The ecological characteristics of the main temperate plants composing the natural forests in Hokkaido were clarified by means of direct gradient analysis. The behaviour of individual species along the thermal, snow, and precipitational gradients was shown. In addition, from the most concentrated position of distribution in the graph, plants were divided into commodal species groups. From a comparison between the behaviour to environmental factors and the geographical distribution of each species, it was possible to identify some indicator species groups from their similarity in ecological requirements.
Annual population fluctuations of a habitat group of the Japanese toad, Bufo japonicus japonicus, breeding at a pond (H) in the Botanical Garden of Kanazawa University, were observed and estimated from 1971 to 1981. The production of young toads of this pond group was very large during 1971,1972 and 1975,low during 1973,and zero during 1974 and from 1976 to 1981. The population structure of the pond H group at the spring of 1973 consisted of 1971 (35%) and 1972 (62%) year classes and, at the spring of 1976,of 1972 (20%), 1973 (3%) and 1975 (42%) year classes. Population fluctuations of the pond H group were as follows ; about 3,000 individuals at the spring of 1973,1,800 in 1974,1,100 in 1975,1,700 in 1976,1,100 in 1977,700 in 1978,500 in 1979,250 in 1980,and 100 in 1981.
In studies of both pedogenesis and of the interaction between organisms and the soil, it is important to observe the soil micromorphology. Unfortunately, however, due to the difficulties involved in making larger-sized thin sections of soil, micromorphological methods have not been widely utilized in soil study in Japan. To remedy this situation the suthors developed a simple method of making medium-sized thin sections of soil using a rather inexpensive apparatus, and also modified and imprived the equipment used for impregnation with polyester resin. Using this method and apparatus, medium-sized thin sections of soil from a core sampler (5 cm in diameter×5 cm in height) and a Kubiena box (8×8×5 cm3) can easily be made. Some exsamples of thin sections produced using this method are shown in reference to the crumb structure of an Andosol and mor of a Podozol.
Among the groups of secondary producers, Chironomidae were the most productive, both in standing and running waters. A regression analysis was performed on the reported secondary productiondata for 39 herbivorous and detritivorous chironomid species in 37 standing waters. Annual mean biomass (Ba) was positively related to the maximum body weight of fourth-instar larvae (W4max), P/B ratio was positively related to annual mean bottom temperature (Tmean) and inversely related to W4max. Production (P) decreased with increasing mean water depth (zmean). The latter relationship was also true for herbivorous and detritivorous zoobenthos. Secondary production of hervivores and detritivores including zooplankton and zoobenthos was ca. 10% of primary production in lakes, Zoobenthos production became comparable to that of zooplankton in lakes where primary production exceeded ca. 10000 kJ m-2y-1. Emerging biomass (E) of chironomids amounted to 0.1-1.6% of the sum of primary production and allochthonous organic matter. E/P value lay within 0.2-0.5 and tended to decrease with increasing P. Collection of emerging insects is recommended as a valid means of estimating species production. Annual chironomid production may be estimated by multiplying species annual emerging biomass by a factor of 2.8. The role of secondary producers in the nutrient cycling in a ecosystem is discussed.
Existing literature on seasonal replacement in forest tree-leaves was reviewed from the viewpoints of phenology, leaf biomass, leaf fall, leaf survivorship-curves and defoliation by insects. Many of the investigations which had focused on phenological and leaf fall analyses were found to be inadequate to obtain accurate information about the life span of individual leaves. Life table analysis of leaves should be introduced into this type of investigation in order to construct an economic life table from a combination of life-tables with photosynthetic or respiratory activities. Leaf longevity is considered to be determined by the balancing of the cost of leaf construction, leaf maintenance, and the benefit or photosynthetic gain from the leaves. Therefore, leaf longevity is one adaptive strategy of plants to environmental conditions. The leaf survival strategy of pioneer species is characterized by long term leaf-emergence and short leaf-longevity, whereas tree species which are members of climax forests show simultaneous leaf-emergence and leaf-fall. Leaf longevity of forest-understory species is usually long. Leaf survival strategies are considered to have resulted from the evolutionary adaptive radiation of each species to various environments, accompanied by the evolution of morphological features such as shoot structure.