Effects of winter buds on winter nitrogen uptake and allocation in Pinus densiflora saplings

Studies of nitrogen (N) use by plants have confirmed some winter N uptake; however, the mode of regulation of plant N use in winter is unknown. The regulation of N use by plants during winter may differ from that in the growing season, as plant growth strongly affects N use. We investigated the effects of winter buds on winter N use by Japanese red pine (Pinus densiflora), as a previous study demonstrated that N absorbed during winter contributes significantly to leaf growth in the following spring. We conducted a bud pruning experiment during winter to examine the effects of winter buds on winter N uptake and allocation among plant organs using ¹⁵N labeling. Over a three-week labeling period, the ¹⁵N content in roots increased to 0.20 ± 0.12 mg N g DW^?1, which is equivalent to 1.8 ± 1.1 % of the total N content in the roots. However, this absorbed ¹⁵N rarely appeared in needles and buds. Bud pruning did not affect ¹⁵N uptake and allocation. On the other hand, significant total N retranslocation was found within the crowns of saplings without bud pruning, but N was not retranslocated in bud-pruned plants. The bud pruning experiment indicated that N was retranslocated from needles into winter buds. Since soil N availability changes dramatically and is unstable in many forest ecosystems, N contained in needles would be a more stable source of N than newly absorbed N.     

Interannual variation in leaf photosynthetic capacity during summer in relation to nitrogen, leaf mass per area and climate within a Fagus crenata crown on Naeba Mountain, Japan

During the summers (July and August) of 2002-2005, we measured interannual variation in maximum carboxylation rate (V(cmax)) within a Fagus crenata Blume crown in relation to climate variables such as air temperature, daytime vapor pressure deficit (VPD) and daily photosynthetic photon flux, leaf nitrogen per unit area (N(a)) and leaf mass per unit area (LMA). Climatic conditions in the summers of 2002-2004 differed markedly, with warm and dry atmospheric conditions in 2002, cool, humid and cloudy conditions in 2003, and warm clear conditions in 2004. Conditions in summer 2005 were intermediate between those of summers 2002 and 2003, and similar to recent (8-year) means. In July, marked interannual variation in V(cmax) was mainly observed in leaves in the high-light environment (relative photon flux > 50%) within the crown. At the crown top, V(cmax) was about twofold higher in 2002 than in 2003, and V(cmax) values in 2004 and 2005 were intermediate between those in 2002 and 2003. In August, although interannual variation in V(cmax) among the years 2003, 2004 and 2005 was less, marked variation between 2002 and the other study years was evident. Multiple regression analysis of V(cmax) against the climate variables revealed that VPD of the previous 10-30 days had a significant influence on variability in V(cmax). Neither N(a), LMA nor leaf CO(2) conductance from the stomata to the carboxylation site explained the variability in V(cmax). Our results indicate that the long-term climatic response of V(cmax) should be considered when estimating forest carbon gain across the year.     

Effects of acidic fog and ozone on the growth and physiological functions of Fagus crenata saplings

The effects of simulated acid fog (SAF) and ozone (O₃) stress on the growth and physiology of beech (Fagus crenata) saplings were investigated. Three-year-old beech saplings were exposed to SAFs of pH 3 and pH 5 (control) during May 2007 to July 2008. In each SAF treatment group, half of the saplings were exposed to 60 ppb of O₃ during September 2007 to July 2008. In comparison to the control saplings, those from the pH 3 treatment had lower total plant biomasses, epicuticular wax amounts, Ca²⁺ concentrations in their leaves, and lower starch concentrations in their leaves and roots. The effect of O₃ was significant only for the starch concentration in the roots, but the O₃ exposure also negatively affected the growth and physiology of beech saplings. Results show that acid fog exerts various severe effects, and that both chronic acid fog and O₃ exposure suppressed the physiological functions of beech saplings.     

Detection of the endophyte Discula umbrinella in buds and twigs of Fagus sylvatica

Endophytic fungi have been isolated from buds and twigs of beech trees collected at four different sites in Switzerland. Discula umbrinella. was recovered at high frequencies from the bud scales and the twig pieces contiguous to the buds, but was virtually absent from the rolled up leaves enclosed by the scales. In addition to infection by air-borne inoculum, thalli of D. umbrinella may grow from the twigs into the leaf tissues.     

Factors affecting the dynamics of the population of Fagus crenata in the Takakuma Mountains, the southern limit of its distribution area

The refugee population of Fagus crenata in the Takakuma Mountains, Kyushu, Japan, represents the southern limit of this species' distribution area. Because this population is the most exposed to the global warming effect, records of this population are likely to provide useful information on the response of this species to global warming. The aim of this study was to record the present status of this valuable population, enabling judgment of its sustainability. The density of successive F. crenata trees and saplings was low regardless of the coverage of dwarf bamboo. Moreover, the proportion of empty nuts observed was considerably high, suggesting to be the likely major factor limiting recruitment of saplings or successors in this population. Radial growth of F. crenata was shown to have been decreasing for the past 50 years, and there was a significantly negative correlation with the warmth index. The decreasing growth rate and poor regenerative ability caused by the high proportion of empty nuts suggest the possibility that this population will degrade further in the future, possibly being replaced by shrubs and small tree species.     

The receptivity of graft-polyacrolein on powdered beech wood (Fagus crenata) to hydroxylamine

Summary The receptivity of graft-polyacrolein on wood to hydroxylamine is discussed in terms of a geometric model for the voids and surfaces formed in wood by the swelling action of water. The receptivity of the carbonyl group of graft-polyacrolein varies inversely with the number of graft sites. This relationship is a consequence of decrease in the spacing between graft chains on the primary surface. The receptivity increases gradually with an increase in the amount of graft polymer, and this is a result of the swelling action of graft-polyacrolein which extends to the microscopically visible macropores of wood.     

Induced response of the Siebold's beech (Fagus crenata Blume) to manual defoliation

Siebold's beech (Fagus crenata) was manually defoliated for two successive years. The beech caterpillar (Quadricalcarifera punctatella) was used in a bioassay to determine insect performance. Survival and body size were low on foliage from defoliated trees. Reduced foliar nitrogen and increased tannin content were probably the main causes of the low insect performance. Leaves were less tough on defoliated trees than in controls. Two sucessive years of manual defoliation caused stronger induced resistance than one year defoliation. The quality, as well as the quality of the foliage, decreased the year following manual defoliation; total weight of leaves on a tree was less than one half of that before treatment. Severe defoliation may cause a decrease of leaves the following year and starvation may limit populations. Delayed induced resistance of beech trees is proposed as a possible cause of the cyclical population dynamics ofQ. punctatella. The delayed induced response also affected folivorous insects other thanQ. punctatella.     

Spatial and seasonal variations in photosynthetic properties within a beech (Fagus crenata Blume) crown

The light response curve and the intercellular CO₂ concentration response curve of CO₂ assimilation rate were investigated together with the light conditions at the four different heights within the beech crown from 1995 to 1997 on Mt. Fuji in Japan. On the seasonal fluctuation, the CO₂ assimilation rate at light saturated condition increased rapidly in May, and attained to the maximum between the end of June and July, thereafter, slightly decreased until the middle of August and rapidly decreased in September and October. The daily sum of photosynthetic photon flux density attenuated with deeping within the crown, and particularly, the relative value on 2nd position dropped to only 30%. TheA _max decreased from 10 to 5μmol m⁻² s⁻¹, approximately, with deeping within the crown. The light saturation point, quantum yield, light compensation point and dark respiration rate also varied with deeping. These results suggest that the photosynthetic properties vary gradually from sun to shade leaves along the light attenuation within a beech crown. At light saturated condition, the stomatal conductance and mesophyll conductance were strongly correlated withA _max among the four different heights (r > 0.96, respectively). TheC _i/C _a ratio was around 0.8, and there were no remarkable differences among the four different heights. These results suggest that the vertical gradient ofA _max depends on the variation of mesophyll conductance. The stomatal conductance may be also one of the major factor in the vertical gradient ofA _max. However the intercellular CO₂ concentration doesn’t influence the vertical gradient ofA _max within the crown. This work is supported by the Sasagawa Scientific Research Grant from The Japan Science Society and Grant-in-Aid for Scientific Research (C).     

Mechanisms of xylem recovery from winter embolism in Fagus sylvatica

Hydraulic conductivity in the terminal branches of mature beech trees (Fagus sylvatica L.) decreased progressively during winter and recovered in the spring. The objective of this study was to determine the mechanisms involved in recovery. Two periods of recovery were identified. The first recovery of hydraulic conductivity occurred early in the spring, before bud break, and was correlated with the occurrence of positive xylem pressure at the base of the tree trunk. Active refilling of the embolized vessels caused the recovery. The second recovery of hydraulic conductivity occurred after bud break and was correlated with the onset of cambial activity. Formation of new functional vessels, leading to an increase in xylem diameter, was largely responsible for the increase in xylem conductivity. The two mechanisms were complementary: active refilling of embolized vessels occurred mostly in the root and the trunk, whereas formation of new functional vessels occurred mainly in young terminal shoots.     

Ester linkages between lignin and glucuronoxylan in a lignin-carbohydrate complex from beech (Fagus crenata) wood

Summary A water-soluble lignin-carbohydrate complex (LCC) isolated from beech (Fagus crenata) MWL was investigated. Results from gelfiltration chromatography and the infrared spectrum of the LCC treated with alkali under mild conditions indicated that the LCC contained alkali-labile bonds. Decrease of uronic acid content and the detection of 4-O-methylglucose in the sodium borohydride-reduced LCC suggested the presence of an ester linkage between lignin and glucuronic acid in the glucuronoxylan. Conductometric titration also indicated the existence of glucuronic acid ester linked to lignin. From these results, it is concluded that the LCC contained an ester linkage between lignin and glucuronoxylan and that about one-third of the glucuronic acid present in the LCC was involved in this ester linkage.     

Annual and seasonal variations in photosynthetic capacity of Fagus crenata along an elevation gradient in the Naeba Mountains, Japan

Canopy photosynthetic capacity, measured as leaf maximum carboxylation rate (V (cmax)), is a key factor in ecosystem gas exchange models applied at different scales. We report seasonal and interannual variations in V(cmax) of natural beech stands (Fagus crenata Blume) along an altitudinal gradient in the temperate climate zone of Japan. Estimates are based on 6 years of gas exchange measurements. Pronounced seasonal and interannual variations in V(cmax) normalized to 25 degrees C (V(c,25)) were found for sun leaves. The seasonal pattern of V(c,25) generally followed an inverse parabolic curve, with an increase in spring, peak values in the middle of the growth period and a decline in autumn. Leaf nitrogen concentration (N(l)) and leaf mass per area were significantly related to V(c,25) during spring and summer, but were unrelated in autumn when V(c,25) declined. Annual peak V(c,25) ranged from 40.1 to 97.0 micromol m(-2) s(-1) and varied over as much as a twofold range at a particular site. Annual peak V(c,25) occurred about 28 days before annual peak N(l), with which it was poorly related. Our results show that it can be inappropriate to include constant values of photosynthetic parameters in ecosystem gas exchange models.     

Influences of environmental factors on the radial profile of sap flux density in Fagus crenata growing at different elevations in the Naeba Mountains, Japan

Sap flux density was measured continuously during the 1999 and 2000 growing seasons by the heat dissipation method in natural Fagus crenata Blume (Japanese beech) forests growing between 550 and 1600 m on the northern slope of the Kagura Peak of the Naeba Mountains, Japan. Sap flux density decreased radially toward the inner xylem and the decrease was best expressed in relation to the number of annual rings from the cambium, or in relation to the relative depth between the cambium and the trunk center, rather than as a function of absolute depth. The relative influences of radiation, vapor pressure deficit and soil water on sap flux density during the growing season were similar for the outer and inner xylem, and at all sites. Measurements of soil water content and water potential at a depth of 0.25 m demonstrated that sap flux density responded similarly and sensitively to water potential changes in this soil layer, despite large differences in rooting depth at different elevations, localizing one important control point in the functioning of this forest ecosystem. Identification of the relative influences of radiation, vapor pressure deficit and drying of the upper soil layer on sap flux density provides a framework for in-depth analysis of the control of transpiration in Japanese beech forests. In addition, the finding that the same general controls are operating on sap flux density despite climate gradients and large differences in overall forest stand structure will enhance understanding of water use by forests along elevation gradients.     

油松毛虫越冬状况及其对冬防效果的影响

赤峰地区油松毛虫 Dendrolimus tabulaeformis Tsai et L iu在树干垂直方向上虫口分布百分率呈递减趋势 ,树干不同部位越冬松毛虫死亡率无显著差异 ,山坡不同坡向之间 ,山坡与平地之间树干上越冬松毛虫死亡率也无显著差异 ,树干上越冬的松毛虫仅占越冬总虫口的 3.7% ,且保持了 98%的高死亡率 ,不足以对冬季防治松毛虫构成影响     

Molecular properties of lignin-carbohydrate complexes from beech (Fagus crenata) and pine (Pinus densiflora) woods

Summary Lignin-carbohydrate complexes (LCC) were isolated from pine (Pinus densiflora) and beech (Fagus crenata) milled-wood lignins. The LCCs were treated with enzyme to obtain precipitates (A-P, B-P) and water soluble fractions. The water soluble fraction from beech LCC was subjected to gel filtration to give LCC fragments (B-E-I). In order to protect the phenolic hydroxyl group, B-E-I and B-P were methylated with diazomethane, resulting in nonphenolic LCC fractions B-E-Ip and B-Pp, respectively. On treatment of B-E-I and B-P with sodium hydroxide, a remarkable amount of xylose and a trace of arabinose were detected as monomeric sugars. However, the same alkaline treatment of B-E-Ip and B-Pp gave only a faint trace of xylose. With DDQ treatment of acetylated B-E-I and B-P, monomeric sugars were released in the same amount as those obtained on alkaline treatment. Methylation of the monomeric sugars gave monomethylated xylose. From these results, it was concluded that xylose residues participate in lignin-carbohydrate linkages, and that lignin is linked to xylose at the 0–2 or 0–3 positions through an alkali-labile benzyl ether bond. The molecular-weight distributions of the lignin moieties, measured by HPLC, indicate that the lignin moieties of beech LCC are 100 times larger but less frequent than those of pine LCC. This nonuniformity of distribution of lignin and carbohydrate moieties in hardwood LCC molecules would result in less hydrophobic interaction in aqueous solutions.     

Dynamics of physicochemical properties and occurrence of fungal fruit bodies during decomposition of coarse woody debris of Fagus crenata

The pattern of changes in the physicochemical properties of wood, and its relationship with fungal succession during decomposition of coarse woody debris (CWD) of beech (Fagus crenata Blume) were investigated. In total, 47 snags and 66 logs were assigned to a system of five decay classes, and were used for analysis of the decomposition process. The decomposition process consists of two phases characterized by their dominant organic chemical constituents. In the first phase (decay class 1–3), acid-unhydrolyzable residue (AUR) and holocellulose decreased simultaneously. In the second phase (decay class 3–5), holocellulose decayed selectively. Fruiting bodies of ten fungal taxa occurred frequently on decomposing logs and/or snags. These fungi were divided into early and late colonizers according to their occurrence during CWD decomposition. The relationship between fungal community composition and the physicochemical properties of CWD was analyzed by canonical correspondence analysis (CCA). According to the Monte Carlo permutation test, decay class, water content, and type of CWD (log or snag) significantly affected the fungal community structure. Our results suggested that white-rot basidiomycetes, especially Omphalotus guepiniformis, play a central role in the simultaneous decomposition of AUR and holocellulose in the first phase of decomposition. On the other hand, fungal taxa occurring in the second phase of decomposition may not be responsible for the decomposition of holocellulose. Three possible mechanisms of holocellulose decomposition and AUR accumulation in the second phase of decomposition are proposed and discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Vertical, horizontal and azimuthal variations in leaf photosynthetic characteristics within a Fagus crenata crown in relation to light acclimation

An understanding of spatial variations in gas exchange parameters in relation to the light environment is crucial for modeling canopy photosynthesis. We measured vertical, horizontal and azimuthal (north and south) variations in photosynthetic capacity (i.e., the maximum rate of carboxylation: Vcmax), nitrogen content (N), leaf mass per area (LMA) and chlorophyll content (Chl) in relation to relative photosynthetic photon flux (rPPF) within a Fagus crenata Blume crown. The horizontal gradient of rPPF was similar in magnitude to the vertical gradient of rPPF from the upper to the lower crown. The rPPF in the north quadrant of the crown was slightly lower than in the south quadrant. Nitrogen content per area (Narea), LMA and Vcmax were strictly proportional to rPPF, irrespective of the vertical direction, horizontal direction and crown azimuth, whereas nitrogen content per dry mass, Chl per area and photosynthetic capacity per dry mass (Vm) were fairly constant. Statistical analyses separating vertical trends from horizontal and azimuthal trends indicated that, although horizontal and vertical light acclimation of leaf properties were similar, there were two significant azimuthal variations: (1) Vcmax was lower in north-facing leaves than in south-facing leaves for a given Narea, indicating low photosynthetic nitrogen-use efficiency (PNUE) of north-facing leaves; and (2) Vcmax was lower in north-facing leaves than in south-facing leaves for a given LMA, indicating low Vm of the north-facing leaves. With respect to the low PNUE of the north-facing leaves, there were no significant azimuthal variations in leaf CO2 conductance from the stomata to the carboxylation site. Biochemical analysis indicated that azimuthal variations in nitrogen allocation to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and in nitrogen allocation between carboxylation (Rubisco and other Calvin cycle enzymes) and light harvesting machinery (Chl pigment-protein complexes) were not the main contributor to the difference in PNUE between north- and south-facing leaves. Lower specific activity of Rubisco may be responsible for the low PNUE of the north-facing leaves. Anatomical analysis indicated that not only high leaf density, which is compatible with a greater fraction of non-photosynthetic tissue, but also thick photosynthetic tissue contributed to the low Vm in the north-facing leaves. These azimuthal variations may need to be considered when modeling canopy photosynthesis based on the Narea-Vcmax or LMA-Vcmax relationship.     

Interacting effects of irradiance and water stress on dry weight and biomass partitioning in Fagus sylvatica seedlings

Abstract

Actual climate models for central Europe predict prolonged summer droughts. Knowledge on how the interaction between light and water availability affects regeneration will hence be of major importance. In an experiment carried out under controlled conditions, newly emerged beech seedlings were grown in pots with sand during 54 days. Three treatments applying three different light levels (2, 9 and 43% relative light intensity) were combined with two soil water treatments (control and drought). At the end of the experiment, seedlings were separated into leaves, stem and root and the seedlings’ dry mass, leaf area and stem length was determined. Low irradiance (2%) had a strong negative effect on dry weights of seedling components, leaf area and specific leaf mass. Drought clearly affected biomass partitioning for seedlings at high irradiance levels (43%). An interaction between irradiance and drought on biomass partitioning in beech seedlings was observed at medium irradiance level (9%). Within a wide range of light levels in the forests, both light and drought may affect biomass partitioning in young seedlings.     

Basic density determination for Swedish softwoods and its influence on average moisture content of wood packages estimated by measuring their mass

In this work, a set-up with a device measuring the mass of wood packages is examined as an aid to estimate the average moisture content (MC) of wood packages. As the basic density needs to be presumed in the set-up, an estimator of the basic density as a function of log diameter is determined for Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris). In total, 1920 specimens were collected at two different sawmills and analysed for this purpose. Specimens collected at the butt-end of pine had the greatest variation in basic density and it is recommended that they should be omitted when sawmills create their own functions for basic density estimation. Furthermore, the variation in basic density was shown to have the greatest impact on the estimated MC. A maximum error estimator of the MC became 14% at a MC of 70% and 9% at a MC of 10%. It was therefore concluded that the described method should not be used to estimate the MC of packages after drying but can serve as a valuable indicator of average green MC of a drying batch.     

Photosynthetic induction responses to variable light under field conditions in three species grown in the gap and understory of a Fagus crenata forest

Photosynthetic induction responses to abrupt increases in photon flux density (PFD) to 800 and 1500 &mgr;mol m(-2) s(-1) from either darkness or 100 &mgr;mol m(-2) s(-1) were examined in situ in leaves of Fagus crenata Blume, Daphniphyllum humile Maxim., and Acer rufinerve Siebold & Zucc. growing in a gap and the understory of an F. crenata forest. Among the species studied, F. crenata exhibited the highest assimilation rate (A(100)), stomatal conductance (g(s100)) at the background PFD of 100 &mgr;mol m(-2) s(-1), and A(100)/A(max) (A(max) = maximum assimilation rate), in both the gap and the understory. Time required for full induction depended on both background PFD and maximum PFD. The induction period was 2-4-fold shorter at a background PFD of 100 &mgr;mol m(-2) s(-1) than in darkness. For the three understory species, time required to full induction was 2-3-fold longer when irradiance was increased from darkness to 800 &mgr;mol m(-2) s(-1) than when irradiance was increased from darkness to 1500 &mgr;mol m(-2) s(-1). Acer rufinerve showed higher initial stomatal conductance (g(s0)) and a shorter induction period in the understory than in the gap. Fagus crenata exhibited a similar g(s0) and induction period in both habitats. Daphniphyllum humile demonstrated lower g(s0) and a longer induction period in the understory than in the gap. These findings indicate that initial stomatal conductance is closely correlated with the photosynthetic induction response. We conclude that the photosynthetic induction response is affected by the light conditions experienced by plants before the sudden increase in irradiance and by the extent of the increase in irradiance.     

Reproduction affects partitioning between new organs of a pulse of 15N applied during seed ripening in Fagus crenata

Seasonal internal nitrogen (N) cycling is an important strategy for trees to uncouple growth from N acquisition. While N uptake, allocation and storage has been intensively studied in association with leaf phenology and vegetative growth, influence of reproduction on these key processes is still poorly understood. Therefore, we applied pulse ¹⁵N labelling to three fruiting and three non-fruiting trees in a 92-year-old Fagus crenata forest on 18 July and traced ¹⁵N content per organ dry mass (¹⁵N_excess) in all new shoot organs from the upper crowns periodically until leaf fall. The amount of ¹⁵N_excess recovered in the whole new shoots in fruiting trees did not differ from non-fruiting individuals, although up to 70% of ¹⁵N_excess was recovered in fruits of fruiting trees but 87% in leaves of non-fruiting individuals. In addition, dramatic increase in ¹⁵N_excess amount in nuts was accompanied by about twofold increase in nut N content. These results indicate that new N uptake from the soil contributed greatly to seed ripening, which in turn resulted in less allocation to leaves in fruiting trees. In non-fruiting individuals, on the other hand, ¹⁵N_excess allocated to leaves was not accompanied by concomitant increase in leaf N content because biomass growth had ceased when ¹⁵N was applied. These results suggest that N uptake in the late growing season contributed to internal N storage in non-fruiting trees. These reproduction-related variations in seasonal N cycle have implications for N dynamics in the plant–soil system during environmental change.