaches, where a complex structure of floodplains and riparian forests develops in association with a braided channel pattern. These relations are transferable to other systems with similar relations of coarse woody debris piece length to channel width.

ISSN:0045-5067    

DOI:10.1139/x94-309

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Osmotic adjustment was studied in 6-month-old seedlings ofEucalyptuscamaldulensisDehnh.,EucalyptustereticornisSmith,EucalyptusviminalisLabill., andEucalyptusgrandisHill ex Maiden. Because osmotic adjustment is related to water-stress tolerance, it can be used as a selection criterion of material adapted to drought. Half of the individuals of each species were submitted gradually to water stress, while the rest were maintained in soil at field capacity. Twenty-five days later the effect of stress on the development of osmotic adjustment was analyzed. All species had adjusted osmotically. The lowest osmotic adjustment was observed inE.camaldulensisandE.grandis(14.1% and 15.2%, respectively).EucalyptusviminalisandE.tereticornishad values of 32.3% and 41.9%, respectively. Our results demonstrate that species differ significantly in their extent of osmotic adjustment under drought stress, and that it is possible to use this inductive plant feature as one of the criteria to select, during early developmental stages,Eucalyptusgenotypes adapted to drought-prone environments. Some phylogenetic considerations are presented.

ISSN:0045-5067    

DOI:10.1139/x94-310

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Boron deficiency is identified as one of the more important causes of poor stem form and malformed leaves in plantations ofEucalyptusglobulusin Yunnan Province, and ofEucalyptusgrandis,Eucalyptustereticornis, andEucalyptusurophyllain Guandong Province. Symptoms of B deficiency inE.globuluswere rolled and malformed leaves, stem dieback, and a prostrate form. InE.urophylla, leaf margins became chlorotic then necrotic, leaves turned brittle and corky, shoots died back, and the upper stem nodes were enlarged supporting numerous short-lived axillary shoots. InE.grandis, stem dieback was preceded by the basipetal accumulation of anthocyanin in leaves. Boron-deficientE.tereticornisleaves developed marginal and interveinal chlorosis and recurved margins. Depressed foliar B concentrations were associated with visible symptoms. InE.globulus, the mean B concentration in young leaves of healthy trees was 31 mg/kg dry matter compared with 10 mg/kg in prostrate trees. Symptoms did not appear inE. globulustrees supplied with B fertilizer at planting. Normal shoot growth was restored inE.urophyllaby the addition of B to the soil.

ISSN:0045-5067    

DOI:10.1139/x94-311

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Mature pollen of lodgepole pine (PinusconcortaDougl.), yellow cypress (Chamaecyparisnootkatensis(D. Don) Spach), western hemlock (Tsugaheterophylla(Raf.) Sarg.), jack pine (PinusbanksianaLamb.), and black spruce (Piceamariana(Mill.) B.S.P.) was bombarded with gold particles coated with four different plasmid constructions, pRT99GUS, pBM113Kp, pAct1-D, and pGA984, using the biolistic PDS-1000/He device. A protocol was devised for efficient gene transfer and gene expression assay in pollen. False positive results for expression of the β-glucuronidase (GUS) gene assayed with the substrate X-glucuronide were observed with pollen of yellow cypress, western hemlock, and lodgepole pine. The highest levels of transient GUS gene expression were obtained with plasmid pBM113Kp, which carried the GUS gene under the control of the wheat abscisic acid inducible early methionine promoter. The plasmids pRT99GUS (35S promoter) and pAct1-D (rice actin promoter) yielded similar intermediate levels of transient GUS gene expression. The pollen-specific promoter of the α-tubulin gene fromArabidopsisthaliana(pGA984) yielded the lowest levels of gene expression in pollen. Of the four species, yellow cypress showed the lowest levels of transient GUS gene expression and black spruce yielded the highest levels. The neomycin phosphotransferase II (NPT II) gene was also tested as a reporter gene for pollen transformation and was easily assayed via ELISA. The fusion gene between NPT II and GUS genes was detected at a lower level than the nonfused NPT II gene when under the control of the same 35S promoter. The method devised here could be used for the study of tissue-specific gene expression in conifer pollen.

ISSN:0045-5067    

DOI:10.1139/x94-312

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

To determine if western red cedar (ThujaplicataDonn) litter contributes to low N availability in cedar–hemlock forests, we measured concentrations of N and rates of net N mineralization in forest floors from single-species plantations of cedar, western hemlock (Tsugaheterophylla(Raf.) Sarg.), and Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) on the same site in coastal British Columbia. Concentrations of total and extractable N and rates of net N mineralization during laboratory incubations were lowest in the cedar forest floor and highest in Douglas-fir. Less C was mineralized in the cedar forest floor during incubation, and the amount of N mineralized per unit C was least in cedar. Rates of mass loss of foliar litter of the three species were similar during the first 50 weeks of a 70-week laboratory incubation, but cedar lost mass more quickly during the final 20 weeks. Rates of net N mineralization in the forest floors were significantly correlated with the initial percent N, C/N, % Klason lignin, and lignin/N of foliar litter. Foliar litter of cedar had lower concentrations of N and greater proportions of alkyl C (based on13C NMR spectroscopy) than Douglas-fir litter. These characteristics of cedar litter may contribute to low N availability in cedar–hemlock forest floors. Concentrations of alkyl C (waxes and cutin) may be better than lignin for predicting rates of mass loss and N mineralization from litter.

ISSN:0045-5067    

DOI:10.1139/x94-313

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The potential for amendments of simple C compounds or lime to improve N availability in humus from cedar–hemlock cutovers was tested in laboratory incubations and a greenhouse bioassay. Rates of C and N mineralization in samples of humus and woody humus during aerobic incubations in the laboratory were not affected by additions of potato starch. Mineralization of C was stimulated and net N mineralization was reduced after glucose addition. Microorganisms in humus may not be capable of degrading starch, and simpler C sources such as glucose increase immobilization of N in microbial biomass. The biomass of seedlings of western red cedar (ThujaplicataDonn), western hemlock (Tsugaheterophylla(Raf.) Sarg.), and Sitka spruce (Piceasitchensis(Bong.) Carr.) grown in pots containing cedar–hemlock humus amended with dolomitic lime was similar to the biomass of seedlings grown in unamended humus after 18 months. Seedlings grown in humus amended with N and P fertilizers were significantly larger than those grown in unamended or lime-amended humus. It is unlikely that applications of C or lime to cedar–hemlock cutovers would increase rates of N mineralization from humus. Additions of nutrients appear to be the only practical means of alleviating the nutrient supply problems on these sites.

ISSN:0045-5067    

DOI:10.1139/x94-314

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Sawlogs are in short supply in northern Ontario, and thinning has been suggested as one way to improve the situation. The only rotation-age jack pine (PinusbanksianaLamb.) thinning trial in the region was examined to assess how commercial thinning influenced wood quality. This report covers an unreplicated trial of a 65-year chronology of pith to bark relative densities and growth rates based on X-ray densitometry of breast-height increment cores taken from trees on two thinned plots (average spacing 2.6 and 3.4 m) and an unthinned control (average spacing 1.7 m). The trees on the treatment plots responded to thinning by producing wood with significantly lower relative density than those on the control plot. This trend continued much longer than reported for other pines and could negatively affect pulp yield or mechanical properties of lumber. Enhanced earlywood growth caused a drop in the proportion of latewood that resulted in the decline in density. Thinning may have improved moisture availability during the early and middle season and encouraged earlywood growth. Density and growth rate differences became apparent soon after treatment. Early, rapid, and inexpensive estimates of the product potential of younger thinning trials are possible using the techniques demonstrated here.

ISSN:0045-5067    

DOI:10.1139/x94-315

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The effects of three basal areas (9.2, 13.8, and 18.4 m2/ha), maximum diameters (30.5, 40.6, and 50.8 cm), and site indices (≤24.6, 24.7–27.4, and ≥27.5 m at 50 years) on establishment and development of loblolly pine (PinustaedaL.) regeneration and competing vegetation were determined on 81 permanent, 0.20-ha plots in south Arkansas and north Louisiana. Plots were harvested to the designated basal areas, maximum diameters, and aq-factor of 1.2 using the single-tree selection method during 1983 (a bumper seed year) and 1985 (a seed year failure); this necessitated including the year of harvest as a fourth variable. Pine regeneration and competing vegetation were evaluated 4 or 5 years after treatment. Models were developed to predict the number and percent stocking of pine seedlings and saplings and the percent coverage of competing vegetation. Fit indices ranged from 0.21 to 0.52 for pine regeneration and from 0.15 to 0.73 for coverage of competing vegetation. Pine regeneration was generally greatest for the 1983 harvest, the largest maximum diameters, and the poorest sites. Coverage for vines, hardwoods, and total vegetation was greatest on the good sites and generally for the lowest basal areas. Coverage of grasses, herbs, and shrubs did not vary significantly among treatments. Results suggest that seed production and competing vegetation influence the initial amounts of loblolly pine regeneration obtained with uneven-aged silviculture using single-tree selection.

ISSN:0045-5067    

DOI:10.1139/x94-316

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

During the first year of a 2-year field experiment (1989–1990), 3-year-old Scots pine (PinussylvestrisL.) seedlings were watered with phosphorus-deficient nutrient solutions containing no phosphorus (0%) or 30% of the optimal phosphorus supply. A complete nutrient solution was used as the control. In the second growing period, the seedlings were divided into two groups, a deficiency and a recovery treatment, to follow the further development of, and recovery from, symptoms. Phosphorus contents in both current- and previous-year needles in both deficiency groups decreased clearly during the first growing period. Limited growth was observed at both deficiency levels after 10 weeks of treatment. The first ultrastructural symptom, swelling of cristae and subsequent dilatation of whole mitochondria, was observed after 16 weeks of treatment in the current-year needles. In addition to this symptom, the previous-year needles had an increase in the number and translucency of plastoglobuli, a decrease of granum thylakoids, and an increase in the density of the stroma in chloroplasts. After the second growing period, the same changes were observable in the phosphorus-deficient seedlings. In the young needles grown during the recovery fertilization period, slight swelling of mitochondria was detected and recovery of the previous-year needles was not complete. The results of this experiment suggest that the swelling of mitochondria is a characteristic symptom of phosphorus deficiency at the ultrastructural level in different needle generations. All the symptoms, when occurring together, may be used in identifying a moderate phosphorus-deficiency stress in seedlings.

ISSN:0045-5067    

DOI:10.1139/x94-317

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The responses of pine engravers,Ipspini(Say), in British Columbia to ipsdienol-baited traps containing low, medium, and high dose rates of the antiaggregants verbenone and ipsenol, released from impregnated polyethylene and polypropylene beads, respectively, remained significantly lower than responses to ipsdienol-baited control traps throughout the spring. During the summer, the responses remained low only in traps containing medium and high dose rates of impregnated beads. Antiaggregant treatment densities of 100 and 400 bubble cap release points per hectare reduced the numbers of pine engravers caught in ipsdienol-baited, multiple-funnel traps by 66.1 and 76.8%, respectively. In 50 × 50 m thinning-simulation plots treated with a broadcast distribution of antiaggregant-impregnated beads in 1990, 32.9% of the felled lodgepole pines,PinuscontortaDougl., were attacked; in untreated control plots, 53.1% were attacked. The mean attack density per square metre of available bark surface in the treated plots (1.3) was significantly lower than that in the untreated plots (1.9); however, where attack occurred there was no difference (8.8 and 9.4 attacks/m2, respectively). In a 1991 experiment, verbenone- and ipsenol-impregnated beads were applied to 15 × 15 m thinning-simulation plots at initial release rates of 2.5 mg of verbenone and 0.05 mg of ipsenol per square metre of ground surface per day, and at double these rates. For three treatments, low and high rates 3 weeks prior to the first attack byI.piniand a high rate 2 weeks prior to attack, the mean attacks per square metre of available bark surface per week were reduced by 77.1, 82.9, and 97.1%, respectively, compared with attacks on felled pines in untreated control plots. The results of these experiments suggest that a timely application of broadcast antiaggregants would prevent the development of an outbreak population ofI.pini.

ISSN:0045-5067    

DOI:10.1139/x94-318

出版商:NRC Research Press    

年代:1994

数据来源: NRC