摘要:

This study investigated the relationship between climatic variables and the abundance of red pine (PinusresinosaAit.). Two aspects of this climate–abundance relationship were addressed. First, a model was developed to fit the present day range and abundance of red pine using available climatic variables in the expectation of better understanding the processes controlling distribution. Second, general circulation models were used to explore the implications of a 2 × CO2(greenhouse warming) environment on the range and abundance of red pine. Using a response surface, growing degree-days (base 10 °C), and precipitation explained 54% of the variance in an independent data set of red pine volume per unit area. Possible explanations for the present day boundaries of red pine are competition for the southern limit, insufficient moisture for the southwestern limit, and insufficient warmth during the growing season at the northern limit. The greenhouse warming simulation suggested a dramatic northeastward shift of 600–800 km in the potential range of red pine and a decrease in total area, but it also suggested higher volumes per unit area.

ISSN:0045-5067    

DOI:10.1139/x94-154

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Forest managers need new approaches for maintaining high stand volumes while keeping forests continuously productive and economically profitable. The Silvicultural Management System (SMS) accomplishes these objectives by increasing large-sized trees for periodic harvest, and continuously maintaining stand volumes at their highest possible levels. This system takes advantage of the diversity in growth, vigor, and longevity of dominant trees from a wide range of tree species found in natural forest ecosystems. Under the SMS developed at the Tokyo University Forest in Hokkaido, 13–17% of the stand volume is harvested at a cutting cycle of 8–10 years by removing the oldest mature trees. Residual stand volumes are maintained at about 70–80% of the levels found in natural old-growth stands. This removal of the oldest trees keeps the stands in a continuously healthy and productive state. The cutting level is planned to ensure a sufficient harvest to cover the construction costs of a necessary high-density forest road network that provides the great logging efficiency and limited maximum yarding distances. This form of selection cutting has proven to be highly productive, surpassing even the production realized under clear cutting. Well-managed cuttings under SMS improve the quality and quantity of the timber resource, with particular emphasis upon premium-quality hardwoods. Guidelines are given for individual tree selection cutting to produce premium-quality hardwoods, and based upon a high-density forest road network. The value of this high-quality timber makes such low-volume logging operations profitable. The SMS also maintains a favorable forest ecosystem for diverse wildlife and flora, and several endangered or threatened wildlife species that depend upon less dense mature forests occur in SMS forests. Managed forests with high-volume stocking also serve as an effective carbon dioxide sink.

ISSN:0045-5067    

DOI:10.1139/x94-155

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Mean annual aboveground leafless biomass production averaged 14.8, 11.4, and 24.3 Mg•ha−1•year−1at harvest at 4 years of age forPopulustrichocarpaTorr. & Gray,PopulusdeltoidesMarsh., andP.trichocarpa × P.deltoideshybrids, respectively. These trees were planted at 1 × 1 m spacing on a medium- to coarse-textured alluvial soil in western Washington. Branches accounted for 13.2–20.3% of the aboveground weight. Total weight of stumps and coarse roots at harvest varied from 12.3 to 29.6 Mg•ha−1, or 22–33% of the weight of aboveground leafless biomass. Small and fine roots sampled to a depth of 3.17 m using soil cores amounted to an additional 6.6–11 Mg•ha−1of roots. Stumps and all roots as a ratio of aboveground biomass (root/shoot ratio) ranged from 0.34 to 0.42, with hybrids accounting for the entire range of values present. Mass of the fine roots (less than 0.5 mm diameter) ranged from 4.0 to 6.5 Mg•ha−1, or an average of 6.8% of the aboveground biomass. The smallest of the fine roots measured 0.06 mm in diameter. Specific root length of fine roots averaged 50.7 m•g−1forP.deltoides, 42 m•g−1forP.trichocarpa, and 30–47 m•g−1for hybrids. Total length of fine roots to a depth of 3.17 m ranged from 179 000 to 284 000 km•ha−1. Density of fine roots by length per unit soil volume was greatest at the surface with the range of means for clones in the top 0.18 m being 2.4–6.3 cm•cm−3; at 1.0–3.17 m soil depth, density was 0.02–0.6 cm•cm−3. For two of the hybrid clones, the density of fine roots at the soil surface was half that of the other clones. The distribution of fine roots in the stratified soil profile was correlated with soil depth, Kjeldahl N, and organic matter, with the latter two parameters showing the highest coefficients of determination (0.73 and 0.71, respectively). In the more sandy but layered subsoil (0.36–3.17 m depth), soil depth, Kjeldahl N, and sand content were most strongly correlated with fine root density, with depth and sand content giving the highest coefficients of determination (0.32 and 0.31, respectively). Roots in sandy subsoil were coarser and much less branched than in adjacent finer textured layers.

ISSN:0045-5067    

DOI:10.1139/x94-156

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The potential for use of a partial canopy for controlling growth ofCalamagrostiscanadensis(Michx.)•Beauv., andEpilobiumangustifoliumL. among regeneratingPiceaglauca(Moench) Voss saplings was assessed in the understory of 24 established stands in theP.glauca–Viburnum–Rubuspubescensassociation of the lower boreal cordilleran ecoregion of Alberta. Stand overstories were dominated byPopulustremuloidesMichx.,P.glauca, or were a mixture of these two species The composition, basal area, and light transmission of the overstory of each stand were measured. Hardwood-dominated overstories transmitted between 14 and 40% of incoming light whileP.glaucacanopies transmitted between 5 and 11 % of light. Cover and height ofC.canadensisandE.angustifoliumdecreased with decreasing light transmission; at 40% light, both species were greatly reduced compared with open-grown conditions and both were virtually eliminated from stands with less than 10% light. The annual height increment ofP.glaucasaplings increased from 5 cm at 10% light to 25 cm at 40 % light; the latter increment was approximately equal to growth in 100% light conditions. The number of buds, the diameter of the current leader, and the height to diameter ratio of the tree also increased with light transmittance.

ISSN:0045-5067    

DOI:10.1139/x94-157

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Productivity and nutrient-use efficiency were investigated in plantations of similar age of poplar clone D121 (PopulusdeltoidesMarsh.) that differed mainly in plant density. The plantations were located in the Tarai belt (low-lying area with high water table) of the Indian Central Himalaya. The total net primary productivity of the high-density plantation (4 years old with 666 trees/ha) was conspicuously higher (32.4 tones•ha−1•year−1) than that of the low-density (20 tonnes•ha−1•year−1) plantation (5 years old with 400 trees/ha), while nutrient-use efficiency was similar in these plantations. The net primary productivity/leaf nutrient ratios and percent nutrient retranslocation from senescing leaves were higher in the high-density than in the low-density plantations. In these young plantations leaf litterfall accounted for most of the litterfall (96–97%). The amount of nutrients that returned through litterfall to the soil was distinctly greater in the high-density plantation than in the low-density plantation. The greater nutrient return was due to first, the greater dry weight of litterfall and the lower proportional nutrient retranslocation from leaves during senescence in the high-density plantation. The high-density plantation also showed greater nutrient extraction efficiency from soil. Compared with aEucalyptustereticornisSm. plantation, and with natural forests of the study region, the nutrient use efficiency of poplar, regardless of its density, was lower.

ISSN:0045-5067    

DOI:10.1139/x94-158

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The behaviour of137Cs from the Chernobyl nuclear power plant accident in the Ukraine on 26 April 1986 was monitored during a 3-year period in the canopy of a young Scots pine (PinussylvestrisL.) stand in southern Finland. Needle samples were collected from the same whorls on 13 sample trees marked at the beginning of the study. The137Cs activity of throughfall water was determined in summer 1986. The oldest needles at the time of the radioactive deposition (formed in 1983) had the highestl37Cs activity (20 000 Bq/kg) in June 1986, when the monitoring was started, 58 days after deposition. About 50% lower137Cs activity was observed in the needles formed in 1984 and 1985, and an even lower activity of 3050 Bq/kg in the needles formed in 1986 following the incident. During the summer of 1986, the137Cs activity of the whole canopy decreased from 106 000 to 42 500 kBq/ha, corresponding to a weathering half-life of 72 days. Washout by throughfall accounted for 79% of the decrease, while the rest was mainly due to the gradual shedding of the highly contaminated 1983 needles. The needles formed in the summers of 1987 and 1988 had rather high137Cs activities of 2700 and 4800 Bq/kg, respectively. The reduction in the137Cs activity of the canopy was considerably less in 1987 and 1988, with weathering half-lives of 435 and 242 days, respectively. The total137Cs activity of the canopy was still 13 500 kBq/ha on 20 October 1988, which was 896 days after deposition. An increase in the137Cs activity was observed in the autumns 1987 and 1988, and to a lesser degree in the autumn of 1986, a time of year when needle potassium concentrations normally tend to increase. It was concluded that the Chernobyl137Cs had become mixed with the chemically analogous K, and was recirculated within the trees together with K.

ISSN:0045-5067    

DOI:10.1139/x94-159

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Woody vegetation was surveyed in 58 forest stands in northern Virginia to examine the effects of previous land-use history on past and present-day forest composition and dynamics. Stands were separated using detrended correspondence analysis (DCA) and overstory importance values into three forest groups: (i) white oak (QuercusalbaL.)–tulip-poplar (LiriodendrontulipiferaL.) (ii) white oak–scarlet oak (QuercuscoccineaMuenchh.) and (iii) Virginia pine (PinusvirginianaMill.) The first DCA axis represents a successional continuum from more recently disturbed areas containing young pine forests to less disturbed mature oak stands, and is negatively correlated with stand age and species diversity. White oak and red oak (QuercusrubraL.) dominated presettlement forests in the area. Following European settlement, forests experienced intense logging associated with the charcoal iron industry, large-scale clearing for agriculture, and subsequent land abandonment. By coupling radial growth analysis with age–diameter figures, we evaluated the responses of stands to disturbances associated with various land-use practices. This analysis indicated that many Virginia pine stands resulted from agricultural abandonment during the early 1900s, while a majority of oak stands experienced peak recruitment and radial growth following periodic logging disturbances in the 1800s. Canopy closure, forest protection, and reduced fire and logging disturbance this century led to increases in dogwood (CornusfloridaL.) and blackgum (NyssasylvaticaMarsh.) in area forests. The oldest stands exhibited a lack of tall oak regeneration; however, they also contained a scarcity of potential oak replacement species. Therefore, oak will seemingly share future dominance with several mixed-mesophytic species, although the exact successional status of these stands is unresolved.

ISSN:0045-5067    

DOI:10.1139/x94-160

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Genetic variation and covariation among traits of tree size and structure were assessed in an 18-year-old Douglas-fir (Pseudotsugamenziesiivar.menziesii(Mirb.) Franco) genetic test in the Coast Range of Oregon. Considerable genetic variation was found in size, biomass partitioning, and wood density, and genetic gains may be expected from selection and breeding of desirable genotypes. Estimates of heritability for partitioning traits, including harvest index, were particularly high. Foliage efficiency (stem increment per unit leaf area) was strongly correlated with harvest index and may represent an alternative measure of partitioning to the stem. Estimates of foliage efficiency where leaf area was estimated based on stem diameter or sapwood area were unrelated to foliage efficiency where leaf area was measured directly. Strong negative genetic correlations were found between harvest index and stem size, and between wood density and stem size. Achieving simultaneous genetic gain in stem size and either harvest index or wood density would be difficult.

ISSN:0045-5067    

DOI:10.1139/x94-161

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Genetic variation and covariation among traits of tree size and structure were assessed in an 18-year-old Douglas-fir (Pseudotsugamenziesiivar.menziesii(Mirb.) Franco) genetic test in the Coast Range of Oregon. Considerable genetic variation was found for relative crown width; stem increment per crown projection area; leaf area and branch weight relative to crown size; branch diameter and length adjusted for stem size; branch stoutness; cross-sectional area of branches per crown length; and needle size. Little genetic variation was found for branch numbers per whorl, branch angle, and specific leaf area. At both the phenotypic and genetic level, large trees growing well relative to growing space had tall, narrow crowns, high leaf areas per crown projection area or branch length, greater partitioning to leaves versus branches, and stouter branches. Thus, large, efficient trees were those that invested more in the photosynthetic machinery of leaf area and the branch biomass necessary to support that leaf area, but distributed that leaf area over a greater vertical distance. Unfortunately, these traits also were associated with increased branchiness, and selection for these traits would be accompanied by reductions in harvest index and wood quality.

ISSN:0045-5067    

DOI:10.1139/x94-162

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Clonal propagation by tissue culture of Afghan pine (PinuseldaricaMedw.) could be useful for improving Christmas tree production and afforestation of semiarid lands in North America. The objectives were (i) to develop organogenesis procedures for clonal propagation and (ii) to evaluate plantlet performance in the field. Shoot production from cotyledon explants was accomplished on solid Shenk and Hildebrandt medium amended with kinetin (11 μM) and benzyladenine (11 μM). Over 100 shoots per clone were obtained with this method. Spontaneous rooting was prevalent in some of the induced shoots. Shoots without root primordia were induced to form roots with naphthalene acetic acid (5 μM), indole butyric acid (10 μM), and benzyladenine (0.22 μM) in 1/2 strength Shenk and Hildebrandt medium. The rate of plantlet elongation in the field was similar to that of seedlings; however, survival of plantlets was lower than that of seedlings. The lower survival of plantlets was directly related to their smaller size at the time of planting. Organogenesis appears to be a very suitable method for mass micropropagation of this environmentally and economically useful tree.

ISSN:0045-5067    

DOI:10.1139/x94-163

出版商:NRC Research Press    

年代:1994

数据来源: NRC