bluuebunny/crossref_metadata_2025 huggingface dataset:
Three‐dimensional dispersion of drosophilid flies in a cool temperate forest of northern Japan
Authors: Toda Masanori J.
Published: March 2006

Three‐dimensional dispersion of drosophilid flies was studied within a secondary broad‐leaved forest in relation to forest structure. The survey area included the forest margin and old canopy gaps and varied in the foliage height profile from place to place. Using multivariate analyses on the data of drosophilid dispersion, five microhabitats which were different from one another for drosophilids were recognized: (i) canopy layer; (ii) middle layer; (iii) floor layer of forest interior; (iv) upper layer of forest margin; and (v) herbaceous layer of forest margin and gap. The height of living space of canopy species was remarkably lowered at the forest margin. The forest edge was richer in both numbers of individuals and species than the forest interior from the overlap of the grassland and the forest canopy subcommunities and the addition of invaders from other habitats. However, no ‘edge’ species, which were mostly restricted to or spend most of their time in ecotones, were found. It is hypothesized that the above‐ground forest structure consists fundamentally of three zones: (i) the canopy; (ii) the floor; and (iii) the edge. A significant positive correlation was found between the foliage height diversity and the degree of vertical habitat segregation among drosophilid species. The patchiness of vegetation structure influential to the three‐dimensional dispersion in a forest drosophilid community was estimated to be on the scale of 110–450 m2. This scale of subjective habitat patchiness or ‘ecological neighbourhood’ corresponds well with the most prevalent size of canopy gaps occurring in various forests.
Dynamics and dry matter production of belowground woody organs of Pinus pumila trees growing on the Kiso mountain range in central Japan
Authors: Kajimoto Takuya
Published: March 2006

Size, biomass and spatial distribution patterns of belowground woody organs of Pinus pumila trees were investigated. Dry weight estimates of five sample trees were between 14 and 36 kg tree−1. Belowground stems accounted for about 32% of the total tree weight. However, the belowground stems had extensive barkless portions, indicating that the decomposition of dead belowground stems was an important source of organic matter in the soil. The, basal diameters of adventitious roots tended to become smaller as their orginating positions neared the ground surface. It was suggested that P. pumila trees regenerate by successively producing adventitious roots from their buried stems and moving down the slope.
Carbon isotope ratio and photosynthetic activity of phytoplankton in the eutrophic Mikawa Bay, Japan
Authors: Takahashi Kazushi , Wada Eitaro , Sakamoto Mitsuru
Published: March 2006

Primary production by phytoplankton in the eutrophic Mikawa Bay, Japan, was studied by simultaneous measurements of natural carbon isotope ratio (δ13C) and short‐term carbon uptake rates (13C tracer study) of size‐fractionated nannoplankton (<10 μm) and net plankton (>10 μm) samples. Short‐term photosynthetic rates, which represent the physiological state of algae, were variable regardless of standing stock sizes. The δ13C values of particulate organic carbon (POC) in June and July displayed horizontal variations for both the net plankton fraction (−19.8 to −12.7‰) and the nannoplankton fraction (−22.0 to −12.8‰). For both fractions, low concentrations of POC had more negative δ13C values (−22 to −18‰). High δ13C values for the net plankton were found when POC concentrations were much higher, due to red tide. This suggests that the increase in algal standing crop for the net plankton fraction resulted from accelerated photosynthetic activity. However the nannoplankton fractions with higher POC values have relatively low δ13C values.
Detection of xylem cavitation in field‐grown pine trees using the acoustic emission technique
Authors: Ikeda Takefumi , Ohtsu Masayasu
Published: March 2006

The relationship between the ultrasonic acoustic emission (AE) and the needle water potential in field‐grown Japanese black pine,Pinus thunbergii, and excised‐pine shoots was investigated in summer. The AE technique was employed as a reliable indicator of cavitation events in the water columns of xylem tracheids even under field conditions. In excised shoots. AE events detected when the needle water potential fell below about‐0.9 MPa. In the case of field‐grown pine trees, however, relatively few AE event were detected when needle water potential was lower than‐0.9 MPa. This suggests that the occurrence of cavitation events in Japanese black pine growing under field conditions is comparatively rare, even in summer.
Effect of carbon dioxide concentration on microbial respiration in soil
Authors: Koizumi Hiroshi , Nakadai Toshie , Usami Youzou , Satoh Mitsumasa , Shiyomi Masae , Oikawa Takehisa
Published: March 2006

In order to assess the validity of conventional methods for measuring CO2 flux from soil, the relationship between soil microbial respiration and ambient CO2 concentration was studied using an open‐flow infra‐red gas analyser (IRGA) method. Andosol from an upland field in central Japan was used as a soil sample. Soil microbial respiration activity was depressed with the increase of CO2 concentration in ventilated air from 0 to 1000 ppmv. At 1000 ppmv, the respiration rate was less than half of that at 0 ppmv. Thus, it is likely that soil respiration rate is overestimated by the alkali absorption method, because CO2 concentration in the absorption chamber is much lower than the normal level. Metabolic responses to CO2 concentration were different among groups of soil microorganisms. The bacteria actinomycetes group cultivated on agar medium showed a more sensitive response to the CO2 concentration than the filamentous fungi group.
Impact of extreme run‐off events from the River Sakasagawa on the Senjogahara ecosystem, Nikko National Park III. Pattern of alluvial deposition and effects on the growth of Malus Toringo and Betula platyphylla var. japonica
Authors: Hukusima Tukasa , Mizoguchi Keiko
Published: March 2006

In the study area at Senjogahara, there are 13 vegetational groups forming a space‐time continuum in response to alluvial deposition from the River Sakasagawa. The pattern of deposition changes markedly from time to time, and the vegetation is thus a mosaic of recovery phases in different stages of development.

There is marked zonation of layers of gravel, silt and organic matter in the soil profile, running sequentially from the mouth of the river back to the moor. Furthermore, there is a decrease in the depth of the water table with distance from the river mouth. The growth increment of Malus Toringo is poor under the canopy of Ulmus Davidiana var. japonica forest, with maximum growth occurring in the areas of active alluvial deposition. The changing patterns of Malus growth have been used to approximate the dates of major changes in the erosion channels and areas of alluvial deposition.

There were five main channels in the study area. The oldest was on the west side and active ca. 35–40 yr prior to 1984, the year of sampling. Subsequently, adjacent areas further east became major drainage and erosion channels about 25–30 yr before 1984. However, after 1985 the erosion channels again showed a marked change in pattern, and currently flow into an entirely different sector, being responsible for the continuous dynamic patterns of vegetational change in this area.
Downhill movement of litter and its implication for ecological studies in three types of forest in Japan
Authors: Tsukamoto Jiro
Published: March 2006

The amount of litter moving down the slope was measured in three types of forest, together with an examination of rain as a factor in bringing this about. The three forest types were a natural mixed stand of Pinus densiflora and hardwood trees (plot A), a Cryptomeria japonica plantation (plot S) and a Chamaecyparis obtusa plantation (plot H). The amount of moved litter was quite large in plots A and H, but relatively small in plot S. The rain factor had little influence on litter movement in plot A, but was the main cause of movement in plot S and (especially) plot H. It is suggested that measurement of litter input and output not only by traps above ground level, but also by ones on the ground is essential for determining the cycling of elements in C. obtusa forests. It is also suggested that the decomposition of leaf litter should be studied both on the soil surface and in the soil in C. obtusa forests.
Productivity‐independent initial growth of individual leaves in sunflower (Helianthus annuus L.)
Authors: Oishi Yuji
Published: March 2006

Growth rates of individual leaves attached to sunflower (Helianthus annuus) plants were measured experimentally under different levels of environmental productivity, modified by irradiance and nutrient conditions. The unfolding rate and final area of an individual leaf increased with increasing environmental productivity. The final area of an individual leaf also varied according to differences in leaf order. The declining pattern of relative leaf area growth rate (RLGR) varied with environmental productivity; leaves in a productive environment had a longer period of high sustained initial RLGR than leaves in a less productive environment. However, maximum RLGR was hardly influenced by leaf order or environmental factors such as irradiance and mineral nutrition.
Factors limiting the distribution of Digitaria adscendens and Eleusine indica on coastal sand dunes in Japan
Authors: Park Yong‐Mok
Published: March 2006

Fate of Digitaria adscendens and Eleusine indica seedlings under field conditions and their responses to salt spray, drought and nutrients were experimentally investigated in order to evaluate the possible mechanisms controlling the different distributions of the two species in coastal sand dune areas. Salt spray produced no apparent positive effect on the growth or survival of both species. Seeds of each species germinated well in the field, although 80% of E. indica seedlings died during a summer drought and surviving seedlings neither grew nor bore fruit. The mortality of D. adscendens seedlings due to the drought was less than 10% and the survivors mostly bore fruit by the end of the growth season. No major difference in the sublethal water saturation deficit was noticed between the two species. However, D. adscendens individuals extended their roots into the deep sandy soil to a much greater extent in water‐stressed conditions than in well watered conditions, whereas E. indica showed no such behavior. Additional watering in a dune environment did not help the growth of E. indica seedlings, but additional nutrients had a markedly stimulatory effect. D. adscendens maintained its growth and fruition with much smaller amounts of nutrients than E. indica. Soil nitrogen content at a site where E. indica and D. adscendens were distributed sympatrically was higher than that at a site where only D. adscendens was present. Based on these findings, it is proposed that E. indica seedlings are unable to become established because of their lower resistance to summer drought and the poor nutrient conditions present in a coastal rear sand dune habitat.
Principal component analyses of bagged wheat infested with Sitotroga cerealella (Lepidoptera: Gelechiidae) and Sitophilus oryzae (Coleoptera: Curculionidae)
Authors: Imura Osamu , Sinha Ranendra N.
Published: March 2006

Interrelations among biological and abiological variables over 22 weeks at 28°C and 60% RH were revealed by principal component analysis (PCA) on data collected from simulated bagged wheat (Triticum aestivum L.) which was not infested by insects (control system), was infested by Sitophilus oryzae (L.) (SO system), by Sitotroga cerealella (Olivier) (SC system) or by both species (SC+SO system). The variables measured were temperature, grain moisture, CO2, dust weight, fat acidity value, grain weight, germination, insect numbers and frequency of occurrence of microfloral species. The analysis indicated the interrelations among variables involved in degradation of the wheat. In the control system, the dominant interrelations were those among abiological variables, indicating that deterioration of the wheat was minimal. In the SO system, principal components which represented insect effects, seed quality and temperature‐fungal relationships, were predominant. Similar factor‐loading patterns were extracted both in the SC and SC+SO systems; the principal components suggested that S. cerealella was mainly responsible for heavy deterioration of the wheat. The principal components, which were rotated orthogonally by 45δ, indicated that the process of wheat degradation in both systems proceeded gradually until week 10 or 15 and thereafter the rate of degradation was accelerated and serious grain quality loss occurred.
The ecosystem concept: A search for order
Authors: Golley Frank B.
Published: March 2006

The development of the ecosystem concept illustrates the search for order in science and shows how individuals and the social‐cultural environment of the science influence concept evolution. Ecosystem was coined in 1935 and replaced a variety of inappropriate terms which all referred to a system of biotic and inorganic interactions in nature. It was popularized after the second World War and became a dominant paradigm in ecology world wide. As such, it dominated the development of productivity studies within the International Biological Program. The ecosystem concept became mature when it was realized that the ecosystem was an object that could be studied directly, using conventional scientific methods. Currently the ecosystem concept exists along side a variety of ecological concepts which represent the guiding research foci of ecological subfields.
Insects and plants in the pollination ecology of the boreal zone
Authors: Kevan P. G. , Tikhmenev E. A. , Usui M.
Published: March 2006

Pollination systems in the boreal zone range from generalist to specialist, both entomologically and botanically. The relative importance of wind pollination, insect pollination, sexual separation between and within plants, and between flowers, hermaphroditism of flowers, and various breeding systems are related to plant growth form and habitat. The diversity and specializations of anthophilous insects parallel those in other biogeographic zones, but seem less developed. We suggest that this reflects the combined effects of evolutionary youth, severity of climate, restriction of symbiont ranges within those of their hosts, and the naturally frequent perturbations by fire or insect outbreaks in the zone, requiring faunal and floral vagility and constraining specialization in mutualism. Modern perturbations by logging and pesticides seem to be well buffered because of the relative openness of the ecosystem (compared to others), although damage has been documented. Insect pollination is as much a keystone process in the boreal forest as elsewhere, despite the immediate counter‐impression given by the dominance of wind‐pollinated conifers. Nevertheless, there are few studies, botanical or entomologicalin situ. The boreal system offers important opportunities in general and applied research in pollination ecology and synecology generally.
Harvesting rate of the termite, Drepanotermes tamminensis (Hill) within native woodland and shrubland of the Western Australian wheatbelt
Authors: Park H. C. , Majer J. D. , Hobbs R. J. , Bae T. U.
Published: March 2006

The Western Australian termite, Drepanotermes tamminensis (Hill), harvests various plant materials according to biomass availability. The main litter components harvested by this termite in a woodland dominated by Eucalyptus capillosa are bark and leaves of the major tree species, while in shrubland dominated by Allocasuarina campestris, shoots of this species are taken. Harvesting mainly occurs during the autumn (April–May) and spring (September–October) seasons. The commencement and duration of harvesting appears to depend partly on weather conditions, with harvesting taking place at temperatures between 15 and 25°C after periods of rain. This species of termite harvests approximately 15.6 g m−2 year−1 and 3.2 g m2 year−1 (dry weight of plant material) in the woodland and shrubland, respectively.
Spatial variation in composition and richness of fish communities in a southwestern Australian river system
Authors: Hutchison Michael J.
Published: March 2006

Thirteen species of fish were recorded from the non‐tidal reaches of the Murray River system, southwestern Australia. Of these, nine were indigenous species. Although this system occurs in a zone of moderate to high rainfall, the species richness of this system is comparable to that of much harsher environments, such as the Canadian boreal zone or the Nevada desert. Species richness tends to increase in a downstream direction, and most changes in species composition are due to addition, rather than replacement of species. Stream order was strongly and significantly positively correlated with species richness (P < 0.001), but was in effect functioning as a composite variable. Stepwise multiple regression analysis showed that stream width, pH range, distance from the main stream, distance from the estuary, barriers and stream gradient together explained more than 80% of the variation in species richness. The variables, barriers, distance from the main stream and distance from the estuary, support island biogeography type explanations for variations in species richness, while the variable, stream width complies with the river continuum concept. A predictive model for species richness of any given reach of a lower west coastal stream in Australia was tried using variables that can be gathered almost entirely from detailed topographic maps and aerial photographs.
Interception of photosynthetic photon flux density by woody elements in a hinoki (Chamaecyparis obtusa [Sieb. et Zucc.] Endl.) stand
Authors: Hagihara Akio , Yamaji Kazuyoshi
Published: March 2006

A hinoki stand was divided into the following two layers: one was a leafed upper layer consisting of leaves and woody elements, such as stems, living branches and dead branches; the other was a leafless layer consisted of woody elements, such as stems and dead branches. Photosynthetic photon flux density (PPFD) penetrating through the stand was measured in relation to the silhouette area of leaves and woody elements. The silhouette area, on a ground area basis, was 11.2 ha ha−1 for leaves (leaf area index), 0.26 ha ha−1 for stems, 0.40 ha ha−1 for living branches and 0.69 ha ha−1 for dead branches, yielding a total wood silhouette area of 1.35 ha ha−1. The apparent extinction coefficient, K, was computed to be 0.420 ha−1 ha for the leafed layer, while the extinction coefficient of woody elements, Kc, was computed to be 1.01 ha−1 ha for the leafless layer. The cumulative wood silhouette area density from the top of the canopy down to a given depth increased with an increase in the corresponding leaf area density within the leafed layer. The extinction coefficient of leaves, KF, was estimated to be 0.367 ha−1 ha. Of the PPFD extinguished within the canopy, the fraction (KF/K) due to leaves alone was evaluated to be 87.4%.
Canopy photosynthetic production in a Japanese larch forest. II. Estimation of the canopy photosynthetic production
Authors: Kurachi Nahoko , Hagihara Akio , Hozumi Kazuo
Published: March 2006

Seasonal changes and yearly gross canopy photosynthetic production were estimated for an 18 year old Japanese larch (Larix leptolepis) forest between 1982 and 1984. A canopy photosynthesis model was applied for the estimation, which took into account the effect of light interception by the non‐photosynthetic organs. Seasonal changes in photosynthetic ability, amount of canopy leaf area and light environment within the canopy were also taken into account. Amount of leaf area was estimated by the leaf area growth of a single leaf. The change of light environment within the canopy during the growing season was estimated with a light penetration model and the leaf increment within the canopy. Canopy respiration and surplus production were calculated as seasonal and yearly values for the three years studied. Mean yearly estimates of canopy photosynthesis, canopy respiration and surplus production were 37, 13 and 23 tCO2 ha−1 year−1, respectively. Vertical trend, seasonal changes and yearly values of the estimates were analyzed in relation to environmental and stand factors.
A preliminary study of nectar production of the field cress, Rorippa indica, in relation to the age of its flowers
Authors: Muraoka Kazuyuki , Watanabe Mamoru
Published: March 2006

Floral nectar production quantity and changes in sugar concentration of the nectar of Rorippa indica were investigated. Flowers were sorted by age. The small flower size was a major factor for the use of BCG test paper in nectar sampling. In flowers of the youngest age category, the nectar volume increased toward the night and decreased during the day. The amount of sugar in the nectar decreased with flower age. The sugar concentration was lower at night than daytime. The variability and changes in nectar concentration enabled various species of insects to forage for nectar.
Carbon stock and cycling in a bamboo Phyllostachys bambusoides stand
Authors: Isagi Yuji
Published: March 2006

Gross production and carbon cycling in a Phyllostachys bambusoides stand in Kyoto Prefecture, central Japan, were determined, and then a compartment model showing the carbon stock and cycling within the ecosystem was developed. Aboveground carbon stock was 52.3 tC ha−1, increasing at a rate of 3.6 tC ha−1 year−1. Belowground carbon stock was 20.8 tC ha−1 in the root system and 92.0 tC ha−1 in the soil. Aboveground net production was 11.2 tC ha−1 year−1. Belowground net production was crudely estimated at 4.5 tC ha−1 year−1. The gross production was estimated at 41.8 tC ha−1 year−1 by summing the amount of outflow to the environment and the increment in biomass. Leaves consumed 13.7 tC ha−1 year−1 by respiration; the rest (41.8−13.7=28.1 tC ha−1 year−1) was surplus production of the leaves and flowed into the other compartments. The amounts of construction and maintenance respiration of the aboveground compartments were 3.4 and 18.5 tC ha−1 year−1, respectively. The annual amount of soil respiration was 11.2 tC ha−1 year−1. Soil respiration levels of 4.3 and 3.1 tC ha−1 year−1 were estimated for the flow of root respiration and root detritus. The proportion of net to gross production was 37%, which fell within the range of young and mature forests. A shorter life span of culms, compared to tree trunks, resulted in smaller biomass accumulation ratio (biomass/net production) in the ecosystem, of 4.66.
The regeneration of pioneer tree species under browsing pressure of Sika deer in an evergreen oak forest
Authors: Shimoda Katsuhisa , Kimura Katsuhiko , Kanzaki Mamoru , Yoda Kyoji
Published: March 2006

The effects of Sika deer (Cervus nippon) browsing on the regeneration of pioneer species were studied in relation to canopy gaps in a warm temperate evergreen oak forest in Kasugayama, Nara City. Four study sites, three in canopy gaps and one under a closed canopy, were selected and each divided into fenced and unfenced plots. Under the closed canopy, seedlings of all the pioneer species died irrespective of browsing pressure. However, in the canopy gap sites, seedlings of the pioneer species could establish and grow well. The seedling survival ratio in the fenced plots in the canopy gaps was >60% 1 year after germination. However, in the unfenced plots, only <20% of the seedlings survived 1 year, with all dying within 3 years after germination. Thus, the regeneration of pioneer trees in this forest was strongly inhibited by deer browsing. Successful regeneration of a pioneer, Zanthoxylum ailanthoides, occurred for several years even after two major wind disturbances during the past 90 years. This may be due to less browsing pressure from the deer.
Comparative analyses on food habits of Japanese marten, Siberian weasel and leopard cat in the Tsushima islands, Japan
Authors: Tatara Masaya , Doi Teruo
Published: March 2006

Food habits of three sympatric carnivore mammals in the Tsushima islands of Japan were studied during 1986–91. Scats of the Tsushima marten (n=1236), the Siberian weasel (n=218) and the Tsushima leopard cat (n=350) were collected monthly and the food items were determined by scat contents analysis. Marten was omnivorous showing a high level of diversity of food throughout the year. The important foods for marten were fruits and berries from spring to autumn, insects in summer and autumn and small mammals all year round. Leopard cat preferred to hunt wood/mice and birds, and remained a flesh meat specialist throughout the year. Weasel was intermediate between marten and leopard cat, but was slightly biased towards the flesh meat eater. The three carnivores do not compete against one another for food, except for small rodents. A conflict for food between leopard cat and weasel was suggested to be more intense than that of other combinations based on diet overlapping. Marten may be characterized as an opportunistic generalist. When interspecific competitors existed, or human disturbance to the habitat occurred, the preferential flexibility of the marten to alternative food resources might become more advantageous than the other two species.
Effects of leaf blade narrowness and petiole length on the light capture efficiency of a shoot
Authors: Takenaka Akio
Published: March 2006

Effects of the length: width ratio of a leaf blade and petiole length on shoot light capture were studied with computer simulation. Both a larger length: width ratio and longer petiole contributed to larger light capture per unit leaf area due to a reduced aggregation of leaf area around the stem. Other conditions being equal, shoots with narrow leaves and no petioles and those with wide leaves with petioles showed similar light capture as long as the mean distance of the leaf blade from the stem was the same. In shoots with a short internode and/or distichous phyllotaxis, however, narrow leaves contributed more to avoiding mutual shading than wide leaves with petioles. The predominance of light coming from a higher angular altitude also favored narrow leaves. The possible consequences of these results in the adaptive geometry of plant architecture are discussed.
Female reproductive cycles in the northernmost populations of the two gekkonid lizards, Hemidactylus frenatus and Lepidodactylus lugubris
Authors: Ota Hidetoshi
Published: March 2006

Lepidodactylus lugubris, a parthenogenetic gekkonid lizard of possible tropical origin, occurs on Kita‐Daitojima Island of the Ryukyu Archipelago and lays eggs almost throughout the year. The oviposition season of the sympatric population of another primary tropical, but bisexual gecko, Hemidactylus frenatus, is confined to between April and September. Laboratory experiments indicate that the hatching ratio of the egg reduces with the decrease of incubation temperature in both species. Some eggs of L. lugubris develop at 14°C of ambient temperature, wheras eggs of H. frenatus always die at temperatures of 18°C or lower. Examinations of stomach contents and fat body mass in the monthly samples suggest that food availability is not severely low for the geckos even during the winter, rejecting the previous assumption that food stress suppresses vitellogenesis in H. frenatus. No other environmental factors that may induce reproductive seasonality as phenotypic physiological responses were detected either. Tropical populations of H. frenatus and L. lugubris are known to lack distinct annual reproductive cyclicity. Thus, it is probable that the East Asian H. frenatus has evolved the winter quiescence of reproduction, presumably due to the poor embryonic tolerance of low temperatures. The absence of such seasonality in the sympatric L. lugubris seems to be attributable to its clonal nature which predicts the low genetic variability of the population from the colonization stage.
Classification and ordination of communities of soil arthropods in an urban park of Osaka City
Authors: Natuhara Yoshihiro , Imai Chobei , Takeda Hiroshi
Published: March 2006

To assess the effect of management of a park on soil arthropods, communities of Oribatida and Collembola were analyzed at 11 sites of different vegetation in Tsurumi Park, an urban park of Osaka City. The type of canopy layer and soil density strongly affected the community parameters, such as species diversity. Ordination revealed that soil density, contents of organic matter, and shrub layer were important for variety in the oribatid community; the shrub layer was important for the collembolan community. Species richness of both arthropod groups was highest in a mixed forest and lowest on bare land, while the abundance of Collembola was highest on a lawn site. Areas of a common vegetation type had a similar oribatid community;Trichogalumma nipponica dominated in deciduous forests, Eohypochthonius crassisetiger in mixed forests and one of coniferous forests. On the other hand, collembolan communities did not correspond with the vegetation. Sminthurinus sp. was collected from every site, and the most abundant species was Cryptopygus thermophilus that exhibited an outbreak on lawn sites. A significant correlation existed between species diversities but not between abundances of Oribatida and Collembola.
Abundance patterns of soil micro‐arthropods at aPinus pumilascrub in an alpine range of central Japan
Authors: Hijii Naoki
Published: March 2006

Seasonal changes in abundances of major soil micro‐arthropods were assessed at aPinus pumilascrub in an alpine range of central Japan during a period with no snow coverage. The total abundance showed a peak in late August, reaching no less than 140 000 m−2, which was comparable to that in an evergreen coniferous plantation in the cool‐temperate zone. Collembola was the most dominant group of soil micro‐arthropods, comprising about 50% of the total, followed by oribatid mites (Acari [O]) occupying 20%. Annual mean air temperature was no more than 2.1 °C and the daily fluctuation in temperature was less in soil layers. The thickness of the A0layer reached 9–10 cm and soil organic matter accumulation was estimated to be 45–58 ton dry weight ha−1. The large amount of litterfall and organic matter accumulation in the soil, comparable to those of sub‐alpine evergreen coniferous forests, and a lower decomposition rate due to severe environmental conditions, suggest the relative importance of litter processing by soil micro‐arthropods such as Collembola and Acari, especially in alpine regions.
Aboveground net production and dry matter allocation of Pinus pumila forests in the Kiso mountain range, central Japan
Authors: Kajimoto Takuya
Published: March 2006

Aboveground net production rates of the subalpine stone pine (Pinus pumila) forests in central Japan were estimated by the summation method; net production was defined as the sum of annual biomass increment and annual loss due to death. In the two pine stands of different scrub heights, P1 (200 cm) and P2 (140 cm), aboveground biomass reached 177 and 126 ton ha−1, respectively. Leaf biomass was about 14 ton ha−1 in each stand. The estimates of aboveground net production during the 2 year period (1987–1989) averaged 4.1 and 3.7 ton ha−1 y−1 in P1 and P2, respectively, which were at the lowest among the pine forests in the world. Two indices of efficiency of energy fixation, that is, the ratio of net production to the total radiation during a growing season and the ratio of net production to total radiation per unit of leaf weight, were evaluated. Both efficiency indices for the two P. pumila stands fell in the range obtained for other Japanese evergreen conifer forests. This suggested that the low annual net production of the stone pine stands were mainly due to a limitation in the length of the growing season. The pine forests were also characterized by a small allocation (about 17%) of aboveground net production into biomass increment, in comparison with other evergreen conifer forest types. Annual net carbon gain in the P. pumila forests was suggested to be largely invested in leaf production at the expense of the growth of woody parts.
Seedling establishment ofPolygonum cuspidatumandPolygonum weyrichiivar.alpinumat high altitudes of Mt Fuji
Authors: Maruta Emiko
Published: March 2006

Seedling establishment ofPolygonum cuspidatum(Seib. et Zucc.) andPolygonum weyrichii(F. Schmit) var.alpinum(Maxim.), dominant early‐successional species in a volcanic gravel area on Mt Fuji, Japan, was compared for current‐year seedlings at 2500 m a.s.l. The rate of survival in the first winter after germination at 2500 m was 2% and 24% forP. cuspidatumandP. weyrichiiseedlings, respectively, and correlated with the upper distribution limit of each (2500–2600 m forP. cuspidatum; 3200–3300 m forP. weyrichii). The critical size for survival was 12 mg dry weight for overwintering current‐year seedlings of both species. At 2500 m, the percentage of seedlings that attained the critical size for survival at the end of the first growing season was 19% and 85% forP. cuspidatumandP. weyrichii, respectively. Growth curves indicated that the larger‐seeded characteristic ofP. weyrichiicontributed to larger end‐of‐season size and resulted in higher rate of seedling survival at 2500 m, compared with smaller‐seededP. cuspidatum. Current‐year seedlings ofP. weyrichii, at least up to 3250 m, attained the first year annual growth critical for overwintering and therefore for successful seedling establishment, due to the large‐seeded characteristic. At the top (3770 m) beyond the upper distribution limit ofP. weyrichii, most seedlings raised artificially failed to attain the critical size for survival in the first growing period due to the reduced growing period. Failure of seedling establishment would thus appear to restrict the distribution of the species at altitudes higher than 3300 m.
A mass‐mortality of Sika deer on Kinkazan Island, northern Japan
Authors: Takatsuki Seiki , Suzuki Kazuo , Suzuki Ikuo
Published: March 2006

A Sika deer (Cervus nippon) population had been maintained at a level of around 600 head on Kinkazan Island (960 ha), northern Japan during the 1970s and the early 1980s. However, in the spring of 1984 which followed an uncommonly cold winter, a mass‐mortality occurred and about half of the deer population died. A total of 293 recovered carcasses indicated that many had died during a short period (late March and mid‐April). More carcasses were found in the lower altitudinal areas than expected numbers relative to area sizes, suggesting that the deer had moved down from the higher areas to avoid snow. Rumen contents of the carcasses contained much low quality food. Malnutrition caused by the exceptional coldness and late snow was considered to be the factor responsible for mortality.
Role of interspecific competition in the coexistence of Apodemus argenteus and A. speciosus (Rodentia: Muridae)
Authors: Sekijima Tsuneo , Sone Koichi
Published: March 2006

Reciprocal‐removal experiments with two replicates were conducted to test for the role of interspecific competition in the coexistence of Apodemus argenteus and A. speciosus. Population density, rate of appearance of new (unmarked) individuals, reproduction, survival rate and habitat use were monitored during pre‐ and removal periods. In both removal experiments, the removal of A. argenteus had little effect on A. speciosus, while that of A. speciosus affected several population characteristics of A. argenteus. Namely, the removal of A. speciosus shifted the distribution of A. argenteus to the habitat with a denser shrub cover in one experiment. Also, the removal increased the population densities and appearance rates of new individuals of A. argenteus in another experiment. Interspecific interactions between the two species appeared to be a one‐way action from A. speciosus to A. argenteus. In removal periods in both experiments, the rates of appearance of new individuals in each species were the highest on the grid where that species was removed. These results suggest that, though interspecific competition occurred between the two species, intraspecific competition had greater effects than interspecific competition on the abundance and habitat use of A. argenteus and A. speciosus. This implies that the fundamental niches of A. argenteus and A. speciosus differ potentially, which may play an important role in the coexistence of the two species.
Forest canopy structure analyzed by using aerial photographs
Authors: Nakashizuka Tohru , Katsuki Toshio , Tanaka Hiroshi
Published: March 2006

A method was developed using aerial photographs to analyze forest canopy structure. Digital elevation models of both the land and canopy surface in a mesh of 5 m intervals were made from aerial photographs taken in winter (without tree leaves) and summer (with leaves), respectively, in a 60 ha area of temperate deciduous forest. The difference between the two elevation values at each point was regarded as the canopy height, and a canopy height profile was constructed. The estimated canopy structure was compared with that obtained by ground observations in a 6 ha part of the study area. Large gaps (>100 m2) were adequately detected by the method, and the gap size distribution obtained was similar to the one observed on the ground. The method was found to be effective in analyzing the forest canopy structure of large areas, but it is not suitable for the detection of small gaps.
Gap characteristics and gap regeneration in subalpine old‐growth coniferous forests, central Japan
Authors: Yamamoto Shin‐Ichi
Published: March 2006

Gap characteristics and gap regeneration were studied in three old‐growth stands of subalpine coniferous forests in the northern Yatsugatake and the northern Akaishi mountains, central Japan. With the results of the present study and those of a previous study conducted in another locality, general features of gap characteristics and gap regeneration behavior of major tree species in subalpine coniferous forests of central Japan were summarized and discussed. Of the total 237 gaps investigated in the 14.48 ha of forested area, the percentage gap area to surveyed area, gap density and mean gap size were 7.3%, 17.2 ha−1, and 43.3 m2, respectively. The gap size distributions were similar among stands and showed a strong positive skewness with a few large and many small gaps; gaps <40m2 were most frequent and those >200 m2 were rare. Gaps due to the death of multiple canopy trees comprised 44.7% of the total ones. Canopy trees died in various states; standing dead (42.6%) or trunk broken (43.7%) were common and uprooted (12.2%) was an uncommon type of death of canopy trees. These figures indicate that general features of gap characteristics in this forest type are the low proportion of gap area and the high proportions of small gap size and multiple‐tree gap formation. In general, shade‐tolerant Abies frequently, and Tsuga, infrequently, regenerate in gaps from advance regenerations recruited before gap formation, while Picea and shade‐intolerant Betula possibly regenerate in gaps from new individuals recruited after gap formation. Gap successors of conifers occurred in a wide range of gap size and did not show the clear preference to species specific gap size. In old‐growth stands without large‐scale disturbance (≥0.1 ha in area) of subalpine coniferous forests of central Japan, major tree species may coexist with their different gap‐regeneration behaviors and, probably, different life history traits.
Feeding, reproductive and locomotor activities in diapausing and non‐diapausing adults of Drosophila
Authors: Matsunaga Katsutoshi , Takahashi Hiroshi , Yoshida Takao , Kimura Masahito T.
Published: March 2006

Feeding, reproductive and locomotor activities of four Drosophila species were studied under short and long daylengths at 15°C. A short daylength induced firm reproductive diapause in experimental strains of D. subauraria and D. triauraria from northern Japan, but very shallow diapause in those of D. lutescens and D. rufa from southern Japan. A subtropical strain of D. triauraria had no diapause. The influence of diapause on feeding activity was detected only in aged (> 12 day old) females; that is, the feeding activity was lower in diapausing females than in non‐diapausing ones. Females that do not produce eggs would not require so much energy. On the other hand, young adults of the study species exhibited a high feeding activity and rapidly increased bodyweight irrespective of sex and the diapause state. They would need nutrition to build up their adult body. In males, the feeding activity decreased with age irrespective of the diapause state. Males would not require so much energy for reproductive activity. Diapausing males became heavier than non‐diapausing males, perhaps because they accumulated triacylglycerols in fat bodies. However, female bodyweight did not differ by the diapause state, perhaps because diapausing females accumulated triacylglycerols and reproducing females had eggs in their ovaries. In D. triauraria, diapausing individuals exhibited somewhat lower locomotor activity than non‐diapausing ones.
A 5 year study of litter decomposition processes in aChamaecyparis obtusaEndl. forest
Authors: Takeda Hiroshi
Published: March 2006

Decomposition of needle litter in aChamaecyparis obtusaforest was studied over a 5 year period using a litter bag method. Organic matter, nitrogen and carbon mass and faunal abundance were monitored. The pattern of weight loss was represented by three phases: the initial leaching of carbon and nitrogen (0–3 months), nitrogen immobilization (3–15 months), and nitrogen mobilization (15–60 months). The decomposition rate of needle litter was expressed by Olson's decomposition constant (k) which was−0.113 over a 5 year period. The decomposition rate decreased with the advance of decomposition processes. The role of soil fauna in the decomposition process was assessed by comparing decomposition rates between the control and defaunated plots. In the leaching phase, soil animals had no significant role in the decomposition processes. During the immobilization phase, soil animals contributed to the immobilization processes through their grazing activities, and there were significant differences in weight loss between the control and defaunated plots. In the mobilization phase, saprovorous soil animals such as Collembola and Acari contributed to the mobilization processes by feeding on decomposing litter. Decomposition processes observed in this study were compared with other similar studies.
Dominance order and resting site fidelity in the intertidal pulmonate limpetSiphonaria sirius(Pilsbry)
Authors: Iwasaki Keiji
Published: March 2006

Consequences of ‘pushing contests’ between pairs of the intertidal pulmonate limpetSiphonaria siriuswere analyzed, focusing on the relationship between dominance order and resting site fidelity. The pushing contests occurred near patches ofEnteromorphasp., their favorite algal food resource. Three or four dominance ranks were determined from the consequences of the contests in different seasons. Individuals in lower dominance ranks tended to shift their resting sites significantly more than those in higher ranks. The dominance order of limpets is considered to play an important role in migration by its effect on resting site fidelity. Density dependent dispersal, from the lower to the upper part of limpets' habitats, was observed in late summer to winter when desiccation was not a problem and food resources became abundant in less populated areas. In late spring to summer, however, migration was directed downwards, from less to more populated areas, where desiccation pressure was relatively weaker. This migration is considered to have a survival advantage, and the behavior of the limpets may have masked density‐dependent dispersal during the two seasons. Distribution of home site was also considered affected by aggressive social behavior during the two periods.
Density‐dependent mortality, growth and size inequality in roadside populations of the annual herbGalium aparineL.
Authors: Puntieri Javier G. , Hall Roger L.
Published: March 2006

Biomass, plant size, plant density and the inequality of sizes were assessed for autumn‐emerging roadside populations dominated byGalium aparineduring early stages of growth in two independent studies. A third data set dealt with the survival of labelled seedlings belonging to different cohorts of emergence. One data set showed that the slope of the log‐log size/density relationship for all plant species present in the samples was closer to −1.5 and that forG. aparinewas closer to −1.0 in five separate populations. Biomass increase and density decrease was not found to take place in any of these simultaneously. The size inequality ofG. aparinetended to increase or to remain constant during periods of high mortality, and in the early harvests it was negatively related to population density. The second data set revealed simultaneous decreases of both biomass and density ofG. aparineand of all plant species during a period of a month soon after emergence, and a higher size inequality ofG. aparinein those patches where plant density (and that ofG. aparine) was lower. The labelling of seedlings indicated density‐dependent mortality and a higher probability of survival for seedlings emerging very early. The size/density relationship of roadside populations dominated byG. aparinemay follow a trajectory over time similar to that predicted by the 3/2 power law of self‐thinning, but this species seems to have a weak size hierarchy development and limited individual growth at high population densities. The importance of plant architecture in relation to this response is discussed.
Application of radiotelemetry to the survey of acorn dispersal by Apodemus mice
Authors: Soné Koichi , Kohno Aki
Published: March 2006

We examined the applicability of radiotelemetry to studies of acorn dispersal by Apodemus mice and compared its efficiency with the of this spool‐and‐line method. Installation of a transmitter (2.2 g) onto acorns did not interfere with the transporting and feeding behavior of the mice. We were able to detect all transmitter‐installed acorns and follow the daily changes in the sites in which they were hoarded, while we missed 59% of the spool‐tied acorns due to mice breaking the threads. Mice carried transmitter‐installed acorns farther than spool‐tied ones. The radiotelemetry method is superior to the spool‐and‐line method and useful for the study of hoarding behavior in rodents.
Effects of the common cormorant, phalacrocorax carbo, on evergreen forests in two nest sites at Lake Biwa, Japan
Authors: Ishida Akira
Published: March 2006

The effects of the habitation of the common cormorant on vegetation were evaluated in two colonies in Lake Biwa, central Japan. The state of the vegetation of each colony was classified arbitrarily into the following three types according to the appearance of the tree, shrub and herb layers; dense tree layer (Type 1), sparse tree layer and herb layer (Type 2), and sparse tree layer with dense herb layer (Type 3). The density of cormorant nesting was almost similar among the three types, except for part of Type 2. Trees, especially large ones on which cormorants nested, were found to be heavily damaged, and there were few seedlings and saplings found under the canopy trees. Chamaecyparis obtusa and Cryptomeria japonica were more heavily damaged than other evergreen and deciduous trees. In the herb layer, only a few species such as Reynoutria japonica or Phytolacca americana were abundant. These results suggest that the habitation of cormorants could simplify the structure and the species composition of forests.