Frost hardiness, bud phenology and growth of containerized Picea mariana seedlings grown at three nitrogen levels and three temperature regimes

We studied the influence of temperature and near- and sub- optimal mineral nutrition of black spruce seedlings (Picea mariana [Mill.] B.S.P.) during their second growing period on bud set, bud development, growth, mineral content and cold tolerance. Bud break and growth after bud break were also studied. Seedlings were grown for 106 d in growth chambers under three temperature regimes in combination with three concentrations of a fertilizer. They were then cold hardened for 56 d and dehardened for 66 d.Under these near- and sub-optimal N levels, bud formation occurred during the growing season. Bud formation was accelerated with decreasing fertilization, but was not affected by temperature treatments. Needles from seedlings with 0.64% N (dry mass basis) before hardening did not harden. Those with 0.87% N showed a lesser degree of hardiness than those with 1.28% N. Stem diameter increased at the beginning of the hardening period. During this acclimation period, shoot dry mass decreased with time at a constant rate and at the same rate over time for all treatments whereas root dry mass was more variable. Total number of needle primordia was low and no difference was observed among growing conditions. Bud break was similar in all treatments. Following bud break, shoot height and stem diameter increases were small but their magnitude varied with the nutritional regimes applied during the previous growing period. During hardening, nitrogen concentration of shoot tissues first increased and then decreased; phosphorus concentration first increased and then remained stable; potassium concentration remained stable. Concentration of these three elements generally decreased in the roots during this hardening.     

A two-step modification treatment of solid wood by bulk modification and surface treatment

A combination of bulk and surface modification of wood could lead to a product that shows the advantages of both treatments. This study evaluates the penetration of melamine resin into acetylated and silylated cell walls and possible side effects of melamine impregnation on this bulk treatment in order to clarify the feasibility of a combination of the chosen bulk modification (acetylation or silylation) and surface treatments (hardening by melamine modification). UV microscopy confirmed that melamine resin penetrates into wood cell walls even after acetylation and silylation treatment. Energy dispersive X-ray analysis showed that the melamine treatment did not lead to substantial washing out of silyl groups with the silylation reagent used. The possibility of a combination of the selected bulk and surface modification methods is given.     

Adaptation of the LIGNUM model for simulations of growth and light response in Jack pine

LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, that combines tree metabolism with a realistic spatial distribution of morphological parts. We hypothesize that its general concepts, which include the pipe model, functional balance, yearly carbon budget, and a set of architectural growth rules, are applicable to all trees. Adaptation of the model to Pinus banksiana, a widespread species of economic importance in North America, is demonstrated.

Conversion of the model to Jack pine entailed finding new values for 16 physiological and morphological parameters, and three growth functions. Calibration of the LIGNUM Jack pine model for open grown trees up to 15 years of age was achieved by matching crown appearance and structural parameters (height, foliage biomass, aboveground biomass) with those of real trees. A sensitivity study indicated that uncertainty in the photosynthesis and respiration parameters will primarily cause changes to the net annual carbon gain, which can be corrected through calibration of the growth rate. The effect of a decrease in light level on height, biomass, total tree branch length, and productivity were simulated and compared with field data. Additional studies yielded insight into branch pruning, carbon allocation patterns, crown structure, and carbon stress. We discuss the value of the LIGNUM model as a tool for understanding tree growth and survival dynamics in natural and managed forests.     

Combined effect of wood moisture content,drill bit rotational speed and feed rate on drilling resistance measurements in Norway spruce (Picea abies (L.) Karst.)

ABSTRACT

An IML-RESI PD 400 drilling tool and a standard spade drill bit (IML System GmbH, Wiesloch, Germany) were used to study the combined effect of wood moisture content (MC), drill bit rotational speed and feed rate on drilling resistance (DR) and feeding force (FF). Tests were made with Norway spruce (Picea abies (L.) Karst.) conditioned in a normal climate (20°C/65% RH), at 20°C/95% RH, vacuum-pressure impregnated in water, and oven-dried. Rotational speeds and feed rates had an impact on feed rate per cutting edge for the major cutting edge of the drill bit which was used for correlation with DR and FF for various MC. Impact of MC on DR and FF depended on rotational speeds and feed rates of the drill bit. For feed rates per cutting edge less than 0.09?mm, DR was higher for water saturated (WS) specimens. Negligible differences between DR for various MC were found for feed rates per cutting edge between 0.09 and 0.15?mm. DR was higher at low MC for feed rates per cutting edge which were higher than 0.15?mm. FF extremely increased in conditioned (20°C/95% RH) and WS specimens at feed rates per cutting edge less than 0.1?mm.     

Estimating “autotrophic” belowground respiration in spruce and beech forests: decreases following girdling

Seasonal fluxes of CO₂ from soil and the contribution of autotrophic (root + mycorrhizal) to total soil respiration (SR) were estimated for a mixed stand of European beech (Fagus sylvatica) and Norway spruce (Picea abies) in Central Europe. Mature trees of each species were girdled in August 2002 to eliminate carbohydrate allocation to roots. SR was measured at distances of 0.5, 1.0, and 1.5/2.0 m from the bole of each tree at 1–2 weeks intervals throughout the fall of 2002 and monthly during the spring and summer of 2003. The contribution of roots and mycorrhizae to total SR was estimated by the decrease in SR compared to ungirdled control trees to account for seasonal patterns evident in controls. SR decreased with soil temperature in the fall 2002 and increased again in 2003 as soil warmed. During most of the study period, SR was strongly related to soil temperature. During the dry summer of 2003, however, SR appeared to be uncoupled from temperature and was strongly related to soil water content (SWC). Mean rates of SR in beech and spruce control plots as well as root densities did not show a clear pattern with distance from the bole. SR decreased to levels below controls in beech within a few days after girdling, whereas spruce did not show a significant decrease until October 2002, 6 weeks after girdling. In both beech and spruce, decreased SR in response to girdling was greatest closest to the bole, possibly reflecting increased mycorrhizal activity close to the bole. Autotrophic respiration was estimated in beech to be as much as 50% of the total SR in the stand. The contribution of autotrophic respiration was less certain for spruce, although close to the bole, the autotrophic fraction may contribute to total SR as much as in beech. The large fraction of autotrophic respiration in total SR requires better understanding of tree level stresses that affect carbon allocation below ground.     

Constraints on light interception efficiency due to shoot architecture in broad-leaved Nothofagus species

Shoot architecture may significantly alter mean quantum flux on foliage and thus, photosynthetic productivity. There is currently only limited information about plastic alterations in shoot structure caused by within-canopy variation in mean integrated irradiance (Q(int)) in broad-leaved trees. We studied leaf and shoot structure, and nitrogen and carbon content in late-successional, widely distributed, temperate, broad-leaved Nothofagus taxa to determine the architectural controls on light harvesting and photosynthetic performance. Nothofagus fusca (Hook. f.) Oersted has larger leaves and less densely leaved shoots than the N. solandri varieties. Nothofagus solandri var. solandri (Hook. f.) Oersted is characterized by rounder leaves that potentially have a larger overlap than the ovate-triangular leaves of N. solandri var. cliffortioides (Hook. f.) Poole. Leaf dry mass (M(A)) and nitrogen content (N(A)) per unit area increased with increasing Q(int) in all species, demonstrating enhanced investment of photosynthetic biomass in high light. Although M(A) differed between species at a common irradiance, there was a uniform relationship between N(A) and Q(int) across species. Leaf carbon content per dry mass and leaf dry mass to fresh mass ratio also scaled positively with irradiance, suggesting greater structural investments in high light. In all species, shoots became more horizontal and flatter at lower Q(int), implying an enhanced use efficiency of direct irradiance in natural leaf positions. In contrast, irradiance effects on leaf aggregation varied among species. Across the data, leaf overlap or leaf area density was often greater at lower irradiances, possibly as a result of limited carbon availability for shoot axis extension growth. In N. fusca, leaves of which were more aggregated in high light, the shoot silhouette to total leaf area ratio (S(S)) declined strongly with increasing irradiance, demonstrating a lower light harvesting efficiency at high Q(int). This effect was only moderate in N. solandri var. cliffortioides and S(S) was independent of Q(int) in N. solandri var. solandri. Although the efficiency of light interception at high irradiances was lowest in N. fusca, this species had the greatest nitrogen content per unit shoot silhouette area (2N(A)/S(S)), indicating superior shoot-level photosynthetic potential. These data collectively demonstrate that shoot architecture significantly affects light interception and photosynthesis in broad-leaved trees, and that structural carbon limitations may constrain leaf light harvesting efficiency at low irradiance.     

Laser ablation-combustion-GC-IRMS--a new method for online analysis of intra-annual variation of delta13C in tree rings

We present a new, rapid method for high-resolution online determination of delta13C in tree rings, combining laser ablation (LA), combustion (C), gas chromatography (GC) and isotope ratio mass spectrometry (IRMS) (LA-C-GC-IRMS). Sample material was extracted every 6 min with a UV-laser from a tree core, leaving 40-microm-wide holes. Ablated wood dust was combusted to CO2 at 700 degrees C, separated from other gases on a GC column and injected into an isotope ratio mass spectrometer after removal of water vapor. The measurements were calibrated against an internal and an external standard. The tree core remained intact and could be used for subsequent dendrochronological and dendrochemical analyses. Cores from two Scots pine trees (Pinus sylvestris spp. sibirica Lebed.) from central Siberia were sampled. Inter- and intra-annual patterns of delta13C in whole-wood and lignin-extracted cores were indistinguishable apart from a constant offset, suggesting that lignin extraction is unnecessary for our method. Comparison with the conventional method (microtome slicing, elemental analysis and IRMS) indicated high accuracy of the LA-C-GC-IRMS measurements. Patterns of delta13C along three parallel ablation lines on the same core showed high congruence. A conservative estimate of the precision was +/- 0.24 per thousand. Isotopic patterns of the two Scots pine trees were broadly similar, indicating a signal related to the forest stand's climate history. The maximum variation in delta13C over 22 years was about 5 per thousand, ranging from -27 to -22.3 per thousand. The most obvious pattern was a sharp decline in delta13C during latewood formation and a rapid increase with spring early growth. We conclude that the LA-C-GC-IRMS method will be useful in elucidating short-term climate effects on the delta13C signal in tree rings.     

Anatomical and Morphometric Variations in the Arterial System of the Domestic Cat

We document the anatomical architecture and frequency of occurrence of variations in the branching pattern of the brachiocephalic artery and the origin of the internal iliac arteries in the domestic cat, a widely used model organism in both anatomical training and research. Based on the study of 56 preserved specimens, we observed three distinct arrangements in the branching pattern of the brachiocephalic artery. The most common pattern (52% of the examined specimens) was that in which the brachiocephalic artery was divided into two branches, the left common carotid artery and a common branch for the right subclavian artery and the right common carotid artery. The frequency of occurrence of each variation type was independent of the gender and body size. The internal iliac arteries originated caudal to the point at which the external iliac arteries branched off from the abdominal aorta. However, the portion of the abdominal aorta between the external and internal iliac arteries varied greatly in length and was not significantly correlated with its width, nor with body size or gender. This study is the first to report and quantify the occurrence of such variations in North American cats. Given the anatomical similarity between the cat and other felids, the results of this study can be applied to other species, including endangered species.     

Effects of sex and age on behavior and weight gain in beef calves after abrupt weaning

The effects of weaning on beef calves of different ages were investigated. Forty male and 40 female calves were either weaned at 6 (W6, n = 40) or 8 (W8, n = 40) months of age. The vocalization activity and behaviors (feeding, lying and standing/walking) were observed during the first 3 days following weaning. Body weight was recorded at 6 and 8 months and 2 weeks following weaning. W6 animals vocalized more often than W8 calves and females more than males on day 1 (P < 0.05). The vocalization activity decreased at a higher rate in W8 than in W6 from days 1 to 3. On day 2, W6 calves spent less time lying and more standing/walking than W8 calves (P < 0.05). The behaviors did not differ between males and females. The average daily gain after weaning did not differ between weaning ages (P > 0.05), but W8 calves gained more from 6 to 8 months of age. In conclusion, weaning distress was more pronounced in W6 than in W8 calves. W8 calves also had a superior growth performance during 6 to 8 months of age. The effect of the calves' sex was less pronounced. Therefore, it is recommended to wean beef calves later than 6 months of age.