摘要:

Biomass of fine roots (≤3 mm diameter) in a white spruce (Piceaglauca(Moench) Voss) plantation in Maine was estimated at 696 ± 224 g/m2or 3 kg per tree. Data consisted of 10 samples collected in midsummer from the top 45 cm of an imperfectly drained, silt loam, alluvial soil. Variation among individual samples was great, but appeared to be independent of distance to and size of closest tree. Results of this study compare favorably with published estimates of 2–3 kg per tree for other conifers in different parts of the world. The adequacy of this kind of study for understanding tree–soil relationships is discussed.

ISSN:0045-5067    

DOI:10.1139/x72-029

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Branches of young trees were sampled to determine length, width, thickness, and volume of 6-needle samples, both fresh and dry weights of 100-needle samples, and persistence of needles. Significant differences in needle size and weight were associated with position in crown, tree, year of formation, and species. Therefore special studies are required to document these differences and to determine, for example, influences of fertilizers on needles. Although average needle weights and their proportions of oven-dry weights can be estimated adequately for some studies of biomass and for simulation of forest fuels, sub-sampling for tree-to-tree differences should improve results obtained.

ISSN:0045-5067    

DOI:10.1139/x72-030

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The study tests whether the lethal effect of overwintering Engelmann spruce seed in its O-horizon affects Douglas-fir, lodgepole pine and subalpine fir seeds and whether the O-horizons of the three associated species have the same lethal effect on seeds. All seed treatments of each species were stratified in petri dishes in the pure O-horizon (unsterilized and autoclaved) of each species. Seed treatments were untreated, 10% slurry of 50% Captan and powdered 75% Captan.All untreated seeds demonstrated the lethal quality of unsterilized Engelmann spruce O-horizon. Its effects on untreated seeds and powder treated seeds were as follows: Engelmann spruce seed 3.5 and 77.3% (germination of untreated and powdered respectively), subalpine fir seed 1.3 and 20.8, Douglas-fir seed 9.5 and 84.8 and lodgepole pine seed 11.9 and 85.7. Subalpine fir O-horizon was lethal to its own seeds but only moderately harmful to seeds of other species. Douglas-fir O-horizon had a significant adverse effect on its own seeds and was only moderately harmful to seeds of other species. Lodgepole pine O-horizon was almost neutral to all seeds. Autoclaving of the O-horizons and powder treatment of seeds produced similar results.

ISSN:0045-5067    

DOI:10.1139/x72-031

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Studies were undertaken to determine if approximations of herbage productivity could be made from estimates of tree-crown cover, also whether or not estimates from aerial photographs would be accurate enough for this purpose. Results suggest that there is a sufficiently close relationship between herbage production and crown cover in coniferous stands to make the technique useful in range surveys. Estimation of herbage yields from the ground is too slow to be useful in surveys where large acreages have to be covered in a very short time. Similar results were obtained from ground estimates of crown canopy and those made from aerial photographs. Estimates of herbage yields on a pasture made as a result of the survey were almost identical to those established from an earlier grazing trial.

ISSN:0045-5067    

DOI:10.1139/x72-032

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The influence of light intensity on development of the first periderm and xylem in seedlings ofPinusresinosa,Fraxinuspennsylvanica, andRobiniapseudoacaciaup to 56 days after seed germination was studied. Dark-grown seedlings of all three species lacked periderm at the end of the experimental periods, emphasizing the essentiality of light for periderm development.P.resinosaseedlings grown for 56 days following germination at 70 ft-c (1 ft-c = 10.76 lm/m2) of light andR.pseudoacaciaseedlings grown at 70 or 300 ft-c of light for 30 days following germination failed to develop periderm. Seedlings ofF.pennsylvanicagrown at 70, 300, 600 or 1200 ft-c of light for 30 days following germination developed periderm. Periderm increments did not differ in 56-day-oldP.resinosaseedlings grown at 600 or 1200 ft-c or in 30-day-oldF.pennsylvanicaseedlings grown at 70 or 300 ft-c of light. Phellogen formed sooner and was more active in 30-day-oldR.pseudoacaciaseedlings grown at 1200 ft-c than in those grown at 600 ft-c. Time to periderm initiation decreased and phellem increment increased in 30-day-oldF.pennsylvanicaseedlings with each increase in light intensity from 300 to 1200 ft-c. Secondary xylem was absent in dark-grown seedlings of all three species and inP.resinosaandF.pennsylvanicaseedlings grown at 70 ft-c of light. In other treatments xylem increment increased significantly with each increase in light intensity up to 1200 ft-c.

ISSN:0045-5067    

DOI:10.1139/x72-033

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Effects of temperature over the range 10–30 °C were studied on first periderm and xylem development inFraxinuspennsylvanica,Robiniapseudoacacia, andAilanthusaltissima. Thirty-five days after germination, phellogen activity inF.pennsylvanicaseedlings increased significantly with each temperature increase except from 15 to 20 °C. Periderm was absent inA.altissimaseedlings grown for 35 days at 10 °C; phellogen activity increased with each temperature increase from 15 to 25 °C, then declined as temperature was raised from 25 to 30 °C. Phellogen activity ofR.pseudoacaciaseedlings could not be quantified because outer phellem cells often were crushed, but it depended on temperature in the same general way as inA.altissima. With each increase in temperature from 10 to 25 °C, xylem increments in 35-day-oldA.altissimaandR.pseudoacaciaseedlings increased significantly. As temperature was raised from 25 to 30 °C, xylem increments in these two species decreased significantly. In 35-day-oldF.pennsylvanicaseedlings, xylem increment increased significantly as temperature was raised from 10 to 15 °C and from 20 to 25 °C. Raising temperature from 15 to 20 °C did not increase xylem production, nor did raising temperature from 25 to 30 °C decrease xylem production. Optimum temperature for periderm development was not necessarily the same as that for xylem production and varied among species, indicating differences in physiological controls.

ISSN:0045-5067    

DOI:10.1139/x72-034

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

In germinating pine seedlings, acid soluble nucleotides, initially rich in AMP, accumulated, and were increasingly dominated by ATP. By 7 days, when hypocotyls were green but still dependent on the female gametophyte, the percentage of adenine nucleotides declined as other nucleotides increased. At 11 days, when gametophytic reserves were depleted, and seedlings were exposed to32P- phosphoric acid, adenine nucleotides accounted for over 70% of the recovery of32P from the nucleotide fraction.In seedlings, total RNA per unit weight increased to the 6th day, then levelled off. Comparison of electrophoretic mobilities of pine RNA on 2.5% polyacrylamide gels with ribosomal RNA from other sources revealed the following main types based on estimated molecular weights: 1.3, 1.1, 0.7, and 0.56 × 106daltons, corresponding to 25S, 23S, 18S, and 16S, respectively. On 10% polyacrylamide gels, the mobility of low molecular weight pine RNA was similar to that of yeast tRNA. The 1.3 and 0.7 × 106dalton fractions, representing ribosomal RNA, contributed 60–90% of the total RNA. During germination, the ratio of 1.3 to 0.7 × 106RNA dropped from 2.4 to 1.7 and reciprocated the pattern for water content of the seedling.32P was incorporated mainly into the 25S and 18S RNA by 11-day-old seedlings, indicating that synthesis of ribosomes was a major event in growing seedlings. During germination, the synthesis of RNA corresponded to an increase of total RNA detected cytochemically and to an increase of new cytoplasm with more ribosomes, as observed previously with hypocotyl cells by electron microscopic procedures.

ISSN:0045-5067    

DOI:10.1139/x72-035

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Norway spruce stems were artificially weakened by cutting a hole through them. The wood subsequently formed near the discontinuity was observed after six growing seasons following the cutting. Enhanced xylem development persisted in the zone of the discontinuity long after wounding and partial girdling stimuli could be considered to have an effect. This evidence supports the mechanistic hypothesis of stem-form development because mechanical stress level along the stem, originating from wind loading, would be greatest in the region of the discontinuity.

ISSN:0045-5067    

DOI:10.1139/x72-036

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Roots of Sitka spruce (Picea sitchensis) and western hemlock (Tsugaheterophylla) seedlings were side pruned in nursery beds at semimonthly intervals to produce dense and compact root systems. Root pruning early in the growing season stimulated the growth of existing roots and also initiated new roots. The densest root systems were produced by pruning before the end of June. However, because of the short length of lateral roots on seedlings early in their second growing season, pruning equidistant between rows 18 cm apart was ineffective. The best compromise appeared to be to prune spruce at the beginning of July, and hemlock around the middle of July. Earlier pruning equidistant between rows can be effective on larger seedlings during their third growing season. If early pruning is carried out on 2 + 0 seedlings, a pruning distance of about 6 cm from the row is recommended.

ISSN:0045-5067    

DOI:10.1139/x72-037

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

An average of 10% of the rootlets of nonmycorrhizal jack pine seedlings transplanted to four locations in the Canadian prairies became mycorrhizal after one growing season. When inoculated with a mixture of mycorrhizal root tips and forest humus, an average of 35% of the rootlets of seedlings transplanted to the same areas became mycorrhizal. In the greenhouse, mycorrhizae developed only on seedlings grown in soil from forested areas or in prairie soil inoculated with mycorrhizal root tips and forest humus. The addition of forest inoculum is required for satisfactory development of mycorrhizae during the early seedling stage in prairie soils, if regeneration is by direct seeding or if mycorrhization with forest fungi is not assured in the nursery.

ISSN:0045-5067    

DOI:10.1139/x72-038

出版商:NRC Research Press    

年代:1972

数据来源: NRC