Showing papers in "Ecological Research in 2004"

Theories for ecological restoration in changing environment: Toward ‘futuristic’ restoration

Abstract: Ecological restoration is one of the fastest growing fields in applied ecology providing new ideas and opportunities for biological conservation and natural resource management. Despite countless attempts in the past, large portions of restoration projects have been considered unsuccessful mainly due to: unrealistic goals; inadequate restoration plans based on an ad-hoc approach; lack of explicit and quantified evaluation criteria for restoration success; lack of ecological understanding; social, economic, and political constraints; or combinations of these factors. Existing ecological theories, particularly succession theories, may provide a conceptual framework for a restoration trajectory. However, projecting a ‘desirable’ trajectory and outcome is often challenged by the unpredictability of ecological communities in the changing environment. Particularly, the sustainability of reconstructed ‘historic’ ecosystems appears to be an unlikely goal in the ever-changing and unpredictable future environment. This paper calls for a shift in the restoration paradigm from ‘historic’ to ‘futuristic.’ A ‘futuristic’ restoration is: (i) to set realistic and dynamic (instead of static) goals for future, instead of past, environment; (ii) to assume multiple trajectories acknowledging the unpredictable nature of ecological communities and ecosystems; (iii) to take an ecosystem or landscape approach, instead of ad-hoc gardening, for both function and structure; (iv) to evaluate the restoration progress with explicit criteria, based on quantitative inference; and (v) to maintain long-term monitoring of restoration outcomes. A theoretical framework for ‘futuristic’ restoration, in terms of goals, trajectories, evaluation criteria, and monitoring, along with a historical perspective is presented in this paper.

Does seed production of spring ephemerals decrease when spring comes early

Abstract: To predict the effect of global warming on plant reproductive success, seed-sets of spring ephemerals were compared between a year of extremely warm spring (2002) and normal years at cool-temperate deciduous forests in northern Japan. The spring of 2002 was the warmest in the last 40 years and most spring-ephemeral plants bloomed 7–17 days earlier than usual. The seed-set of bumblebee-pollinated Corydalis ambigua drastically decreased in 2002 in every population. The small bee-pollinated Gagea lutea also significantly decreased in 2002. However, the seed-sets of two fly pollinated species, Adonis ramosa and Anemone flaccida, were not influenced by early flowering. These results indicat that the effect of global warming on seed production of spring ephemerals differs between species depending on the type of pollinators, and that bee-pollinated species can have serious impacts on reproductive success as a result of climate change.

Modeling urban landscape dynamics: A review

Abstract: Reviewed here is the historical development of urban growth models, showing how different disciplines and diverse theories have come together over time to produce the models used today. This review is divided into two sections, the first section reviews the early models that are rooted in transportation and land-use planning and form the foundation on which nearly all modeling efforts are based. These models are already well documented in the literature and an overview here is sufficient. In the second section, an exploration is made into the theories and approaches that have been integrated into urban modeling efforts. The concepts are outlined and one or more contemporary examples are highlighted. These theories and approaches represent the major areas of development that exist in published work.

Accumulation and release of nitrogen and phosphorus in relation to lignin decomposition in leaf litter of 14 tree species

Abstract: Immobilization and mobilization of nitrogen and phosphorus were investigated in relation to the nitrogen (L/N) ratio and lignin to the phosphorus (L/P) ratio as indicators of the nitrogen and phosphorus dynamics. The present study was carried out on upper and lower parts of a forest slope in a cool temperate forest in Japan. Net immobilization and net mobilization characterized the dynamics of nitrogen and phosphorus in 14 litter types and were related to the changes in the L/N and L/P ratio. The critical values of the L/N and L/P ratio at which the mobilization began were 23–25 and 500–620, respectively. In litter types with the L/N and L/P ratio higher than critical values, nitrogen and phosphorus were immobilized until the ratios reached at the critical values and then nitrogen and phosphorus began decreasing. In litter types with initial L/N and L/P ratios lower than or equal to the critical values, nitrogen and phosphorus were released from litter. The critical values of the L/N and L/P ratios showed convergent trends among litter types as compared to their initial values, and were approached to those of underlying humus layers. These results indicated the usefulness of L/N and L/P ratios as indicators of the nitrogen and phosphorus dynamics in the study site. The general validity of the L/N ratio as an indicator of nitrogen dynamics and the convergent trend of critical L/N ratio at 25–30 were demonstrated by a review of literature on lignin and nitrogen dynamics in 47 litter types in temperate and boreal forests.

Below-ground biomass in healthy and impaired salt marshes

Abstract: Twelve salt marshes in south Louisiana (USA) were classified as either ‘impaired’ or ‘healthy’ before a summer sample collection of above- and below-ground biomass and determination of sediment accretion rates. The above-ground biomass of plant tissues was the same at both impaired and healthy salt marshes and was not a good predictor of marsh health. However, below-ground root biomass in the upper 30 cm was much lower in the impaired marshes compared to the healthy marshes. Compromises to root production apparently occur before there is an obvious consequence to the above-ground biomass, which may quickly collapse before remedial action can be taken. The subsequent change in vertical position of the marsh surface may be equivalent to many years of accretion, and be irreversible within decades without considerable effort. These results are consistent with the hypothesis that it is the plant’s below-ground accumulation of organic matter, not inorganic matter that governs the maintenance of salt marsh ecosystem in the vertical plane. Reversing the precursor conditions leading to marsh stress before the collapse of the above-ground biomass occurs is therefore a prudent management objective and could be easier than restoration.

Seasonal migration patterns of female sika deer in eastern Hokkaido, Japan

Abstract: Fifty-seven female sika deer (Cervus nippon yesoensis), captured at the wintering area in the Shiranuka Hills in eastern Hokkaido, Japan, were radio-tracked during 1997–2001 to examine the factors affecting seasonal migration at the individual-landscape level. Ten of the 57 deers migrated between low-altitude summer home ranges and intermediate-altitude winter home ranges (the upward migrants). Twenty-nine migrated between high-altitude summer home ranges and intermediate-altitude winter home ranges (the downward migrants). Twelve used the intermediate-altitude home ranges all year round (the non-migrants). The remaining six were unknown. The summer home ranges of deer were widely scattered over an area of 5734 km2. Migration distances ranged between 7.2 and 101.7 km. Deer showed high site fidelities to their seasonal home ranges. The upward migrants wintered in areas of less snow, higher quality of bamboo grass, and more coniferous cover than their summer home ranges. The downward migrants wintered in areas of less snow, higher quality of bamboo grass, higher winter temperature, and more southern slopes, but less coniferous cover than their summer home ranges. The non-migrants used year-round ranges with little snow, high quality of bamboo grass, and sufficient coniferous cover. We suggest that snow cover and bamboo grass are the factors affecting seasonal migration of the population and that coniferous cover is another factor for the upward migration.

Soil quality regime in relation to land cover and slope position across a highly modified slope landscape

Abstract: Vegetation and land-use mosaics of shrub land, grassland, farmland and reforested land are characteristic for residential areas of the Wolong nature reserve in Sichuan province, southwest China. The patterns represent a stage in long-term human disturbance and natural secondary succession since deforestation. The aim of this paper was to elucidate the soil-land cover types, soil-slope position relationships on a typical disturbed slope in the humid mountainous region. Soils were taken from four typical land cover types (shrub land, grassland, farmland and reforested land) under four slope positions (upper slope, middle slope, lower slope, foot slope) to study the distribution of soil nutrients and moisture on the transect scales of the slope. To elucidate the influence of land-use and slope position on soil quality, two integrated quantitative indexes were developed to compare soil quality under different land-use types (QI) and under different slope positions (PI). The results showed shrub land had the highest QI value, while the QI of reforested land and farmland had lower values. Foot slopes and upper slopes had higher soil quality levels compared to middle slopes and lower slopes. The results indicated that on the slope scale shrub land had high soil quality levels. The results also suggested that in the area of China where the climate favors secondary succession, ‘leave nature as it is’ is a better choice than the policy ‘change farmland to forest land’.

Prey use by web-building spiders : stable isotope analyses of trophic flow at a forest-stream ecotone

Abstract: A forest-stream trophic link was examined by stable carbon isotope analyses which evaluated the relationship of aquatic insects emerging from a stream to the diets of web-building spiders. Spiders, aquatic and terrestrial prey, and basal resources of forest and stream food webs were collected in a deciduous forest along a Japanese headwater stream during May and July 2001. The δ13C analyses suggested that riparian tetragnathid spiders relied on aquatic insects and that the monthly variation of such dependence is partly associated with the seasonal dynamics of aquatic insect abundance in the riparian forest. Similarly, linyphiid spiders in the riparian forest exhibited δ13C values similar to aquatic prey in May. However, their δ13C values were close to terrestrial prey in both riparian and upland (150 m away from the stream) forests during June to July, suggesting the seasonal incorporation of stream-derived carbon into their tissue. In contrast, araneid spiders relied on terrestrial prey in both riparian and upland forests throughout the study period. These isotopic results were consistent with a previous study that reported seasonal variation in the aquatic prey contribution to total web contents for each spider group in this forest, implying that spiders assimilate trapped prey and that aquatic insect flux indeed contributes to the energetics of riparian tetragnathid and linyphiid spiders.

Dragonfly species richness on man-made ponds: effects of pond size and pond age on newly established assemblages

Abstract: We studied the abundance and species richness of adult dragonflies in 11 artificial ponds which were recently established (within 2 years). We found that the adult dragonfly assemblage patterns were influenced by pond size as well as pond age. The species richness was positively correlated with the pond size, which was because the distributional patterns of species were significantly nested according to pond area. The species richness was highly correlated with pond age in association with the vegetation cover within ponds. It was suggested that the species richness was enhanced by the increasing immigration rate of species which favor well-vegetated ponds.

The eco-field : A new paradigm for landscape ecology

Abstract: In the spirit of the theory of biocomplexity and of the non-linear emergent characters of ecological systems, the eco-field is a new paradigm that integrates the vision of the landscape as a neutral matrix (like a habitat) in which organisms are living, and contemporarily as a product of the human mind. Eco-field is defined a ‘cognitive field’ created by the interference between functional traits and the ‘real world’. Species-specific environmental suitability is the result of the quality of the different eco-fields and the landscape becomes a cognitive entity. The eco-field paradigm can be extended to the emergent properties of the systems. The eco-field of emergences is the geographic space in which the emergent properties appear. The eco-field of organisms and the eco-field of emergences, like results of aggregated entities, have in common the multidimensionality of landscapes, refusing the vision of landscape like a neutral geographic matrix for organisms and processes.

Food source of riparian spiders analyzed by using stable isotope ratios

Abstract: We analyzed the food source of riparian spiders in a middle reach of the Chikuma River, Japan, by using stable isotope ratios of carbon and nitrogen. The carbon and nitrogen isotope ratios of attached algae were higher than those of terrestrial plants, reflecting a large carbon isotope fractionation in terrestrial plants and a difference in nitrogen sources. The carbon isotope ratios of terrestrial insects were similar to those of the terrestrial plants, and the ratios of aquatic insects were scattered between those of the terrestrial plants and the attached algae. The carbon and nitrogen isotope ratios of spiders were intermediate between those of the terrestrial and aquatic insects. The two-source mixing model using the carbon isotope ratio showed that the web-building spiders utilized both the terrestrial and aquatic insects, with large contribution by the aquatic insects (54% on average with a maximum of 92% among spider’s taxa collected in each zone), in the riparian area in a middle reach of the Chikuma River. The large contribution of the aquatic insects was often observed for the spiders collected near river channel ( < 5 m) and for the horizontal web-building spiders collected across the riparian area. The relative contribution of the aquatic insects might be related with food availability (distance from river channel) and spider’s food preference reflected in their web types (horizontal vs. vertical). Our results showed that organic materials produced in the river channel, in the riparian area, and in the terrestrial area surrounding the riparian area were mixed at the carnivorous trophic level of riparian spiders.

Social behaviors of all-male proboscis monkeys when joined by females

Abstract: In a riverine forest along the Menanggul River, which is a tributary of the Kinabatangan River, Sabah, Malaysia, I observed an all-male group of proboscis monkey (Nasalis larvatus) consisting of 27–30 (mean: 28.8) individuals. This large size of the all-male group seems to be attributed to habitat fragmentation because of the expansion of oil palm plantations. A few females joined this all-male group. Sub-adult females copulated with subadult or large juvenile males. Since the mean male tenure period of this monkey was estimated to be longer than female maturity, and prematured females might leave their natal one-male groups to avoid inbreeding and temporarily participate in the all-male group where males were permissive to them. Even when females joined this group, no conflicts occurred among males.

Food habits and home range use of Japanese macaques on an island inhabited by deer

Abstract: Food habits and home range use of a troop of Japanese macaque Macaca fuscata Blyth on Kinkazan Island (9.6 km2), northern Japan, were studied from the spring of 2000 to the winter of 2002. The home range of this troop covers the area where vegetation is modified by foraging of sika deer Cervus nippon Temminck. The core areas of the home ranges of the macaque troop corresponded closely to the distributions of the staple food plants in every season. For example, leaves of Berberis thunbergii DC. and leaves of Zelkova serrata Makino in spring, berries of Berchemia racemosa Sieb. & Zucc. in summer, nuts of Zelkova serrata and Carpinus spp. in the fall of 2000 and winter of 2001, seeds of Torreya nucifera Sieb. & Zucc. in the fall of 2001, and bark of Zanthoxylum piperitum DC. in winter of 2002. Among the staple food plants, Berberis thunbergii and Zanthoxylum piperitum are more abundant on Kinkazan Island than other macaque habitats in northern Japan because they are spiny and unpalatable to sika deer, hence survive under the heavy foraging by the deer. Further, another staple food plant, Berchemia racemosa, a liana, grows abundantly at the edges of Illicium forests. Illicium anisatur is toxic and is not consumed by sika deer. Monkeys of this troop using the unique vegetation induced by sika deer grazing, fed on several plants which are not consumed by monkeys in other areas, and the home range was heavily affected by the distributions of these plants.

Carbon dynamics and budget in a Miscanthus sinensis grassland in Japan

Abstract: We investigated the carbon dynamics and budget in a grassland of Miscanthus sinensis, which is widely distributed in Japan, over a 2-year period (2000–2001). Plant biomass began to increase from May and peaked in September, then decreased towards the end of the growing season (October). Soil respiration rates also exhibited seasonal fluctuations that reflected seasonal changes in soil temperature and root respiration. The contribution of root respiration to total soil respiration was 22–41% in spring and summer, but increased to 52–53% in September. To determine the net ecosystem production (carbon budget), we estimated annual net primary production, soil respiration, and root respiration. Net primary production was 1207 and 1140 g C m−2 in 2000 and 2001, respectively. Annual soil respiration was 1387 g C m−2 in 2000 and 1408 g C m−2 in 2001; root respiration was 649 and 695 g C m−2 in 2000 and 2001, respectively. Moreover, some of the carbon fixed as net production (457–459 g C m−2) is removed by mowing in autumn in this grassland. Therefore, the annual carbon budget was estimated to be −56 g C m−2 in 2000 and − 100 g C m−2 in 2001. These results suggest that the Miscanthus sinensis grassland in Japan can act as a source of CO2.

Influence of urbanization on ant distribution in parks of Tokyo and Chiba City, Japan I. Analysis of ant species richness

Abstract: To investigate how progressive urbanization influences the distribution of ant species in cities, I compared the ant species richness in urban parks of different areas and ages of Tokyo, the most intensively developed urban region in Japan, and its developing neighbor, Chiba City. A total of 43 ant species were found from 98 parks. Multiple regression analysis revealed that park area and age had a positive effect on the number of ant species in the parks and that the parks in Tokyo contained fewer species than did comparable parks in Chiba. Thus, the progression of urbanization reduces ant species richness in urban parks, most likely because it isolates the parks from the surrounding area. Next, in order to examine the relationships between the types of landform modification and the ant distribution in urban areas, I compared the ant species richness in urban parks of Chiba City among different landform types (upland + terraces, lowlands, cut and fill, banking, and reclamation). This study showed that the parks in the reclaimed lands and lowlands contained fewer ant species than did parks in other areas. The reason for this decline of ant fauna is discussed.

Asian weaver ants, Oecophylla smaragdina, and their repelling of pollinators

Abstract: The Asian weaver ant, Oecophylla smaragdina, is known to have outstanding predatory power. This ant can protect the host plants from attacks of phytophagous insects and therefore has been used for biological control in the tropics. We present evidence for a possible negative effect of Oecophylla on the performance of host plants. Our observation in a fruit orchard of rambutan in Sumatra suggested that the presence of Oecohylla nests on the trees statistically significantly lowered the flower-visiting rate of flying insects, involving the major pollinator Trigona minangkabau. The visiting rate of Oecophylla workers to each flower shoot of rambutan significantly negatively correlated with the visiting rate of flying insects. Empirical evidence of such an inhibitory effect on flower-visiting of pollinators cased by aggressive ants has been scarce so far.

Proximate mechanisms and evolution of caste polyphenism in social insects: From sociality to genes

Abstract: Evidence has accumulated over several decades to prove the kin selection theory of evolution of social insects, however, proximate mechanisms of social behavior, and/or caste differentiation remain obscure. Genes that regulate these mechanisms are apparently selected through kin selection, and organisms have consequently acquired sociality. Here, I will discuss several studies that were performed recently by Matsumoto Laboratory, University of Tokyo, Tokyo, Japan, in various social insects, such as termites and ants, in order to reveal the regulatory mechanisms of social behavior and the evolutionary processes of sociality. First, I will review the foraging behavior of the black marching termite Hospitalitermes medioflavus, where well-organized task allocation among castes is apparent. This suggests that regulation of postembryonic development is important in social behavior. Next, I will summarize recent progress in identifying caste-specific gene expression in the damp-wood termite Hodotermopsis sjostedti. This constitutes the basis for molecular mechanisms of caste differentiation, and moreover, the genes identified might be good markers for social evolution. Finally, the mechanism underlying winglessness in ant workers is reviewed. Apoptotic cell death was detected at the stage of pupation in wingless worker castes. Furthermore, the areas of study recently designated as ‘sociogenomics’ and ‘ecological developmental biology’ are discussed.

Temporal and spatial variation of forest biomass in relation to stand dynamics in a mature, lowland tropical rainforest, Malaysia

Abstract: To clarify consistency in the size of carbon pool of a lowland tropical rainforest, we calculated changes in above-ground biomass in the Pasoh Forest Reserve, Peninsular Malaysia. We estimated the total above- ground biomass of a mature stand using tree census data obtained in a 6-ha plot every 2 years from 1994 to 1998. The total above-ground biomass decreased consistently from 1994 (431 Mg ha - 1 ) to 1998 (403 Mg ha - 1 ) (1 Mg = 10 3 kg). These are much lower than that in 1973 for a 0.2 ha portion of the same area, suggesting that the the total above-ground biomass reduction might have been consistent in recent decades. This trend contrasted with a major trend for neotropical forests. During 1994-1998, the forest gained 23.0 and 0.88 Mg ha - 1 of the total above-ground biomass by tree growth and recruitment, respec- tively, and lost 51.9 Mg ha - 1 by mortality. Overall, the biomass decreased by 28.4 Mg ha - 1 (i.e. 7.10 Mg ha - 1 ·year - 1 ), which is almost equivalent to losing a 76-cm-diameter living tree per hectare per year. Analysis of positive and negative components of biomass change revealed that deaths of large trees dominated the total above-ground biomass decrease. The forest biomass also varied spatially, with the total above-ground biomass density ranging 212-655 Mg ha - 1 on a 0.2-ha basis ( n = 30 subplots, 1998) and 365-440 Mg ha - 1 on a 1 ha basis. A large decrease of the total above-ground biomass density ( > 50 Mg per ha per 2 years) in several 0.2-ha subplots contributed to the overall decrease in the 6-ha total above-ground biomass. In the present study, we discuss the association between forest dynamics and biomass fluctuation, and the implication for carbon cycling in mature forests with emphasis on forest monitoring and assessments of soil and decomposition systems.

Forest responses to the large-scale east coast fires in Korea

Abstract: The east coast forest fires of April 2000 were Korea’s largest recorded fires. This, along with the fact that they took place in the region most frequently affected by fire, attracted a great deal of attention. Due to the variations in wind, topography and pre-fire forest stands, a heterogeneous landscape mosaic of burn severity was created across the region. It turned out to be an excellent opportunity to study various landscape-scale impacts of fires on forest dynamics. Therefore, we investigated stands in the 23 794 ha of burned forest region, in terms of burn severity, vegetation regeneration and forested landscape change as a measure of community stability. Using the geographic information system technique, we analyzed the differential severity and post-fire recovery of pre-fire forest types of different stand age both at stand and species level. Analysis showed that pre-fire vegetation was composed of mainly pine (Pinus densiflora) stands that occupied 70% of the whole forested area, while pine-hardwood and hardwood stands occupied only 28% and 3%, respectively. In addition, two-thirds of all stands were less than 30-years-old. Pine stands were the most severely burned, while conversely pine-hardwood and hardwood stands were less vulnerable. This implied that pine forests had fire-prone characteristics. Vegetation recovery went the opposite way; that is, the regenerating vegetation cover was 71% at pre-fire hardwood stands, and 65% and 53% at pine-hardwood and pine stands, respectively. However, these recovery rates were strikingly fast, considering that investigation took place about 3 months after the fires. Fire did not initiate successional processes, but tended to accelerate the predicted successional changes by releasing pre-fire understory species that survived the fires and regenerated by sprouting. The dominant pre-fire tree species (P. densiflora) was susceptible to fire and not resilient enough to reestablish in competition with oak species. Contrary to pines, the abilities of oak species, mainly Quercus mongolica and Q. variabilis, to survive fires and to resprout vigorously made them dominant at most post-fire stands. These shifts in species abundance caused drastic changes to the landscape: from pine-dominated to oak-dominated stands without any notable change in species composition. The patterns in forest regeneration that we observed in Korea may be representative of forest responses to any long-term repeated disturbances, including fire.

Landscape ecology as a bridge from ecosystems to human ecology

Abstract: ‘Landscape’ as a subject of (terrestrial) ecology can be interpreted: first, as a piece of land composed of different ecosystems; and second, as a holistic entity of aesthetic perception derived from landscape paintings and parks of the 18th and 19th century. Such entities display a characteristic arrangement of ‘landscape elements’ regarded as a whole and taking them apart for specific investigation will break up and virtually destroy it (e.g. a symphony dissociated into single notes). Landscape as a holistic entity satisfies emotional human needs like identification with regions, and explains the attraction of tourists. ‘Entity features’ are land-use and land cover combined with openness and a certain naturalness. A key question is whether you call a piece of the earth’s surface just ‘land’ or ‘landscape’– and why. Such questions touch the interface between landscape ecology and human ecology. But human ecology must not dismiss landscape functions. The most beautiful landscape will be reduced to a mere picture if it does not also provide basic life-support. Therefore, energy and matter flows and transformations between the ecosystems of a landscape have to be determined along with its climate, geomorphology (relief), soils, hydrology, species and ecosystem diversity. These different approaches, however, may never be combined into a unified whole. There is no ‘superscience’, and incidentally, its complexity would by far exceed human brain capacity. What we can achieve is bridge-building by approximation of selected facts. A conscious spatial arrangement of diversified land-use units (ecotopes) will promote (bio)diversity and may be perceived as an integral landscape pattern. A spatially and temporally differentiated energy input into land-use units will result in a gradient of utilization intensity and allow more species to thrive, again enhancing both diversity and landscape beauty. Modern humans have deliberately chosen artificial surroundings to achieve complete environmental control, even in rural lifestyles. But as far as emotional needs are concerned, this artificiality seems to be neither human nor ecological. Something ‘natural’ is lacking, and landscape in its holistic sense can provide it – be it a landscaped open space in a city, a rural scene, a seashore or a mountain range. Maintaining and managing such ‘naturalness’ requires sound ecological knowledge – not as an aim in itself, but to provide a bridge for humans.

Larval nutritional environment determines adult size in Japanese horned beetles Allomyrina dichotoma

Abstract: The effects of larval nutrition and parental size on offspring horn (male) and body size (male and female) were examined in the Japanese horned beetle Allomyrina dichotoma L. (Coleoptera: Scarabaeidae). Offspring-parent regressions for both horn size and body size of males show no heritable effect, and the magnitudes of these traits were primarily determined by the larval nutritional condition. Male Allomyrina dichotoma also displayed dimorphic horn size-body size allometry, that is, larger males had longer horns relative to their body size and vice versa. Because it has been suggested that males of different body sizes adopt different reproductive tactics, the dimorphic horn size–body size allometry and male reproductive tactics are also a result of the larval environment. Similarly, female body size was determined by larval nutrition, and, thus, larval condition might influence future female fecundity. Females under low nutrition treatment spent longer duration of the third larval instar than females under high nutrition. Females under poor nutrition treatment probably attempted to be as large as possible by the extent of larval duration. Since horn and/or body sizes of males and females affect their fitness, this suggests the evolution of female choice for better oviposition site.

Diet composition of introduced bullfrog, Rana catesbeiana, in the Mizorogaike Pond of Kyoto, Japan

Abstract: I analyzed stomach contents of the American bullfrog, Rana catesbeiana, in the Mizorogaike Pond of Kyoto, Japan As a result, adult bullfrogs were found to feed predominantly on crayfish, and juveniles eat diverse arthropods A wide variety of aquatic organisms occurred in the diet of both adult and juvenile bullfrogs

Impact of exotic fish removal on native communities in farm ponds

Abstract: Introduced largemouth bass (Micropterus salmoides spp.) and bluegill (Lepomis macrochirus spp.) are thought to threaten native aquatic organisms worldwide and hence their eradication has recently begun in Japan. Our previous studies suggested that the removal of largemouth bass increases native fish, shrimp, dragonflies, and exotic crayfish, but decreases macrophytes. To test this prediction, we removed the exotic fishes by draining farm ponds and compared the numbers of these organisms before and after the drain, as well as between drained and undrained ponds. The number of dragonfly Pseudothemis zonata, crayfish, shrimp, and goby increased rapidly after the drain, but the coverage of macrophyte declined. The reduction in macrophyte is assumed to be caused by increased herbivory by crayfish. The number of exuviae of damselfly Cercion calamorum and the total number of species of odonate also decreased after the drain. These decreases can be due to the reduction of macrophyte because reduced odonate species are known to use macrophytes as oviposition sites. Therefore, the removal of largemouth bass has a potential to cause negative effects on some native organisms. We propose that reduction of exotic crayfish should be considered when eradicating the exotic fishes.

Effects of sika deer on tree seedlings in a warm temperate forest on Yakushima Island, Japan

Abstract: High-density herbivore species often play an important role in forest regeneration. Native sika deer (Cervus nippon yakushimae) inhabit a high density (51.5–63.8 head/km2, estimated by a pellet count method) area in the western part of a lowland natural forest on Yakushima Island, Japan. To test experimentally the impact of sika deer on the mortality and the survivability of current-year seedlings, which are at a more vulnerable stage than the later stages, we constructed fenced exclosures, planted seeds of nine sapfruit tree species and compared the mortality and the survivability of current-year seedlings between fenced and unfenced quadrats. Large seeded species had significantly greater survivability in fenced quadrats than in unfenced quadrats. However, the survivability disagreed with feeding preferences. Sika deer activity increased seedling mortality of large-seeded species more than that of small-seeded species, and did not decrease much seedling survivability of not-preferred species. We found that the physical disturbance by the high density of sika deer resulted in mortality for both preferred and not-preferred species, and that deer herbivory was important for preferred species.

Predicting impacts of Arctic climate change: Past lessons and future challenges

Abstract: General circulation models predict increases in temperature and precipitation in the Arctic as the result of increases in atmospheric carbon dioxide concentrations. Arctic ecosystems are strongly constrained by temperature, and may be expected to be markedly influenced by climate change. Perturbation experiments have been used to predict how Arctic ecosystems will respond to global climatic change, but these have often simulated individual perturbations (e.g. temperature alone) and have largely been confined to the short Arctic summer. The importance of interactions between global change variables (e.g. CO2, temperature, precipitation) has rarely been examined, and much experimentation has been short-term. Similarly, very little experimentation has occurred in the winter when General circulation models predict the largest changes in climate will take place. Recent studies have clearly demonstrated that Arctic ecosystems are not dormant during the winter and thus much greater emphasis on experimentation during this period is essential to improve our understanding of how these ecosystems will respond to global change. This, combined with more long-term experimentation, direct observation of natural vegetation change (e.g. at the tundra/taiga boundary) and improvements in model predictions is necessary if we are to understand the future nature and extent of Arctic ecosystems in a changing climate.

Regeneration failure of lakeshore plants under an artificially altered water regime

Abstract: To reveal the effects of artificial alteration of water level regime on the regeneration of lakeshore plants from seeds, we examined the factors causing regeneration failure in Lake Kasumigaura, Japan. A survey of microtopography within and around a remnant fragment of lakeshore vegetation revealed that, over a large range, the habitat is frequently inundated in spring under the current water regime, although it was rarely inundated under past water regimes. Analysis of the patterns of seedling emergence and establishment at microsites at various elevations revealed a significant negative correlation between number of inundation days and abundance or species-richness of seedlings that emerged in the spring. Most seedling deaths occurred when the study site was inundated. We suggest that regeneration failure caused by the artificial raising of the lake’s water level is one of the principal mechanisms of the recent vegetational decline in the lake.

Environmental determinants of the altitudinal variations in relative group densities of Japanese macaques on Yakushima

Abstract: Altitudinal variations in relative group densities of the Japanese macaques on Yakushima were studied. This is an ideal place for studying resource limitations because it avoids various complicating factors that are difficult to quantify but might affect animal densities, such as predation, interspecific competition, and past catastrophes. The relative group density was high in the coastal forest (0–400 m), while it did not differ among the higher zones (400–800, 800–1200 and 1200–1886 m). To examine this variation, three habitat variables were analyzed: total basal area of food trees per unit area, seasonal variations in fruit abundance, and total annual fleshy fruit production. All of these variables indicate that fruit and seeds are most available in the coastal forest. Thus, altitudinal variations in the density of Japanese macaques on Yakushima are determined by the total annual food abundance.

Germination responses of Caragana korshinskii Kom. to light, temperature and water stress

Abstract: Caragana korshinskii Kom. is a very important shrub species for vegetation rehabilitation in northern China for its high ecological and economic values. Experiments were conducted to determine its germination responses to (i) different temperature regimes under light and/or dark conditions, (ii) different light intensities, and (iii) different water potentials combined with varied constant temperatures. Under alternating temperatures (from 5:15 to 25:35°C), final percent germinations of Caragana korshinskii were quite similar. In dark conditions, constant temperatures resulted in lower final percent germinations than alternating temperatures. At a controlled temperature regime of 10:20°C, neither final percent germinations nor germination rates showed significant differences among varied light intensities. As water potentials were reduced from 0 (distilled water) to −0.6 MPa, final percent germinations increased slightly and reached the peak at approximately −0.6 MPa, however, the increment was not significant. Beyond −0.6 MPa, further water potential reduction led to decreased final percent germinations and few seeds could germinate at −1.4 MPa. Water stress also strongly inhibited germination at very high or low temperatures. The experimental results suggested that middle May might be a suitable time for aerial seeding for this species.

Characteristics and habitats of non-native plant species in the city of Chonju, southern Korea

Abstract: Investigations on non-native organisms have become an important task of modern ecology throughout the world. The major objective of this study was to identify the characteristics and habitats of non-native plant species in Korean cities in order to derive conclusions on the success of biological invaders. The city of Chonju in southwest Korea was selected as a representative investigation area. All wild-growing vascular plants were recorded in the city on a total of 106 sample plots located in representative land-use types and within various distances of the city center. Frequency, origin, life forms, and plant families of non-native species were analyzed. Additionally, the percentage of non-native species along a gradient from the city center to the outskirts was investigated. We found that most common non-native species of the flora of Chonju are: (i) native to the Northern hemisphere; (ii) belong to the annuals; (iii) belong to the plant families of the Compositae or Leguminosae; and (iv) they perform best on sites that are continuously disturbed by human impact. In conclusion, non-native species play a significant role in enhancing biological diversity in urban areas.

Biomass, production and nutrient distribution of a natural oak forest in central Korea

Abstract: Biomass, production, and nutrient distribution of a pure Quercus variabilis Bl. stand (stand 1) and two mixed Q. variabilis–Q. mongolica Fisch. stands (stand 2 and 3) were investigated in central Korea. Stand 1 naturally occurred on a site with a southern aspect while stand 2 and stand 3 occurred on sites with a northern aspect. Total (overstory + understory vegetation) biomass (t ha-1) and annual production (t ha–1 year–1) were 137.8 and 11.1 for stand 1, 216.2 and 16.6 for stand 2, and 253.3 and 19.7 for stand 3. Nutrient contents (kg ha–1) in the vegetation were distributed as follows: K, 478–860; N, 471–839; Ca, 428–791; Mg, 72–125; Na, 77–141; and P, 37–71, and were greatest in stand 3 followed by stand 2, and stand 1. Stand density influenced the differences in biomass, annual production and nutrient contents in the vegetation. Forest floor dry mass and N content (kg ha–1) were 13 400 and 169 for stand 1, 10 400 and 133 for stand 2, and 11 200 and 127 for stand 3. Total amounts of N, P and Na in the ecosystem were greatest in the upper 40 cm of mineral soil followed by the vegetation and forest floor. However, the vegetation contained a greater amount of K than the mineral soil. It appeared that microenvironments, such as, aspect influenced the distribution of natural oak species within a relatively small area and resulted in differences in biomass, production and nutrient distribution among the stands.