摘要:

The rate of invasion and height growth of vegetation in logged-over areas were studied on four forest site types in the white spruce – alpine fir (Piceaglauca(Moench) Voss –Abieslasiocarpa(Hook.) Nutt.) forests north of Prince George, B.C. On Cornus–Moss, Aralia–Dryopteris, and Devil's Club site types, which generally had full stocking, vegetation that grew under the canopy of trees was replaced after logging by aggressive pioneer species. Annuals were the first to invade the logged-over area, followed by biennials and perennials. The invasion of shrubs was the slowest. After logging, 6 or 7 years elapsed before vegetation became a serious hindrance to regeneration and, by that time, white spruce seedlings planted immediately after logging were tall enough to withstand competition. On the Alluvium site type, where stocking is usually open and shrubs and grasses that thrive in the logged-over areas are present, spruce seedlings were overtopped during the first growing season and eliminated as the density of shrubs increased.

ISSN:0045-5067    

DOI:10.1139/x81-001

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

In small, dense and open-sided plantings of hybrid poplars, the edge effect extended through several rows, tree mortality increased and diameter at breast height (DHB), dry weight of individual trees, foliage weight, and leaf area index decreased from the border row to the center rows. Edge trees next to unplanted border trees tend to spread outward, thus intercepting solar radiation from a larger area than the area delineated by lower stems. When an oscillating irrigation system is used, the inner rows may receive only a fraction of the water border trees receive. This may be partly responsible for the extent of "edge effect" in this and similar studies. These irregularities could create serious problems in interpreting the results from small plantings. Some ways of reducing edge effect in production studies are proposed.

ISSN:0045-5067    

DOI:10.1139/x81-002

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Equations are given, based on data from 298 balsam fir and 88 white spruce trees in northwestern New Brunswick, for predicting ovendry weight of biomass for balsam fir and white spruce trees. Separate equations are given for each of nine components: stem wood, stem bark, total stem, branches, foliage, total crown, total aboveground weight, roots, and total tree. Independent variables used in the equations include diameter at breast height (dbh), height, crown width, crown length, and indices of basal area, crown area, and crown volume.

ISSN:0045-5067    

DOI:10.1139/x81-003

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Sample plots of five biogeoclimatic subzones of the British Columbia coastal forest were classified into forest types at 5-year intervals during 40 years. Matrices of transition probabilities from one forest type to another were calculated and stationary Markov models were built for each subzone. Simulation runs were tested against observations. The time and composition of steady state were predicted to evaluate the likelihood of the models. Succession and behaviour of forest types were discussed within and between subzones. It was concluded that forest succession was not Markovian for reasons that depended on the data set and on properties of stationary Markov models. The future of a forest type cannot be determined solely on the basis of its present state, and its prediction necessitates a sound knowledge of how the forest got there in the first place.

ISSN:0045-5067    

DOI:10.1139/x81-004

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A northern Vermont provenance test containing 1 Fraser fir (Abiesfraseri(Pursh) Poir.) and 21 balsam fir (Abiesbalsamea(L.) Mill.) provenances was attacked by the balsam twig aphid (MindarusabietinusKoch.) during 1977 and 1978. Balsam fir from eastern provenances had 15–60% greater incidence of attack and averaged nearly twice the crown injury than did that from western provenances. Trees from an Indian Lake, NY, provenance were injured most with an average of 27 and 62% of current-year shoots injured during the 1977 and 1978 infestations. Trees from an Isle, MN, provenance were injured least with an average of 2 and 9% of current year shoots injured during the 2 years. The relative distribution of injury among provenances was similar from year to year. Fraser fir suffered little or no injury and appears to avoid twig aphid attack when planted in the north because it begins growth after the aphid population has peaked. The concentration of β-phellandrene in twigs was strongly correlated with twig aphid injury in balsam fir, whereas height, date of budbreak, needle length, and concentrations of other monoterpenes were weakly or only indirectly correlated with twig aphid injury.

ISSN:0045-5067    

DOI:10.1139/x81-005

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The development of the pollination mechanism and the engulfment of pollen by the stigmatic tip is described for Douglas-fir (Pseudotsugamenziesii(Mirb.) Franco) based on scanning electron microscopy. This information is used to determine and explain the optimal time of pollination and amount of pollen needed for maximum seed set. After dormancy the integument tip of the ovule developed into an unequally two-lobed stigmatic tip covered with long unicellular hairs. Most ovules had fully developed stigmatic tips when the seed cone emerged from the bud scales in early April. The conelets remained open and the stigmatic tip was most receptive for at least 4 days. Pollen freely sifted down between the bracts and ovuliferous scales and adhered to the stigmatic hairs. Six days after the conelets became receptive, stigmatic hairs around the micropyle began to collapse and were ungulfed with the entangled pollen into the micropyle. Also, ovuliferous scales began to thicken, restricting movement of pollen to the stigmatic tips. By 8–10 days after conelets became receptive, the stigmatic tips were completely engulfed, the ovuliferous scales had thickened enough to close the conelet, and the conelet had begun to bend down.Maximum seed set occurred when (1) cones were pollinated within 4 days after seed-cone buds had emerged half of the way out of their bud scales; (2) a minimum of 0.2 g of pollen was used per pollination bag; (3) a minimum of 11 pollen grains adhered to each stigmatic tip; and (4) at least 3 pollen grains were taken into each micropylar canal. The engulfing process occurred at the same rate and in the same manner regardless of whether living or heat-killed pollen was present or absent on the stigmatic surface. Poor seed set as it related to the pollination mechanism is discussed.

ISSN:0045-5067    

DOI:10.1139/x81-006

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The addition of ureainvitroto the coarse humus of a jack pine nursery has led to an increased pH following urea hydrolysis, with the result that the cationic exchange capacity was increased while the organic matter in the humus was partly dissolved. Furthermore, considerable losses of nitrogen due to ammonia volatilization are likely to occur following the application of urea. The use of nitrate mineral fertilizers ((NH4)2SO4, NH4NO3, or (NO3)2Ca), though these are not subject to losses through ammonia volatilization, produces a significant displacement of soil elements. Moreover, the nitrogen in such fertilizers is more prone to leaching than mineral nitrogen freed by urea hydrolysis.

ISSN:0045-5067    

DOI:10.1139/x81-007

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Nine year diameter growth, height growth, survival, change in crown position, and quality responses of 7-year-old dominant and codominant (BetulaalleghaniensisBritton) seedlings to five intensities of cleaning near Marquette, Michigan are reported. The best compromise between survival, growth rate, and quality development without corrective pruning is to clean within a 2.4-m radius of selected crop trees. If corrective pruning is feasible, the 3.7-m cleaning radius treatment would be best because diameter growth is 30% greater.

ISSN:0045-5067    

DOI:10.1139/x81-008

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Seedlings of three birch species were exposed biweekly to 2358 μg/m3(0.9 ppm) SO2for 2 h from May to September 1977. Leaf sulfur content of the birch foliage increased following exposure to SO2, but sulfur accumulation was not correlated with visible injury. Relative susceptibility was significantly correlated with preexposure leaf conductance rates ofBetulanigraL. andB.papyriferaMarsh., but not forB.pubescensEhrh. Leaf conductance rates were not correlated with sulfur accumulation.

ISSN:0045-5067    

DOI:10.1139/x81-009

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

First-order branch characteristics that have a major influence on crown architecture were quantified for nine 4-year-oldPopulusclones grown at three spacings (0.3 m × 0.3 m,0.6 m × 0.6 m, 1.2 m × 1.2 m) under short-rotation, intensive culture (SRIC) in northern Wisconsin, U.S.A. The branch characteristics included the number, length, and diameter of branches and the angles of origin and termination. Clone and spacing had statistically significant effects on all branch characteristics, but the clone–spacing interaction was not significant for any branch characteristic. As spacing increased, the number, sum of lengths, and angle of origin of branches increased, but the angle of termination decreased. Branch length and branch diameter were highly correlated within all clones. The correlation between the angles of origin and termination within a clone was low when pooled over all spacings and height growth increments. The two clones with the lowest angle of origin also had the lowest angle of termination, and the clone with the highest angle of origin had the highest angle of termination. The clonal rankings for angles of origin and termination were not otherwise similar. The results indicate that development of a biologically meaningful variable for effective branch angle may be a complex task for SRICPopulus. However, individual clones are recommended for SRIC growth-spacing trials based upon branch angle and other crown architecture data presented.

ISSN:0045-5067    

DOI:10.1139/x81-010

出版商:NRC Research Press    

年代:1981

数据来源: NRC