Population structure and spatial patterns for trees in a temperate old-growth evergreen broad-leaved forest in Japan

The population structure and spatial pattern of major tree species in a warm-temperate old-growth evergreen broad-leaved forest in the Tatera Forest Reserve of Japan were investigated. All stems 5 cm in diameter at breast height (DBH) were mapped on a 4 ha plot and analyses were made of population structure and the spatial distribution and spatial association of stems in different vertical layers for nine species. This was done in the context of scale dependency. The plot was located on a very gentle slope and 17.1% of its canopy layer was in gaps. It contained 45 woody plant species and 4570 living stems with a basal area of 63.9 m² ha^–1. Castanopsis cuspidata var. sieboldii, the most dominant species for the basal area, had the maximum DBH among the species present, fewer smaller stems and a lower coefficient of statistical skewness of the DBH distribution. The second most dominant species, Dystilium racemosum, had the highest stem density (410 ha^–1), more abundant smaller stems and a relatively higher coefficient of skewness. Most stems in different vertical layers showed a weakly aggregated distribution with loose colonies as basic units. Gap dependency for the occurrence of stems under the canopy layer was weak. Maximum slope degree of the plot also weakly affected the occurrence of stems. Spatial associations varied among intra- and interspecific cohorts in the different layers and spatial scales examined, and positive associations among cohorts were found more frequently as the scales examined became larger. This tendency suggests that key factors forming observed spatial associations might vary with the spatial scales.     

The ecology of very small-seeded shade-tolerant trees and shrubs in lowland rain forest in Singapore

A study was made in Bukit Timah Nature Reserve of niche differentiation among 11 woody species that have very small seeds (22–460 µg) and establish in deep shade, i.e., where the indirect site factor (isf) under cloudy conditions is 2%, and one taxonomically related light-demander (seed mass 33 µg). Comparative observations were made on changing light requirement with age. The species varied from shrubs and treelets (Urophyllum) via small to medium-height trees (Ficus, Pternandra) to tall trees (Gynotroches and Pellacalyx). In general, the shorter species fruited in deep shade while the taller needed direct irradiance. All produced ripe fruit at least once a year.In 1–3% isf seedling mortality over 11 months was 24% for Urophyllum hirsutum and 57% for Pternandra echinata (two strongly shade-tolerant species); survivors produced appreciable new stem and leaf tissue. For two more light-demanding species (Ficus grossularioides and F. fistulosa) mean lamina area was much larger in small gaps (10% isf) than in the understorey (<3% isf), while for Urophyllum hirsutum it was much smaller. These three species showed the greatest difference in SLA. There were few significant intraspecific differences between gaps and understorey in concentrations of N, P or K. In a valley where there was no significant difference in isf between a path and adjacent understorey, seedlings of species with seeds <1 mg mean dry mass were five times as dense on transects along steep pathside banks as in the understorey 5 m upslope. The mean mid-bank slope was 66° (cf. 20° upslope). On mid-bank transects litter had a cover of 36% (cf. 95% upslope), and was thinner (0.8 vs 3.2 cm). The soil at 0–7 cm depth into the mid-bank had much lower concentrations of organic matter, total N and P (but not total K) and fine roots than that of upslope transects. All species were found to have vesicular-arbuscular mycorrhiza when 1–2 m tall in deep shade, several having very dense infections. Seedling form and responses are discussed in relation to potential adaptive value and possible evolutionary origin.     

Winter photosynthesis by saplings of evergreen broad-leaved trees in a deciduous temperate forest

* Here we investigated photosynthetic traits of evergreen species under a deciduous canopy in a temperate forest and revealed the importance of CO2 assimilation during winter for annual CO2 assimilation. * Saplings were shaded by the canopy trees from spring through to autumn, but were less shaded during the winter months. Photosynthetic rates at light saturation (Aarea) were lower during winter than during the growing season. Aarea was higher in Camellia, Ilex and Photinia than in Castanopsis, Cleyera and Quercus during the winter, but differed little during summer and autumn. * Estimated daily CO2 assimilation (Aday) was higher during the winter than during the growing season in Camellia, Ilex and Photinia but was higher than that during the growing season only at the beginning and end of winter in Castanopsis, Cleyera and Quercus. Aday was higher in Camellia, Ilex and Photinia than in Castanopsis, Cleyera and Quercus but differed little among them during the growing season. * These results reveal the importance of winter CO2 assimilation for the growth of Camellia, Ilex and Photinia. Furthermore, differences in annual CO2 assimilation among species are strongly modified by species-specific photosynthetic traits during the winter under deciduous canopy trees.     

Regeneration dynamics of alluvial gaps in a warm temperate rain forest in New Zealand

Gaps formed by stream laid gravels in a warm temperate Podocarp-Angiosperm rain forest in New Zealand were quickly invaded by 41 free-standing woody species. Height-age curves for the eight most frequent species were used to construct a 12 yr chronosequence which showed 18 species arrived by 0.9 yr and 33 by 1.9 yr. This rapid invasion was supplied from both gaps and mature forest and fitted the Initial Floristic Model coupled with a Facilitation Mechanism. Over the 12 yr period, stem density and births peaked at 0.9 yr and deaths at 1.9 yr with a natality of 39.5/m², a mortality of 38.5/m² and nearly 99% dying as seedlings. Plant height increased to 5.1 m at 12.1 yr with height increment peaking at 43 cm/yr at 7.3 yr. Maximum potential heights ranged from 4 to 60 m and were positively correlated with longevity which varied from 20 to 1150 yr for 19 known species. A decline in height increment to 0.9 yr showed a below-ground component in intraspecific competition with significant negative correlations between stem density and height indicating a later above-ground component. There was no significant height competition amongst the 11 most frequent species and only one significant negative interspecific association. This suggests high species coexistence for which Equal chance was probably the major mechanism. Given this coexistence, rapid species arrival, early sexual maturity and similar density and height-age patterns, the main dynamic variables may be maximum height, longevity and height increment, all of which are, partly, genetically programmed. Most dynamic affinities are with tropical forest, although height growth and species richness are warm temperate.     

Spatial distribution patterns of trees at different life stages in a warm temperate forest

We have investigated tree distributions in relation to topography between different tree life history stages, from the seed-dispersal stage to the adult stage in a warm temperate evergreen broadleaved forest on Yakushima Island, Japan, to clarify the critical stages in determining adult tree distributions. We conducted a census of all living trees > or =30 cm tall and collected seed falls over three years using 25 seed traps in a 50 m x 50 m quadrat. Four life stages were defined: stage 1, dispersed seed; stage 2, individuals taller than 30 cm and diameter at breast height (DBH) < 1 cm; stage 3, trunks 1 cm < or = DBH < 10 cm; stage 4, trunks with DBH > or = 10 cm. We classified 17 common tree species into three groups; group A was distributed mainly on the upper slope, group B on the lower slope, and group C on both. Most of group A and B trees at stages 2-4 showed an aggregated distribution along the topographical gradient. The densities at stage 1 showed weaker aggregations according to slope. Topography-specific tree distribution was probably determined at the regeneration stage, and later survival was less effective as a mechanism of vegetation differentiation.     

Population dynamics of coniferous and broad-leaved trees in a Japanese temperate mixed forest

The growth and survival of coniferous and broad-leaved trees were followed over a 5-yr period in a temperate old-growth mixed forest in Japan, and dynamic features of the forest were studied in relation to the life history of the dominants, the coniferous Abies homolepis and the broad-leaved Fagus crenata. During this period, the gap formation rate was 31m² ha^?1yr^?1, the mortality of trees > 2m high was 1.7%/yr, and the rate of loss in basal area 1.4%/yr. These values were much higher than the recruitment, 0.3%/yr, and the total growth of surviving and new trees, 0.6%/yr, owing to the inhibition of regeneration by understorey dwarf bamboo (Sasa borealis). A transition matrix model based on DBH size classes predicts that the basal area of the forest will decrease by 14% in 50 yr, but that the DBH distribution of trees > 10 cm diameter will change little. Equilibrium DBH distributions assuming recruitment being equal to mortality, were quite different between broad-leaved and coniferous trees, reflecting different survivorship curves of the two dominants. The composition and structure of the forest may change depending on the pattern and frequency of disturbances, or episodic events, notably the synchronous death of Sasa borealis.     

Light energy partitioning in photosystems I and II during development of Nothofagus nitida growing under different light environments in the Chilean evergreen temperate rain forest

Nothofagus nitida (Phil.) Krasser (Nothofagaceae) regenerates under the shade. Nonetheless, older seedlings are commonly found at full sun. We tested the hypothesis that light capture and photochemical and non-photochemical energy dissipation of both photosystems PSI and PSII adjust with ontogeny and brighter environment. Light energy partitioning in both photosystems was studied in seedlings of different developmental stages (small 9.7 cm, tall 36 cm) under contrasting light environments (8–200 and 1,800–2,043 μmol photons m⁻² s⁻¹) in the Chilean evergreen temperate forest. Higher A _max, dark respiration, and light compensation and saturation points in sun seedlings of both developmental stages were accompanied by higher rates of electron transport. These seedlings also showed a high fraction of open PSII reaction centres and similar non-photochemical quenching at high-light in both photosystems, showing no effect of developmental stage in these parameters. Conversely, light capture, total thermal dissipation after photoinhibition, active down-regulation of antenna efficiency, and state transitions were higher in smaller seedlings than in taller ones. These changes maintain photostasis, preventing photodamage, while favouring a more oxidized quinone pool. There is an independent effect of seedling development and light acclimation on this transition from shade to sun during early ontogeny. This transition reflects short-term responses of the photosynthetic apparatus to light and longer term responses that depend on seedling developmental stage.     

Canopy structure in a temperate old-growth evergreen forest analyzed by using aerial photographs

We used aerial photographs to create a digital elevation model of the canopy surface of a 10-ha study area in a temperate old-growth evergreen forest. A topographic map of the ground surface in a 4-ha permanent plot within the study area was also drawn from ground measurements. The difference between the two elevation values (i.e., canopy surface – ground surface) at each point in a 5-m grid was considered to be the canopy height, and a canopy height profile was constructed from these data. The canopy structure in the 4-ha plot that was estimated in this way was compared with that obtained by two ground observation methods, i.e., the canopy (vegetation) height profile method and the canopy coverage census method. Large gaps were adequately detected by the aerial photograph method, but small gaps were less often detected. Gap size distribution obtained by the aerial photograph method was similar to that observed on the ground, and was a function of gap depth. This study indicates that if a detailed topographic map can be made, the canopy height profile derived from aerial photography can be effective in analyzing the canopy structure of evergreen forests, such as tropical rain forests, over large areas.     

Community dynamics of evergreen broadleaf forests in southwestern Japan. I. Wind damaged trees and canopy gaps in an evergreen oak forest

The rates of treefall and canopy opening in the evergreen oak forest in southwestern Japan were determined by studying the number and size distribution of overstory trees, wind damaged trees, and canopy gaps in a belt transect in the Kasugayama Forest Reserve in Nara City. Thirty three percent of the overstory trees wereCastanopsis cuspidata. The total area of canopy gaps was about 20% of the total land area in the study area. The ages of the gaps were determined by counting the annual rings of various kinds of trees growing in gaps. By comparing gap ages with meteorological data, it became evident that gap formation was mainly caused by strong typhoons. The mean time interval between strong typhoons visiting the forest reserve, 6.57 years, was determined by applying the MNY method to the meteorological data. The treefall rate and the mean area of canopy openings per year were 0.84 overstory trees/ha·year and 55.6 m²/ha·year, respectively. The mean residence time of the forest canopy was about 180 years.     

Leaf longevity in evergreen shrubs: variation within and among European species

Summary Leaf longevities were determined for 16 species of evergreen shurbs (Ericaceae and Empetraceae) at different habitats at three latitudes (c. 47°, 55–58° and 68°N) in central and north Europe to determine whether any general trends exist in variation in leaf longevity within and among species. Among these species and sites, mean leaf longevity varied between 1.4 and 3.8 seasons, which is similar to the values reported for other evergreen shrubs, but shorter than for many evergreen conifers. Consistent differences in leaf longevity were found when comparing latitudes (ignoring altitude and habitat type): longevities were longer at 68°N than at the two lower latitudes. No consistent trends were found among species within altitudes.     

Roots of pioneer trees in the Amazonian rain forest

. On low fluvial terraces of the Caquetá River, Araracuara region, Colombia, tree root systems were examined with regard to their structure, underground stratification and biomass distribution. Excavations of skeleton roots and microscopic observation of terminal fine roots included ten species belonging to the Cecropia, Vismia, Miconia, Goupia, Clathrotropis and Brosimum genera. Roots of particular species varied in the external features of their periderm and structure of freshly cut slash. Coarse skeleton roots differed in the shape and position of the plagiotropic branches and positively geotropic taproots or sinkers. None of the observed species could be identified as a shallow-rooted tree, in spite of the general fine root concentration in the upper soil horizon. In the two seasons of study, the terminal roots displayed prevailingly secondary anatomical structure and did not maintain much primary anatomical tissue in their apices. Neither ectomycorrhizas nor endomycorrhizas were detected in the samples. In a set of regeneration stages the amount of tree roots linearly increased with the age of growth. However, fine roots below 2 mm in diameter shared 80-90% of all roots in the upper 20 cm layer of all sample plots. In an old-growth forest, the total tree root biomass amounted to 39 ton/ha, thus being comparable to the underground biomass observed in similar tropical forests.     

The effects of a typhoon on Japanese warm temperate rainforests

A powerful typhoon (Typhoon No. 13) affected stands of primary warm temperate rainforest in Yakushima, southern Japan, in 1993. Censuses in three sites 1–5 months after the typhoon showed low levels of mortality resulting from the typhoon (0.4–3.0% of stems). Stems killed by the typhoon were generally larger than surviving stems. Among surviving stems there were generally low levels of damage (e.g. 0.5–1.3% of surviving stems lost crowns) and not all damage was widespread (e.g. defoliation was apparent only in one of three sites). The sizes of uprooted stems, stems that lost crowns and relatively undamaged stems were not different. Different species appeared to be damaged in different ways at different sites. Damage was most evident in higher altitude seaward sites but gap formation was more frequent in lower altitude sites near valley floors. After the typhoon the resultant gap area occupied 9.4% of one site and 8.6% of another, which is greater than that before the typhoon. Fresh sprouts were found on 17.35% of 2161 stems after the typhoon, including many apparently undamaged stems as well as those that were damaged. Species which sprouted most frequently were those that regenerate by seed least frequently in these forests; these species may maintain their relative abundance in part by sprouting. Most tree species in these forests may be relatively resistant to typhoons and there may be more opportunities for their regeneration following gap formation caused by the typhoon.     

Leaf traits and photosynthetic parameters of saplings and adult trees of co-existing species in a temperate broad-leaved forest

In Central European forestry the establishment of broad-leaved mixed forests is attaining increasing importance, but little information exists about gas exchange characteristics of some of the tree species involved, which are less abundant today. In an old-growth forest in Central Germany (Hainich, Thuringia), (i) I compared morphological and chemical leaf traits that are indicative of leaf gas exchange characteristics among eight co-existing species, and (ii) analysed photosynthetic parameters of saplings and adult trees (lower and upper canopy level) in four of these species (Acer pseudoplatanus L., Carpinus betulus L., Fraxinus excelsior L. and Tilia platyphyllos Scop.).Leaves from the upper canopy in the eight species studied varied significantly in their specific leaf area (12.9–19.4 m² kg⁻¹), stomatal density (125–313 stomata mm⁻²), leaf nitrogen concentration (95–157 mmol N m⁻²) and δ¹³C content (–27.81 to –25.85‰). F. excelsior and C. betulus were largely contrasting species, which suggests that the species, which were studied in more detail, include the widest difference in leaf gas exchange among the co-existing species. The saplings of the four selected species exhibited shade acclimated leaves with net photosynthesis rates at saturating irradiance (A_max) between 5.0 and 6.4 μmol m⁻² s⁻¹. In adult trees A_max of fully sunlit leaves was more variable and ranged from 10.5 (C. betulus) to 16.3 μmol m⁻² s⁻¹ (F. excelsior). However, less negative δ¹³C values in F. excelsior sun leaves point to a strong limitation in gas exchange. In the lower canopy of adult trees A_max of F. excelsior (12.0 μmol m⁻² s⁻¹) was also greater than that of A. pseudoplatanus, C. betulus and T. platyphyllos (5.0–5.6 μmol m⁻² s⁻¹). This can be explained by the small leaf area and the absence of shade leaves in mature F. excelsior trees. Thus, a considerable variation in leaf traits and gas exchange was found among the co-existing tree species. The results suggest that species-specific characteristics increase the spatial heterogeneity of canopy gas exchange and should be taken into account in the interpretation and prediction of gas flux from mixed stands.In der Forstwirtschaft Mitteleuropas gewinnt die Begründung von Laubmischwäldern zunehmend an Bedeutung, aber über Eigenschaften im Gasaustausch einiger beteiligter Baumarten, die heute nicht so häufig sind, ist wenig bekannt. In einem Altbestand in Mitteldeutschland (Hainich, Thüringen) habe ich (i) morphologische und chemische Eigenschaften von Sonnenblättern, die Hinweise auf Charakteristika im Blattgaswechsel geben, an acht koexistierenden Baumarten untersucht, und (ii) Photosyntheseparameter von juvenilen und adulten Bäumen (unteres und oberes Kronenniveau) von vier dieser Arten (Acer pseudoplatanus L., Carpinus betulus L., Fraxinus excelsior L. and Tilia platyphyllos Scop.) erhoben.Blätter aus dem oberen Kronenraum der acht untersuchten Arten variierten signifikant in der spezifischen Blattfläche (12.9–19.4 m² kg⁻¹), der Stomatadichte (125–313 Stomata mm⁻²), dem Blattstickstoffgehalt (95–157 mmol N m⁻²) und den δ¹³C-Werten (–27.81 bis –25.85‰). In diesem Kollektiv zeigten F. excelsior und C. betulus groβe Unterschiede, was darauf hindeutet, dass die Arten, die genauer untersucht wurden, die Spannweite an Gaswechseleigenschaften unter den koexistierenden Baumarten umfassen. Die Jungpflanzen der vier ausgewählten Arten besaßen Schattenblätter, deren Netto-Photosyntheserate bei hoher Lichtintensität (A_max) zwischen 5.0 and 6.4 μmol m⁻² s⁻¹ variierte. An Sonnenblättern von Altbäumen war A_max variabler und lag zwischen 10.5 (C. betulus) und 16.3 μmol m⁻² s⁻¹ (F. excelsior). Allerdings weisen hohe δ¹³C-Werte in Sonnenblättern von F. excelsior auf eine starke Limitierung des Gasaustauschs hin. Auch in der unteren Krone der Altbäume war A_max von F. excelsior (12.0 μmol m⁻² s⁻¹) höher als A_max von A. pseudoplatanus, C. betulus und T. platyphyllos (5.0–5.6 μmol m⁻² s⁻¹). Dies kann durch die geringe Blattfläche und die Abwesenheit von Schattenblättern in der Krone adulter Bäume von F. excelsior erklärt werden. Zwischen den koexistierenden Baumarten wurde somit in Bezug auf Blatteigenschaften und Photosyntheseparameter eine erhebliche Variation festgestellt. Die Ergebnisse legen nahe, dass artspezifische Eigenschaften die räumliche Heterogenität des Gaswechsels im Kronenraum erhöhen und bei der Interpretation und Vorhersage von Gasflüssen über Mischbeständen berücksichtigt werden sollten.     

东灵山暖温带落叶阔叶次生林动态监测样地:物种组成与群落结构

群落结构状态是植被演替进程中的重要体现之一,同时也是下一步演替过程发生的基础.暖温带落叶阔叶次生林是中国暖温带森林植被的主要类型.为了更好地研究其演替动态、生物多样性维持机制,我们参照巴拿马Barro Colorado Island(BCI)50 ha热带雨林样地的技术规范,于2009年11月至2010年9月在北京门头沟区小龙门森林公园的暖温带落叶阔叶次生林内建立了一块20 ha的固定样地(简称DLS),对样地内胸径≥1 cm的所有木本植物进行了鉴定、调查及定位,分析了群落的组成和结构.结果表明,样地内木本植物有58种,隶属于18科33属.独立个体的总数为52,136,包括独立个体分枝的总数为103,284,全部为落叶树种.群落的区系类型以北温带成分居多,同时混有一些亚热带和热带成分,属典型的温带森林类型.群落优势种明显,个体数最多的前5个种的个体数占到总个体数的61%,前20个种占到92%,而其余38个种只占8%.群落成层现象明显,垂直结构由主林层(19个种)、次林层(18个种)和灌木层(21个种)组成.样地所有木本植物个体总径级分布呈倒"J"型,群落更新良好.主林层树种的径级结构近似于双峰或正态分布,而次林层和灌木层树种则表现出倒"J"型或"L"型.几个主要树种的空间分布表现出不同的分布格局,随着径级增大,聚集程度降低.空间分布格局显示主要优势种自身个体在其径级大小的空间分分布上互补,不同径级的个体占据了样地内不同的空间位置.     

Size-class differences in genetic structure and individual distribution of Camellia japonica L. in a Japanese old-growth evergreen forest

Size-class differences in genetic structure and individual spatial distribution were investigated for Camellia japonica within a 1-ha plot in a Japanese old-growth evergreen forest using microsatellite markers. Three size-classes were considered containing plants that were: 30-32.5 cm tall, 103.8 cm-200 cm tall and those that had a diameter at breast height > or =5 cm, designated JV1, JV2, and ADL, respectively. Each size-class contained 174 individuals. Morisita's index of dispersion indicated clumping of individuals was present within all size-classes, with JV2 displaying the highest level. The clumped distribution of JV1 individuals may be a result of limited seed dispersal, while that of JV2 may be attributed to heterogenieties of favourable microsites, such as canopy gaps. There were no significant differences in allele frequencies among size-classes. There were, however, some differences in spatial genetic structure among them. Moran's I spatial autocorrelation analysis revealed clear spatial genetic structure in class JV1 probably due to limited seed dispersal. In class JV2, genetic structure was not observed. Overlapping seed shadows, probably in canopy gaps, may lead to blurred genetic structure in JV2.     

Studies on the life history of an evergreen herb,Pyrola japonica,population on a forest floor in a warm temperate region

The life history and matter economy were studied on an evergreen herb,Pyrola japonica Klenze, population growing on the floor of a deciduous forest in a warm temperate region, central Japan. Seasonal changes in standing crop, bulk density and reserve substance of each organ and in leaf area were investigated over a year. Monthly and annual net production of the population were estimated based on the growth in dry weight and the seasonal dynamics of reserve substance. Seasonal peak value of the monthly net production was 16.7 g d.w.m⁻² in May. The annual net production was estimated to be 60.2 g d.w.m⁻². Two phases were recognized in the annual pattern of development and matter economy of this plant. Phase I, from April to June, was characterized by the development of aboveground vegetative organs and the consumption of reserve substance rrom old organs. Phase II, from July to March, was characterized by the development of reproductive and underground organs, and the accumulation of reserve substance. Phase II was further divided into two sub-phases according to the behavior of the reserve substance and the rate of net production. The production process of the population was compared with those of other evergreen herbs growing on the forest floor in warm temperate regions.