Dormancy characteristics and emergence force in relation to seed weight has been studied in two varieties (typical var. and var. sykesii) of Indigofera glandulosa, having similar growth patterns. Inverse relationship holds good between seed weight and intensity of impermeability. Different degrees of correlation are depicted depending upon method of breaking impermeability. Breakage by natural parameter (simulated field conditions) for assessment of intensity of dormancy is significant per se in view of ecological orientation and homogeneous values of correlation obtained herein. Time of emergence is directly proportional to depth of soil from which seedlings emerge. The emergence force is closely related with the seed weight. The variation in emergence force among the seeds of both varieties is due to their respective seed weights. Higher emergence force by virtue of heavier seeds is an asset to typical var. distributed mostly in arable fields where seeds are buried due to cultivation practices as compared to var. sykesii distributed mostly in grass fields. Seed size has therefore important ecological significance in preservation of habitat due to, (1) relative emergence force of seeds in relation to habitat. (2) variable intensity of dormancy of seeds.

View full abstract

Jahrliche Sommertrockenheit erniedrigt in den vulkanischen Gegenden von Mittelkyusyu gewohnlich den bestehenden Ertrag vom Miscanthion sinensis, das fur Rinderweidung im Gebrauch ist. Die hiesigen Pflanzen wurden die ganze Vegetationsperiode hindurch immer an Masse zunehmen, wenn sich die Sommertrockenheit nicht ereignete. Unser Versuchsort liegt im Nordost und ziemlich entfernt vom Zentrum der vulkanischen Gegend, Die Sammerung des Viehs dauert hier ohne Pause bis zum Ende der Vegetationsperiode fort, obwohl die Sammerungspause sozusagen eine allgemeine Gewohnheit in der Mittelkyusyus vulkanischen Gegend ist. Die Pflanzengesellschaft ist aber mit einer und derselben Assoziation, Arundinello-Miscanthelum HORIKAWA et SASAKI (=Arundinaria pygmaeae-Miscanthetum Itoh), identifiziert, obwohl die hiesigen Weidebestande mehr als diejenigen in der vulkanischen Gegend dem Originaltypus ahneln. Zwei Paar Untersuchungsbezirke (A, A', B, B', ) wurden monatlich inspiziert und auf ihre Vegetation und Bodenverhaltnisse untersucht. Das Arundinello-Miscanthetum konstituiert sich gewohnlich aus vier Schichten. In der Oono Weidewiese entwickeln sich diese vier Schichten alle im September am hochsten, sowohl auch jede Pflanzenart. Nur Pteridium aquilinum L. stirbt im September plotzlich ab, Lespedeza cyrtobotria MIQ, die kommen wohl in der ersten Strauchschicht dominant spater als andere Krauter vor. aber wachsen so schnell, daB sie im Juni und August die hochste Schicht erreichen konnen. Arundinaria pygmaea MITF, ob diese schon am fruhesten zu wachsen anfangt, wachst aber sehr langsam und wird fast immer von den Krautem bedeckt. Miscanthus sinensis ANDERSS fangt im Anfang April zu sprieBen, uberschreitet Lespedeza und erreicht im September die hochste Schicht. AuBer dem Pteridium haben die dominanten Arten in jeder Schicht alle zwei Wachstumperioden : Fruhling/Fruhsommer und Spatsommer/Herbst. Auch bestehenden Artenzahlen haben im Juni und Oktober ihren Maximum, also kann man sie deutlich in zwei Saisontypen unter scheiden. Der bestehende Ertrag hat auch vor und nach der minimalen Sommertrockenheit im Juli einen Maximum und erreicht im November wieder seinen Maximum. Die pH-Schwankungen des A-Horizontes veranschaulichen eine Herbsterhebung, welche die Sommerzersetzung des Humus und die Anreicherung von Ca am A-Horizont beschleunigt. Die Sommererschlaffung oder die Sommerfaulnis der Weidewiese wurde zwar bisher einfach als eine Sommererniedrigung von bestehendem Ertrag erfaBt. Sie ware aber auch als ein Lebenserschlaffungsphanomen, das durch das Generalklima verursacht und mit osmotischer Werten, Humuszersetzungen und Ca-Mengen im Boden verknupft ist, zu betrachten.

View full abstract

The waters of the Boso Peninsula and Tokyo Bay are one of the most important fishing grounds for the Japanese sardine, Sardinops melanosticta. The present study aims to determine the developmental periods and yearly life cycle of the Japanese sardine population, especially the Pacific fraction, by referring to the previous works. The author examined the mode of aggregation of the immature and adult sardine, and of the maturation of I-aged fish taken from the area during 1967 to 1971. The results are summarized as follows. 1) The immature sardines appear in places shallower thar. 20 meters depth during summer to autumn. The adults appear off shore at 50-100 meters depth during winter to spring (Fig. 4-9). During northward migration the immature sardines increase in their density during life. An examination of the indices of stock size shows fluctuation in the year class. The classes in 1968 and 1971 dominated over the others during the five years under discussion (Table 6). 2) The Pacific fraction of fish. the Japanese sardine. shows a north-south migration in the waters of the Tokai-Tohoku area, Central Japan. The young fish first appears off the entrance of Tokyo Bay and Boso Peninsula in March through June. The immature mostly appear along shore of the Boso Peninsula during early July through November, and are caught chiefly by two-boat purse seiners. After a while, they gradually migrate northward, to as far as off Joban or Sendai Bay in September through November (Fig. 4. 14). During southward migration, the density of the fish decreases and the distribution becomes restricted to off Boso Peninsula in late November through January (Fig. 5). The adult sardines appear off Boso Peninsula and the entrance of Tokyo Bay during late January through May or June (Fig. 6-9). 3) The immature stock comprises two spawning season groups of, large-sized immatures which have spawned in October through December in the latest year and the small-sized ones in January through April (Fig. 10). The former are found off the Boso Peninsula and in the Kashima-nada, while the latter apparently shows a north-south migration from the Boso Peninsula to Joban or Sendai Bay as mentioned already (Fig. 14). 4) The maturation of I-aged fish was distinctly observed in the spawning season during the last four years, and the eggs appeared in the area, corresponding to the shift of the distribution area of the fish (Figs. 3,8,10,12,13). This fact indicates that I-aged fish of the Japanese sardine is the main producer of the eggs found in the waters around and off the Boso Peninsula.

View full abstract

The mode of life and the morphological characters of the Ayu-fish in the advanced phases after the group formation were studied with special reference to the comparison between their groups. The stream population of the Ayu used to eat zooplankters in the lake, but suddenly changed the food-habit exclusively to adherent algae in the inlet streams. They can be classified into two groups based upon the time of stream ascending and body size. Namely, a group which ascends streams before late-spring and are of relatively larger body size, and another group which ascends streams after late-spring, and are of comparatively smaller size. The lake population of small body size tends to eat zooplankters throughout their life. The lake population of large body size prefers to live at rocky shelves and to eat mainly adherent algae. The fish of the lake population of large and small body sizes were of the typical standing water form. while those of the early ascending group of the typical running water form. The body form of the fish of the late ascending group was intermediate between those two forms in size. There were also significant differences in the numbers of rays of the dorsal and anal fins, among the populations. Several discussions are presented on the relation between the variations in each population and the environmental conditions at the early stage of development of the fish.

View full abstract