Characteristics of carbon (C) mineralization in forest soils were investigated in stands of sugi (Japanese cedar, Cryptomeria japonica D. DON) and hinoki (Japanese cypress, Chamaecyparis obtusa ENDL) in east Gunma, and stands of sudajii (Castanopsis cuspidata var. sieboldii NAKAI) and matebasii (Pasania edulis MAKINO) in central Chiba, Japan. The soil C mineralization process was formulated mathematically using a kinetics model, and three parameters (early C mineralization potential (C0), rate constant of mineralization (k), and apparent activation energy (Ea)) were examined in relation to temperature and soil properties. Soil samples from different depths (0-5 cm (surface) and 5-10 cm, 10-20 cm (subsurface)) were used in a natural state. The fresh soil samples were sieved through a 4-mm mesh, and incubated at 20,25,and 30℃. The samples were extracted at 3-60 days intervals, and the rate of CO2 evolution was measured by the alkali adsorption method. The degree of soil C mineralization was calculated by integration of the CO2 evolution. The integration of C mineralization was fitted to a simple type of non-linear kinetics model. The minimum incubation time was estimated to be about 140 days using the equation for obtaining k. The total C and C0 were greater at sugi and hinoki sites than at sudajii and matebasii sites, and in surface soils than in subsurface soils. The percentages of C0 to total C were 4-9% at sugi and hinoki sites, 8-14% at sudajii sites and 18-19% at matebasii sites. The value of k was greater in surface soils than in subsurface soils, and in surface soils at sudajii sites than at other sites. However the amount of early C mineralization per day (C0・k) was smaller at sudajii sites than at other sites. The turnover of C0・k for total C was greater at matebasii, sudajii, sugi and hinoki sites descending order. The value of Ea was greater at matebasii sites than at other sites. Because the higher Ea organic was included in the C0,the percentage of C0 (or C0・k) to total C was great at matebasii sites.
The removal of fallen seeds of Aesculus turbinata was investigated by simple marking methods. In order to clarify the agent animals, an experiment was carried out to examine the sizes of the animals using a set of netted cages with different-sized apertures, together with wood mouse censuses. Current-year seedlings were found on the upper part of the slopes than the upper front line of the crowns of A. turbinata, where no seeds had fallen in the previous autumn. Of the total fallen seeds, 96% were removed from their original location and then disappeared by the end of autumn. Line marking revealed that the mean interval for transportation was 12 days, and that the mean and maximum transportation distances for non-missing seeds were 0.61 m and 2.11 m, respectively, although the lines of most of marked seeds had been cut and the seeds were missing. The maximum distance from the original location to the missing point was 6.45 m, and seeds were buried in cases of 31.5% of transportation. The agent animals were assumed to be small enough to allow them to pass through as aperture size of less than 40 mm but more than 16 mm. Feeding signs on seeds, and droppings found around seeds, seemed to be those of wood mice. The mouse censuses showed that Apodemus speciosus and A. argenteus were dominant. Thus, it is concluded that fallen seeds of A. turbinata were transported through the scatter-hoarding behavior of wood mice, mainly A. speciosus.
Zonation and species diversity in dune vegetation were investigated focusing on the impact of an exotic tree species, Robinia pseudo-acacia, in Atakabayashi National Forest, Central Japan. The vegetation was classified into 11 types. R. pseudo-acacia forests were divided into two types according to the dominance of herbaceous species and shrubs in the undergrowth. R. pseudo-acacia forests appeared on all transects, and covered 36.1% of the transects. Natural zonation was summarized as four zones : strand zone (0-29 m from the shoreline), grassland (30-50 m), small scrub (51-158 m) and forest (over 159 m). The R. pseudo-acacia community was established mainly in small scrub zone, although it is a tall woody species and had a wide ecological niche ranging from the strand zone (14.5 m) to the forest zone (301 m). Hence, this community caused disharmony in the coastal zonation. In contrast to the increase in species diversity of the native communities with distance from the shoreline, R. pseudo-acacia community decreased the species diversity. It was suggested that nitrophilous plants such as Briza maxima and heliophilous plants such as Cocculus orbiculatus had a co-dominance effect with R. pseudo-acacia to decrease the species diversity.
It is well known that the soil fauna changes with altitudinal gradient, corresponding to gradual changes in certain environmental factors such as climatic conditions and / or vegetation structure. Both climatic conditions and vegetation structure are significant parameters affecting the soil arthropod fauna. Although there have been many studies of fauna with respect to altitudinal gradient, few have attempted to separate the effects of climatioc and vegetation factors. Therefore, for this purpose, we surveyed the myrmecofauna in pine forests with different altitudes (210-810 m) and physiognomies in the Setouchi region, Hiroshima Prefecture. Ant species richness was explained mainly by the two environmental parameters, vegetation structure and altitude. On the other hand, ant species composition seemed to change with altitude.
To elucidate arboreal habitat use by Apodemus argenteus and A. speciosus, the foot print recording method was applied in the field. The footprints of Apodemus argenteus and A. speciosus obtained previously in the laboratory were clearly distinguishable by linear discriminant analysis. The footprint recording method showed that arboreal habitat use by A. argenteus became active from early summer to autumn, while that by A. speciosus was low throughout the year. By comparing the footprint recording with the live-trapping method, it was suggested that the frequency of arboreal activity of A. argenteus measured by footprint recording reflected the number of individuals captured in an arboreal habitat as well as the arboreal activity per individual.