How plant seeds secure root penetration into soil to obtain good seedling establishment is one of the basic ecological problems. In this study, seminal root growth was investigated to clarify the cause of varietal difference of seedling establishment in direct seeding of rice in flooded paddy fields, with special reference to root tip rotation. In a field experiment, seedling establishment percentage had a weak correlation with seminal root elongation rate but was not correlated with apparent seedling weight in water, which has been reported to be the cause of floating seedlings resulting in poor seedling establishment. Root tip rotation was analyzed for indoor‐grown seedlings using spectrum analysis: the maximum entropy method (MEM) was used. Maximum entropy method power spectrum analysis clarified that maximum MEM power density (practically corresponds to spiral angle) detected in the frequency range above 0.1 cycles mm‐1 was highly and positively correlated to seedling establishment percentage in the field experiment. Maximum MEM power density in high correlation with seedling establishment was mostly found around frequencies of 0.2 cycles mm–1, which corresponded to 2.0–3.4 cycles of root tip rotation per day. From these results, root tip rotation (circumnutation) with a larger spiral angle was suggested to play an important role in the establishment of rice seedlings on flooded and very soft soil. A possible explanation for why a larger spiral angle was advantageous for seedling establishment is that if buoyancy and seedling weight are constant, a larger pushing force of the seminal root is available without causing floating of a seedling, due to the upward force being a reaction of the seminal root pushing force.

We report the four-year (2006)(2007)(2008)(2009)) measurements of the net ecosystem CO 2 exchange flux (NEE) over a deciduous needle-leaf plantation forest in the foothills of Japan's highest mountain, Mt. Fuji. We focus on the characteristics of temporal variations in NEE and their relationships to environmental factors and phenology in a forest stand. We evaluate year-to-year variations in the seasonal patterns of flux components and investigate factors controlling the NEE. During the growing season, light availability is likely to affect the photosynthetic uptake of CO 2 at the site. We found significant differences in the length of the growing season for the four years; these are due mainly to variations in the timing of the progress of the autumnal coloring of leaves. The timing for the start of the autumnal coloring of leaves is highly dependent on when the daily lowest air temperature drops below 10℃. Secondly, we investigate the characteristics of short-term and long-term variations in the structure of CO 2 storage in the forest stand using a newly developed profiling system. We demonstrate the characteristics of temporal variations in the vertical distribution of CO 2 .

ABSTRACT:The objective of this study is to collect basic information on vegetation in road crack, especially in curbside crack of road, for evaluating plant biodiversity in urban landscape. A curbside crack in this study was defined as a linear space (under 20 mm in width) between the asphalt pavement and curbstone. The species composition of plants invading curbside cracks was surveyed in 38 plots along the serial National Route, over a total length of 36.5 km, in Fukuoka City in southern Japan. In total, 113 species including native plants (83 species, 73.5%), perennial herbs (57 species, 50.4%) and woody plants (13 species, 11.5%) were recorded in curbside cracks. Buried seeds were also obtained from soil in curbside cracks, which means the cracks would possess a potential as seed bank. Incidentally, no significant differences were found in the vegetation characteristics of curbside cracks among land-use types (Kolmogorov-Smirnov Test, P > 0.05). From these results, curbside cracks would be likely to play an important role in offering habitat for plants in urban area.

1995 9 12 −1 Castanopsis sieboldii (Makino) Hatusima ex Yamazaki et Mashiba Machilus thunbergii Sieb. et Zucc. Eurya japonica Thunb. Buxus microphylla Sieb. et Zucc. var. japonica (Muell. Arg. ex Miq.) Rehd. et Wils.

Typhoon 9512 hit Mikura-jima Island, Izu Islands, Japan in 1995, producing many landslide slopes. Torino-o No.3 landslide slope was fascined with fallen trees and planted with seedlings of native species (Alnus sieboldiana tree and Miscanthus condensatus grass) as part of vegetation recovery efforts, and was subsequently seeded by helicopter in 2002 with exotic pasture grasses. To elucidate the influence of fertilization on the growth of transplanted seedlings of native species, exotic pasture grasses and newly invading trees and herbs, we designated seven plots in 2004, and surveyed vegetation every summer until 2013: four fertilized plots (fowl manure applied at 0.2 g/m 2 ) and three non-fertilized plots. The native species seedlings grew steadily irrespective of fertilization, but with self-thinning in A. sieboldiana. Exotic pasture grasses decreased gradually and almost disappeared in 2013. Fertilizing temporarily enhanced the growth of some species, but seemed to induce species competition, judging from the delay of invading of native trees and the increase of climbing plants in herbaceous layer in fertilized plots.