Seasonal variations in water relations in current-year leaves of evergreen trees with delayed greening

We investigated seasonal patterns of water relations in current-year leaves of three evergreen broad-leaved trees (Ilex pedunculosa Miq., Ligustrum japonicum Thunb., and Eurya japonica Thunb.) with delayed greening in a warm-temperate forest in Japan. We used the pressure-volume method to: (1) assess the extent to which seasonal variation in leaf water relations is attributable to leaf development processes in delayed greening leaves versus seasonal variation in environmental variables; and (2) investigate variation in leaf water relations during the transition from the sapling to the adult tree stage. Leaf mass per unit leaf area was generally lowest just after completion of leaf expansion in May (late spring), and increased gradually throughout the year. Osmotic potential at full turgor (Psi(o) (ft)) and leaf water potential at the turgor loss point (Psi(w) (tlp)) were highest in May, and lowest in midwinter in all species. In response to decreasing air temperature, Psi(o) (ft) dropped at the rate of 0.037 MPa degrees C(-1). Dry-mass-based water content of leaves and the symplastic water fraction of total leaf water content gradually decreased throughout the year in all species. These results indicate that reductions in the symplastic water fraction during leaf development contributed to the passive concentration of solutes in cells and the resulting drop in winter Psi(o) (ft). The ratio of solutes to water volume increased in winter in current-year leaves of L. japonicum and E. japonica, indicating that osmotic adjustment (active accumulation of solutes) also contributed to the drop in winter in Psi(o) (ft). Bulk modulus of elasticity in cell walls fluctuated seasonally, but no general trend was found across species. Over the growing season, Psi(o) (ft) and Psi(w) (tlp) were lower in adult trees than in saplings especially in the case of I. pedunculosa, suggesting that adult-tree leaves are more drought and cold tolerant than sapling leaves. The ontogenetic increase in the stress resistance of I. pedunculosa may be related to its characteristic life form because I. pedunculosa grows taller than the other species studied.     

Photosynthetic nitrogen-use efficiency in evergreen broad-leaved woody species coexisting in a warm-temperate forest

Photosynthetic nitrogen-use efficiency (PNUE, photosynthetic capacity per unit leaf nitrogen) varies among species from different habitats and correlates with several ecological characteristics such as leaf life span and leaf mass per area. We investigated eight evergreen broad-leaved woody species with different leaf life spans that coexist in a warm-temperate forest. We determined photosynthetic capacity at ambient CO(2) concentration in saturated light, nitrogen concentration, and the concentration of ribulose-1,5-bisphosphate carboxylase (RuBPCase), a key enzyme of photosynthesis and the largest sink of nitrogen in leaves. Each species showed a strong correlation between photosynthetic capacity and RuBPCase concentration, and between RuBPCase concentration and nitrogen concentration. Photosynthetic capacity of leaves decreased with increasing leaf life span, whereas PNUE did not correlate significantly with leaf life span. There was a twofold variation in PNUE among species. This relatively small variation in PNUE is consistent with the argument that species that coexist in a single habitat maintain a similar PNUE. The two components of PNUE-photosynthetic rate per unit RuBPCase and RuBPCase per unit leaf nitrogen-were not significantly correlated with other leaf characteristics such as leaf life span and leaf mass per area. We conclude that differences in PNUE are relatively small among coexisting species and that differences in absolute amounts of photosynthetic proteins lead to differences in photosynthetic productivity among species.     

Differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia × fraseri and Osmanthus fragrans

Leaf functional traits are adaptations that enable plants to live under different environmental conditions. This study aims to evaluate the differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia 9 fraseri and Osmanthus fragrans. Specific areas of red leaves are higher than that of green leaves in both species. Thus, the material investment per unit area and per lamina of red leaves is significantly lower than that of green leaves, implying an utmost effort of red leaves to increase light capture and use efficiency because of their low leafchlorophyll concentration. The higher petiole length of green leaves compared with that of red leaves indicates that adult green leaves may have large fractional biomass allocation to support the lamina structures in capturing light with maximum efficiency and obtaining a high growth rate. The high range of the phenotypic plasticity of leaf size, leaf thickness,single-leaf wet and dry weights, and leaf moisture of green leaves may be beneficial in achieving efficient control of water loss and nutrient deprivation. The high range of phenotypic plasticity of leaf chlorophyll concentration of red leaves may be advantageous in increasing resource(especially light) capture and use efficiency because this leaf type is juvenile in the growth stage and has low leaf-chlorophyll concentration.     

Differences in leaf functional traits between red and green leaves of two evergreen shrubs <Emphasis Type="Italic">Photinia</Emphasis> × <Emphasis Type="Italic">fraseri</Emphasis> and <Emphasis Type="Italic">Osmanthus fragrans</Emphasis>

Leaf functional traits are adaptations that enable plants to live under different environmental conditions. This study aims to evaluate the differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia × fraseri and Osmanthus fragrans. Specific areas of red leaves are higher than that of green leaves in both species. Thus, the material investment per unit area and per lamina of red leaves is significantly lower than that of green leaves, implying an utmost effort of red leaves to increase light capture and use efficiency because of their low leaf-chlorophyll concentration. The higher petiole length of green leaves compared with that of red leaves indicates that adult green leaves may have large fractional biomass allocation to support the lamina structures in capturing light with maximum efficiency and obtaining a high growth rate. The high range of the phenotypic plasticity of leaf size, leaf thickness, single-leaf wet and dry weights, and leaf moisture of green leaves may be beneficial in achieving efficient control of water loss and nutrient deprivation. The high range of phenotypic plasticity of leaf chlorophyll concentration of red leaves may be advantageous in increasing resource (especially light) capture and use efficiency because this leaf type is juvenile in the growth stage and has low leaf-chlorophyll concentration.     

Intra-plant variation in cyanogenesis and the continuum of foliar plant defense traits in the rainforest tree Ryparosa kurrangii (Achariaceae)

At the intra-plant level, temporal and spatial variations in plant defense traits can be influenced by resource requirements, defensive priorities and storage opportunities. Across a leaf age gradient, cyanogenic glycoside concentrations in the rainforest understory tree Ryparosa kurrangii B.L. Webber were higher in young expanding leaves than in mature leaves (2.58 and 1.38 mg g(-1), respectively). Moreover, cyanogens, as an effective chemical defense against generalist herbivores, contributed to a defense continuum protecting foliar tissue during leaf development. Chemical (cyanogens and phenolic compounds) and phenological (delayed greening) defense traits protected young leaves, whereas mature leaves were largely protected by physical defense mechanisms (lamina toughness; explained primarily by leaf mass per area). Cyanogen concentration was considerably higher in floral tissue than in foliar tissue and decreased in floral tissue during development. Across contrasting tropical seasons, foliar cyanogenic concentration varied significantly, being highest in the late wet season and lowest during the pre-wet season, the latter coinciding with fruiting and leaf flushing. Cyanogens in R. kurrangii appear to be differentially allocated in a way that maximizes plant fitness but may also act as a store of reduced nitrogen that is remobilized during flowering and leaf flushing.     

Relative importance of photosynthetic physiology and biomass allocation for tree seedling growth across a broad light gradient

Studies of tree seedling physiology and growth under field conditions provide information on the mechanisms underlying inter- and intraspecific differences in growth and survival at a critical period during forest regeneration. I compared photosynthetic physiology, growth and biomass allocation in seedlings of three shade-tolerant tree species, Virola koschynii Warb., Dipteryx panamensis (Pittier) Record & Mell and Brosimum alicastrum Swartz., growing across a light gradient created by a forest-pasture edge (0.5 to 67% diffuse transmittance (%T)). Most growth and physiological traits showed nonlinear responses to light availability, with the greatest changes occurring between 0.5 and 20 %T. Specific leaf area (SLA) and nitrogen per unit leaf mass (N mass) decreased, maximum assimilation per unit leaf area (A area) and area-based leaf N concentration (N area) increased, and maximum assimilation per unit leaf mass (A mass) did not change with increasing irradiance. Plastic responses in SLA were important determinants of leaf N and A area across the gradient. Species differed in magnitude and plasticity of growth; B. alicastrum had the lowest relative growth rates (RGR) and low plasticity. Its final biomass varied only 10-fold across the light gradient. In contrast, the final biomass of D. panamensis and V. koschynii varied by 100- and 50-fold, respectively, and both had higher RGR than B. alicastrum. As light availability increased, all species decreased biomass allocation to leaf tissue (mass and area) and showed a trade-off between allocation to leaf area at a given plant mass (LAR) and net gain in mass per unit leaf area (net assimilation rate, NAR). This trade-off largely reflected declines in SLA with increasing light. Finally, A area was correlated with NAR and both were major determinants of intraspecific variation in RGR. These data indicate the importance of plasticity in photosynthetic physiology and allocation for variation in tree seedling growth among habitats that vary in light availability.     

广东乳源19个枫香自由授粉家系在东江林场的生长表 现与初步评估

以广东乳源 19 个枫香 Liquidambar formosana 自由授粉家系为研究对象,调查不同家系苗期苗 高和 10.5 年生测定林的生长指标,并分析两个阶段生长指标的相关性,以期为枫香种质早期评价提供理 论依据。分析结果表明：枫香苗高在不同家系间存在显著差异（P<0.05）,且随着年龄的增长,差异呈逐 渐减小的趋势;枫香幼龄林树高、胸径、材积和干形质量在不同家系间存在显著差异,而分枝数、枝下 高和叶色等级无显著差异,19 个家系的单株树高、胸径、材积、枝下高、分杈数、干形质量和叶色等级 的平均值分别为 6.07 m、6.07 cm、0.012 2 m3、1.90 m、0.41 个、2.36 和 4.75;幼龄苗高与测定林的枝下 高、分杈数、叶色等级间的相关不显著,而与树高、胸径和材积的相关较强,且幼龄苗高与测定生长指 标间的相关性随苗龄增长呈增强趋势。因此,采用苗高对枫香优良家系进行早期选择具有一定的可行性。     

Effects of water stress on irradiance acclimation of leaf traits in almond trees

Photosynthetic acclimation to highly variable local irradiance within the tree crown plays a primary role in determining tree carbon uptake. This study explores the plasticity of leaf structural and physiological traits in response to the interactive effects of ontogeny, water stress and irradiance in adult almond trees that have been subjected to three water regimes (full irrigation, deficit irrigation and rain-fed) for a 3-year period (2006-08) in a semiarid climate. Leaf structural (dry mass per unit area, N and chlorophyll content) and photosynthetic (maximum net CO(2) assimilation, A(max), maximum stomatal conductance, g(s,max), and mesophyll conductance, g(m)) traits and stem-to-leaf hydraulic conductance (K(s-l)) were determined throughout the 2008 growing season in leaves of outer south-facing (S-leaves) and inner northwest-facing (NW-leaves) shoots. Leaf plasticity was quantified by means of an exposure adjustment coefficient (ε=1-X(NW)/X(S)) for each trait (X) of S- and NW-leaves. Photosynthetic traits and K(s-l) exhibited higher irradiance-elicited plasticity (higher ε) than structural traits in all treatments, with the highest and lowest plasticity being observed in the fully irrigated and rain-fed trees, respectively. Our results suggest that water stress modulates the irradiance-elicited plasticity of almond leaves through changes in crown architecture. Such changes lead to a more even distribution of within-crown irradiance, and hence of the photosynthetic capacity, as water stress intensifies. Ontogeny drove seasonal changes only in the ε of area- and mass-based N content and mass-based chlorophyll content, while no leaf age-dependent effect was observed on ε as regards the physiological traits. Our results also indicate that the irradiance-elicited plasticity of A(max) is mainly driven by changes in leaf dry mass per unit area, in g(m) and, most likely, in the partitioning of the leaf N content.     

Response of Ulmus americana seedlings to varying nitrogen and water status. 2 Water and nitrogen use efficiency in photosynthesis

Photosynthetic utilization of water and nitrogen in Ulmus americana L. seedlings was tightly linked with the relative availability of each resource. During periodic drying cycles, water use efficiency increased as predawn water potential fell from -0.5 to -2.0 MPa. During the later stages of such drying cycles, the relative contribution of stomatal limitations to the total net photosynthetic limitation appeared to be at its greatest, whereas biochemical limitations were predominant in well-watered plants grown under low nitrogen (N) availability. For any level of leaf water status, water use efficiency of photosynthesis (WUE) was always greater in plants with high leaf N content than in plants with low leaf N content. Photosynthetic nitrogen use efficiency (PNUE) was always greater in plants with low leaf N content than in plants with high leaf N content, for any level of water status. In combined N treatments and predawn water status classes, there was a significant inverse relationship between PNUE and WUE.     

湖南主要经济林树种滞留PM2.5等颗粒污染物能力研究

以湖南省7种常见经济林树种为研究对象,研究其在单位叶面积上对空气中PM2.5等颗粒物的滞留量,为揭示湖南省主要经济林树种降低空气中PM2.5等颗粒污染物能力提供科学依据。结果表明:不同树种单位叶面积吸附PM2.5的量各不相同,主要受其叶表微结构、枝叶密集度、叶质地、叶面倾角等因素的影响。各树种单位叶面积吸附PM2.5量由大到小排序依次为板栗(0.144μg/cm~2)、柑橘(0.038μg/cm~2)、油茶(0.034μg/cm~2)、花椒(0.03μg/cm~2)、枣(0.029μg/cm~2)、杜仲(0.023μg/cm~2)、光皮树(0.019μg/cm~2)。各树种单位叶面积吸附TSP、PM1、PM10量大小排序规律基本相同。板栗单位叶面积吸附TSP、PM1、PM10量最大,分别达到1.088、0.04、0.47μg/cm~2,光皮树单位叶面积吸附的TSP、PM1、PM10量最小,分别为0.119、0.006、0.048μg/cm~2。就叶习性而言,单位叶面积吸附的TSP、PM1、PM10、PM2.5量表现为常绿树种大于落叶树种。     

5个阔叶树种叶片的养分特征分析

用半微量凯氏法、钼兰比色法、火焰光度法和原子吸收光度法分别对阔叶树种红锥、红花荷、大叶相思、木荷、樟树叶片的N、P、K、Ca和Mg含量进行了测定。结果表明:红锥叶片的各养分含量中等,红花荷叶片的N、P、K、Ca含量都是5种树种中最低的,大叶相思叶片的N、K含量最高,木荷叶片的Mg含量最高;樟树叶片的P、Ca含量最高,Mg含量最低。聚类分析将5种树种的养分类型分为2类,第1类树种有红锥和红花荷,叶片单位叶面积养分含量较高;第2类为大叶相思、木荷和樟树,叶片单位叶面积养分含量较低。     

喜树幼苗的硝酸还原酶活性及其日变化规律

本文利用体内法测定了喜树幼苗不同器官以及不同叶位叶片的硝酸还原酶活性(NRA),同时观察了喜树幼苗不同叶位叶片的NRA的日变化规律,并考查了NRA与叶面积及比叶重的相关性。结果表明,与根、茎及茎尖中的NRA相比,叶片中的NRA最高。不同叶位叶片的NRA有明显的差异,在所测定的10个不同叶位的叶片中,上数第4~6片叶片的NRA较高。叶片NRA有明显的日变化,呈单峰曲线,峰值出现在中午1230前后。同时,结果表明NRA与叶面积以及比叶重无明显的相关关系。研究结果为进一步研究喜树的氮代谢提供基础资料。图5参18。     

碧玉杨叶形态结构与生理特性对干旱的响应

【目的】以群众杨为对照,探讨干旱胁迫下碧玉杨的叶形态、结构和光合、水分生理特性的关系及其影响植株生物量积累的内在成因,进一步揭示碧玉杨和群众杨的抗旱机制,为区域造林绿化杨树的抗旱生理研究和品种推广提供参考。【方法】以碧玉杨与和群众杨1年生扦插苗为研究对象,应用盆栽控水法模拟干旱条件,对比分析不同干旱胁迫程度下2个品种的叶面积、叶脉密度、叶氮素利用效率、光合特性及叶水分输导能力的响应,及其对植株生物量和抗旱能力的影响。【结果】干旱胁迫程度加剧,2个杨树品种的叶脉密度(LVD)和单位干质量叶氮含量(N_mass)上升,碧玉杨的LVD增幅大、N_mass增幅小;净光合速率(P_n)、植株总光合速率(PTL)、最大净光合速率(P_nmax)、光合日累积量、蒸腾日累积量、叶导水率(K_leaf)、水分利用效率(WUE)、光合氮利用效率(PNUE)、叶面积(LA)以及植株生物量(TB)均下降,碧玉杨的降幅均小。相较群众杨而言,碧玉杨的LA、LVD、PNUE、TB和日均耗水量在干旱胁迫前后均高,P_n、K_leaf、WUE和N_mass在干旱胁迫前后均低,PTL和Tr日累积在中度和重度干旱胁迫下高,P_nmax、P_n日累积和Tr在重度干旱胁迫下高。PTL较Pn与TB相关关系更紧密,PNUE较N_mass与TB相关关系更紧密。【结论】干旱胁迫下碧玉杨的叶形态结构与生理特性呈现出低效水分利用、高效叶形态结构调整、高效氮素利用和高效光合固碳的平衡制约关系。2个品种的抗旱机制不同,抗旱能力强的碧玉杨其叶结构调整更高效,抗旱能力弱的群众杨其光合特性对干旱更敏感,叶结构与抗旱性关联最大,其次是光合特性。     

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.     

Distribution of leaf mass per unit area and leaf nitrogen concentration determine partitioning of leaf nitrogen within tree canopies

Distribution of leaf nitrogen with respect to leaf mass per unit area (M(a)), nitrogen per unit mass (N(m)) and nitrogen per unit area (N(a)) within peach (Prunus persica L.) tree canopies was studied in two field experiments. In one experiment, leaf light exposure and M(a) were measured on leaves from different canopy positions of peach trees subjected to five nitrogen (N) fertilization treatments. Leaf light exposure and M(a) were linearly related and the relationship was independent of N fertilization. In a subsequent experiment, N fertilizer was applied to previously unfertilized trees in midsummer, after shoot growth had terminated. Application of N fertilizer did not affect mean canopy M(a). Fertilization increased N(m) of all leaves throughout the canopy compared with non-fertilized trees. No significant relationship between N(m) and M(a) was found in either fertilized or control trees. There was a linear relationship between N(a) and M(a) and the slope of the relationship was increased by N fertilizer application. We conclude that distribution of N(a) in peach tree canopies is primarily a function of M(a) partitioning with light and N(m), which is related to soil N availability.     

Photosynthetic capacity in relation to nitrogen in the canopy of a Quercus robur, Fraxinus angustifolia and Tilia cordata flood plain forest

We measured gas exchange and various leaf parameters of ash (Fraxinus angustifolia Vahl.) and oak (Quercus robur L.) in the high canopy and of lime (Tilia cordata Mill.) in the lower canopy of a planted, 120-year-old floodplain forest in southern Moravia, Czech Republic. The high-canopy leaves of F. angustifolia and Q. robur had nitrogen concentrations on a leaf area basis (N(area)) that were twice those of low-canopy leaves of T. cordata. Upper-canopy leaves of F. angustifolia had a photosynthetic rate at light saturation (A(max)) of about 16 micromol CO2 m(-2) s(-1), whereas A(max) of the upper-canopy foliage of Q. robur achieved only about two thirds of this value. Contrary to previous investigations of photosynthetic performance in monospecific stands, leaves of the uppermost branches of T. cordata at 15-m height had the highest A(max) and transpiration rate among the species studied. Water-use efficiency (WUE) was low in T. cordata at 15-m canopy height, whereas WUE was significantly higher for Q. robur leaves at 27-m height than for the other species. Leaves of T. cordata at 15-m height showed the strongest relationship between A(max) and N(area) (R2 = 0.90) followed by F. angustifolia (R2 = 0.69). The strong correlation between photosynthesis and nitrogen concentration in T. cordata at 15 m, together with the steep regression slope for the A(max):N(area) relationship, indicated that nitrogen allocation to the photosynthetic apparatus resulted in high nitrogen-use efficiency of light-saturated photosynthesis (PNUE). Despite differences in PNUE among species, PNUE was fairly constant for leaves sampled from the same canopy position, suggesting that single-leaf parameters are matched to optimize PNUE for prevailing light conditions. High PNUE in T. cordata at 15 m partially compensated for the species' subordinate position in the canopy, and may be an important mechanism for its coexistence in highly structured vegetation.     

Leaf orientation,light interception and stomatal conductance of Eucalyptus globulus ssp. globulus leaves

Juvenile and adult leaves of the heteroblastic species Eucalyptus globulus Labill. ssp. globulus did not show active diurnal orientation toward or away from incident radiation. Juvenile leaves of a late-maturing sapling of a Tasmanian provenance were evenly distributed in all azimuth sectors. In contrast, an early-maturing sapling of the same age from Wilsons Promontory, Victoria had a predominance of adult leaf blades facing east and west. Mid-vein and blade angles of juvenile and adult leaves were non-random with an overall vertical declination of the leaves. Both leaf types intercepted a greater irradiance during the morning than at midday. Sub-horizontal juvenile leaves intercepted 22% more irradiance than vertical adult leaves during the middle of the day. The amphistomatal and isobilateral adult leaves intercepted sunlight equally on both leaf surfaces. Stomatal conductance was variable during the period of measurement but was similar for the Tasmanian juvenile (0.4 to 0.9 cm s(-1)) leaves and Wilsons Promontory adult (0.5 to 1.2 cm s(-1)) leaves. Greater light interception by the sub-horizontal juvenile leaves would confer a growth advantage to saplings and regenerating canopies. Reduced light interception and leaf temperature of vertical adult E. globulus leaves would assist in water conservation, particularly at high solar angles.     

Seasonal and spatial variations in leaf nitrogen content and resorption in a Quercus serrata canopy

To elucidate the relationships between spatiotemporal changes in leaf nitrogen (N) content and canopy dynamics, changes in leaf N and distribution in the canopy of a 26-year-old deciduous oak (Quercus serrata Thunb. ex. Murray) stand were monitored throughout the developmental sequence from leaf expansion to senescence, by estimating the leaf mass and N concentrations of all the canopy layers. Seasonal changes were observed in leaf N concentration per unit leaf dry mass (N (m)), which peaked after bud burst, declined for two weeks shortly thereafter, and then remained constant for the rest of the growing season for each canopy layer. Leaf N concentration per unit leaf area (N (a)) was higher in the upper layer than in the lower layer throughout the growing season, and was closely correlated with relative irradiance (RI) in the summer when the air temperature was moderately high. The N concentrations of all leaf layers started to decrease in November, and reached their lowest values in late November, whereas LMA scarcely changed throughout the season. The lowest N concentrations did not differ significantly among the canopy layers. Seasonal changes in the relationship between N (a) and RI were detected, indicating that N (a) is optimized temporally as well as spatially. Nitrogen resorption efficiency was highest in the upper canopy layers where larger amounts of N were invested. Based on the estimates of leaf mass and leaf N concentrations of the canopy layers, total leaf N concentration of the whole canopy was estimated to be 84.1 kg ha(-1) in the summer, and 37.3 kg ha(-1) in late November. Therefore, 46.8 kg ha(-1) of leaf N in the canopy (about 56% of the total N) was resorbed just before leaf abscission.     

Evaluation of leaf display of evergreen broadleaved tree species and deciduous tree species in warm temperate conifer plantations

We investigated the sapling leaf display in the shade among trees of various leaf lifespans co-occurring under the canopy of a warm-temperate conifer plantation. We measured leaf-area ratio (aLAR) and morphological traits of saplings of evergreen broadleaved tree species and a deciduous tree species. Although we found large interspecific and intraspecific differences in aLAR even among saplings of similar size in the homogeneous light environment, we did not find a consistent trend in aLAR with leaf lifespan among the species. While deciduous trees annually produced a large leaf area, some evergreen broadleaved trees retained their leaves across years and had aLAR values as high as those of deciduous trees. Among leaf-level, shoot-level, and individual-level morphological traits, aLAR was positively correlated with current-year shoots mass per aboveground biomass in deciduous trees, and with the area of old leaves per aboveground mass in evergreen broadleaved trees. Thus, tree-to-tree variation in the degrees of annual shoot production and the accumulation of old leaves were responsible for the interspecific and intraspecific variations in aLAR.     

Species Composition,Distribution, and Diversity of Woody Species in a Tropical Dry Forest of India

We investigated the composition of tropical dry forest woody species at adult, sapling, and seedling stages, in terms of plant diversity, distribution, and importance value index (IVI), and identified the dominant and ubiquitous species in the five study sites having variable edaphic properties. Species varied markedly in the composition and IVI at different sites. The semi-evergreen species, Shorea robusta, was dominant at the wettest site at all the three growth stages; at the driest site, highly deciduous species Lannea coromandelica was the dominant adult species and Nyctanthis arbortristis the dominant sapling and seedling species. Soil moisture content (SMC) altered the distribution of about 8% of the adult species. ANOVA indicated significant site-wise differences in the Shannon-Wiener index, Whittaker’s evenness, Margalef’s species richness, and β-diversity for the woody species at all the three stages. The Shannon-Wiener index, Whittaker’s evenness, Margalef’s species richness, and β-diversity were greater in seedlings as compared to adult and saplings of tree species. These variations in species composition and distribution are evidently on account of different levels of SMC as well as habitat heterogeneity as indicated by β-diversity which was independent of SMC.