Male mating success of the Japanese toad, Bufo japonicus japonicus, in relation to age and size, was investigated in 15 breeding groups at 3 ponds in the Botanical Garden of Kanazawa University. Correlations between the rates of male mating success and age (2-10 years old) were nearly constant (about 15%), except for males aged 2 (21.4%) and 7 (26.3%). There was a nonsignificant difference between body length of paired males and that of unpaired males. These results suggest that male-male competition for females reported in some Bufo spp. does not occur in B. japonicus japonicus.
The distribution of Oomycetes zoospores was investigated in the Kokenuma Sphagnum bog at the west foot of Mt. Kurikoma (the Kurikoma quasi-national park, Akita Prefecture). Oomycetes floras in the dystrophic acid water (pH 3.0-4.2) in Sphagnum communities were different from those in the dystrophic acid waters of ponds in the bog (Blanken) (pH 4.2-6.0) and a circumferential pond (pH 4.3-6.0) at the edge of the bog ; i.e., Saprolegnia turfosa was dominant in the former, whereas Achlya flagellata, A. racemosa, A. treleaseana, S. diclina were dominant in the latter two water areas. S. turfosa is believed to be adapted to the dystrophic acid water in Sphagnum communities. The density of Oomycetes zoospore, which is considered as an indicator of their potential growth, was+〜1/10 ml in the dystrophic acid water in Sphagnum communities, +〜2/10ml in the dystrophic acid waters of ponds (Blanken) and +〜5/10ml in the dystrophic acid water of the circumferential pond. These zoospore densities were much less than those previously reported in non-acid rivers and lakes.
A new sampling method was presented for studying a microphagotroph community in a lentic litter layer. In this method, plastic vessels containing litter disks of a plant species were placed on the pond bottom and were sampled periodically (a litter-vessel method). The densities of dominant taxa per litter surface area in the vessels were compared with those in adjacent natural litter scooped directly from underwater by using other plastic vessels (a scooping method). The litter-vessel method minimized any sampling error caused by leaf-litter heterogeneity and, during the sampling process, caused by turbulence of aufwuchs on the leaf litter surface. Therefore this method was more suitable than the scooping method to quantitatively study temporal changes in the community, and it seems applicable to study the specific characteristics of spatial distribution and dispersal ability within a habitat.
The pollen analysis of core samples from the Hatchodaira moor (alt. 810m) in the montane zone at the northern part of Kyoto City, revealed seven vegetational changes to have occured there during the last 25,000 years. 1. Conifer・Betula stage (ca. 25,000-15,000 y.B.P.) : subarctic coniferous forest. 2. Fagus・Lepidodalanus-Conifer・Betula stage (ca. 15,000-12,000 y.B.P.) : the ecotone between subarctic coniferous and cool temperate broad-leaved forests. 3. Conifer・Betula stage (ca. 12,000-10,000 y.B.P.) : subarctic coniferous forest. 4. Fagus・Lepidobalanus・Betula stage (ca. 10,000-9,000 y.B.P.) : the ecotone between subarctic coniferous and cool temperate broad-leaved forests. 5. Fagus・Lepidobalanus・Carpinus stage (ca. 9,000-4,500 y.B.P.) : cool temperate beech (F. crenata) forest. 6. Lepidobanlanus・Carpinus・Betula stage (ca. 4,500-1,500 y.B.P.) : cool temperate oak (Quercus mongolica var. grosseserrata) forest. 7. Pinus stage (ca. 1,500 y.B.P.-present) : pine (P. densiflora) forest reflecting the destruction of natural forests by human activities.
Dynamics of woody materials in a forest ecosystem is closely related to the regeneration process and nutrient cyclings in it. The decomposition process of wood litter under field conditions was discussed in this paper. Some physico-chemical progress of dead wood change successively and accelerate the decay rate with the progress of decomposition. This produces a characteristic decomposition process being different from one of other substrates. The relationships between the decay rate and some environmental factors were explained. A logistic equation for dry weight loss was derived from a linear relation between decay rate and bulk density and the characteristics of the equation were examined. An estimation of annual decomposition rate of wood litter in a forest was demonstrated, and a simulation of dynamics of woody materials was tried using some empirical formulations.