Allometry and Competition between Saplings of Picea jezoensis and Abies sachalinensis in a Sub-boreal Coniferous Forest, northern Japan

The crown shape and the mode of competition between saplings(<2m in height) of the two conifers,Picea jezoensis andAbiessachalinensis, of a sub-boreal forest, northern Japan, wereinvestigated based on the diffusion model. A model for individualsapling growth considering both inter- and intraspecific competitionwas developed. The effect of species-specific crown shape onthe sapling growth and competition of the two species were examined.PiceajezoensisandAbies sachalinensissaplings had deep conic and shallowflat crowns, respectively.Picea jezoensishad more foliage massthanAbies sachalinensisof the same sapling mass. It was suggestedthat thePicea jezoensissapling has a high cost for assimilation–respirationbalance under dark conditions of closed canopies, whereas theAbiessachalinensissapling maintains effective assimilation even undersuppressed conditions. Widely spaced saplings, such as gap successors,ofPicea jezoensishad a greater relative growth rate (a₀) thanwidely spacedAbies sachalinensis. The crown shape of saplingsof the two species shows different adaptations for efficientpersistence in the sub-boreal forest. Saplings ofPicea jezoensisandAbies sachalinensiswere not uniformlydistributed, but aggregated in different sites as the saplingsgrew, indicating habitat segregation between the two speciesat the sapling stage. Intraspecific sapling competition wasone-sided in each of the two conifers. Interspecific saplingcompetition was one-sided in the direction only fromAbies sachalinensistoPiceajezoensis. Therefore, asymmetric competition prevailed at thesapling stage of the two species. These results contrast withweak symmetric competition or the almost absence of competitionbetween trees (2m in height) of the two species (Kubota andHara,Annals of Botany76: 503–512, 1995). The mode of competitionchanged with the life-history stage from the sapling (intenseand asymmetric) to the tree (weak and symmetric or almost absent). In conclusion (1) asymmetric and intense competition betweensaplings brought about habitat segregation between the dominantspecies,Picea jezoensisandAbies sachalinensis, in the earlystage of life-history; (2) therefore, the coexistence ofPiceajezoensisandAbies sachalinensisof the sub-boreal forest wasdetermined by the boundary conditions for the growth dynamicsof the trees, as segregation of establishment sites resultingfrom asymmetric and intense competition between saplings; (3)then the species composition of the forest was maintained byweak symmetric competition or the almost absence of competitionbetween trees. Crown shape; growth dynamics; species coexistence; habitat segregation; diffusion model     

Recruitment Processes and Species Coexistence in a Sub-boreal Forest in Northern Japan

We investigated the recruitment of saplings (across the 2 m-heightthreshold) of six species,Picea jezoensis, Abies sachalinensis,Betula ermanii, Picea glehnii, Acer ukurunduense andSorbus commixta,in a sub-boreal forest, northern Japan. Data were collectedin a 2.48-ha plot over six growing seasons (1989–1994).We used path analysis to analyse the relationships between therecruitment rates of saplings and the stand structural attributessuch as mother tree abundance, stand crowdedness, stand stratification,Sasabamboo density on the forest floor, and fallen log abundance.The combination of stand structural attributes affecting recruitmentrates of the six sub-boreal forest tree species differed markedlyamong the species and corresponded to species composition. Itis suggested that the size-structure dynamics of adult treesof the sub-boreal forest are regulated largely by differentregeneration processes among the species and only slightly byinterspecific competition between adult trees because interspecificcompetition between adult trees was not evident. The dynamicsof species coexistence of the sub-boreal forest should be describedas a process combining the diversity of recruitment processesof saplings of the component species and the diversity of interspecificcompetition between adult trees. We propose the boundary conditionhypothesis for species coexistence in the sub-boreal forest,that the persistence of each component species is ascribed largelyto the different recruitment processes of saplings (boundaryconditions for adult tree growth dynamics) and only a littleto interspecific adult tree competition. Climax forest; safe site; regeneration niche; mode of competition; species diversity     

Demographic traits of understory trees and population dynamics of aPicea-Abies forest in Taisetsuzan National Park, northern Japan

The size structure transition matrices ofPicea jezoensis, Picea glehnii andAbies sachalinensis of a sub-boreal forest in Hokkaido, northern Japan were constructed based on the demography of each species (Picea jezoensis andPicea glehnii were dealt with together asPicea) during a 4-year period. Two types of matrices, density-independent and density-dependent population dynamics models, were investigated for evaluating the ‘waiting pattern’ betweenPicea spp. andA. sachalinensis. For the density-dependent model, it was assumed that the demographic traits of understory trees, the recruitment rate, the understory mortality rate and the transition probability from the understory to canopy stages, were regulated by the one-sided competitive effect of canopy trees. The observed size structure ofPicea was almost consistent with the stationary size structure obtained in both the density-independent and the density-dependent models, whereas the observed size structure ofA. sachalinensis was not realized in the two models. The effects of both the transition probability from the understory to canopy stages and the recruitment rate on the dynamics of canopy trees were investigated. ForPicea, two parameters—recruitment rate (e _i ) and transition probability from the understory to canopy stages-exponentially affected the dynamics of canopy trees. In contrast, forAbies sachalinensis, the two parameters affected linearly the dynamics of canopy trees. In conclusion, the population dynamics ofPicea andA. sachalinensis was determined by the parameters of the recruitment rate and the transition probability from the understory to canopy stages, relating to waiting patterns of understory trees for future gap formation. InPicea, the demographic parameters of understory trees intensively regulated the dynamics of canopy trees if compared withA. sachalinensis, suggesting that the performance of understory trees plays a key role in the population dynamics ofPicea. This reflects the growth pattern of understory trees in the regeneration of the two species.     

Stand development and regeneration during a 33-year period in a seral Picea glehnii forest, northern Japan

Stand development and regeneration were studied during a 33-year period (1965-1998) in a 1-ha plot in a seral Picea glehnii forest in northern Japan. P. glehnii was mono-dominant in the upper canopy layer, but its understory trees were rarely found in 1965. Other species were scarcely observed in 1965. Many recruited saplings of Abies sachalinensis which had grown to > 5 cm diameter at breast height (DBH) by 1998 had become dominant in the understory layer. Mortality of P. glehnii canopy trees was low. Therefore, the stand basal area increased during the census period due to the growth of surviving canopy trees. Stand development brought about intense competition among trees by increasing local crowding for each tree, and promoted dominance of larger trees and suppression of smaller trees. Although growth rates of understory trees of the two conifers decreased with the increase in local crowding, the growth rate of A. sachalinensis was consistently higher than that of P. glehnii at all extents of local crowding. The recruitment rate (growing to 5 cm DBH) of the two conifers was less affected by local crowding. However, the number of recruits of P. glehnii was only about a quarter of that of A. sachalinensis during the census period because the regeneration of P. glehnii was largely restricted to fallen logs and within 1 m of the base of any live tree > 20 cm DBH. Therefore, our long-term study suggests that A. sachalinensis will dominate over P. glehnii in the seral forest because of higher recruitment and growth rates of the former than the latter in the understory.An erratum to this article can be found at     

Regeneration process of coniferous forests in northern Hokkaido I.Abies sachalinensis forest andPicea glehnii forest

Regeneration of natural forests was studied in the Nakagawa Experiment Forest of Hokkaido University using age distribution surveys made by the clear felling method. In Plot 1 (30 m × 65 m),Abies sachalinensis dominated the canopy layer but there were also a fewBetula ermanii trees.Sasa senanensis densely covered the forest floor. Most of the canopy trees were from 122 to 195 years old. Seedlings younger than 50 years old ofA. sachalinensis were found on fallen logs and root bases. There were, however, few trees from 50 to 120 years old. The present canopy trees seemed to have regenerated after competitive pressure from old canopy andSasa disappeared 180 years ago. Plot 2 (50 m × 100 m) on serpentinite soil was dominated byPicea glehnii. Sasa kulirensis covered the floor but not as densely asS. senanensis in Plot 1. The ages ofP. glehnii ranged from 1 to 586 years old, and the age distribution ofA. sachalinensis was L-shaped. A small gap in the canopy formed about 290 years ago, and it gradually extended. Conifers regenerated continuously in the extending gap butB. ermanii did not. One hundred thirty years ago, part of Plot 2 was again destroyed andA. sachalinensis andB. ermanii regenerated. Thus, two types of regeneration were found. One regenerated both conifers andBetula after a sudden disturbance of canopy layer or death ofSasa, and the other, under an extending gap, regenerated only conifers.     

Relationship between plant cover type and soil properties on Syunkunitai coastal sand dune in eastern Hokkaido

A survey of soils and trees was conducted on Syunkunitai coastal sand dune in eastern Hokkaido to clarify the relationships between the soil properties and the plant cover type. A belt transect of 360m in length was established across the dune. Three community types, that is, a Picea glehnii forest, an Abies sachalinensis forest, and a salt marsh were recognized. Soil types at the study area were determined to be sandy immature soil and peat soil. Their horizon sequences were described as A₀–V–C or T–V–C layers (A₀, T, V, and C indicate layers of leaf litter, peat, volcanic deposit, and parent material, respectively). The Abies sachalinensis forest was characterized by a relatively high calcium concentration in the surface soil layer and a tendency for podzolization in the volcanic deposit layer. The Picea glehnii forest was characterized by peat accumulation because of the high ground water table, volcanic deposits in the soil profile, and the strong influence of sea salt on the soil chemistry. The roots in the Picea glehnii forest were distributed more shallowly than those in the Abies sachalinensis forest, thus avoiding the high water table level as well as the influence of seawater in the soil. The salt marsh showed an extremely high sodium concentration and base saturation, indicating that this area was directly affected by seawater. Recently, the periphery of the Picea glehnii forest on Syunkunitai sand dune has been declining because of seawater inundation caused by ground subsidence.     

Phenological Development in Bambara Groundnut (Vigna subterranea) at Constant Exposure to Photoperiods of 10 to 16 h

The flowering and fruit-set of a bambara groundnut selectionfrom Ankpa, Nigeria, were studied in greenhouses at constantexposure to photoperiods of 10, 12, 12·5, 13, 14 and16 h. The development of embryos was determined in ovaries fromplants under photoperiods of 11·5 h and 14 h. The beginningof flowering, recorded as the number of days from sowing tothe first open flower, was delayed by lengthening the photoperiod.It started 7 d later under 16 h than under 10 h. This differenceincreased during the production of the next nine open flowers.Lengthening the photoperiod also caused a delay in the beginningof fruit development. Under 13 h it was delayed by more than40 d compared with fruit development under 10 h. Some plantsunder 14 and 16 h even failed to produce pods. After the beginningof fruit development dry matter partitioning to pods was substantiallyless under 14 and 16 h photoperiods than under photoperiodsof 13 h or less; this was reflected in a strong reduction ofpod growth rates. Under an 11·5 h photoperiod two groups of ovaries couldbe distinguished. In both, embryo development was identicalup to 17 d after anthesis, but then the embryos in the firstgroup continued to develop until they were full-grown at about41 d after anthesis, whereas the growth of the embryos in thesecond group stopped. Embryo development under a photoperiodof 14 h was similar to that in the ovaries with discontinuedembryo growth under the 11·5 photoperiod. Healthy-lookingembryos were found in ovaries up to 32 d after anthesis undera photoperiod 14 h. From then onwards embryos started to shriveland degenerate. Finally, the ovaries aborted.Copyright 1993,1999 Academic Press Vigna subterranea, Voandzeia subterranea, bambara groundnut, phenology, photoperiod, day-length, embryo development, harvest index, dry matter partitioning     

Effects of life history strategies and tree competition on species coexistence in a sub-boreal coniferous forest of Japan

We examined the effects of different life history strategies and tree competition on species coexistence in a northern coniferous forest. We investigated the growth and demography of trees with stems ≥1 cm dbh in a 2-ha study plot in the Taisetsu Mountains of northern Japan. Three species, Abies sachalinensis, Picea jezoensis, and Picea glehnii, were found to be dominant in the forest. A. sachalinensis was the most dominant species in the understory, while the two Picea spp. were more abundant in the larger dbh size classes. The turnover rate of A. sachalinensis was about twice that of the Picea spp. The relative growth rate of understory trees in each species did not differ between different canopy conditions (closed canopy or canopy gap). The competitive advantage between A. sachalinensis and P. glehnii switched as they grew from understory (A. sachalinensis superior competitor) to canopy trees (P. glehnii superior competitor). Meanwhile, A. sachalinensis and P. jezoensis exhibited different environmental preferences. We propose that reversal in competitive superiority between different growth stages and trade-off between longevity and turnover are more important factors to promote their coexistence than regeneration niche differentiation related to canopy gaps in this sub-boreal coniferous forest.     

Formation and maintenance of community boundaries in a sub‐alpine forest landscape in northern Japan

Abstract. We focused on community boundaries in a sub‐alpine forest landscape in the Shiretoko Peninsula, northern Japan. Gradient‐directed transects were conducted on the northwestern slope (ranging 500–600 m a.s.l.) of Mount On'nebetsu (1331 m), where complex topography was formed by past landslides. Pioneer Picea glehnii made up a mosaic of pure stands related to landslides. Structural and compositional changes from P. glehnii pure stands to P. glehnii and Abies sachalinensis mixed stands were characterized by ca. 20 m transitional zones over the landscape. Stand density of the species changed across boundaries. A. sachalinensis preferred less undulated slopes with deep soil and P. glehnii preferred undulated rocky sites. Positive spatial associations between overstorey‐understorey P. glehnii were found at undulated core parts of P. glehnii pure stands. Short‐lived A. sachalinensis grew faster to the smaller maximum size than long‐lived P. glehnii. Undulated topography controlled the increase of A. sachalinensis and provided regeneration sites for P. glehnii, which prevented the general trend of canopy replacement from P. glehnii to late‐successional A. sachalinensis. However, the locations of current boundaries were not accordant with the topographic changes in the meso‐scale landscape. Initial P. glehnii pure stands would extend to larger areas if current patterns reflect vegetation recovery since the last landslide. P. glehnii pure stands with accurate boundaries were not maintained by topographic complexity, but were dynamically arranged by the one‐sided canopy replacements from P. glehnii to A. sachalinensis at less undulated slopes in the sub‐alpine forest landscape.     

Water Relations of Sitka Spruce Seedlings After Root Damage

Sitka spruce[Picea sitchensis(Bong.) Carr] seedlings were subjectedto varying degrees of root damage in a growth room, rangingfrom careful transplanting to exposure of the root system toair for up to 3 h. After replanting, transpiration (E), leafwater potential (₁) and growth of the shoot and root were measuredand observations made on plant survival. Some plants in the root exposure treatments died 20–85days after planting. In plants which eventually died, E wasdepressed directly after treatment, but ₁ showed a variableresponse. In some plants ₁ decreased from —8·0x 10⁵ to —30 x 10⁵ Pa after only 10 days but in othersthere was little change in ₁ for 50 days. In spite of the maintenanceof a high water potential in some of the latter plants for longperiods, no root or shoot growth occurred. In plants which lived, the root damage reduced root and shootgrowth relative to untreated controls, and most treatments stronglydepressed E but had little or no effect on ₁. The changes of E and ₁ in treated plants suggest that the suppressionof E was often independent of ₁ although water stress eventuallydeveloped in some of the severely treated plants. Sitka spruce, Picea sitchensis (Bong.)Carr, water relations, root damage, transpiration, leaf water potential     

Genetic diversity and geographic differentiation in endangered Ammopiptanthus (Leguminosae) populations in desert regions of northwest China as revealed by ISSR analysis

• Background and Aims The desert legume genus Ammopiptanthuscomprises two currently endangered species, A. mongolicus andA. nanus. Genetic variability and genetic differentiation betweenthe two species and within each species were examined. • Methods Inter-simple sequence repeat (ISSR) marker datawere obtained and analysed with respect to genetic diversity,structure and gene flow. • Key Results Despite the morphological similarity betweenA. mongolicus and A. nanus, the two species are geneticallydistinct from each other, indicated by 63 % species-specificbands. Low genetic variability was detected for both populationlevel (Shannon indices of diversity H_pop = 0·106, percentageof polymorphic loci P = 18·55 % for A. mongolicus; H_pop= 0·070, P = 12·24 % for A. nanus) and specieslevel (H_sp = 0·1832, P = 39·39 % for A. mongolicus;H_sp = 0·1026, P = 25·89 % for A. nanus). Moderategenetic differentiation was found based on different measures(AMOVA _ST and Hickory ^B) in both A. mongolicus (0·3743–0·3744)and A. nanus (0·2162–0·2369). • Conclusions The significant genetic difference betweenthe two species might be due to a possible vicariant evolutionaryevent from a single common ancestor through the fragmentationof their common ancestor's range. Conservation strategies forthese two endangered species are proposed.     

Morphogenetic Responses of Browallia Leaf Sections and Callus

Leaf sections of Browallia viscosa and B. speciosa were placedon Murashige and Skoog (1962) salts and vitamins medium (MS)containing auxins and cytokinins, singly or in combination,to elicit morphogenetic responses. B. viscosa developed extensiveroots in 4 weeks on media supplemented with indolebutyric acid(IBA), indol-3-yl acetic acid (IAA) or naphthalene acetic acid(NAA) (0·01, 0·1, 1·0, 5·0 and 10·0mg^–1), but with 2, 4-D (0·1 mg^–1) only lightyellow friable callus was obtained. Shoot initiation and elongationoccurred consistently in 4–6 weeks on leaf sections inthe presence of 6---dimethylallyl amino purine (2iP). Similarly,shoot regeneration from leaf-derived callus, initiated and sub-culturedon MS + benzyladenine (BA) + NAA only induced callus on leafexplants of both species. B. speciosa did not respond exceptfor moderate and prolific callus formation on MS + BA + NAAand Uchimiya and Murashige (1974) media respectively. Browallia viscosa, Browallia speciosa, tissue culture, regeneration, morphogenetic potential     

Carotenoids of Rowan Berries

The berries of Sorbus aucuparia have been investigated for theircarotenoid contents. The pigments identified were: phytofluene,-, ß-carotene, cryptoxanthin, monoepoxy--carotene,monoepoxy-ß-carotene, aurochrome, and mutatochrome.Usually when green fruits ripen the control of carotenoid synthesisis removed when the chlorophylls disappear, there is a rapidincrease of carotenoids in an over-all oxidative manner anddifferent carotenoids appear. However, the results obtainedsuggest that a different mechanism takes place in S. aucuparia.This may be the exception that proves the rule.     

Phytosociological study of thePicea jezoensis forests of the far east

Forest communities dominated byPicea jezoensis (Yezo spruce) are described from across their entire distributional range in eastern Asia, including the territories of the Russian Far East and Japan. A total of 476 relevés are used representing the following dominant types of spruce forests: pureP. jezoensis, mixedP. jezoensis andAbies sachalinensis, mixedP. jezoensis andAbies nephrolepis, and purePicea glehnii communities. The vegetation is classified into 11 associations, 2 community types, 6 subassociations, 25 variants and 8 subvariants. Nine associations, including theAsaro heterotropoidis-Abietetum sachalinensis, Weigelo middendorffianae-Piceetum jezoensis, Lysichito-Piceetum glehnii, Swido albae-Piceetum obovatae, Oplopanaco elati-Piceetum jezoensis, Philadelpho tenuifolii-Piceetum jezoensis, Vaccinio-Piceetum jezoensis, Rhododendro aurei-Piceetum jezoensis, andMoneseto uniflorae-Piceetum jezoensis, are described for the first time. The ecology and structure of all communities are described and their syntaxonomy discussed. The communities are placed in three alliances,Piceion jezoensis, Abieti nephrolepidis-Piceion jezoensis andPino pumilae-Piceion jezoensis, all. nov. All of the communities described are considered to belong to the orderAbieti-Piceetalia of the classVaccinio-Piceetea.     

Modelling environmental variation in Young's modulus for Pinus radiata and implications for determination of critical buckling height

• Background and Aims Although density-specific stiffness,E/, (where E is Young's modulus and is wood density) is oftenassumed constant by the elastic similarity model, and in determinationof critical buckling height (H_crit), few studies have testedthis assumption within species. Here this assumption is testedfor Pinus radiata growing across an environmental gradient,and theory is combined with data to develop a model of Young'smodulus. • Methods Analyses use an extensive series of environmentalplots covering the range of climatic and edaphic conditionsover which P. radiata is grown in New Zealand. Reduced majoraxis regression was used to determine scaling exponents betweenlog–log plots of H_crit vs. groundline diameter (D), andE/ vs. D. Path analysis was used to identify significant directand indirect (through stem slenderness) edaphic and climaticinfluences on E. • Key Results Density-specific stiffness exhibited 3-foldvariation. As E/ scaled positively with D, the exponent of 0·95between H_crit and D exceeded the assumed value of 0·67under constant E/. The final path analysis model included meanair temperature in early autumn (T_aut) and slenderness as significant(P < 0·05) positive direct influences on E. Tree leafarea index and T_aut were indirectly associated with E throughtheir significant (P < 0·05) positive direct relationshipwith stem slenderness. Young's modulus was most sensitive toT_aut, followed by stem slenderness then leaf area index, andthe final model explained 76 % of the variance in E. • Conclusions The findings suggest that within speciesE/ variation may influence H_crit and the scaling exponent betweenD and H_crit so important in assumptions regarding allometricrelationships. The model presented may provide a useful meansof determining variation in E, E/ and H_crit across environmentalgradients.     

Intraspecific Competition in a Natural Stand of Betula ermanii

Density and size of naturally regenerated Betula ermanii weremonitored for six years in a 100 m² plot located in Hokkaido,northern Japan. Natural thinning of 10- to 15-year-old treesoccurred at a negative exponential rate related to tree volume,demonstrating the –3/2 power rule of self-thinning. Diameterdistributions were unimodal at ages 10–13 years and bimodalat 14 and 15 years. Changes in diameter distribution were accompaniedby changes in structure, from a one- to two-storied stand. Mortalitywas highest among smaller trees and where density was greatest.The spatial distribution of trees changed from random to uniformwith increased stand age. Betula ermanii Cham., Self-thinning, mortality, spatial distribution, size distribution     

Rate of Change in Dormancy Level and Light Requirement in Weed Seeds During Stratification

The rate of change in dormancy level and light requirement,induced during stratification at 3.2 °C, was investigatedin seeds ofStellaria media, Cerastium fontanum, Veronica agrestisandTaraxacumofficinale.Two stratification environments, soil and wet filterpaper in petri-dishes, were used. On nine occasions during a6 week stratification period, germination was tested under threelight conditions at 3.5/18.5 °C: (1) darkness; (2) light;and (3) short-term light exposure followed by darkness. Priorto stratification, germination in all species was 89% in lightand 53% in darkness. Within 2 weeks of stratification, germinabilityinV. agrestisandS. mediaseeds decreased in all treatments. InC.fontanumandT. officinaleseeds, germinability also decreasedafter 2 weeks but only in the dark treatment, indicating inductionof a light requirement. After two more weeks of stratification,the induced dormancy inS. mediaseeds stratified in soil becameweaker and the light requirement inT. officinaleseeds was lost.Differences between the two stratification environments and/orinteractions between light conditions, stratification environmentsand time were found for all species. These results suggest that:(1) the dormancy level and the light requirement of seeds maychange dramatically over relatively short-time periods duringstratification; and (2) germinability depends on the stratificationenvironment experienced by the seeds. Predicting the dormancylevel or light requirement in a seed batch is difficult andrequires a thorough knowledge of the effect of the stratificationconditions used.Copyright 1997 Annals of Botany Company Burial; Cerastium fontanumBaumg.; chickweed; cold stratification; common mouse-ear; dandelion; dormancy; light requirement; seed; Stellaria media(L.) Vill.; speedwell; Taraxacum officinalegroup; Veronica agrestisL.; weed     

Variation and Allometry of Seed Weight inAeschynomene americana

One hundred and fifty seeds from each of 72Aeschynomene americanapopulationswith world-wide origin were weighed individually and the meanand distribution of seed weight were calculated and comparedbetween populations. Mean seed weight varied less than five-foldbetween populations with about 80% having a mean seed weightbetween 2–3 mg. However, differences between the largestand smallest seeds (2–8 mg) ranged two-17-fold withinpopulations. Populations that had larger mean seed weights alsohad larger maximum and minimum seed weights but not larger standarddeviations than those with smaller mean seed weights. Seed distributionsfor populations with a mean seed weight2 mg were positivelyskewed while those for all populations with a mean seed weight4mg were negatively skewed. Populations that flowered later producedsmaller seeds than those that flowered earlier.Copyright 1998Annals of Botany Company. Seed weight, weight distribution, inter-population variation, correlation among traits,Aeschynomene americana.     

Differential photosynthetic characteristics between seedlings and saplings of Abies sachalinensis and Picea glehnii, in the field

Abies sachalinensis and Picea glehnii are co-dominant tree species and major components of the forests of Hokkaido, Japan. Recent work suggests that a reversal in potential competitive superiority at different developmental stages could be important to explain their coexistence. Such shifts in competitive advantage can be mechanistically understood by studying the corresponding physiological differences between distinct life stages. Accordingly, our objective was to investigate in the field the photosynthesis of shade-growing juveniles of these species from two different size-classes, seedlings and saplings. Our results show that seedlings of both species had higher concentrations of photoprotective xanthophylls than saplings, especially in spring, and suggest that seedlings have a lower threshold of stress tolerance than saplings. Photosynthetic capacity per needle area and lateral shoot extension rate decreased from the seedling to the sapling stage in A. sachalinensis, while in P. glehnii, both increased from the seedling to the sapling stage. Abies sachalinensis had higher photosynthetic rates at the seedling stage but lower rates at the sapling stage than P. glehnii. Nevertheless, A. sachalinensis had a higher lateral shoot extension rate than P. glehnii at both stages. Our physiological results support previous ecological observations that A. sachalinensis is a superior competitor to P. glehnii in the understory, and show that its competitive advantage is higher at the seedling stage than at the sapling stage.     

Fine-scale genetic structure among genetic individuals of the clone-forming monotypic genus Echinosophora koreensis (Fabaceae)

• Background and Aims For rare endemics or endangered plantspecies that reproduce both sexually and vegetatively it iscritical to understand the extent of clonality because assessmentof clonal extent and distribution has important ecological andevolutionary consequences with conservation implications. Asurvey was undertaken to understand clonal effects on fine-scalegenetic structure (FSGS) in two populations (one from a disturbedand the other from an undisturbed locality) of Echinosophorakoreensis, an endangered small shrub belonging to a monotypicgenus in central Korea that reproduces both sexually and vegetativelyvia rhizomes. • Methods Using inter-simple sequence repeats (ISSRs) asgenetic markers, the spatial distribution of individuals wasevaluated using Ripley's L(d)-statistics and quantified thespatial scale of clonal spread and spatial distribution of ISSRgenotypes using spatial autocorrelation analysis techniques(join-count statistics and kinship coefficient, F_ij) for totalsamples and samples excluding clones. • Key Results A high degree of differentiation betweenpopulations was observed (_ST(g) = 0·184, P < 0·001).Ripley's L(d)-statistics revealed a near random distributionof individuals in a disturbed population, whereas significantaggregation of individuals was found in an undisturbed site.The join-count statistics revealed that most clones significantlyaggregate at 6-m interplant distance. The Sp statistic reflectingpatterns of correlograms revealed a strong pattern of FSGS forall four data sets (Sp = 0·072–0·154), butthese patterns were not significantly different from each other.At small interplant distances (2 m), however, jackknifed 95% CIs revealed that the total samples exhibited significantlyhigher F_ij values than the same samples excluding clones. • Conclusion The strong FSGS from genets is consistentwith two biological and ecological traits of E. koreensis: bee-pollinationand limited seed dispersal. Furthermore, potential clone matesover repeated generations would contribute to the observed highF_ij values among genets at short distance. To ensure long-termex situ genetic variability of the endangered E. koreensis,individuals located at distances of 10–12 m should becollected across entire populations of E. koreensis.