Water relations and morphological development of bare-root jack pine and white spruce seedlings: seedling establishment on a boreal cut-over site

Bare-root jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) seedlings were planted on a boreal cut-over site and subsequent growth and seedling water relation patterns were monitored over the first growing season. Comparison of morphological development between white spruce and jack pine showed jack pine seedlings had greater new root development and a lower new shoot/new root ratio, while white spruce seedlings had greater new shoot development. Seasonal water relation patterns showed white spruce seedlings to have a greater decrease in xylem pressure potential (_x) per unit increase in transpirational flux density in comparison to jack pine seedlings. These results suggest that the greater resistance to water flow through the soil-plant-atmosphere continuum in white spruce seedlings compared to jack pine seedlings may be due to the relative lack of new root development in white spruce. Stomatal response of the seedlings showed that as absolute humidity deficit between the needles and air (AHD) increased, needle conductance (gwv) decreased in both species, but at low AHD levels white spruce had gwv approximately 35% higher than jack pine. For white spruce seedlings, gwv decreased as _x became more negative in a predictable curvilinear manner, while gwv of jack pine seedlings responded to _x with a threshold closure phenomenon at approximately - 1.75 MPa. Tissue water potential components for jack pine and white spruce seedlings at the beginning and end of the growing season showed jack pine to reach turgor loss at 76% relative water content while white spruce reached turgor loss at 88% relative water content. White spruce seedlings showed osmotic adjustment over the growing season, with an osmotic potential at turgor loss of - 1.27 MPa and - 1.92 MPa at the beginning and end of the growing season, respectively. Jack pine did not show any osmotic adjustment over the growing season. The implication of morphological development on water relation patterns are discussed with reference to successful seedling establishment.     

Morphological characteristics associated with tolerance to competition from herbaceous vegetation for seedlings of jack pine,black spruce,and white pine

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.     

Root characteristics and growth potential of container and bare-root seedlings of red oak (<Emphasis Type="Italic">Quercus rubra</Emphasis> L.) in Ontario,Canada

Root characteristics and field performance of container and bare-root seedlings of red oak (Quercus rubra L.) were compared during the first growing season after planting. Sixty seedlings of each stock type were planted on a clearfell and weed-free site near Restoule, Ontario. Twenty-four additional seedlings from each stock type were compared at the start of the study in terms of shoot and root parameters. Measurement of root and shoot parameters were repeated at three dates during the first growing season in the field. The root systems of container stock had a larger number of first order lateral long roots and were significantly more fibrous than bare-root stock. These differences were sustained throughout the first growing season. In terms of field performance, container seedlings had 100% survival and achieved significant increases in both biomass and shoot extension. Bare-root seedlings suffered 25% mortality, significant shoot dieback and more variable growth. The mean relative growth rate (RGR) of container seedlings increased throughout the study period to a maximum of 30 mg/g/day, whereas the mean RGR of bare-root stock remained close to or below zero. Overall, the container seedlings proved less prone to transplanting shock than the bare-root seedlings, most likely due to favourable root architecture and the pattern of root development. Further work may be warranted in container design, growing regimes and root architecture to fully realise the potential of container systems for the production of high quality red oak seedlings across a range of site conditions.     

Site preparation: Water relations and growth of newly planted jack pine and white spruce

Bareroot jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) were planted near Elliot Lake, Ontario, on a boreal reforestation site. Site preparation treatments were mixed, mineral and undisturbed (i.e., control) soil. Seedling water relations and growth were examined during the first field season. During the first 28 days after planting, jack pine base (i.e., predawn) and minimum xylem water potential readings were more negative in the control site preparation treatment. White spruce, during the first 10 days, in all site preparation treatments had base and minimum xylem water potential readings more negative than –1.7 MPa. By day 28 base xylem water potentials of white spruce had increased to approximately –1.0 MPa in all site preparation treatments. As the growing season progressed, white spruce minimum xylem water potential readings ceased exceeding the measured turgor loss point first in the mixed followed by the mineral and then control site preparation treatment. Jack pine minimum xylem water potential readings, in all site preparation treatments, almost never exceeded the measured turgor loss point. Water stress and stomatal optimization integrals, day 28 and 125, for both species showed least water stress and greater stomatal optimization in the mixed, mineral and control site preparation treatments, respectively. Both species had less new root growth in the field during the first 28 days after planting compared to seedlings grown for 28 days in a greenhouse for root growth capacity testing. Root growth at 28 days and both shoot and root development at the end of the growing season, were greatest to least in mixed, mineral, and control site preparation treatments, respectively.     

Planting stress in newly planted jack pine and white spruce. 2. Changes in tissue water potential components

Water relations of bare-root jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) planted in a greenhouse and on a boreal cut-over site were examined during the first growing season. In field-planted trees, maximum stomatal conductances (g(wv)) were initially low (< 0.10 cm s(-1)). Base and minimum xylem pressure potentials (Psi(x(base)) and Psi(x(min))) were less than -1.5 and -1.7 MPa for jack pine and -2.0 and -2.6 MPa for white spruce, respectively. During the growing season, maximum g(wv) increased in both species to around 0.2 cm s(-1). Base and minimum xylem pressure potentials also increased in both species to around -0.5 and -1.0 MPa in jack pine and -1.0 and -1.5 MPa in white spruce, respectively. Minimum xylem pressure potentials in white spruce fell below the turgor loss point during the first half of the growing season. Osmotic potential at the turgor loss point Psi(pi(TLP)) decreased after field planting to around -2.7 and -2.3 MPa in jack pine and white spruce, respectively. In the greenhouse, minimum values of Psi(pi(TLP)) were -2.2 and -2.3 MPa in jack pine and white spruce, respectively. Maximum bulk modulus of elasticity was greater in white spruce and underwent greater seasonal change than in jack pine. Relative water content (RWC) at turgor loss ranged between 71 and 74% in jack pine and 80 and 87% in white spruce. Available turgor (T(avail)), defined as the integral of turgor over the range of RWC between Psi(x(base)) and xylem pressure potential at the turgor loss point, was similar in jack pine and white spruce just after field planting. For the rest of the growing season, however, T(avail) in jack pine was two to three times that in white spruce. Diurnal turgor (T(diurnal)), defined as the integral of turgor over the range of RWC between Psi(x(base)) and Psi(x(min)), as a percent of T(avail) was higher in field-planted white spruce than jack pine until the end of the season. Dynamics of tissue water potential components are discussed in relation to plantation establishment.     

Effect of uninucleate Rhizoctonia on Scots pine and Norway spruce seedlings

One‐year‐old container‐grown seedlings were planted in spring on clear cut areas: the Norway spruce (Picea abies) on a moist upland site (Myrtillus‐type) and Scots pine (Pinus sylvestris) on a dryish upland site (Vaccinium‐type). While still in the nursery, half of the seedlings of each species had been inoculated during the previous summer, with a uninucleate Rhizoctonia sp., a root dieback fungus. At outplanting all the seedlings appeared healthy and had a normal apical bud, although the height of the inoculated seedlings was less than that of the uninoculated control seedlings. At the end of the first growing season after planting, the mortality of inoculated Scots pine and Norway spruce seedlings was 25 and 69%, respectively. After two growing seasons the mortality of inoculated seedlings had increased to 38% for Scots pine and 93% for Norway spruce. The mortality of control seedlings after two growing seasons in the forest was 2% for Scots pine and 13% for Norway spruce. After outplanting the annual growth of inoculated seedlings was poor compared with the growth of control seedlings. These results show that, although Rhizoctonia‐affected seedlings are alive and green in the nursery, the disease subsequently affects both their survival and growth in the forest.     

多重复干旱循环对北美短叶松和黑云杉苗木气体交换及水分利用效率的影响

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     

Effect of planting stocktype and cultivation treatment on the establishment of Norway spruce on cutaway peatlands

In order to determine the effect of stocktype and cultivation treatment on the field performance (survival and growth) and physiological status of Picea abies in cutaway peatlands, small bare-root, large bare-root and containerised seedlings were planted in a deep ploughed and a control site. Survival after 2 years was good across all treatment (>90%) except for the large bare-root seedlings growing in the control site (84%). For all the morphological characteristics assessed in this study, there was no significant interaction between stocktype and cultivation treatment indicating that the growth response to site cultivation was not stocktype dependent. After two growing seasons, all Norway spruce seedlings performed better in the deep ploughed site and displayed also better nutritional and physiological status. Regardless of cultivation treatment, mean height, diameter and volume increment were significantly smaller for the large bare-root seedlings while the small bare-root seedlings displayed the greatest growth rates. In order to promote early height growth in container and small bare-root stock, large diameter is important. Other initial characteristics such as foliar nitrogen content may also have a strong influence on first year field performance. The physiological status of the seedlings during the first year after outplanting was assessed using chlorophyll fluorescence (CF) measurements. CF measurements detected a higher level of stress for the large-bare root stock (low Fv/Fm). On the other hand, small bare-root stock displayed highest maximum potential photochemical activity which corresponded to greatest growth rates. Container seedlings demonstrated higher capacity for photosynthetic electron transport during the first five months after planting suggesting that they recovered from planting stress quicker and optimised better light interception and utilization than bare-root stock. It can be concluded that intensive management systems including deployment of best-adapted stocktype and site cultivation can be used to enhance early height growth of Norway spruce on cutaway peatlands.     

Effect of early transplanting upon growth and development of spruce and pine seedlings in paperpot containers

Black spruce (Picea mariana [Mill.] B.S.P.) and jack pine (Pinus banksiana Lamb.) seedlings were transplanted into Japanese paperpots at five different stages of development between the occurrence of an erect hypocotyl and 14 days after initiation of primary needles. Transplanting difficulty increased between the first and last treatments, and transplanting generally became impracticable after the stage of primary-needle initiation. Transplanting had a relatively minor effect on the eventual size of 12-week-old pine and 16-week-old spruce seedlings, although the incidence of root deformities inside the container increased rapidly as transplanting was delayed beyond the erect-hypocotyl stage. These deformities persisted after seedlings were outplanted, but did not appear to have a negative effect on the subsequent growth of new roots into the planting medium. Despite the absence of major adverse effects, it is recommended that transplanting be avoided as a routine practice for supplementing stocking in trays of containerized seedlings because of possible biological risks, the difficulty of ensuring careful transplanting and high labor costs.     

Root and shoot allometry of bareroot and container Douglas-fir seedlings

Detailed root and shoot development of bareroot and container Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling stocktypes were compared during the first growing season after outplanting. The study was installed in raised beds with ideal environmental conditions and at a field reforestation site. Survival at both sites was 98% and did not differ between stocktypes. Seedlings were excavated in spring (5, 8, 12, and 16 weeks after planting) and in fall (35, 40, and 45 weeks after planting). In spring, container seedlings had more numbers of new roots and greater new root and shoot biomass than bareroot seedlings at both sites. In fall, bareroot seedlings consistently averaged more new root growth (though nonsignificant) than container seedlings suggesting that stocktype differences may not continue long-term. Container seedlings had significantly greater water percent than bareroot seedlings at the field site (all sample dates) and the raised bed site (weeks 5, 8, and 40 only). Regardless of environmental conditions or season, seedlings at both sites maintained water percent between 60 and 70% of fresh weight. Seedlings grown in the raised beds had much greater growth than those grown in the field. However, relative growth patterns for the two stocktypes were very similar on each site. The data generated establish baseline differences between stocktypes for root initiation, growth, and allometry during the first year after planting. Challenges associated with root development research are discussed.     

Effects of soil temperature on biomass production and allocation in seedlings of four boreal tree species

One-year old seedlings of trembling aspen (Populus tremuloides Michx.), black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss), and jack pine (Pinus banksiana Lamb.) were subject to seven soil temperatures (5, 10, 15, 20, 25, 30 and 35 °C) for 4 months. All aspen seedlings, about 40% of jack pine, 20% of white spruce and black spruce survived the 35 °C treatment. The seedlings were harvested at the end of the fourth month to determine biomass and biomass allocation. It was found that soil temperature, species and interactions between soil temperature and species significantly affected root biomass, foliage biomass, stem biomass and total mass of the seedling. The relationship between biomass and soil temperature was modeled using third-order polynomials. The model showed that the optimum soil temperature for total biomass was 22.4, 19.4, 16.0 and 13.7 °C, respectively, for jack pine, aspen, black spruce and white spruce. The optimum soil temperature was higher for leaf than for root in jack pine, aspen and black spruce, but the trend was the opposite for white spruce. Among the species, aspen was the most sensitive to soil temperature: the maximum total biomass for aspen was about 7 times of the minimum value while the corresponding values were only 2.2, 2.4 and 2.3 times, respectively, for black spruce, jack pine and white spruce. Soil temperature did not significantly affect the shoot/root (S/R) ratio, root mass ratio (RMR), leaf mass ratio (LMR), or stem mass ratio (SMR) (P>0.05) with the exception of black spruce which had much higher S/R ratios at low (5 °C) and high (30 °C) soil temperatures. There were significant differences between species in all the above ratios (P<0.05). Aspen and white spruce had the smallest S/R ratio but highest RMR while black spruce had the highest S/R but lowest RMR. Jack pine had the highest LMR but lowest SMR while aspen had the smallest LMR but highest SMR. Both LMR and SMR were significantly higher for black spruce than for white spruce.     

Planting stress in newly planted jack pine and white spruce. 1. Factors influencing water uptake

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.     

Early root morphology of jack pine seedlings grown in different types of container

Abstract

This study compared the effects of container type on early root system morphology of jack pine (Pinus banksiana Lamb.) seedlings to determine impacts of container type on root characteristics that may be important for tree stability. Seedlings were grown for one season in Multipots®, Ventblocks®, Copperblocks®, Starpots® and Jiffy® pellets, and for a second season in sand culture in pots. After the first growing season, roots that had grown between Jiffy plugs were cut using a knife, either “early”, in September, or “late”, in November. Seedlings produced in non-pruning containers, Multipots and Ventblocks, had more vertical structural roots, less even root distribution and high shoot:root mass after a second season. Seedlings grown in pruning containers, Copperblocks, Starpots and Jiffy pellets, had more horizontal structural roots and more evenly distributed roots. Jiffy seedlings had high shoot:root mass after pruning, but ratios decreased to low levels similar to Starpots and Copperblocks after a second season in pots. Early pruning of Jiffy seedlings removed less root mass than late pruning, but total live root mass of early and late pruned seedlings was similar after the potting trial. Pruning containers thus produced structural root forms with more desirable characteristics for tree stability. These characteristics were evident after the first season and persisted after the second season in the potting trial.     

Parameterization and testing of a coupled photosynthesis-stomatal conductance model for boreal trees

A coupled photosynthesis-stomatal conductance model was parameterized and tested with branches of black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) trees growing in the Northern Study Area of the Boreal Ecosystem-Atmosphere Study (BOREAS) in Manitoba, Canada. Branch samples containing foliage of all age-classes were harvested from a lowland old black spruce (OBS) and an old jack pine (OJP) stand and the responses of photosynthesis (A(n)) and stomatal conductance (g(s)) to temperature, CO(2), light, and leaf-to-air vapor pressure difference (VPD) were determined under controlled laboratory conditions at the beginning, middle, and end of the growing season (Intensive Field Campaigns (IFC) 1, 2, and 3, respectively). The parameterized model was then tested against in situ field gas-exchange measurements in a young jack pine (YJP) and an upland black spruce (UBS) stand as well as in the OBS and OJP stands. Parameterization showed that Rubisco capacity (V(max)), apparent quantum yield (alpha') and Q(10) for sink limitation were the most crucial parameters for the photosynthesis sub-model and that V(max) varied among different measurement series in the laboratory. Verification of the model against the data used to parameterize it yielded correlation coefficients (r) of 0.97 and 0.93 for black spruce and jack pine, respectively, when IFC-specific parameters were used, and 0.77 and 0.87 when IFC-2 parameters were applied to all IFCs. For both measured and modeled g(s), the stomatal conductance sub-model, which linearly relates g(s) to (A(n)h(s))/c(s) (where h(s) and c(s) are relative humidity and CO(2) mole fraction at the leaf surface, respectively), had significantly steeper slopes and higher r values when only the VPD response data were used for parameterization than when all of the response data were used for parameterization. Testing the photosynthesis sub-model against upper canopy field data yielded poor results when laboratory estimates of V(max) were used. Use of the mean V(max) estimated for all upper canopy branches measured on a given day improved model performance for jack pine (from a nonsignificant correlation between measured and modeled A(n) to r = 0.45), but not for black spruce (r = 0.45 for both cases). However, when V(max) was estimated for each branch sample individually, the model accurately predicted the 23 to 137% diurnal variation in A(n) for all stands for both the upper and lower canopy. This was true both when all of the other parameters were IFC-specific (r = 0.93 and 0.92 for black spruce and jack pine, respectively) and when only mid-growing season (IFC-2) values were used (r = 0.92 for both species). Branch-specific V(max) estimates also permitted accurate prediction of field g(s) (r = 0.75 and 0.89 for black spruce and jack pine, respectively), although parameterization with all of the response data overestimated g(s) in the field, whereas parameterization with only the VPD response data provided unbiased predictions. Thus, after parameterization with the laboratory data, accurately modeling the range of A(n) and g(s) encountered in the field for both black spruce and jack pine was reduced to a single unknown parameter, V(max).     

Microbial Inoculants for Sustainable Forests

Abstract

Fungal root pathogens are widespread and may cause substantial seedling losses in conifer nurseries. Furthermore, poor seedling survival and growth on reforestation sites results in reduced forest regeneration. Use of microbial inoculants for disease control and plant growth promotion has become an important endeavour. A microbial culture collection of 500 strains was assessed for biological control of fungal root pathogens and/or plant growth promotion of conifer seedlings. Seven of these strains showed significant suppres-sive effects on various soil-bome fungal pathogens. On Douglas fir, two strains, RAL3 and 64-3, reduced disease caused by Fusariumby. 7-42% in repeated growth room assays. The same strains significantly increased healthy stand of white spruce seedlings inoculated with Fusariumand Pythiumin a conifer nursery, and increased the survival of bare-root white spruce seedlings planted on a reforestation site by 19-23%. Both strains also significantly increased new root and total plant dry weights. Strain RAL3 in commercial formulation maintained a viable population of about log 8-9 cfu/ml for over a year when stored at 5°C. Strain survival on seed varied with conifer species. No decreases in bacterial populations were observed on seeds of jack pine or Douglas fir after 37 to 44 days storage at 5°C, but decreases were observed on seeds of white spruce and Scots pine. This study has provided candidate beneficial microbial inocu-lants which offer promise for development of commercial inoculants for the forestry industry.     

Field survival of containerized red and jack pine seedlings inoculated with mycelial slurries of ectomycorrhizal fungi

Red pine and jack pine seedlings growing in styroblocks were inoculated 8 wk after sowing with mycelium/agar slurries of 3 mycorrhizal fungi (Laccaria bicolor, Scleroderma citrinum, and an unidentified basidiomycete), and one suspected mycorrhizal fungus (Cantharellula umbonata). Seedlings inoculated with L. bicolor developed mycorrhizae earlier and in greater numbers than the other inoculation treatments, with red pine out-performing jack pine in both respects. At 34 wk following sowing, seedlings were outplanted on a cleared xeric site in Baraga Co., in Michigan's Upper Peninsula. Seedlings inoculated with C. umbonata failed to form mycorrhizae and were not outplanted. Inoculation treatments did not affect shoot or root weight at outplanting. Red pine inoculated with L. bicolor averaged 21% and 19% greater survival compared with control seedlings after one and two years in the field, respectively. Other inoculation treatments failed to increase seedling survival for either tree species. Jack pine demonstrated higher overall survival than did red pine for both years in all corresponding inoculation treatments.     

Determining thresholds of low soil temperature for ecophysiological traits of black spruce and jack pine seedlings

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...     

Root growth capacity and field performance of Pinus sylvestris and Picea abies seedlings

Correlations between root growth capacity (RGC), at the time of planting, and field performance were studied for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings. Before planting a gradient in seedling viability was generated through exposure to low root temperatures and different winter storage regimes. The hypothesis that high RGC values would improve field performance was to some extent verified for pine seedlings while no correlations could be registered for spruce. Reasons for these results are discussed.     

Effects of root temperature on growth and photosynthesis in conifer seedlings during shoot elongation

Growth and gas exchange characteristics were studied in pine (Pinus sylvestris L.) and spruce (Picea abies Karst.) seedlings grown in hydroponic culture in the presence of N (50 mg l(-1)) and transferred at the start of their second growing season to tap water at 5, 8, 12, 16 or 20 degrees C (air temperature between 18-20 degrees C) for 3 weeks (pine) or 5 weeks (spruce). Root growth of both species was completely inhibited at root temperatures of 5 and 8 degrees C, but increased almost exponentially as root temperature increased. Shoot growth was maximal at 12 degrees C in both pine and spruce and decreased at low root temperatures. In both species, CO(2) uptake was decreased at low root temperatures and appeared to be influenced by the pattern of nitrogen retranslocation. In pine seedlings, as root temperature increased, an increasing proportion of the total nitrogen pool was retranslocated to the new shoot, whereas in spruce seedlings nitrogen was retranslocated to the roots. Differences in the retranslocation of nitrogen in the two species were reflected in the amount of soluble protein in needles, which at the end of the experiment increased with increasing root temperature in pine, but decreased in spruce. Our data suggest that in spruce, but not pine, CO(2) uptake was limited by the amount of Rubisco.     

Herbicides and planting date affect early performance of container-grown and bare-root loblolly pine seedlings in Alabama

The survival of bare-root and container-grown loblolly pine (Pinus taeda L.) seedlings exceeded 90% when outplanted in March at two sites in Lee County, Alabama. At both sites, soil moisture and seedling survival were greater in March than in May. A March herbicide application reduced weed biomass by 75–80% at both sites. At the moist site, herbicide application did not affect survival. However, at the drier site, a reduction in weed biomass increased both the percent soil moisture and the survival of May-planted bare-root seedlings. When soil moisture at planting time was less than 13% on a dry weight basis container-grown seedlings survived better than bare-root seedlings. At both sites, reduced weed competition resulted in greater seedling heights and diameters.Alabama Experiment Station Journal Series No. 9-85802.