bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the faster initial decomposition of tropical floating leaves of Nymphaea elegans Hook
Authors: Ikusima Isao , Gentil Jóse Geraldo
Published: March 2006

Contributions of abiotic and biotic processes to the decomposition of floating leaves of Nymphaea elegans were separately evaluated by comparing the rate obtained from an in situ experiment of submerging dry leaf material in a lake, and that from a laboratory experiment of submerging dry leaf material in lake water with a bio‐fixing reagent. It took 8 days to decompose 79.4% of the initial dry weight of the floating leaf of N. elegans in a tropical lake. Of the dry weight loss, 32.9% and 67.1% were atributed to abiotic and biotic decomposition, respectively. The relationship between decomposition rate and the mesh size of the leaf litter bags was examined by the application of a mathematical model. A reasonable value of decomposition loss at an early stage could be obtained using a bag with a mesh opening of 9.9 mm2. The decomposition rate of floating leaves is faster than that of other aquatic plants. Rapid decomposition of N. elegans leaves may be attributed to the fact that the plant has a low carbon to nitrogen ratio.
An experiment on ant predation in soil using a new bait trap method
Authors: Yamaguchi Takeshi , Hasegawa Masami
Published: March 2006

To examine which species of ant are underground predators, we invented a simple bait trap using live mealworms as bait. A total of 75 bait traps were buried in soil at various depths (10, 20, 30 and 50 cm) to investigate the vertical distribution of predatory ants. The ants captured in approximately 50% of the traps were mostly Tetramorium caespitum and Solenopsis japonica. Solenopsis japonica was captured at greater depths (>30 m) than T. caespitum. Eight kinds of soil invertebrate (the earthworm, wood louse, pill bug, millipede, adults of the dung beetle and carabid beetle, larvae of a cetoniine beetle and the earwig), placed in traps at a depth of 10 cm, varied greatly in attractiveness and vulnerability to ant predation. The earthworm and the wood louse were both attractive and vulnerable to ant predation, whereas the pill bug, the dung beetle and the millipede were attractive but not vulnerable. The larvae of a cetoniine beetle, the carabid beetle and the earwig were mostly unattractive.
Analysis of the multi‐stem clump structure of Litsea japonica Juss. growing in a coastal dwarf forest
Authors: Ito Satoshi , Gyokusen Koichiro
Published: March 2006

The multi‐stem clump structure of a coastal dwarf forest dominated by Litsea japonica Juss. was investigated in order to clarify the sprouting characteristics and self‐maintenance of clumps by stem alternation. The size and age distribution of multi‐stem clumps were analyzed using cumulative relative frequency curves. L. japonica had a large number of stems and an even height distribution or young age‐biased distribution of stems within a clump. These results indicated the sequential flushing of sprouts at high frequency. Height distribution within a clump of L. japonica was relatively even compared to other species. This clump structure suggested the stable self‐maintenance of individuals in all ranges of size and age without disturbances. It originated specific sprouting characteristics as a response to the severe stress of salty wind. Ardisia sieboldii Miq. had few stems within a clump. Although the stem height distribution of large individuals tended to be even, most clumps had a large size‐biased distribution of stem height which indicated simultaneous sprouting. From this structure, sprouts of this species were thought to be of less significance in the stable self‐maintenance of individuals than L. Japonica.
Gnawing damage by rodents to the seedlings of Fagus crenata and Quercus mongolica var. grosseserrata in a temperate Sasa grassland‐deciduous forest series in southwestern Japan
Authors: Ida Hideyuki , Nakagoshi Nobukazu
Published: March 2006

The effects of dwarf bamboo, Sasa, cover on the initial morrality of hardwood seedlings were investigated by transplanting 1‐year‐old beech (Fagus crenata) and current‐year oak (Quercus mongolica var. grosseserrata) seedling to three different stands; old‐growth beech and secondary oak forests with Sasa undergrowth, and a Sasa grassland in a grassland‐forest series near the top of Mt Jippo, southwestern Japan. The most frequent cause of seedling morrality was gnawing of the stems by rodents. In the beech forest, the gnawing was more likely to occur under Sasa cover, suggesting that it provides a good habitat for rodents on the beech forest floor. The Sasa under growth may thus play an imporrant role in regeneration of beech forest. In the oak floor, mortality of both species was low and only a little gnawing occurred during a year. However, no natural oak seedling were found in the forest even after a mast year. This may be because most of the acorns disappeated before establishment. The early‐stage demography of hardwood seedling as oak may thus play an imporrant role in regeneration of oak forest. In the Sasa grassland where the seed supply is small, almost all of the seedlings died fromo gnawing regardless of the presence of Sasa cover. These factors prevent the recruitment of a sizable seedling bank. Rodents may thus play an imporrant role in maintenance of the Sasa grassland.
The impact of intralacustrine introductions with regard to space utilization and competition for territories to a cichlid fish community in Lake Malawi, Africa
Authors: Hert Eva
Published: March 2006

At Thumbi Island West in Lake Malawi, a number of cichlid species was introduced from elsewhere in the lake some 20 years ago. These are now, in part, well established and could have an effect on the indigenous fish fauna. Repeated removals of the males of the introduced species from their territories were undertaken and artificial miniature reefs were established to find out whether the emptied existing territories or the newly established potential territories would be occupied by indigenous species. The results show that the emptied territories were almost invariably re‐occupied by either a male of the introduced species conspecific to the previous territory holder or they remained empty. The newly established miniature reefs were not occupied by territorial males of either introduced or indigenous species but by young fish of a variety of species.
Distribution of hydraulic resistance in seedlings, sprouts and an adult tree of Pasania edulis Makino
Authors: Ito Satoshi , Sakuta Kotaro , Gyokusen Koichiro
Published: March 2006

Hydraulic resistance is an important factor in predicting water status. Hydraulic resistance of petiols, stems and branches, and roots was measured in Pasania edulis Makino in order to compare the distribution of resistance between current seedlings, current stump sprouts and a 16 year old adult tree. Total resistance showed only minor variations despite large variations in plant size. This result is thought to be consistent with allometry between leaf mass and supportive organ mass, and with changes in permeability of conductive organs. Root resistance was low in sprouts and the adult tree due to their mature root systems. Current seedlings with undeveloped root systems had high root resistance. The proportion of petiol resistance in total resistance was high compared to the proportion of their conductive distance, and was thought to be a limiting factor of tree water status. The petiol resistance of the adult tree leaves was higher than for seedling and sprout leaves. From a comparison with the leaf water relation characteristics, the petiol resistance was thought to be provided as low values for intolerant leaves against water stress in order to compensate water inflow, and high values for tolerant leaves to regulate water inflow.
Fluctuation of nut production and seedling appearance of a Japanese beech (Fagus crenata Blume)
Authors: Hiroki Shozo , Matsubara Teruo
Published: March 2006

The nut productivity, density of fallen nuts, seedling appearance and seedling survival of a Japanese beech (Fagus crenata Blume) were investigated at three localities, Mt Gozaisho, Mt Hodaka and Mt Bandai, Japan, from 1976 to 1992. Two patterns of cycles, a short cycle and a long one, were confirmed in the beech nut productivity. Synchronization in the long cycle was recognized both on Mt Hodaka and Mt Bandai. On Mt Gozaisho, the beech nut productivity was quite low, and the seedlings disappeared within 1 year. The phenomenon on Mt Gozaisho seemed to be caused by the low matter production mainly due to erosion and poor soils. A large number of seedlings appeared in the next spring of heavy mast years on Mt Hodaka and Mt Bandai. The large beech nut productivity contributed to the large seedling supply, and this enhanced the survival probability of beech seedlings. This demonstrates the possibility that beech seedlings survived longer even under dense dwarf bamboos, particularly if the seedling supply was large.
Factors limiting the distribution of the annual legume Kummerowia striata in a river floodplain
Authors: Nakatsubo Takayuki
Published: March 2006

The annual legume Kummerowia striata often predominates in river floodplains forming a large population, but it is rare in gravelly areas adjacent to it. In order to clarify the factors limiting the distribution of K. striata, its distribution pattern, germination and survival of seeds sown artificially were studied in the floodplain of the Ohta River. There was a positive correlation between the cover value of K. striata and the percentage of fine particles (<0.2 mm) in the soil. In the winter season, there was a number of seeds (up to 47 seeds 20 cm−2) on the ground where a K. striata population had existed in the previous year, but they were very sparse in areas apart from the population. Only a small proportion of seeds sown in the gravelly area germinated. Many of the germinated individuals died before the first leaf unfolded, but the rest survived to maturity despite repeated floodings. Plants germinated in the gravelly area and those inoculated with soil from the gravelly area bore nodules, showing the presence of Rhizobium in the gravelly area. It was concluded that the colonization of K. striata in the gravelly area was limited by slow dispersal, and by a low percentage of germination and high mortality in the early stage of establishment.
Seasonal changes in the Modulus of Elasticity of living branches of three coniferous species
Authors: Onwona‐Agyeman Siaw , Morioka Noboru , Kondo Minoru , Kitagawa Katsuhiro
Published: March 2006

The seasonal changes in the Modulus of Elasticity (E) of living branches of Cryptomeria japonica, Chamaecyparis obtusa and Larix leptolepis were investigated over a period of 1 year by means of a quick and non‐destructive method previously introduced by the authors. Two sample trees were used for each species and 12 branches were selected from each tree. Readings of the experiments began in summer 1992 and were successively conducted in autumn 1992, winter 1993, spring 1993 and finally in summer 1993. Our investigations revealed that mean E values increased in cold seasons and decreased in warm or hot seasons. Mean values of E estimated in summer (1993) were relatively close to those estimated in summer 1992 indicating that any changes that occurred were the direct result of the environmental factors prevailing in the intervening seasons. Extremely high mean E values were measured when the branches were in a frozen state in winter; 69.4%, 29.9% and 24.6% higher than the previous summer for branches of Cryptomeria japonica, Chamaecyparis obtusa and Larix leptolepis, respectively. This sharp increase over the initial E values measured in summer 1992 was quite likely due to the freezing effect of rime on the branches.
The effect of growth form on the evaporation in some subalpine mosse
Authors: Nakatsubo Takayuki
Published: March 2006

In order to evaluate the importance of growth of mosses in controlling evaporative water loss, the evaporation rates of some subalpine moss species of various growth forms were compared with each other. The growth forms of the xerophytic species examined were large cushion and compact mat, while those of the mesophytic species in the coniferous forest floor were smooth mat, weft and tall turf. The evaporation rate per moss dry weight (Ew) was much smaller in the xerophytic species than in the mesophytic species. However, the evaporation rate per basal area of moss colony (Ea) was not necessarily smaller in the xerophytic species. The relation between Ea and dry weight per basal area of the colony (Wa) had a close correlation with the growth form. It was concluded that the difference in the evaporation rate per weight between the exerophytic species and the mesophytic species was largely due to the difference in Wa, and that the growth forms of the xerophytic species were suitable for increasing Wa without increasing surface roughness.
Topographical pattern of the forest vegetation on a river basin in a warm‐temperate hilly region, central Japan
Authors: Sakai Akiko , Ohsawa Masahiko
Published: March 2006

The relationship between tree distribution and topography was examined in a small river basin (3.4 ha) comprising a complex mosaic of topographical units at 102 to 103 m2 order, each of which had a shallow valley bordered by small ridges or breaks of slopes. Twenty‐five major woody species were divided into two groups (groups A and B) based on a cluster analysis using the distribution data in the basin. Group A, which mainly consisted of early‐successional species, was distributed around the valley sites of the topographical units, while group B, which mainly consisted of late‐successional species, was distributed around the ridge sites of the topographical units. This vegetation pattern coincided with erosional condition in the basin. That is, the valley sites were eroded more actively than the ridge sites, as soil depth tended to be thin in the valley sites and thick in the ridge sites, and because large (canopy) trees were restricted in the ridge sites. There was no tendency that group B was replacing group A, and hence it was suggested that repeated disturbance by slope failures or small‐scale shallow landslides have prevented compositional change from the early‐successional (group A) to the late‐successional (group B) species by preventing the invasion of the latter into valley sites.
Gap regeneration in primary evergreen broad‐leaved forests with or without a major canopy tree, Distylium racemosum, southwestern Japan: A comparative analysis
Authors: Yamamoto Shin‐Ichi
Published: March 2006

Gap regeneration was studied in a typical primary evergreen broad‐leaved forest without Distylium racemosum, at the Kasugayama Forest Reserve, southwestern Japan and the results were compared with those from other primary evergreen broad‐leaved forests in southwestern Japan, where D. racemosum was the dominant species. Several common types of gap regeneration behavior were recognized among the major tree species and forests with or without D. racemosum consisted of three typical regeneration guilds which could be detected in the principal component analysis. Castanopsis cuspidata frequently regenerated in gaps from saplings recruited before gap formation in the forest without D. racemosum, although elsewhere, in forests with D. racemosum, it lacked advanced regeneration and regenerated in gaps from saplings recruited after gap formation. Some evergreen Quercus had their regenerations in gaps of the forest without D. racemosum, although elsewhere, in forests with D. racemosum, evergreen Quercus might not regenerate. The results indicate that tree species may change their regeneration behavior depending on the presence or absence of another key dominant species. This suggests that the presence and the dominance of a potential competitor induces shifts in the regeneration niche of other coexisting tree species.
Vegetation structure along the altitudinal gradient at the treeline of Mount Paektu, North Korea
Authors: Šrůtek Miroslav , Kolbek Jiří
Published: March 2006

Vegetation structure of the treeline was studied on the southeastern slope of Mount Paektu (North Korea). Fifteen temporary plots (20m×20m) were situated along the altitudinal transect. Seven square samples (phytosociological relevés 5 m×5 m) were analyzed in each plot. Although the character of the vegetation was rather continuous altitudinally, five similar groups of vegetation samples were distinguished by the TWINSPAN procedure. The distribution of samples in the classification showed not only the effect of altitude but also the effect of competition between the tree and the shrub layers and other factors. In the canonical correspondence analysis (CCA) ordination several environmental variables were used (such as altitude of each plot, distance of each plot from the forest edge and the cover percentage of tree, shrub, herb and moss/lichen layers). The variable ‘cover of tree layer’ had the strongest relation to the species data. Continuous changes of species richness along the altitude were confirmed. Species richness decreased significantly with altitude.
Tropical fruitflies (Diptera: Tephritidae) of the Krakatau Archipelago in 1990 and comments on faunistic changes since 1982
Authors: Schmidt E. R. , Thornton I. W. B. , Hancock D. L.
Published: March 2006

Three of the Krakatau islands, in Sunda Strait, some 40 km from both Java and Sumatra, are believed to have been totally devastated by the famous cataclysmic eruption of 1883. The fourth, Anak Krakatau, is an emergent volcanic island which rose from Krakatau's submerged 1883 caldera in 1930, suffered a self‐devastating eruption in 1952/3 and several severely damaging ones since then. In 1990 the tephritid fauna was monitored on all the islands with Steiner traps. Nine species were found, five of which appeared to have been found by Yukawa in 1982 (Yukawa 1984) using similar methods and lures, when he noted a total of six species. As in 1982, the fauna in 1990 was characterized by the numerical dominance of Bactrocera albistrigata (de Meijere) although this appeared to be less marked than in 1982 and Bactrocera papayae Drew & Hancock appeared to have increased in relative numbers. The distribution of three species over the islands of the archipelago had increased and four species not found in 1982 were present. Rakata, Krakatau's remnant and by far the largest and highest island, carried seven species (six in 1982), Sertung three (two in 1982), Panjang four (one in 1982) and Anak Krakatau four (one in 1982). Capture rates were lower than in 1982 but still higher than those obtained on the Javan mainland in 1982. There was a marked difference between the tephritid faunas of Anak Krakatau's two forelands, which were at different stages of biotic succession.
Stand structure and growth patterns of understorey trees in a coniferous forest, Taisetsuzan National Park, northern Japan
Authors: Kubota Yasuhiro , Konno Yasuo , Hiura Tsutom
Published: March 2006

Stand structure was studied with special reference to growth and mortality patterns of sapling and understorey trees in a coniferous Picea jezoensis and Abies sachalinensis forest in Taisetsuzan National Park, Hokkaido, northern Japan. Picea jezoensis was dominant in the basal area, while A. sachalinensis was abundant in large numbers in the canopy. Estimated mortalities increased significantly with diameter at breast height (DBH) for both P. jezoensis and A. sachalinensis in the canopy, but the tendency was different between the two species. Picea jezoensis had a lower mortality rate than A. sachalinensis, especially at small DBH classes. The spatial distribution of understorey individuals of A. sachalinensis did not show any significant correlation with the spatial distribution of canopy gaps, but that of P. jezoensis showed a significant correlation. Abies sachalinensis can grow higher than P. jezoensis under suppressed conditions; while P. jezoensis requires canopy gaps for steady height growth. This growth pattern leads to a different waiting height in the understorey (≥2 m in height and 10 cm in diameter at breast height). Abies sachalinensis waited for an improvement in light conditions at higher strata (max. 7 m), while P. jezoensis waited at lower strata (max. 3 m). The estimated mortality of understorey A. sachalinensis increased with size, while that of understorey P. jezoensis decreased. Therefore, P. jezoensis gives priority to survival while A. sachalinensis gives priority to understorey growth. The difference in the ‘waiting pattern’ between the two species in the understorey was considered a significant feature for the canopy recruitment process of P. jezoensis and A. sachalinensis.
Contribution of the Western Australian wheatbelt termite, Drepanotermes tamminensis (Hill), to the soil nutrient budget
Authors: Park H. C. , Majer J. D. , Hobbs R. J.
Published: March 2006

The role of soil modification by the mound‐building termite, Drepanotermes tamminensis (Hill), was studied during 1991 in the Durokoppin Nature Reserve, Western Australia. Soil chemical parameters were quantified for ‘soils’ in nests and for surrounding soil in both a Wandoo (Eucalyptus capillosa) woodland and a Casuarina (Allocasuarina campestris) shrubland plot. All ‘soils’ in nests were more acidic than the surrounding soil within each study plot. Generally, nutrient levels in the nested soils were higher than the un‐nested soil within each study plot and were also higher in the woodland than in the shrubland plot. Depending on the nuttient concerned, the nested soil contained between 0.3 and 21.9% of the total nutrient load per hectare within each study plot. The quantities of nutrients per hectare in termite mounds were higher in the woodland than in the shrubland plot. It is concluded that mounds of this species of termite form a significant bank of nutrients, although time for release of such nutrients depends on the degree of erosion and on the longevity of mounds.
Reproductive ecology of three ocypodid crabs II. Incubation sites and egg mortality
Authors: Henmi Yaushisa
Published: March 2006

Mortality of eggs during incubation was estimated for three ocypodid crabs, Scopimera globosa, Ilyoplax pusillus and Macrophthalmus japonicus, and the influence of incubation sites was discussed. These crabs all lived in isolated burrows and fed on sediments during day time low tide. S. globosa and I. pusillus inhabited the upper intertidal sandflats, whereas M. japonicus inhabited the lower intertidal mudflats. Females of both S. globosa and I. pusillus remained in their plugged burrows without feeding throughout incubation and the mortality of eggs was low despite large broods relative to body size. On the other hand, females of M. japonicus fed actively on surface mud during incubation and the mortality of eggs was high despiite small broods relative to body size. In S. globosa and I. pusillus, the ovaries of ovigerous females were small until egg‐hatching, whereas in M. japonicus, the ovaries grew rapidly during incubation and females were able to produce consecutive broods. I conclude that incubation of eggs in burrows may be advantageous in species which inhabit the upper interidal sandflats, even though the crabs cannot forage during incubation, since otherwise their eggs would be exposed to strong heat stress and desication during the summer. Furthermore, such species may produce few large broods because of less frequent interruption of feeding than that associated with production of many small broods.
Carbon‐cycling changes during regeneration of a decinduous broadleaf forest after clear‐cutting II. Aboveground net production
Authors: Kawaguchi Hideyuki , Yoda Kyoji
Published: March 2006

Growth and death rates of aboveground plant parts were measured in a mature forest and four different‐aged deciduous broadleaf forests regeneratede after clear‐cutting, with special reference to rates for woody parts (stems and branches) of different diameters (ø) in rerms of the pipe model theory (Shinozaki et al., 1964). The total biomass increment of woody parts of trees higher than 1.3 m varied within a range of 2.1‐4.6 ton ha−1 yr−1, the increase beingdue largely to the growth of canopy trees exposed to direct sunlight. Biomass increments of small (ø<1 cm) and medium (1≤ø<5 cm) woody parts were negligibly small except in the youngest forest, and changes in aboveground woody biomass with forest age after clear‐cutting mainly resulted from accumulation of large (5 cm<ø) woody parts of canopy trees. Biomass loss of trees due to death and grazing increased with forest age from 4.0 to 8.3 ton ha−1 yr−1. Recovery of leaf and small wood falls was observed at the early stage of regeneration, while large wood falls increased during regeneration. Flower and fruit fall was markedly higher in the mature forest than in the other four forest types. Mortality of woody parts became higher with forest age and was 20, 5.0 and 0.46% yr−1 for small, medium and large parts, respectively, at the mature stage. Aboveground net production of the forest was in therange 7.6‐13.3 ton ha−1 yr−1 with the undergrowth vegetation lower than 1.3 m being 0.4‐1.4 ton ha−1 yr−1. Production recovered rapidly at an early stage of regeneration and was highest in mature forest.
Edge effects created by clear‐cutting on habitat use by sika deer on Mt. Goyo, northern Honshu, Japan
Authors: Takatsuki Seiki
Published: March 2006

Clear‐cutting increased the species diversity and amount of undergrowth plants in a habitat of Sika deer (Cervus nippon) on Mt. Goyo, northern Japan. The number of species increased from 15 to 48 as a result of clear‐cutting. Among the plants, Sasa nipponica (a dwarf bamboo), an important forage plant for Sika deer, was predominant. Fecal pellets of deer were abundant in the forest and at the “adjacent zone” (from the edge to 150 m out of the forest) and thereafter decreased suddenly. The intensity of utilization of Sasa nipponica was also heavy in the forest, moderate at the adjacent zone and light 200 m from the forest edge. Since the amount of the bamboo in the forest was small, the removal of bamboo was greatest at the adjacent zone. Clear‐cutting creates a favorable feeding area for Sika deer in this zone by increasing the available plant production and securing forest cover.
Comparative ecophysiology of Larix kaempferi (Lamb.) Carr. and Abies veitchii Lindl. II. Mechanisms of higher drought resistance of seedlings of L. kaempferi as compared with A. veitchii
Authors: Yura Hiroshi
Published: March 2006

The underlying mechanisms of drought resistance in seedlings of Larix kaempferi as compared with those in Abies veitchii were investigated. First, seedlings of the two species were desiccated in air of differing water potential, and their survival rates were compared to detect any difference in desiccation tolerance between them. Contrary to differences in their drought resistance, A. veitchii showed higher survival. Next, the shoot heights and root depths of the two species were compared to detect any difference in desiccation avoidance. Although the shoot height differed little between the two species, the roots of L. kaempferi seedlings were much deeper than those of A. veitchii seedlings, and the death rate under progressing drought was well correlated with the root extensibility of each species. It was thus concluded that L. kaempferi seedlings are able to avoid desiccation by extending their roots in deep soil faster than A. veitchii seedlings, thereby resisting to drought.
How to avoid becoming a prey: Predatory encounters between an orb‐weaving spider, Araneus pinguis (Karsch) (Araneae: Araneidae) and flying insects
Authors: Endo Tomoji
Published: March 2006

Insects flying into the web of an orb‐weaving spider Araneus pinguis (Karsch) and their avoidance of (pre‐hitting process) and escapes from (post‐hitting process) the web were examined by direct observation under natural and semi‐natural conditions. In the pre‐hitting process, mobile insects such as Brachycera, Lepidoptera and Hymenoptera showed a low hitting ratio (number of insects hitting/number of insects flying within 1 m3 space around the web‐site) because of active web avoidance and flying activity in layers lower or higher than those in which the webs are usually laid. In contrast, less mobile insects like Heteroptera, Coleoptera and Homoptera showed a high hitting ratio. In the post‐hitting process, Brachycera, Lepidoptera and some Nematocera frequently escaped without being detained by the web. Many Orthoptera and Hymenoptera escaped without any sign of detection by the spider. Coleoptera frequently escaped during the spider's attack. Small insects from the Homoptera, Nematocera and Hymenoptera rarely escaped from the web, but were not immediately attacked. Mean escape time of insects was correlated significantly with capture success of the spider. Overall most of the escapes occurred in the early phases of the predation process. This indicates that escapes are unlikely to result in heavy loss of time and energy expenditure due to unsuccessful predation. Escape patterns of insects seem to be related to their mobility.
An analysis of age‐and size‐dependent flowering: A critical‐production model
Authors: Yokoi Yota
Published: March 2006

Three critical phenomena of flowering can be recognized in nature: critical age, critical initial size and critical switchover size. In order to understand the ecological significance of these flowering phenomena from the viewpoint of matter production, a simple model of flowering phenomean (critical‐production model) was studied, assuming that plant flowering is controlled by the productive capacity of the plant (critical‐production model, under the condition that plants forecast environmental conditions affecting matter production. Thus, we concluded that all three critical phenomena are various manifestation of the same critical‐production principle. Then, using the model simulation, the reliability of each critical phenomenon for securing a given critical production was investigated in relation to the photosynthetic productivity of the habitat. The main predictions obtained from the simulation were as follows: 1) Only annual and biennial plants will show critical age phenomena, and most biennials will be facultative. 2) Among perennials, the critical initial size phenomenon will appear in low productive habitats, whereas in high productive habitats the critical switchover size phenomenon will be observed.
Parasitoid complexes of lepidopteran leaf miners on oaks (Quercus dentata and Quercus mongolica) in Hokkaido, Japan
Authors: Sato Hiroaki
Published: March 2006

Parasitoid complexes of four microlepidopteran leaf‐mining genera, Phyllonorycter, Caloptilia (Gracillariidae), Tischeria (Tischeriidae) and Stigmella (Nepticulidae), which make mines on two oaks, Quercus dentata and Quercus mongolica, were studied at the Ishikari Coast, Hokkaido, northern Japan. In total, twenty‐five parasitoid species were recognized. Phyllonorycter showed the highest parasitoid‐species richness among the four leaf‐mining genera. The number of parasitoid species associated with leaf miners on Q. dentata was nearly equal to that associated with miners on Q. mongolica, but a considerable difference was observed in the faunal make‐up of parasitoids between leaf miners on the two oaks. The dominant parasitoid species differed between Phyllonorycter leucocorona and Phyllonorycter similis even on the same oak, Q. dentata. Factors influencing the host ranges of parasitoids and the parasitoid richness of host species or genera are discussed on the basis of the koinoparasitism/idioparasitism categorization.
Effects of human trampling and multispecies competition on early‐phase development of a tread community
Authors: Ikeda Hiroaki , Okutomi Kiyoshi
Published: March 2006

Effects of human trampling and multispecies competition on the development of a tread community in the first year were examined by comparing changes in the relative abundance of three main component species of tread communities, Plantago asiatica, Eragrostis ferruginea and Eleusine indica, between monoculture and mixed culture along a trampling gradient. At low trampling levels in mixed culture, Ambrosia artemisiifolia var. elatior and Digitaria adscendens, which are common pioneer species of secondary succession, predominated and suppressed the tread community species. Severe trampling reduced markedly the predominance of the pioneer species, but not that of the tread community species. The maximum cover of the three tread commiunty species was lower in mixed culture than in monoculture. The trampling levels supporting the maximum cover were higher in mixed culture than in monoculture. The differences in these levels between monoculture and mixed culture varied among the three:P. asiatica< Eragrostis ferruginea<Eleusine indica. These results suggest that (1) the pioneer species interfere with the establishment of tread community species under lower trampling intensity, (2) heavier trampling reduces the competitive ability of pioneer species, while it favors the establishment of tread community species, (3), there are competitive interactions among the tread community species under higher trampling intensity, and (4) the species more susceptible to multispecies competition and tolerant to trampling are established in more heavily trampled habitats.
Estimation of chronological age for sporophyte maturation in three semi‐evergreen ferns in Hokkaido
Authors: Sato Toshiyuki
Published: March 2006

To elucidate the life cycle time schedule of semi‐evergreen ferns at natural sites in Sapporo, the chronological age for sporophyte maturation was estimated from the increase in the number of veins (NV, number of midrib branches) from overwintered to newly expanded leaves. The measurements were conducted on populations of Polystichum braunii, Polystichum tripteron and Dryopteris crassirhizoma at altitudes of 50–650 m on Mt. Teine to compare the interspecific maturation age of sporophytes. The mean age for sporophyte maturation was estimated to be 7.6 yr for P. braunii, 16.5 yr for P. tripteron and 12.6 yr for D. crassirhizoma. The minimum ages (1% fertility rate) for sporophyte maturation of P. braunii, P. tripteron and D. crassirhizoma were 5.8, 11.0 and 7.9 yr, respectively. The maturation age was shortest for P. braunii and longest for P. tripteron. The maturation age of a species thus seems to differ according to altitude and habitat, and that of the present three species seems to be influenced by the geographical location of the species distribution.
Nutrient dynamics in a floating mat and pond system with special reference to its vegetation
Authors: Haraguchi Akira , Matsui Kiyoshi
Published: March 2006

Chemical properties of waters and their seasonal changes were studied in Mizorogaike Pond, a system of pond and floating mat. The following six sites including contrasting habitats and water conditions were monitored to assess nutrient dynamics in the system: 1) a pool on the mat, 2) margin of a Sphagnum cuspidatum community, 3) an artificial ‘well’ (water layer beneath the floating mat), 4) a Menyanthes trifoliata community in a hollow, and 5) & 6) two sites in the open water. On the floating mat, the water around the Sphagnum community had lower pH values, while that in the M. trifoliata community had higher pH values. This difference was related to the influence of flood water, the extent of which was determined by the microtopography. Seasonal changes in water chemistry on the mat suggested that pond water flooding the mat in late autumn and winter is important for the nutrient supply to the mat surface vegetation in this system. Water chemistry of the ‘well’ suggested that the diffusion of inorganic nitrogen occurs from beneath the peat layer. Two types of cluster analysis based on the mean values for chemical variables and the patterns of fluctuation in these variables were performed. The six sites were classified into similar groups which were identified by water type (pool, hollow, well and open water) by both types of analysis. The results showed that a common kind of perturbation should operate in determining the status of nutrient dynamics in the various water types.
Vegetation changes around the last glacial maximum and effects of the Aira‐Tn ash, at the Itai‐Teragatani site, central Japan
Authors: Oor Nobuo , Minaki Mutsuhiko , Noshiro Shuichi
Published: March 2006

On the basis of fossil pollen, plant macrofossils and fossil wood, vegetation existing around the Itai‐Teragatani Site between 26000 and 20000 yr ago was reconstructed. On the upland, there were mixed forests of conifers and deciduous broad‐leaved trees throughout the studied period. The forests consisted mainly of Pinus subgen. Haploxylon and Quercus subgen. Lepidobalanus, together with Tsuga, Cryptomeria and Ulmus‐Zelkova. In the wetland, there were stands of Betula and Alnus in grassland consisting of Cyperaceae, Gramineae, Lysichiton, Thalictrum, Sangusiorba, Umbelliferae and Compositae. The vegetation changed three times during the studied period. The first change, which occurred prior to the fall of the Aira‐Tn ash, was characterized by an increase in Abies, Pinus subgen. Haploxylon and hygrophytes, and a decrease in Cryptomeria and Alnus. This is considered to reflect a cooler climate, and expansion of grassland. The second change was caused by the fall of the Aira‐Tn ash, which caused serious damage to the vegetation. Many taxa, except for Alnus, Cyperaceae and Lysichiton, decreased or vanished after the ash fall. The third change was the process of recovery after the damage. The regenerated forests differed from those before the ash fall. With the regeneration conifers and Artemisia increased. This seemed to reflect the changes in climate and ground conditions caused by the accumulation of the ash.
Estimation of leaf area at the level of branch, tree and stand in Cryptomeria japonica
Authors: Katsuno Masumi , Hozumi Kazuo
Published: March 2006

The frequency distribution of diameter (x) in foliage shoot segments, ø(x), was examined in 18 branches at different height levels of three trees in a 25‐yr‐old sugi (Cryptomeria japonica D. Don) plantation. The ø‐x relationships were approximated by power‐form equations, in which the exponent differed among the branches from −0.6 to −4.2. Leaf area (SB) and leaf weight (WB) of a branch were estimated on the basis of the ø‐x relationship, and the dependency of specific leaf area (SLA0) and density (ρ0) of a foliage shoot segment on its x. SLAB value of a branch defined by SB/WB ranged from 27 to 80 cm2 g. d.w.−1 according to the exponent in the function of ø(x). Total leaf area (u) and leaf weight (wl) of a tree were estimated by summation of SB and WB for seven sample trees. The SLAT value of a tree defined by u/wl ranged from 65 to 76 cm2 g d.w.−1 and increased with stem diameter at clear length (DB). By use of the allometric equations between u and DB, LAI of the plot was estimated to be 17.3 ha ha−1 (half of the total surface area of needles). By a process similar to that used for calculating LAI, the amount of woody tissues included in sugi foliage was evaluated to be about 10% of the stand foliage biomass.
Dynamics of aboveground big woody organs in a foothill dipterocarp forest, West Sumatra, Indonesia
Authors: Yoneda Tsuyoshi , Tamin Rusdij , Ogino Kazuhiko
Published: March 2006

The dynamics of aboveground big woody organs over 10 cm diameter was studied at a mature foothill dipterocarp forest in West Sumatra. The biomass of big woody organs was estimated to be 519 m3 ha−1 or 408 metric ton ha−1 by means of a pipe model theory. The diameter distribution showed a convex curve and the mode was found at a diameter of about 20 cm. The standing mass of big dead woody litter on the forest floor was 116 m3 ha−1, which accounted for 22% by voume or 9.5% by weight of the biomass of living organs respectively. The dbh observation with two 1‐ha plots for 4 yr and 5 yr respectively revealed that the average net production rate was 9.5 ton ha−1 yr−1. The death rate (7.9 ton ha−1 yr−1) accounted for 83% of the net production rate and was nearly equivalent to the decay rate (7.5 ha−1 yr−1) of dead wood on the forest floor. The balance between the death and decay rates was confirmed for each diameter class. Average turnover periods for big woody organs and dead woody litter were estimated to be 43 and 8.1 yr, respectively. Standing masses of live anddead woody materials accumulated in the study forest were approximately equal to those obtained in a mature tropical lowland rainforest, whereas the flow rates were lower, being only 70% of the corresponding values.
Optimal time of seedling emergence in a dune‐population of Oenothera glazioviana
Authors: Kachi Naoki , Hirose Tadaki
Published: March 2006

Oenothera glazioviana (= O. Erythrosepala) behaves as a facultative biennial in an infertile sand‐dune system in Japan. In the field, seedlings emerge mainly in autumn following seed ripening in late summer with an additional small peak in spring. The effects of emergence time on subsequent survival and fecundity, and the ultimate numbers of seeds produced per emerging seedling (Fs) were examined by a demographic model. The model showed that seedlings emerging either in March or in September–October will attain higher Fs than those emerging in other months. If mortality in the seed bank is taken into account, autumn seems to be the best season for emergence to maximize the number of seedlings in the next generation.
Seasonal variations of microsite light availability within a Miscanthus sinensis canopy
Authors: Tang Yanhong , Washitani Izumi , Iwaki Hideo
Published: March 2006

Photosynthetic photon flux density (PPFD) at 15 cm above the ground was measured at 20 microsites in gaps and grass patches within a Miscanthus sinensis Anderss community at 10 s intervals during 5 days every month from May to September 1989.

Microsite light availability, which was characterized by daily total PPFD, sunfleck PPFD (PPFD above a threshold value of 50 or 400 μmol m−2 s−1) and the diffuse site factor, showed evident seasonal changes, with a marked reduction between June and July due to the rapid growth of the grass canopy. The monthly median value of daily total PPFD among the microsites decreased from 10.3 mol m−2 day−1 in May to 0.77 mol m−2 day−1 in September, with a reduction in the diffuse site factor from 31 to 4%. During the summer, the median value of the total time of sunflecks exceeding 50 μmol m−2 s−1 contributed 7–18% of measurement time, but the contribution of these sunflecks to daily total PPFD ranged from 29 to 59%.

There was considerable microsite variation in light availability throughout the measurement period. Rank correlation analysis revealed that some microsites, such as those in gaps, consistently received more total PPFD, more sunfleck PPFD and had a higher diffuse site factor than those in grass patches. The diffuse site factor had a linearly positive relationship with daily total PPFD and total sunfleck PPFD for the 20 microsites during the measurement period, confirming that the diffuse site factor is a useful index for microsite light availability within M. sinensis canopies.
Dynamics of the fungal symbionts in the gallery system and the mycangia of the ambrosia beetle, Xylosandrus mutilatus (Blandford) (Coleoptera: Scolytidae) in relation to its life history
Authors: Kajimura Hisashi , Hijii Naoki
Published: March 2006

The dynamics of the fungal symbionts in the gallery system and the mycangia of the ambrosia beetle, Xylosandrus mutilatus, were studied in relation to its life history using both isolation experiments and scanning electron microscopy (SEM). In the galleries, Ambrosiella sp. was predominant during the larval stages but its relative dominance gradually decreased during the development of the larvae. In contrast, yeasts (mainly Candida sp.) and Paecilomyces sp. dominated continuously in the galleries after eclosion. Ambrosiella sp. was consistently stored in the mycangia in all adult stages, except in the teneral and overwintering adults when the other fungi were dominant. No fungal spores occurred in the mycangia of the adult beetles reared under aseptic conditions from the pupal stage, while only Ambrosiella sp. was stored in those reared from the teneral‐adult stage. These results suggest that: (i) Xmutilatus is associated with at least three fungal species, among which Ambrosiella sp. is the most essential food resource for development of the broods; (ii) immediately after eclosion, new female adults may take at least four associated fungal species, with no or incomplete selection, into their mycangia from the walls of the cradles; and (iii) conditions may well be produced in the mycangia of both matured and dispersing beetles whereby only the spores of Ambrosiella sp. can proliferate.
Photosynthetic and stomatal responses of Larix kaempferi seedlings to short‐term waterlogging
Authors: Terazawa Kazuhiko , Maruyama Yutaka , Morikawa Yasushi
Published: March 2006

The effects of short‐term waterlogging on net photosynthesis, stomatal conductance and shoot water status of 2 year old seedlings of Larix kaempferi (Lamb.) Carr. were studied under controlled environmental conditions. Waterlogging for 8 days induced significant stomatal closure and reduced net photosynthesis. After 3 days of waterlogging, stomatal conductance was reduced to 35% of that of non‐waterlogged plants, and net photosynthesis was reduced to 25% of the pre‐waterlogged level. At the beginning of waterlogging, slight shoot dehydration was observed. However during the latter stage of the waterlogging shoot dehydration disappeared and stomatal conductance and net photosynthesis increased. No adaptive morphological changes to waterlogging were observed in the stems and roots. Recovery of stomatal conductance and net photosynthesis after drainage was not observed within 11 days.
Comparison of ecophysiological responses to heavy snow in two varieties of Aucuba japonica with different areas of distribution
Authors: Kume Atsushi , Ino Yoshio
Published: March 2006

Aucuba japonica varieties are common evergreen understory shrubs in Japan. Aucuba japonica var. borealis is distributed on the Sea of Japan side of Honshu and Hokkaido where heavy snow cover lasts for more than 3 months in winter. Aucuba japonica var. japonica is distributed in areas with shallow or no snow on the Pacific Ocean side of Honshu and Shikoku. The ecophysiological characteristics of var. borealis were compared with those of var. japonica to examine the effects of heavy and long‐term snow cover on the life cycle of var. borealis. Shoots of both varieties were shaded in crushed ice for 110 days, but their photosynthetic activities, chlorophyll contents and the chlorophyll a/b ratio was not affected. The leaves of var. borealis were no less frost tolerant than those of var. japonica. In spite of the difference in environmental factors, both varieties had similar characteristics in seasonal changes of photosynthesis, respiration and chlorophyll a/b ratio. These results suggest that var. japonica could survive in areas with heavy snow where it does not normally occur. Leaf net production (LNP) was estimated based on the microclimatic data and seasonal photosynthetic and respiration rates. The difference in the annual LNP between the two varieties was equivalent to the difference in the LNP during the snow season. One of the major effects of snow cover is to interrupt and reduce the production period of var. borealis.