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1.
本文研究了多重复干旱循环对１年生北美短叶松（ＰｉｎｕｓｂａｎｋｓｉａｎａＬａｍｂ．）和黑云杉（Ｐｉｃｅａｍａｒｉａｎａ［Ｍｉｌ］Ｂ．Ｓ．Ｄ．）苗木的气体交换速率及水分利用效率的影响。结果表面，多重干旱循环对它们的气体交换（Ｃｓ，Ｐｎ，Ｔｒ）有显著影响（Ｐ＜０．５），而对其水分利用效率（ＷＵＥ）影响不大（Ｐ＞０．１）。尽管北美短叶松的气孔对轻度干旱胁迫不如黑云杉敏感，但是它对中度及严重干旱胁迫的敏感程度却高于黑云杉。在轻度及中度干旱胁迫下，北美短叶松的光合作用主要受非气孔因素的影响，而黑云杉则主要受气孔因素的影响。解除干旱胁迫后，黑云杉的气孔敏感性、光合能力及水分利用效率的恢复都要比北美短叶松更快．我们认为，延迟脱水是北美短叶松的主要耐旱机理，而忍耐脱水则是黑云杉重要的耐旱途径。轻度的干旱胁迫锻炼可以帮助北美短叶松在更严重的干旱胁迫下保持固有而较强的耐旱能力。然而，通过多重复干旱循环锻炼后黑云杉在改善耐旱能力的强度方面则大于北美短叶松  相似文献   

2.
Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysiological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce (Picea mariana) and jack pine (Pinus banksiana) seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35°C soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), water use efficiency (WUE) and specific l...  相似文献   

3.
Tolerance of bareroot and container-grown seedlings of black spruce (Picea mariana (Mill.) B.S.P.), jack pine (Pinus banksiana Lamb.), and eastern white pine (Pinus strobus L.) to competition from herbaceous vegetation was examined in the first five years after planting on a site in the Great Lakes/St. Lawrence forest of Ontario, Canada. Shoot and root morphological characteristics of various stocktypes were measured before planting and correlated with 5-year survival and growth following control and no control of herbaceous vegetation. For black spruce and jack pine, medium-sized bareroot stocktypes had greater relative 5-year stem volume growth in the presence of herbaceous vegetation than did container stock of either species or large bareroot stock of spruce. Relative volume growth was measured as the ratio of the cumulative stem volume increment in the presence of vegetation (Veg) to that in the absence of vegetation (NoVeg), i.e., the Veg:NoVeg ratio. In white pine, the Veg:NoVeg ratio of volume increment of medium container and large bareroot stocktypes exceeded that of small container and medium bareroot stocktypes. In jack pine, root collar diameter at planting and number of first-order lateral roots were positively correlated with 5-year Veg:NoVeg ratio of volume increment. In white pine, the Veg:NoVeg ratio was also positively correlated with root collar diameter at planting and with root volume. In black spruce, the ratio was not related to pre-plant morphology. Thus, for white pine and jack pine, certain pre-plant morphological features may be useful in forecasting the relative ability of different stocktypes to grow under herbaceous competition conditions in the field.  相似文献   

4.
While aspen (Populus tremuloides Michx.) cover provides protection from growing season radiative frosts, reduced light levels can limit growth of understory white spruce (Picea glauca (Moench) Voss). The creation of openings around individual spruce can provide more light, but the chance of radiative frost damage increases as gaps become larger. We examined the relationship between opening size and light and temperature levels in the center of circular gaps created in young aspen stands ranging from 1.8 to 8 m tall. Models for predicting transmittance as a function of sky view factor and transmittance under intact stands are presented. Results indicated a strong relationship between light levels and opening size after considering pre-treatment light levels. The relationship between opening size and temperature was weak with minimum temperatures being more affected by the height and density of the surrounding stand than opening size.  相似文献   

5.
Height–diameter relationships based on stand characteristics (trees/ha, basal area, and dominant stand height) were investigated for balsam fir, balsam poplar, black spruce, jack pine, red pine, trembling aspen, white birch, and white spruce using data from permanent growth study plots in northern Ontario, Canada. Approximately half the data were used to estimate model parameters with the rest used for model evaluation. Multiple Chapman–Richards functions with parameters expressed in terms of various stand characteristics were fit to determine the best models for predicting height.  相似文献   

6.
Bareroot jack pine (Pinus banksiana Lamb.) seedlings (2 + 0) and bareroot white spruce (Picea glauca (Moench) Voss) transplants (1 1/2 + 1 1/2) were taken from cold storage and planted on a clearcut forest site in northeastern Ontario on several dates between May 6 and June 5 during which period soil temperature at 15 cm depth increased from 0 to 18 degrees C. Additional cold-stored trees were transferred to a greenhouse where they were grown in pots for 0, 7 or 28 days and then placed with their roots in aerated water maintained at one of a range of constant temperatures between 0 and 22 degrees C. In both species, daytime xylem pressure potentials (Psi(x)) and needle conductances (g(wv)) decreased with decreasing soil or water temperature. At all root temperatures, g(wv) was lower, and Psi(x) higher, in jack pine than in white spruce. After 28 days in the greenhouse, g(wv) of jack pine seedlings, and Psi(x) of white spruce, was higher than in plants just removed from cold storage. In both species, water-flow resistance through the soil-plant-atmosphere continuum (RSPAC) increased as root temperature decreased. At all root temperatures, RSPAC was higher in plants just removed from cold storage than in plants grown in the greenhouse for 28 days, during which time many new unsuberized roots were formed. At root temperatures above 10 degrees C, RSPAC of both species was higher in trees newly planted in mineral soil than in trees with roots in aerated water; presumably because the roots of planted trees had limited hydraulic contact with the soil. On the day following removal from cold storage, relative plant water flow resistance increased, in both species, more rapidly with declining root temperature than could be accounted for by the change with temperature in the viscosity of water, thus indicating an effect of temperature on root permeability. The same effect was evident in jack pine seedlings, but not white spruce transplants, that had been grown for 28 days in the greenhouse after removal from cold storage.  相似文献   

7.
We used field measurements and Monte Carlo simulations of canopy gap-size distribution and gap fraction to examine how beam radiation interacts with clumped boreal forest canopies of aspen (Populus tremuloides Michx.), black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.). We demonstrate that the Beer-Lambert law can be modified to accommodate transmission of radiation through a clumped forest canopy as a function of path length or sun zenith angle. Multiband Vegetation Imager (MVI) measurements and Monte Carlo simulations showed that values of the zenith element clumping index (Omega(e)(0)) are typically between 0.4 and 0.5 in jack pine and black spruce and 0.65 in aspen. Estimates of LAI obtained from MVI measurements of the canopy gap fraction and adjusted for canopy clumping and branch architecture yielded LAI values of 3.0 in jack pine, 3.3 in aspen, and about 6.0 in black spruce. These LAI estimates were within 10-25% of direct measurements made at the same sites. Data obtained with the MVI, along with numerical simulations, demonstrated that assumptions of random foliage distributions in boreal forests are invalid and could yield erroneous values of LAI measured by indirect techniques and false characterizations of atmosphere-biosphere interactions. Monte Carlo simulations were used to develop a general equation for beam radiation penetration as a function of zenith angle in clumped canopies. The essential measurements included stem spacing, crown diameter, crown depth, and within-crown gap fraction.  相似文献   

8.
Stem deformation has often been observed in young black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) plantations. Whenever important stem deformations are observed at the time of harvesting, timber value is negatively affected especially during the wood transformation process. The present work was undertaken to quantify and qualify the importance of stem deformation of black spruce and jack pine in the boreal forest of central Quebec at the stand and tree levels. In 30 black spruce and jack pine plantations, approximately 22% of spruce trees and 27% of pine trees exhibited stem deformation. The proportion of deformed trees was higher in the youngest plantations and decreased with the age of the plantations. Stem deformation caused the formation of compression wood which is another factor that can reduce the value of wood products. Thirty-nine black spruces and 34 jack pines were analysed at the tree level. On average, compression wood represented 14% and 20% of stem volume in 7- and 10-year old black spruce plantations, respectively. These proportions ranged from 18% in the youngest jack pine plantation to 26% in the oldest one. Stems of both species classified as normal contained a lower volume of compression wood than stems classified as deformed or very deformed. Annual percentages of compression wood and annual shoot length increased significantly with tree age (p < 0.0001 for both variables). Statistically significant correlations were also found between the range of displacement of the stem and the percentage of compression wood. The fewer number of trees with deformed stems in older plantations combined with high compression wood formation suggests that, over time, a deformed tree can become normal and straight in appearance.  相似文献   

9.
Cai T  Dang QL 《Tree physiology》2002,22(12):819-827
To examine the effects of soil temperature on a coupled photosynthesis-stomatal conductance model, seedlings of trembling aspen (Populus tremuloides Michx.), jack pine (Pinus banksiana Lamb.), black spruce (Picea Mariana (Mill.) B.S.P.) and white spruce (Picea glauca (Moench) Voss) were exposed to soil temperatures ranging from 5 to 35 degrees C for 4 months. Light and CO(2) response curves of foliar gas exchange were measured for model parameterization. The effects of soil temperature on four key model parameters, V(cmax) (maximum rate of carboxylation), J(max) (maximum rate of electron transport), alpha (energy conversion efficiency or quantum efficiency of electron transport) and R(d) (daytime dark respiration), were modeled using two third-order polynomial equations and a modified Arrhenius equation. In all species, V(cmax) and J(max) increased with soil temperature up to an optimum, and then decreased with further increases in soil temperature. In the conifers, alpha showed a similar response to soil temperature as V(cmax) and J(max), but soil temperature had no significant effect on alpha in aspen. Soil temperature had no significant effect on R(d) in any species. The three equations described the relationships between soil temperature and the model parameters reasonably well, but performed best for V(cmax) and worst for alpha. No significant relationships were identified between soil temperature and the parameters of the stomatal conductance model.  相似文献   

10.
Tree diversity is an important component of biodiversity. Management intensification is hypothesized to affect tree diversity. However, evidence to support the relationship between management intensity and tree diversity in northern forests is lacking. This study examined the effects of fertilization, site preparation, and brush control on tree species diversity, shade tolerance diversity and size diversity of jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana [Mill.] B.S.P.), white pine (Pinus strobus L.) and white spruce (Picea glauca [Moench] Voss) plantations, 15 years after planting in Ontario, Canada. Species diversity and shade tolerance diversity were highly correlated, so were diameter size diversity and height size diversity. Fertilization did not affect the tree diversity indices of any plantations. Species diversity and shade tolerance diversity was interactively influenced by site preparation and brush control in the black spruce, white pine, and white spruce plantations, showing that the highest diversity occurred on sites with intensive site preparation without brush control, whereas on sites with brush control, diversity was higher with least intensity of site preparation. However, in the jack pine plantation, neither species diversity nor shade tolerance diversity differed with management intensification, and is attributed to the fast capture of site resources by the planted crop trees of jack pine which minimized establishment of non-crop species. Tree size diversity increased with site preparation intensity in the jack pine and black spruce plantations, while it decreased with brush control in the white pine and white spruce plantations. We concluded that (1) the effects of management intensification on diversity of northern plantations differ with growth habit of planted crop tree species and (2) species diversity and tree size diversity tend to be highest at intermediate levels of silvicultural intensification during the stand establishment phase, supporting the intermediate disturbance hypothesis.  相似文献   

11.
The acquired thermotolerance of first-year seedlings of jack pine (Pinus banksiana Lamb.) hardened at 36, 38, 40 or 42 degrees C for 90, 180 or 360 minutes and of black spruce (Picea mariana (Mill.) B.S.P.) hardened at 34, 36, 38 or 40 degrees C for 30, 90, 180 or 360 minutes was determined by comparison of needle damage to that of non-hardened seedlings (25 degrees C) following exposure to temperatures of 49 and 47.5 degrees C, respectively. Compared to seedlings kept at 25 degrees C, heat injury sustained from exposure to high temperatures was markedly reduced following hardening for 180 minutes at 36 and 38 degrees C in jack pine and black spruce, respectively. Increasing the exposure time at 36 degrees C in jack pine, and at 36 to 40 degrees C in black spruce, also reduced needle damage. The duration of increased thermotolerance was investigated in jack pine, black spruce and white spruce (Picea glauca (Moench) Voss) by comparing heat injury from high temperatures in non-hardened seedlings and in seedlings hardened at 38 degrees C for 180 minutes a day for either 1, 3 or 6 days. In all three species, the duration of acquired thermotolerance increased with the number of days of heat hardening. For jack pine and white spruce seedlings hardened at 38 degrees C for 6 days, increased thermotolerance persisted for at least 14 and 10 days, respectively, after the end of the hardening treatment. In contrast, the thermotolerance of black spruce seedlings hardened at 38 degrees C for 6 days remained elevated for only 4 days.  相似文献   

12.
The aim of this study was to determine how soil chemistry and the distribution of fine roots (<1 mm) in the organic and upper mineral soil horizons were affected by an admixture of birch (Betula pendula Roth and B. pubescens Ehrh.) in Norway spruce (Picea abies (L.) Karst) stands. The surface organic horizons (LF and H) and mineral soil were characterized to a depth of 10 cm on three sites in southern and central Sweden. On these sites, replicated plots had been established that contained either ca. 30-year-old birch growing as a shelter over similar-aged spruce (mixed plots) or spruce only. The treatments had been created 8–11 years before this study was done. A fourth site, with plots containing ca. 90-year-old spruce or birch/spruce, and a fifth site, with 30-year-old spruce and a low admixture (12% by basal area) of birch, were also included in the study. Concentrations of Ca and Mg and pH in the LF layer were significantly higher in plots with a birch admixture. In the H-horizon, concentrations of K, Ca and Mg were significantly higher in mixed plots than in plots with pure spruce. Consequently, base saturation was higher in mixed plots than in pure spruce plots. A shelter of birch decreased the total amount of spruce fine roots (<1 mm), as revealed at one of the sites. Total fine root biomass (birch + spruce) in the organic and mineral soil horizons (to 10 cm) did not differ significantly between the pure spruce stands and the spruce stands with a birch shelter.  相似文献   

13.
North American jack pine (Pinus banksiana Lamb.) stands are generally characterized by an even-aged structure resulting from high intensity fires (HIF). However, non-lethal fires of moderate intensity (MIF), which leave behind surviving trees, have also been reported. The objectives of this study were two-fold: (1) assess the concurrent dynamics of live trees, understory vegetation and different types of coarse woody debris (CWD) during succession after HIF; and (2) document how MIF affects stand structure component dynamics compared to HIF. Stands affected by both HIF and MIF were selected. Tree characteristics and age structure, understory biomass, and CWD volume were assessed. Our results suggest that the structural succession of jack pine stands following HIF comprises three stages: young stands (<48 years), premature and mature stands (58–100 years) and old stands (>118 years). Canopy openness and jack pine density significantly decreased with time since HIF, while black spruce density and CWD volume significantly increased. The highest structural diversity was measured in the premature and mature stands. Compared to HIF, MIF increased mean jack pine basal area, decreased average stand density, delayed the replacement of jack pine by black spruce replacement in the canopy, decreased CWD volume, and significantly increased bryophytes mass. MIF increased the diversity of live trees and generally decreased CWD structural diversity. The study confirms the diversity of natural disturbance magnitude and successional processes thereby initiated. Thereafter, it appeared to be relevant for adjustment of disturbance emulating forest-management systems.  相似文献   

14.
A site index model based on the Weibull cumulative distribution function was fitted to three stem analysis data sets of black spruce (Picea mariana (Mill) BSP), white spruce (Picea glauca (Moench) Voss) and aspen (Populus tremuloides Michx.). The resulting equations were compared with those based on the modified Richards' (1959) biological growth function (Ek 1971; Payandeh 1977, 1978). The Weibull-type model performed as well as or better than the biological growth function for white spruce and aspen, respectively, but it performed less accurately in the case of black spruce. The Weibull-type model appears to behave better, i.e., it produces more realistic height growth patterns, than the Richards function upon extrapolation particularly at young ages.  相似文献   

15.
Between 1987 and 2000, a spruce beetle (Dendroctonus rufipennis) outbreak infested 1.19 million ha of spruce (Picea spp.) forests in Alaska, killing most of the large diameter trees. We evaluated whether these forests would recover to their pre-outbreak density, and determined the site conditions on which spruce germinated and survived following the spruce beetle outbreak in forests of the Anchor River watershed, Kenai Peninsula, Alaska. White spruce (Picea glauca) and Lutz's spruce (Picea × lutzii), a hybrid between white and Sitka spruce (Picea sitchensis), dominate the study area. We measured the pre- and post-outbreak density of spruce in 108 3 m × 80 m plots across the study area by recording all live trees and all dead trees >1.5 m tall in each plot. To determine the fine scale site conditions on which spruce germinated and survived, we measured ground surface and substrate characteristics within 20 cm circular plots around a subset of post-outbreak spruce seedlings. The density of post-outbreak spruce (855/ha) was adequate to restock the stands to their pre-outbreak densities (643/ha) for trees >1.5 m tall. We could not accurately estimate recovery for pre-outbreak spruce seedlings because dead seedlings may have decayed in the 5–18 years since the beetle outbreak occurred. At the fine scale, spruce that germinated post-outbreak grew on a wide variety of substrates including downed log, stump, mesic organic mat, peat, hummocks and mineral soil. They exhibited a strong preference for downed logs (53%) and stumps (4%), and most (91%) of the downed logs and stumps that spruce rooted on were heavily decayed. This preference for heavily decayed logs and stumps was especially evident given that their combined mean cover was only 2% in the 3 m × 80 m plots. Within the 3 m × 80 m plots, spruce seedling survival was negatively correlated with bluejoint (Calamagrostis canadensis) litter cover.  相似文献   

16.
Measures of forest productivity for various site conditions are necessary for forest management planning, where timber production is the objective. This study was undertaken to test whether autecological productivity relationships developed for lodgepole pine (Pinus contorta) and interior spruce (Picea engelmannii×P. glauca) using the biogeoclimatic ecosystem classification system of British Columbia are useful as practical field-based procedures to predict site index. Independent data sets consisting of 111 plots for pine and 114 plots for spruce were collected for use in testing the bias and precision of the models. A regression on residuals (predicted minus test values) indicated that the lodgepole pine model was unbiased in estimating site index (p=0.08). However, there was a lack of precision, with a square root of the mean squared prediction error (root-MSPR) of 2.8 m. Only 56% of the test plots had differences from the predicted values of 2.0 m or less. Residual analysis showed that the interior spruce model was biased in estimating site index (p<0.01), generally predicting greater site index than the test values. The model also lacked precision, with a root-MSPR of 3.2 m. Only 44% of the test plots had differences from the predicted values of 2.0 m or less. Forest managers requiring a site-index prediction tool need to decide whether the degree of accuracy precision provided by these models is acceptable.  相似文献   

17.
Stem form is often used as a sawlog assortment criterion and has an important effect on lumber recovery and mechanical properties. Based on 7018 stems collected from the natural stands in 3 regions in eastern Canada, this study quantified the variations in stem form (taper, sweep and eccentricity) for five major commercial softwood species, viz., jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana), white spruce (Picea glauca), red spruce (Picea rubens) and balsam fir (Abies balsamea). The majority of the stems had a diameter at breast height (DBH) ranging from 10 to 32 cm and total tree height from 10 to 20 m. Stem taper and butt taper increased steadily from 0.38 to 1.75 cm/m and from 0.74 to 4.23 cm/m, respectively, with DBH increasing from 8 to 48 cm. Stem sweep and basal sweep ranged from 0.12 to 7.28 cm/m and from 0.12 to 9.85 cm/m, respectively, with mean values of 0.87 and 0.95 cm/m. There were no significant differences in stem sweep and basal sweep between DBH classes and both sweeps distributed over a wide range within DBH classes, species and regions. About 0.77% of the stems and 1.2% of the butt logs had seriously curved shapes (sweep >3.0 cm/m). Eccentricity (ratio of smaller diameter to larger diameter) at the breast height (0.96) was very close to 1. Balsam fir and jack pine had the best and worst stem forms, respectively, while stem forms in black spruce were in-between. Butt logs were most seriously curved in red spruce and most tapered in white spruce. Region C (mainly eastern Quebec and the Atlantic Provinces) produced stems with smaller butt taper, basal sweep and stem sweep and larger eccentricity compared with other regions in eastern Canada. Overall stems in eastern Canada have a good stem form in terms of taper, sweep and eccentricity. The evaluation of stem form provides valuable timber quality information for the wood industry to optimize wood processing as well as for forest managers to define appropriate silvicultural regimes to improve stem form and economic value.  相似文献   

18.
The effect of seed water content (WC) (2–3, 5–6 and 22–25%, on a fresh weight basis), storage temperature (+4, −20, −80 and −196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2–3% and 5–6% WC declined after 48 months of storage at −80 and −196°C, with a further decline at 60 months at −20, −80, −196°C. Germination remained high when control white spruce seeds and seeds with 2–3, 5–6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2–3% and 5–6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22–25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, −20 and −80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at −20 and −196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22–25% WC, where MGT increased for white spruce seed stored 48 months at −80 and −196°C, and for black spruce seed stored 24 months at +4 and −80°C and 60 months at −196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, −20, −80, and −196°C for black spruce and lodgepole pine, and 2–6% water content is optimal for all 3 species at these temperatures.  相似文献   

19.

Whole root systems of 2-yr-old containerized white spruce [Picea glauca (Moench) Voss], black spruce [Picea mariana (Mill.) B.S.P.] and jack pine (Pinus banksiana Lamb.) seedlings, with intact root plugs, were exposed to various frost temperatures, which a preliminary test indicated would induce approximately 0 (control), 20, 40, 60, 80 and nearly 100% frost damage. Damage to root systems was evaluated using: (1) two measures of electrolyte leakage (relative conductivity and total tissue leakage after autoclaving); (2) water loss after pressurization; (3) chlorophyll fluorescence (Fv/Fm, maximal PSII photochemical efficiency) measured 4, 21 and 30 days after the beginning of seedling regrowth and (4) live root dry mass measured 21 days after the artificial frost and 60 days after the beginning of regrowth. Seedling survival and growth after the artificial frost were evaluated using live root dry mass measured after 60 days of regrowth and new shoot length, stem diameter, and root and shoot dry mass. Live root dry mass, dead tissue leakage, jack pine root water loss and fluorescence measurements were all significantly correlated with one or more of the growth variables and the number of significant correlations varied with species. Dead tissue leakage measurements appear to be the most promising method for evaluating root damage to 2-yr-old well-developed root systems of these species.  相似文献   

20.
The number of fertile and infertile scales, filled and empty seeds, cone volume, seed efficiency and the incidence of insect and disease damage to seed were evaluated for seven jack pine (Pinus banksiana Lamb) and six black spruce (Picea mariana [Mill.] B.S.P.) seedling seed orchards in northern Ontario, Canada. On average, the seed potential of jack pine and black spruce cones was 50 and 82 seeds, respectively. Cone volume and the number of fertile scales were under strong genetic control and well correlated with one another for both species. Seed efficiency values were high for jack pine (60%) but poor for black spruce (24%). The incidence of seed insect damage was less than 2.5% for both species and nil for seed diseases.  相似文献   

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