摘要:

The rate of upward advance and intensification of dwarf mistletoe on immature coastal western hemlock were determined by reconstructing the infection history of individual trees from data on age, height above ground, and sex of mistletoe infections present at the time of observation. The vertical rate of spread was 30 ± 4 cm/year in a dense stand (750 trees per hectare, 19 m in height) and 65 ± 4 cm/year in an open stand (250 trees per hectare, 26 m in height). This compares with height growth of the trees of 33 and 58 cm/year in the two stands, respectively. The number of new infections per year increased logarithmically with time, doubling roughly every 4 years. An asymtotic stabilization of the rate of intensification over the last 6 years probably reflects crown closure. The results suggest that dwarf mistletoe may not be a serious threat to thrifty, immature, dense, coastal hemlock stands in southern British Columbia, unless such stands are overtopped by infected residual trees.

ISSN:0045-5067    

DOI:10.1139/x72-049

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Cone production increases of 2.5, 5.0 and 1.5 times that of control were obtained the year following treatment with 400 lb nitrate nitrogen per acre (1 lb/acre = 1.12 kg/ha), applied 6 weeks before vegetative bud break, at the start of bud break, and 10 days after the midpoint of the bud break period, respectively, on 20-year-old Douglas fir (Pseudotsugamenziesii(Mirb.) Franco.). Cone counts of 15, 26, 72, 142 and 155 were obtained from 0, 200, 400, 800 and 1600 lb nitrate nitrogen per acre, applied to 13-year-old trees during early bud break. Ammonium nitrogen, applied at the same rates and times, was ineffective for stimulation of cone production on either age of tree. There were no differences in rate of accumulation of total nitrogen in buds and foliage, shoot-growth responses, or total number of buds per shoot due to form of nitrogen. Nitrate treatment enhanced cone production through a reduction in bud failure during the shoot elongation period. These results suggest responses are not primarily due to improved mineral nutrition, but to a specific chemical stimulation from critically timed changes in type of nitrogen metabolism. Possible influences of temperature and rainfall on natural cone crop periodicity and on proper timing of nitrate treatment are discussed.

ISSN:0045-5067    

DOI:10.1139/x72-050

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Twenty-year-old Douglas fir (Pseudotsugamenziesii(Mirb.) Franco.) were treated in May with 0, 50, 100, 200,400, 800 and 1600 lb nitrogen per acre (1 lb/acre = 1.12 kg/ha) as ammonium nitrate. In 5 subsequent years, cone production with annual and biennial retreatment at one rate was compared with no retreatment. Heavy rainfall after the initial fertilization appeared responsible for small, similar cone-production responses the next year from the 100–1600 lb rates. Retreatment at 400 lb increased cone production of the third year but overfertilization occurred in combination with the higher initial rates. Initial overfertilization or annual refertilization reduced long-term responses. Responses were greatest when dry conditions followed treatment. It was concluded that 400 lb nitrate nitrogen per acre at the start of vegetative bud break, applied biennially to alternate halves of an area, would provide optimum long-term cone production.Stem growth benefited from increasing foliar nitrogen levels up to about 2%, obtained with 200–400 lb nitrogen per acre, and was adversely affected by foliar nitrogen above 3%. Response to fertilization consisted of: (1) direct effects of improved nitrogen status lasting about 2 years, (2) accumulative increases in leaf area favoring shoot and stem responses up to the 4th or 5th year, and (3) continued stem-area increases due to growth over the greater circumference resulting from factors 1 and 2. Over the full duration of effect in young stands, the optimum economic treatment for increased wood production may correspond closely to the 400 lb nitrogen per acre which provided near-optimum physiological responses. The 200 and 400 lb rates increased 5-year stem-volume increment by 62 and 90%.

ISSN:0045-5067    

DOI:10.1139/x72-051

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The North Carolina State University – Industry Cooperative Tree Improvement Program has followed two major lines of development: (1) Production seed orchards to supply large quantities of genetically improved stock, (2) research clone banks to be used as a gene pool for advanced-generation seed orchards.Results from current progeny tests reveal the occurrence of parent trees with strong general combining ability and occasional outstanding specific combinations. Thus, many of the best trees selected from open-pollinated or pollen-mix progenies would be half-sibs or full sibs. It is, therefore, essential that the parentage of trees used in advanced-generation orchards be known if the presumed detrimental effects of inbreeding are to be avoided. A conscious effort must be continuously made to maintain a broad genetic base for advanced-generation breeding populations.Where the cost of testing in terms of time and money is critical it is important to use a progeny-testing scheme that: (1) gives an assessment of parental breeding value, and (2) provides unrelated families of known parentage from which selections for advanced-generation orchards can be effectively made. The tester design satisfies these criteria for organizations having several orchards, each with different testers, so that material can be freely exchanged for future generations. A suggested alternative for organizations with limited resources or specialty orchards is a partial diallel design.

ISSN:0045-5067    

DOI:10.1139/x72-052

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Studies of forage yield, standing stock of browse, and utilization of browse by moose (AlcesalcesamericanaClinton), deer (OdocoileusvirginianusborealisMiller), and hares (LepusamericanusstruthopusBangs) were made on commercially cut forest areas of five age classes in New Brunswick. The 6-year old cuts yielded most forage, while the 10–12-year old cuts had the greatest standing stock. Older cuts produced less forage and had smaller standing stock. Moose and white-tailed deer fed most heavily on the 2-year old cuts; hares on the 15–18-year old cuts, probably because more suitable shelter was available. The three browsers shared a preference for some species but the total weights they ate were small compared to the amounts available.

ISSN:0045-5067    

DOI:10.1139/x72-053

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Calculations are presented on the quantities of N, P, K, Mg and Ca in the soil and above-ground portions of two spruce-pulpwood stands on sites of average fertility in northern and southern Quebec. The magnitude of the depletions of these nutrients from the site, in full-tree and tree-length methods of logging, are compared with the available and total quantities of them in the soil. The ranges of values, from the literature, for the input of these nutrients in dust and precipitation, and the losses in leaching, are presented and discussed in relation to the logging losses.It is concluded that on both sites it is unlikely that full-tree logging will result in any reduction in growth, due to nutrient removal, during the second rotation of trees. However, nutrient depletion due to full-tree logging, particularly with respect to Ca, K and N, may require correction by means of fertilizers in forest ecosystems of marginal fertility. These are usually either dry sites with low reserves of organic matter and low exchange capacity or wet sites with excessive accumulations of organic matter. The need for further detailed studies of the nutrient cycle in different forest ecosystems is stressed.

ISSN:0045-5067    

DOI:10.1139/x72-054

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Reproductive buds were initiated concurrently with the development of roots on cuttings of western hemlock (Tsugaheterophylla) set in a rooting bed. The ovulate cones were pollinated the following spring and cones from most cuttings produced viable seeds. The subsequent growth of the seedlings was good.

ISSN:0045-5067    

DOI:10.1139/x72-055

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A general method to convert taper and volume equations from one unit system to another is explained. Four examples are added.

ISSN:0045-5067    

DOI:10.1139/x72-056

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A photo-electric device suitable for determining projected area of up to 60 Douglas fir needles at a time is described. Arrangement of the light source, lens, and selenium cell, and the method of operation, were designed to take into account seven points considered important for satisfactory measurements.

ISSN:0045-5067    

DOI:10.1139/x72-057

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Western hemlock, Douglas-fir and lodgepole pine were grown on three different sources of nitrogen. At 18 weeks the relationship between leaf area and leaf dry weight was determined for each species. A linear relationship was found between leaf area and leaf dry weight for all three species. Different nitrogen treatments had no effect on this relationship.

ISSN:0045-5067    

DOI:10.1139/x72-058

出版商:NRC Research Press    

年代:1972

数据来源: NRC