bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of overgrazing on seed predation by rodents in the Thar desert, northwestern India
Authors: Wada Naoya , Narita Kenji , Kumar Suresh , Furukawa Akio 
Published: March 2006

AbstractWe compared the vegetation structure, rodent density and seed loss rate between protected and disturbed sites affected from grazing by cattle, goats and sheep, in the Thar desert of India. A perennial tussocky grass Lasiurus sindicus Hent. was largely dominant in the protected site, while L. sindicus was rare and replaced by undershrub species Aerva pseudotomentosa Blatt. & Halb. and Crotalaria burbira Buch.‐Ham. in the overgrazed site. In the grazed site, plant coverage was low, but the density of rodent burrows and the frequency of rodent captures were significantly high as compared to the protected site. Corresponding with the density of desert rodents, seed predation was significantly higher in the grazed site than in the protected site. These results suggest that overgrazing by large mammals has strong effects on plant succession by altering not only the species composition and abundance of plant community, but also the habitat suitability for seed‐eating rodents.
Stochastic population dynamics of clonal plants: Numerical experiments with ramet and genet models
Authors: Eriksson Ove 
Published: March 2006

AbstractDynamics of ramer and genet populations were analyzed by use of stochastic matrix models. Based on field data, population development and extinction rates during 50 simulated years were estimated for ramet populations of three species Potentilla anserina, Rubus saxatilis and Linnaea borealis. Only small initial populations (below 125–250 ramets), experienced a detectable risk of extinction within this time interval. For P. anserina and R. saxatilis, population increase occurred in some simulations despite negative average growth rates. A model for stochastic genet dynamics was constructed by combining field data and hypothesized parameter values. Growth rate and population structure were insensitive to variation in disturbance intensity and frequency, whereas variation in recruitment affected population structure but only to a minor extent growth rate. Decreasing recruitment causes extinction of genet populations, but the time‐scale for the decline is in the magnitude of centuries for initial genet populations of about 1000 individuals. Dynamics of genets in clonal plants thus incorporate processes occurring on widely different scales. Some implications of the results for models of population dynamics in long‐lived clonal plants are discussed.
The number of species occurring in a sample of a biotic community and its connections with species‐abundance relationship and spatial distribution
Authors: Kobayashi Shiro , Kimura Katsuhiko 
Published: March 2006

AbstractConnections among species‐abundance (i‐mi), species‐frequency (i‐Fi), and species‐sample size (Sn‐n) relationships were examined on the basis of the mapping data of a natural forest in Thailand. The spatial distribution of individual trees without any discrimination of species was nearly random. Provided that the spatial distribution of each species was random, the i‐mi and the i‐Fi relationship was reconstructed from each other in terms of the total number of species (S) and the total number of individuals (N) in the data. The number of species (Sn) in a subsample consisting of n individuals was then obtained from the i‐Firelationship. Logarithm of Sn increased with log n and showed a convex curve through the origin. The values of diversity indices based on N and S(or n and Sn) were affected by sample size. These trends were further examined on the basis of 944 data sets of biotic communities and three mathematical models of an S‐N relationship. The properties of species‐area relation were discussed in the light of these results.
Field evidence of plastic growth responses to habitat heterogeneity in the clonal herb Ranunculus repens
Authors: Waite Stephen 
Published: March 2006

AbstractStolon internode lengths were measured on plants of the clonal herb Ranunculus repens growing in a hay meadow which was subject to disturbance by mole (Talpa europaea) activity. Within the site three habitat types were recognized: closed grassland, the open ground of fresh molehills and the grass‐molehill boundary. The lengths of stolon internodes of R. repens differed significantly in each of the three habitats. The shortest internodes occurred on stolons on the open molchills. The longest occurred in the closed grassland habitat. The type of habitat in which parent ramets were rooted did not significantly influence the length of internodes on their daughter stolons. The length of a stolon internode was determined by its immediate surrounding habitat type. Consecutive internode lengths on a given stolon showed considerable plasticity, shortening significantly as stolons spread onto molehills from surrounding habitats, and increasing significantly as stolons advanced from a molehill into the surrounding closed grassland habitat. These results are consistent with the proposition that under favorable conditions (on the molehills, where resources are expected to be more abundant, and competition absent) internode lengths shorten and the plant forages intensively, whereas under conditions of low resource availability (in the closed grassland, where competition occurs) internode lengths increase, allowing R. repens to forage extensively. Such morphological plasticity may promote more efficient exploitation of resource‐rich sites and more rapid vacation of resource‐poor sites.
Field tests of a balloon‐suspended trap system for studying insects in the canopy of tropical rainforests
Authors: Fukuyama Kenji , Maetô Kaoru , Kirton Laurence G. 
Published: March 2006

AbstractA system of suspending traps from a movable balloon was developed and tested on pollinating and wood boring Coleoptera in a tropical rainforest canopy in Pasoh Forest Reserve, Peninsular Malaysia. The balloons, 2.5 m in diameter, were filled with helium gas for levitation and moored in different directions by three pieces of thin rope. Traps in which benzyl acetate and ethanol were used as attractants for the pollinators and wood borers, respectively, were suspended from the balloon at different heights. The trapping results show that the balloon system can be used for studying canopy insects and their vertical distribution on a spatial and temporal scale.
The influence of microclimatic conditions on potential photosynthesis of Usnea sphacelata: A model
Authors: Bölter Manfred , Kappen Ludger , Meyer Michael 
Published: March 2006

AbstractAt a boulder on a hill near Casey Station, Wilkes Land, sensors for light, temperature and humidity were installed facing the four cardinal directions. The measurements lasted for about two months of the summer season 1985/86. The data recording was carried out at intervals of 6 minutes for all probes by automatic recording instruments.Data analysis was carried out with special regard to the biological effects of the parameters analyzed. These data of the microclimatic features taken from its original place of growth were used to a regression model of potential photosynthetic activity of Usnea sphacelata, which is a characteristic species of this area.Although the individual time courses of the above mentioned parameters show long periods of favourable conditions for possible growth and metabolic processes, the combined analysis of these variables considering threshold values for metabolism shortens these time spans drastically. Thus, cross relationships within the physical descriptors and their effects on the actual values of photosynthesis as well as respiration become evident. They are illustrated by the results of models on photosynthesis and respiration of U. sphacelata regarding the different cardinal directions.
Influence of overwintering Daphnia on spring zooplankton communities: An experimental study
Authors: Hanazato Takayuki , Yasuno Masayuki 
Published: March 2006

AbstractTo evaluate the influence of overwintering individuals of zooplankton on spring zooplankton communities, the dynamics of zooplankton communities with or without overwintering individuals were observed in experimental ponds from fall to spring. An insecticide, carbaryl, was used to regulate the overwintering individuals. In ponds which received insecticide applications in November or January, all cladoceran and rotiferan species were eliminated by the treatments and did not reappear until late March or early April, even when the chemical disappeared rapidly. The low water temperature may delayed the establishment of the populations from resting eggs. In these ponds, populations of various cladoceran and rotiferan species, which seemed to be originated from resting eggs, were built up in the spring. In control ponds, Daphnia ambigua or D. longispina overwintered as juveniles and adults and established a large spring population earlier than other cladocerans and rotifers overwintering as resting eggs. The latter zooplankters did not increase in the spring probably because their growth was suppressed by the preceding Daphnia species through competition. In nature, even if the number of overwintering individuals is small, they may have a potential to build up a large population earlier than the individuals hatching from resting eggs. As a result, the species which have overwintered as individuals seem to predominate in the spring and have a large influence on the spring zooplankton community.
Effects of herbivory by chrysomelid beetles on the growth and survival of Rumex plants
Authors: Suzuki Nobuhiko 
Published: March 2006

AbstractThe effects of herbivory by the guild of chrysomelid beetles on the growth and survival of Rumex plants were examined in relation to the distribution and size of the plants.Gastrophysa atrocyanea never appeared on solitary plants whereas Mantula clavareaui showed even utilization of solitary and clumped plants. Galerucella vittaticollis utilized large solitary plants most frequently. In patches of the host plants, the frequency of withering of the aerial parts was higher on small plants. The regrowth rate was higher when the aerial parts withered in spring than in summer. In patches of the host plants, the regrowth rate was higher on small plants. On the other hand, it was lower on small solitary plants than on large solitary plants and small plants in patches. In large plants, no difference in survival rate was recognized between solitary and clumped plants, because both the frequency of withering of the aerial parts and the regrowth rate were lower in clumped than solitary plants. The high vigor against intense herbivory by the chrysomelid beetles brought on the delay in the phenology of Rumex plants. This shift permits in parts the existence of G. vittaticollis in mid summer. The temporal and spatial interactions between herbivore guild and the host plants were discussed.
Interspecific competition for seed production between two naturalized dandelions under different levels of fertilizer supply
Authors: Suehiro Kiyokazu 
Published: March 2006

AbstractTwo naturalized dandelions, Taraxacum officinale and Taraxacum laevigatum, were grown in mixed stands at various plant densities and mixing ratios with various levels of fertilizer supply until seeds were produced. The effect of fertilizer supply on the competitive relationship for seed production between the species was analyzed. In pure stands, the simultaneous effects of plant density and fertilizer supply on mean plant weight were formulated for each species. By introducing the density conversion factor, the results of plant weight growth in mixed stands were formulated successfully. T. laevigatum produced more seeds than T. officinale at the same plant weight. The relationship between mean plant weight and mean number of mature seeds produced per plant was also formulated for each species. Ratio diagrams were predicted with these formulas. The density conversion factors showed that T. officinale was always dominant over T. laevigatum for plant weight growth within a generation. The ratio diagrams showed that T. officinale became dominant over T. laevigatum for seed production with repeating generations at higher levels of fertilizer supply, but that the species with a larger ratio of plant density became dominant over the other species at lower levels of fertilizer supply.
Niche characteristics of Cladonia lichens associated with geothermal vents in Japan
Authors: Glime Janice M. , Iwatsuki Zennoske 
Published: March 2006

AbstractTo characterize the niche preferences of Cladonia species associated with geothermal areas, we sampled ten thermal areas in Japan. It appears from the current study and related studies that some members of the Cladonia genus can have a wide tolerance for both soil temperature and pH conditions. Cladonia mitis is the most abundant Cladonia and occurs throughout most of the vent system. Cladonia theiophila occurs most frequently at a soil pH of less than 3.5, but occurs mostly at lower soil surface temperatures (below 29°C). Cladonia floerkeana is very restricted in its distribution and is most abundant where the root zone temperature (15 cm) is above 70°C, the surface temperature is above 40°C, and the pH is 5–5.5. Tolerances to low pH, high soil temperatures, and low to moderate humidity permit Cladonia species to grow where vascular plants and even mosses cannot grow and thus they avoid the competition such plants would provide to these slow‐growing organisms.
Reproductive ecology of a freshwater amphipod, Jesogammarus suwaensis Morino, inhabiting Lake Suwa in central Japan
Authors: Kusano Harumi 
Published: March 2006

AbstractThe reproductive traits of Jesogammarus suwaensis Morino (1986) were estimated by field survey and rearing experiments. According to the relationship between clutch interval and water temperature, one clutch interval under 15°C corresponded to 212 degree days of the effective cumulative temperature. Thus a female could produce about three clutches during the reproductive period from November to early May in the field. Reproduction was somewhat inhibited at 20°C. The clutch size was positively correlated with female body length, and the regression coefficient was large (4.470 on log‐transformed data). Oviposition was somewhat synchronized in the field, and the proportion of paired females increased as their reproductive development approached oviposition. The precopula duration was estimated to be 60–80% of the clutch interval in the field. Positive size‐assortative mating was observed in precopula pairs and pairing males were usually larger than single ones.
A case study on the effects of a transmission‐line corridor on Sika deer habitat use at the foothills of Mt Goyo, northern Honshu, Japan
Authors: Takatsuki Seiki 
Published: March 2006

AbstractForage biomass and habitat use of Sika deer (Cervus nippon) at a transmission‐line corridor were studied at the foothills of Mt Goyo, northern Japan. Summer forage biomass in the corridor was five times greater than in the adjacent Betula grossa forest. Among the plants that increased in the corridor, Sasa nipponica (a dwarf bamboo), an important forage plant for Sika deer, was predominant. Winter utilization of S. nipponica by Sika deer was slightly heavier in the corridor, and estimated removal of Sasa leaves was twice as great there as in the forest. However fecal pellets were more prevalent in the adjacent forest in winter. Sika deer seemed to use the transmission‐line corridor as a feeding site and the adjacent forest as cover as it reduces wind speed. A transmission‐line corridor is more beneficial than a large clear‐cut area because it provides more forest edges.
Effect of bryophytes on survival of conifer seedlings in subalpine forests of central Japan
Authors: Nakamura Toshihiko 
Published: March 2006

AbstractBryophytes form the major seedbed for coniferous trees in the subalpine forests of central Japan. Field experiments were conducted on the floor of a closed stand dominated by Tsuga on Mt Fuji to examine the seedling survival of Abies veitchii and Tsuga diversifolia in seven substrate types in relation to the morphological characteristics of the seeds and seedlings. Neither Abies nor Tsuga seedlings could survive on dwarf‐bamboo litter beyond 2 years after the seed rain. Abies seedlings survived not only in all types of bryophyte communities but also in larch litter. In contrast, the survival of Tsuga seedlings was restricted to communities of smaller‐statured bryophytes found on logs. The seeds and 1st year seedlings of A. veitchii were larger than those of T. diversifolia. Abies seedlings produced hypocotyls taller than any bryophyte community and radicles which were long enough to penetrate into the moist humus layer, whereas Tsuga seedling radicles presumably penetrate into humus only in bryophyte communities forming a thin mat on logs. The effect of bryophytes on survival of tree seedlings therefore depends on the relationships between the morphology of seeds and seedlings and the structure of bryophyte communities.
Home range and mating system of two sympatric field mouse species, Apodemus speciosus and Apodemus argenteus
Authors: Oka Teruki 
Published: March 2006

AbstractThe size and spatial distribution of home ranges in two sympatric field mouse species, Apodemus speciosus and Apodemus argenteus, were revealed by the capture‐recapture method in a temperate deciduous forest from June 1987 to June 1990. In A. speciosus, the home ranges of males were significantly larger tha those of females, and overlapped with those of other males and females during the breeding season. In A. argenteus, the home range of each male overlapped only that of a single female throughout the year. These results suggested that A. speciosus was promiscuous or polygynous and A. argenteus was monogamous.
Laboratory observations of prey behaviour for prey acquisition by a predator among three larval mosquitoes
Authors: Yasuda Hironori , Mitsui Takashi 
Published: March 2006

AbstractThe effect of prey behaviour on prey acquisition by a predator was examined in the laboratory, using three larval mosquitoes. Aedes albopictus was acquired by the predator, Toxorhynchites towadensis, at a higher rate than Orthopodomiya anopheloides. Toxorphynchites towadensis was a sit‐and‐wait predator. Aedes albopictus was more active than O. anopheloides. Orthopodomiya anopheloides ran away before the predator attacked, but A. albopictus did not. The escape ratio in O. anopheloides was higher than that in A. albopictus. These results suggest that the difference in the prey acquisition ratio by the predator between prey species is caused by different behavioural patterns of the prey to the predator.
Ecological characteristics of Agriophyllum squarrosum, a pioneer annual on sand dunes in eastern Inner Mongolia, China
Authors: Nemoto Masayuki , Lu Xiaoyun 
Published: March 2006

AbstractA field survey was conducted in a semi‐arid region of Inner Mongolia, China, to clarify the ecological characteristics of Agriophyllum squarrosum (Chenopodiacea), which is an ephemeral in shifting sand dunes. The habitat of A. squarrosum is extremely unstable, that is, the surface substrate frequently shifts, the soil water‐content is highly variable and the site does not permit the growth of any other plant species. Agriophyllum squarrosum is able to invade as a pioneer because of the elongation of its fine roots, which are well adapted to dry sandy soil and able to penetrate deep soil layers containing moisture. The biomass and the pod numbers increased under conditions where enough water was supplied. However the biomass at sites where the wind was strong was relatively small.
Leaf carbon gain simulation for tree seedlings acclimatized to microsite light regimes of a temperate pine forest
Authors: Washitani Izumi 
Published: March 2006

AbstractLeaf carbon gain simulation was performed for Quercus serrata seedlings with previously reported 6 day photosynthetic photon flux density (PPFD) histograms from 20 understorey microsites of a pine forest (Washitani & Tang 1991). This simulation was performed with or without an assumption of the acclimatization of photosynthetic capacity (Pmax) to microsite light availability. A constant ratio of respiration rate to Pmax, within, the range of 0.07–0.1, was assumed as a constraint. In relatively well illuminated microsites with a diffuse site factor above 0.1, predicted optimal Pmax was about 5 μmol m−2 s−1, with the predicted mean daily net carbon gain being about 50 mmol m−2 day−1. Each of the predicted optimal Pmax and the simulated mean daily net carbon gains with a constant Pmax (5 μmol m−2 s−1) or the predicted optimal Pmax was linearly related to the microsite light availability index, diffuse site factor. Simulated net carbon gain was negative at diffuse site factors below 0.04, if the constant of Pmax was assumed. The predicted linear relationship between net carbon gain and diffuse site factor could provide an ecophysiological basis for the observed linear dependency of the relative growth rate of biomass of Q. serrata seedlings on the microsite diffuse site factor (Washitani & Tang 1991).
Seasonal change in specific needle weight of Pinus thunbergii
Authors: Kimura Makoto 
Published: March 2006

AbstractTo evaluate the reserve dynamics in pine needles, an index of specific needle weight (SNW; dry weight per unit length of needles) was provided. Developed needles of Pinus thunbergii did not show any additional elongation in their second year. Thus the seasonal change in SNW of developed needles was proved to indicate the dynamics of reserves in needles. SNW showed distinct seasonal change. It increased from autumn to carly spring, followed by a decrease by mid summer. This pattern of change was similar to the change in specific leaf weight (SLW) of evergreen broad leaves in temperate regions. It was concluded that the change in SNW indicated clearly the dynamics of reserves in needles, showing the accumulation in non‐growth seasons and the consumption in subsequent growth seasons. The decrease in SNW during the growth season was 10–15% of the maximum found in early spring.
Biomass and net production in a bamboo Phyllostachys bambusoides stand
Authors: Isagi Yuji , Kawahara Teruhiko , Kamo Kouichi 
Published: March 2006

AbstractBiomass and net production were measured in a Phyllostachys bambusoides stand in Kyoto Prefecture, central Japan, which had carried out gregarious flowering in 1969 and has been recovering vegetatively. The culm density fluctuated around an average value of 12 040 ha−1 during the research period (1985–91). Annual recruirment and mortality rates of culms were 1340 and 1133 ha−1, respectively. The mean diameter at breast height increased from 7.28 cm in 1985 to 8.68 cm in 1991, and the biomass of culms increased from 71.3 to 111.6t ha−1 over the same time period. Branch and leaf biomasses were almost constant, 10.0 and 9.4t ha−1 on average, respectively. The leaf area index of the stand was 11.6 ha ha−1, which is one of the largest values found in Japanese forests. The belowground biomass of 32.6t ha−1 for rhizomes and 14.8t ha−1 for fine roots resulted in the smaller ratio of aboveground parts to the root system (2.38) than those determined for forest stands. The amount of litterfall, excluding culms and large branches, was large (9.13t ha−1 year−1), corresponding to those measured in equatorial stands. The aboveground net production was 24.6t ha−1 year−1, larger than the average value reported for forest stands under similar weather conditions.