It has been reported that in Oku-Nikko, central Japan, the biomass of earthworms is higher outside deer-proof fences (forest floors with Aster ageratoides leiophyllus, hereafter Aster) than it is inside the fences (forest floor with Sasa nipponica, hereafter Sasa). In order to assess the factors influencing the increase in earthworms outside the fences, we examined the relationship between earthworms and the biomasses of Sasa and Aster. The number and biomass of litter-feeding epigeic earthworms increased significantly as the biomass of Aster increased, although no relationship was observed between the depth of the A₀ layer and the biomass of Aster. These results indicate that the palatability of Aster to epigeic earthworms would be high. However, only one epigeic earthworm was collected inside the fences, and the depth of the A₀ layer increased significantly as the biomass of Sasa increased. Therefore, Sasa is probably not a good resource for the earthworms. It has been reported that bamboo growth outside the fences was eliminated by deer grazing and that the understory is now dominated by Aster. Thus, the elimination of Sasa by the deer grazing, and the subsequent increase in Aster growth, has probably contributed to an increase in the number of earthworms outside the fences in this area.

View full abstract

Rattan, rubber and oil palm, are produced in the tropics, of which previous researches were focused on the aspects of ecology and economy. This article aims to clarify the preference of swiddenners to such products and to understand their emic livelihood strategy. As a result, it was clarified that villagers selected the rubber production as the source of cash income because of high ‘returns to works’, and sustained the rattan production because of high ‘flexibility’ in terms of daily use and so on. Villagers hesitated to introduce oil palm because of low ‘flexibility’ and ‘autonomy’ caused by oil palm company. On the other hand, villagers have expectation to high ‘return to works’. Therefore villagers accepted the development of oil palm plantation in upper river area where villagers have not practiced swidden yet, but refused around the village areas where the lands are de facto owned by villagers. We can conclude that the people take the ‘mosaic’ livelihood strategy, where they try to combine the advantages and disadvantages of rattan and rubber production, and introduce oil palm plantation partially for avoiding the risks.

View full abstract

To investigate effects on the abundance and community structures of Orthorrhapha (predacious flies) inhabiting coarse wood debris (CWD) by the improvement cutting of natural forests, we report here abundances of predaicious flies emerged from CWD on the forest floor of the Yambaru. The volume, size and degree of wood decay were recorded and the emergence traps containing CWD were installed for collecting flies. Distribution of these CWD in the forests affected abundances of flies in each operated and non-operated stand. It caused different fly assemblages among the one year-old operated stands and seven year-old and older operated stands. Abundance of predacious flies, expecially dolichopodid flies, was positively correlated with the volume of CWD. Increasing the volume of CWD of the early stage of decay by cutting has indirect bottom-up effect on abundance of the dolichopodid genus Medetera via changes in abundance of bark beetles. We conclude that predacious fly diversity may best be maintained in the Yambaru through forest management practices that do not influent amount of CWD and make various sizes and degrees of wood decay present in a forest.

View full abstract

Soil erosion has been progressing over a large area on the forest floor with an understory impoverished by the feeding of deer (Cervus Nippon) in Doudaira (East Tanzawa of Kanagawa prefecture). Soil erosion investigation plots 5 m long by 2 m wide were set up on the hillside slope in the beech (Fagus crenata) forest in 17 Doudaira to monitor the amount of soil erosion. We monitored the amount of the soil erosion from 2006 to 2008 once a month from April to November. At the same time we monitored the forest floor cover percentage (the total values of understory cover percentage and litter cover percentage) by using the photographs we had taken in the same period. As a result, we have discovered that there is a strong negative correlation expressed by an exponential function (E=65 exp (−0.0615×F) ) between the amount of the soil erosion per mm of the rainfall (E) and the forest floor cover percentage (F). From the equation, a little change in the forest floor cover percentage has a bigger influence on the amount of soil erosion where the forest floor cover percentage is in the small range than when it is in the large range. This result is very different from previous studies which have shown a negative linear relationship between the amount of soil erosion and the litter cover percentage in a rainfall simulator experiment.

View full abstract

In order to estimate the heterotrophic respiration of fine dead root (R_hr), we tested a new method of direct measurement of dead roots buried in the L-layer of forest soil using a small chamber system. CO₂ efflux from the dead roots ranged 83.3∼577.3 mg CO₂ kg⁻¹ h⁻¹ and was inferred to be from the decomposition of the dead roots. The CO₂ efflux showed seasonal change and increased exponentially with increasing soil temperature. In addition, CO₂ efflux increased with decreasing mean root diameter, and the relationship could be described by a power function. Our results suggested that seasonal change and decomposition of very fine roots morphology need to be considered in estimating CO₂ efflux from fine root litter in forest soils.

View full abstract

The frequency of walking in forested areas was surveyed in residents attending health check-ups in Yakumo Town, a rural area of southern Hokkaido. A total of 578 participants (215 men, 363 women; 39 to 89 years old, mean±SD age; 64.4±10.2) were included in the analysis. Of these, 14.4% (n=83) responded that they walked in a forested area at least once a month; and 31.1% (n=180) that they walked in forested areas at least once a year. Of the participants in their 70 s and 80 s, 9.8% and 14.3%, respectively, responded that they walked in a forested area at least once a week. Frequency of forest walking was significantly lower for participants in Yakumo than for those in west and central areas of Shizuoka Prefecture, after adjusting for age, sex, job and levels of enjoyment of forest walking. However, in men compared to women, in higher age groups, and those in a group enjoying higher levels of enjoyment of forest walking, frequencies of forest walking were significantly higher in Yakumo, the same as in the Shizuoka area.

View full abstract