Springtime resumption of photosynthesis in balsam fir (Abies balsamea)

Photosynthesis in balsam fir (Abies balsamea (L.) Mill.) was measured in the field at two locations in New Brunswick, Canada from late winter to late spring in 2004 and 2005. No photosynthesis was detectable while the soil remained below 0 degrees C throughout the rooting zone. In both years, photosynthesis began once soil temperature rose to 0 degrees C. In potted seedlings in growth chambers, there was no photosynthesis at an air temperature of 10 degrees C if the pots were frozen. These findings suggest that, once air temperatures permit photosynthesis, it is the availability of unfrozen soil water that triggers the onset of photosynthesis. In the field, full recovery of photosynthetic capacity following the onset of soil thaw was dependent on air temperature and took 5 weeks in 2005, but 10 weeks in 2004. There were two substantial frost events during the recovery period in 2004 that may explain the extended recovery period. In 2005, recovery was complete after the accumulation of 200 growing degree days above 0 degrees C after the start of soil thaw.     

Inter-tree and intra-tree variations in ring width and wood density components in balsam fir (Abies balsamea)

This study quantified and compared intra-tree and inter-tree variations in ring width and wood density components in balsam fir (Abies balsamea) grown in Quebec, Canada. In addition, the study examined correlations between ring width and wood density components at different stem positions from the stump level to the stem top. Ring width and wood density components of individual rings were measured by X-ray densitometry. Both the intra- and inter-tree variations in balsam fir are large, but the inter-tree variation is relatively smaller than the intra-tree variation. Much of the intra-tree variation is due to the radial variation, whereas the axial variation is much smaller. Compared to ring width and its components, wood density characteristics show a considerably smaller variation at both the inter- and intra-tree level. In almost all wood characteristics studied (except for latewood width), the intra- and inter-tree variations are more or less influenced by tree age. Cambial age explains more intra-tree variation in wood density components than ring width, whereas more intra-tree variation in ring width components is due to ring width. Cambial age and ring width explain a comparable percentage of variation in ring density. Only a few of the correlations between ring width and wood density components vary significantly with stem position from the stump to the stem top at the inter-tree level. In balsam fir, a negative correlation between ring density and ring width is significant in the butt log, but the correlation decreases to an insignificant level at and above a height of 3.0 m.     

Vulnerability of low temperature induced needle retention in balsam fir (Abies balsamea L.) to vapor pressure deficits

Low temperature (LT) exposure has been shown to delay postharvest needle abscission and senescence (NAS) in balsam fir and changes in vapor pressure deficit (VPD) are expected to alter these processes. Two and half year-old seedlings were exposed to a LT of 5°C for 15 days while the control (CT) group was maintained at 22°C. Seedlings were then exposed to four different VPD (0.22, 0.87, 1.3 and 1.86?kPa) and observed for relative water content (RWC), xylem pressure potential (XPP), membrane injury index (MII), stem capacitance (SC) and NAS. An interactive effect of LT and VPD was observed in RWC, XPP, MII and NAS. Low VPD (0.22 and 0.87?kPa) resulted in less negative XPP, lower electrolyte leakage, higher SC and ultimately higher NAS than those at high VPD. Maximum NAS was recorded at 0.22?kPa. At 1.86?kPa, LT had 5× lower RWC (13%), 3× more negative XPP (?1.1?MPa), 1.8× higher membrane damage and 35% lower NAS (47 days) than CT. The SC declined with an increase in VPD with no effect of LT. The XPP and RWC of LT seedlings showed a positive relationship with NAS with R² values of 0.54 and 0.59, respectively. LT offered no benefits to NAS at high VPD environments.     

Importance of needle age and shoot structure on canopy net photosynthesis of balsam fir (Abies balsamea): a spatially inexplicit modeling analysis

We have developed a spatially inexplicit model of canopy photosynthesis for balsam fir (Abies balsamea (L.) Mill.) that accounts for key processes of light-shoot interaction including irradiance interception by the shoot, spatial aggregation of shoots into branches and crowns, the differential propagation of diffuse and direct light within the canopy, and an ideal representation of penumbra. Also accounted for in the model are the effects of the average radiative climate and shoot age on needle retention, light interception, and photosynthetic capacity. We used reduced versions of this model to quantify the effects of simplifying canopy representation on modeled canopy net photosynthesis. Simplifications explored were the omission of direct beam transformation into penumbral light and the use of different constant shoot properties throughout the canopy. The model was parameterized for a relatively dense balsam fir stand (leaf area index of 5.8) north of Québec City, Canada, and run using hourly meteorological data obtained at the site. The overall performance of the complete model was satisfactory, with maximum values of canopy net photosynthesis of 23 micromol (m(2) ground)(-1) s(-1) (83 mmol m(-2) h(-1)), and a near-saturation of the canopy at a photosynthetically active radiation photon flux density of about 750 micromol m(-2) s(-1) (2.7 mol m(-2) h(-1)). The omission of penumbral effects through the use of unattenuated direct (beam) radiation at all layers of the canopy, as used for broad-leaved species, reduced canopy net photosynthesis by 3.7%. Analysis of the results show that the small impact of penumbra on canopy net photosynthesis stems from the high proportion of diffuse radiation (73%) estimated from our meteorological data set; single-hour results under clear sky conditions approach theoretical bias values of about 30%. Use of mean shoot photosynthetic, light capture and light transmission properties throughout the canopy biased canopy net photosynthesis by less than 3%. However, simulations carried out based on properties of 1-year-old shoots throughout the canopy overestimated canopy net photosynthesis by 9%. Use of the shoot as our smallest functional unit was a potential source of bias because the differential absorption of direct and diffuse radiation within the shoot could not be factored into the model. Other sources of potential bias are discussed.     

Effects of soil moisture manipulations on fine root dynamics in a mature balsam fir (Abies balsamea L. Mill.) forest

We tested the hypothesis that moisture stress affects fine root dynamics during and after the stress. To this end, we investigated the effects of soil moisture on annual and seasonal fine root production and mortality over 4 years in a mature balsam fir (Abies balsamea L. Mill.) stand using a minirhizotron and soil coring. Droughting and irrigating treatments were imposed for 17 weeks during the third year of the study, and post-treatment recovery was measured during the fourth year. Monthly fine root production was often reduced by low soil water content (SWC) during July-September in the pre-treatment years and by imposed drought. Irrigation resulted in higher summer fine root production than in pre-treatment years. In the recovery year, increased fine root production was observed in the previously droughted plots despite low SWC in August and September. Droughting decreased year-end fine root biomass in the treatment year, but biomass returned to pre-treatment levels during the recovery year. Droughting and irrigating did not affect foliage production during the treatment and recovery years. Our results suggest that for balsam fir, establishment and maintenance of a functional balance between foliage and fine root biomass, with respect to moisture supply and demand, can depend on fine root dynamics occurring over more than one growing season. In addition, our findings provided insights into tree growth responses to interannual variation in moisture supply.     

Plantlet regeneration through somatic embryogenesis in Nordmann's fir (Abies nordmanniana)

I studied the influence of various combinations of auxin and cytokinin concentrations, and the increased content of zinc and enzymatic casein hydrolizate in SH medium on initiation and proliferation of embryogenic callus of Abies nordmanniana(Steven) Spach. Additionally, the effect of ABA, PEG-4000 and different wavelengths on the maturation of somatic embryos was tested.The use of optimum composition of modified SH medium with BA, KIN and 2.4-D while simultaneously ensuring appropriate external conditions resulted in 15.5 % embryogenesis. Finally, satisfactory results of micropropagation of A. nordmanniana by somatic embryogenesis were obtained providing seven lines of embryogenic callus with high proliferation capacity. Those lines gave properly developed seedlings in white LED light with a wavelength of 400-700 nm, preceded by eight-week vernalization treatment of the callus. This paper may provide a protocol by which all stages of somatic embryogenesis of A. nordmanniana can be carried out, including the preceding 24-h seed disinfection with Na OCl and PVP, which resulted in 100 % frequency of uninfected zygotic embryos that were capable of starting embryogenesis.     

Allometry and partitioning of individual tree biomass and carbon of Abies nephrolepis Maxim in northeast China

Abies nephrolepis Maxim is an important commercial conifer species in northeastern China. In this study, we compared the partitioning and variations of biomass and carbon concentration for four tree components (i.e. stem, root, branch, and foliage). The results indicated that foliage had the largest carbon concentration, which was significantly different from other tree components. Above-ground biomass or carbon accounted for about 78% of the total tree biomass or carbon, whereas below-ground biomass or carbon corresponded to about 22%. The root-to-shoot ratio averaged .28 for biomass and .27 for carbon. We applied likelihood analysis to investigate the error structure of allometric relationship W?=?a·D^b and found that the multiplicative error structure was favored. Thus, the additive systems of biomass and carbon equations in a log-transformed scale were constructed using nonlinear seemly unrelated regression. The model fitting results showed that all biomass and carbon equations fitted the data well. Further, five approaches for calculating carbon stock of individual trees were evaluated and compared. The carbon allometric equations and the estimated biomass multiplied by weighted mean carbon concentration were more advantageous, whereas using the generic carbon concentration constants produced significant biases in estimating the carbon stock of individual trees.     

Ethylene production and premature senescence of needles from fir trees (Abies alba)

Measurements of ethylene production, free and conjugated ACC concentrations, chlorophyll content, and length of needles from fir trees (Abies alba Mill.) growing in stands affected by “Waldsterben” showed that during the development of the disease two consecutive stages can be distinguished: a. long-term, low ethylene production and accumulation of conjugated ACC (MACC) in response to chronic stress, associated with reduced needle growth, and b. high ethylene production associated with chlorophyll breakdown, followed by premature abscission of the needles.     

Factor in Abies balsamea Responsible for Coremia Formation of Ceratocystis piceae

Compounds are present in sapwood of Abies balsamea (L.) Mill., triggering the formation of coremia by Ceratocystis piceae (Münch) Bakshi. From several unsaturated fatty acids, linoleic acid is the most active coremia inducer.     

Ring-level models for predicting wood and fibre properties of Abies balsamea

Wood and fibre properties such as wood density, microfibril angle, and modulus of elasticity are industrially relevant factors in determining the mechanical properties of wood. Radial ring-level predictive models of these properties were developed using balsam fir data from a long-term trial in New Brunswick (Canada), where precommercial thinning was applied 8 years after the site was harvested. The mixed effects models developed accounted for most of the variability in wood density (68 %), microfibril angle (94 %), and modulus of elasticity (77 %) with low RMSE. This study shows that balsam fir wood and fibre properties are strongly related to distance from the pith, particularly in the first 20 mm, and much less to annual ring width. Disk height and selected weather variables related to air temperature during the growing season significantly improved the models, whereas the effect of precommercial thinning was not significant. These equations can be incorporated into computer models, such as Optitek, that simulate mill recovery and wood properties to obtain accurate information on wood products. The unexplained variation in these models is likely related in part to between-tree genetic variation, which is unknown in this study.     

Defence reactions of developing somatic embryos of Algerian fir (Abies numidica)

Defence reactions of embryonal suspensor mass (ESM), precotyledonary, cotyledonary and desiccated cotyledonary somatic embryos of Abies numidica were tested by dual cultures with Phaeolus schweinitzii. Defence reactions were expressed at a very early stage of somatic embryo development. Both ESM and early somatic embryos inhibited mycelial growth, but the strongest defence was shown by the precotyledonary somatic embryos. The cotyledonary and desiccated cotyledonary embryos also showed defence reactions but with less intensity. Eight major components of soluble proteins, already present in the ESM, increased in concentration during subsequent developmental stages. Synthesis of two low‐molecular components of 6 and 3 kDa appeared in desiccated embryos. Probable regulation of defence reactions by auxins in early somatic embryos, as well as by abscisic acid content and storage proteins in subsequent developmental stages, is discussed.     

Estimating cumulative defoliation of balsam fir from hemlock looper and balsam fir sawfly using aerial defoliation survey in western Newfoundland,Canada

Both hemlock looper (Lambdina fiscellaria fiscellaria (Guen.)) and balsam fir sawfly (Neodiprion abietis (Harris)) undergo periodic outbreaks in eastern Canada and cause significant growth and mortality losses to forests. Tree growth and mortality are closely related to cumulative defoliation estimates, which integrate annual defoliation over multiple years. Our objective was to determine a method to estimate cumulative defoliation of balsam fir (Abies balsamea [L.] Mill) due to these insects in western Newfoundland, using aerial defoliation survey data, as an essential input to modeling impacts for Decision Support Systems. Interpretation of aerial defoliation survey data for hemlock looper and balsam fir sawfly is problematic because both insects feed upon multiple age classes of foliage. Current-year (2008) aerial defoliation survey data were compared with ground estimates of defoliation by age class from 45 plots (450 trees and 395 mid-crown branch samples), representing a range of defoliation severity classes for each insect. Cumulative defoliation was calculated using defoliation per foliage age class, weighted by relative foliage mass for a given age of foliage. Three significantly different severity classes were defined based on cumulative defoliation values derived from aerial defoliation survey: (i) 1-year moderate (30–70%) defoliation, (ii) 1-year severe (71–100%) defoliation with calculated cumulative defoliation values of 19 and 39%, respectively, for balsam fir sawfly, 21 and 34% respectively for hemlock looper; and (iii) 2–3 years of moderate–severe defoliation, with cumulative defoliation ranging between 59 and 64% for balsam fir sawfly and 49% for hemlock looper. Defoliation severity from aerial defoliation survey alone hence can be misleading if defoliation measurements are not converted to cumulative defoliation values.     

Broom rusts of balsam fir and black spruce in Newfoundland

The broom rusts of balsam fir and black spruce occur sporadically throughout the island of Newfoundland, but they are not a serious threat to the forests. The incidence and intensity of the rusts vary, but no tree mortality can be attributed to the diseases. The average number of brooms per tree was higher in black spruce than in balsam fir. Also, more brooms occurred on brandies than on tree trunks. Height and diameter growth was less in infected trees than in uninfected trees of both the species.     

Certain seasonal changes in balsam fir cambium and its derivatives

Summary The seasonal cambial activity of balsam fir producing normal and compression wood was observed. Samples were taken throughout one growing season. Activity was initiated in normal wood with the precocious development of one sieve cell per file 2 weeks before activity was initiated in compression wood with the formation of one new sieve cell per file. Deactivation dates in normal and compression wood were the same.Dating of the phloem adjacent to normal wood can be carried out using crushed sieve cells or an annually formed band of tannin filled parenchyma whereas adjacent to compression wood, only crushed sieve cells can be used.The maximum cambial zone widths in normal and compression wood were 15 and 16 cells, respectively. The final xylem to phloem ratio in normal wood was 14:1 while in compression wood it was 21:1.Time required for development of tracheids was examined throughout the growing season. Growth trends for the radial growth and differentiation phases were studied in both normal and compression wood. Tracheid development in normal wood took between 14 and 33 days while in compression wood it varied between 5 and 49 days.Research financed under McIntire-Stennis Research Project 5009 and COE Projects R625-173 and R625-195     

An effect of gravity on bud-burst in balsam fir

Bud-burst on first order lateral branches of Abies bafsamea L. (balsam fir) was delayed when the branches were rotated 180 degrees about their long axis. This was not a consequence of injury caused by the treatment because buds rotated 180 degrees on inverted plants flushed at the same time as the controls, whereas flushing of all other buds was delayed. Buds thus appear to be more vigorous when maintained in the same orientation to gravity in which they are formed and the site of gravitational stimulus perception appears to be the bud itself. Except on the leading shoot, leaves from inverted buds turned so that their adaxial surface faced upward, unless there was intense illumination from below. However, both anisophylly and positioning of leaves on lateral shoots were apparently predetermined because the shorter, more forward pointing leaves appeared below the longer distichous leaves on shoots from inverted buds. Shoots with normally oriented leaves appeared the next season.     

Response of balsam fir and hemlock roots to injuries

Drill wounds in balsam fir and hemlock roots activated the nonspecific resistance mechanisms of compartmentalization in wood and necrophylactic periderm in bark. Tangential bands of resin ducts localized around the wounds constituted the barrier zones in the secondary xylem of conifer roots. Barrier zones were more extensive in roots which showed symptoms characteristic of invasion by fungi and bacteria after wounding. This observation supports an expanded definition of barrier zones; barrier zones may form not only in response to mechanical wounds but also in response to xylem injury caused by pathogens. Multiple bands of resin ducts were common in young xylem when bark lesions developed around wounds. Necrophylactic periderms isolared dead bark from living bark. Development of phellem cells with dark contents and thick suberized walls, typical of exophylactic periderm, followed initiation of necrophylactic periderm. The wound responses were similar in both balsam fir and hemlock.     

Ecology of Armillaria species on silver fir (Abies alba) in the Spanish Pyrenees

? We describe the distribution and the ecology of three Armillaria species observed in silver fir (Abies alba) forests of the Pyrenees.

? We surveyed the presence and abundance of Armillaria above and belowground in 29 stands. Isolates were identified by the PCR-RFLP pattern of the IGS-1 region of their ribosomal DNA. We measured several ecological and management parameters of each stand in order to describe Armillaria infected sites.

? Armillaria cepistipes was the most abundant of three species observed. Armillaria gallica was dominant in soils with a higher pH and at lower elevations. Armillaria ostoyae seemed to be more frequent in stands where A. alba recently increased its dominance relative to other forest tree species. Thinning activities correlated with an increased abundance of Armillaria belowground. In 83% of the stands the same Armillaria species was observed above and belowground.

? It seems that in a conifer forest, A. cepistipes can be more frequent than A. ostoyae, a virulent conifer pathogen. Since logging is related to a higher abundance of Armillaria in the soil, the particular Armillaria species present in a given stand could be considered an additional site factor when making management decisions.

     

Separation of eastern spruce and balsam fir by chemical methods

Summary Increased utilization of eastern spruce and balsam fir has led to a need for a quick method of separating these woods in a mill situation. One such method might be the use of a chemical indicator. A test of various classes of chemical agents applied at different seasons of the year showed that a pH indicator might be suitable for achieving a separation. The most suitable indicator was tested on samples from different geographic locations and at three highproduction stud mills. Additional tests were conducted to explore such variables as moisture content and surface condition of the wood, type of solvent, concentration and temperature. The most suitable indicator found was bromophenol blue at a concentration of 0.10 percent in 95 percent ethanol. When applied to green wood which had been allowed to dry for a few minutes to a few hours, this indicator produced various shades of orange, yellow, green or blue with spruce and a dark blue or blue-violet with fir. With an understanding of the variables that affect the reaction, it is felt that bromophenol blue can be used for the separation of eastern spruce and balsam fir on a commercial basis.The authors would like to thank fellow researchers in New York, Vermont, New Hampshire and New Brunswick, Canada, for providing samples for testing. Also, assistance from the following stud mills in Maine is greatly appreciated: Diamond International Corporation (Passadumkeag), Georgia-Pacific Corporation (Woodland) and St. Regis Paper Company (Costigan). This research was financed under McIntire-Stennis Research Project 5-5-39602.     

Effect of knife wear on finger-joint strength of silver fir (Abies alba) wood

Abstract

This study was carried out to determine the effect of knife wear, as measured in hours of use, on the finger-joint strength of silver fir wood (Abies alba), bonded with polyurethane (PU) and polyvinyl acetate (PVAc) adhesives. Wood samples were collected after 1, 32 and 64 h of knife wear. Results showed that as knife wear increased, bending strength or modulus of rupture (MOR) of the finger-jointed samples was reduced by 11.1% (PVAc) to 21.2% (PU) after 32 h of knife wear, and by 19.6% (PVAc) to 27.6% (PU) after 64 h of knife wear, whereas modulus of elasticity (MOE) of the finger-jointed samples was reduced by 10.5% (PVAc) to 12.5% (PU) after 32 h of knife wear, and by 11.7% (PVAc) to 10.0% (PU) after 64 h of knife wear. Tension strength of the finger-jointed samples was reduced by 2.1% (PVAc) to 1.5% (PU) after 32 h of knife wear, and by 5.4% (PVAc) to 16.0% (PU) after 64 h of knife wear.     

Provenance variation in Christmas tree characteristics in subalpine fir (Abies lasiocarpa) planted in Denmark and Iceland

A field test with 26 provenances of subalpine fir and corkbark fir was established at three sites in Denmark and one site in Iceland in 1999. Survival, growth and Christmas tree quality were assessed after 10 growing seasons in Denmark and 12 in Iceland. Provenances showed significant differences for all measured traits. The western-most subalpine fir provenances from Washington state and British Columbia showed the overall best results in Denmark with the highest survival (after 15 years), fastest growth in height and highest Christmas tree quality and profitability as well as both good postharvest needle retention and high resistance to pests. The corkbark fir provenances also showed high Christmas tree quality and the lowest frequency of fork formation, but corkbark fir provenances also exhibited the poorest postharvest needle retention. In Iceland, the corkbark fir provenances generally showed the highest survival rate and Christmas tree quality. The White River provenance from British Columbia is recommended for use in Denmark. The Mount Taylor provenance from the Cibola National Forest in New Mexico is recommended for use in Iceland.