Electric pulse transmitters were attached to five Sooty Shearwaters (Puffinus griseus), two Short-tailed Shearwaters (P. tenuirostris), one Buller's Shearwater (P. bulleri), one Laysan Albatross (Diomedea immutabilis), and one Black-footed Albatross (D. nigripes) on board a fisheries research vessel in the northern North Pacific in the summers of 1991 and 1992. The pulses from the transmitters were monitored using the Yagi antennas, and the daily activities of these birds were tracked. Tracking duration ranged from 0.5 to 75.3h and the movements during these periods were estimated from the vessel's track chart to be 2 to 367km. Flight speed in a horizontal direction for the Sooty Shearwater, Short-tailed Shearwater, and Laysan Albatross was estimated to be 0.36 to 0.51 (av. 0.43), 0.64,and 0.55 km・min-1, respectively. Two different flight patterns were recognized. Either the bird followed a straight route and moved fast with a long-range flight or it moved slowly with a short-range flight, changing the bearing of its route continuously. It seemed that the first flight pattern was between foraging sites and that the second was flight within the foraging site. The birds often flew in the daytime, but stayed still on the sea surface during the night. The Sooty Shearwater which was tracked for the greatest duration, 75.3h, showed flying and diving actions around sunrise, noon, and sunset at the foraging site.
The responses of fish populations to experimental habitat improvement in a concrete-lined, altered reach were examined in a fourth-order tributary of the Teshio River, northern Hokkaido, Japan. Concrete blocks in the center of the channel were removed, and log-drop structures were installed across the stream to enhance the fish habitat which had been degraded by the channel alteration. Subsequent changes in habitat variables and characteristics of the fish assemblage were studied in the altered treatment sections, which were compared with adjacent natural, control sections in both the pre- (1993) and post-improvement periods (1994). Before improvement, Oncorhynchus masou, Tribolodon ezoe and Cottus nozawae in the natural sections were considerably more abundant than those in the altered sections having shallower depth, greater current velocity and smaller substrate coarseness than the former. In contrast, the abundance of Noemacheilus toni in the altered sections did not differ from that in the natural ones. The habitat improvement caused marked changes in habitat variables, including increased depth, decreased current velocity and increased substrate coarseness, with development of pool-riffle sequences. After the improvement, significant increases were seen in the abundance of O. masou and T. ezoe, but not in that of C. nozawae. The improvement caused an increase in the body size of N. toni, but not in its abundance. Consequently, this fish population response resulted in a great increase of species diversity of the assemblage during a relatively short period (1 year) after the habitat improvement.
A study was conducted to examine the characteristics of the distribution patterns of tree species in relation to site factors on the plain in Oyafuru, Ishikari City, Hokkaido. Topographical types at Oyafuru include floodplains, sand bars and sand dunes, and soil types include peat soils, lowland soils, brown forest soils and sand dune regosols. Alnus japonica, Fraxinus mandshurica var. japonica and Ulmus davidiana var. japonica dominated on lowland soils on floodplains and between sand bars. A. japonica dominated on peat soils at the wettest sites and was often accompanied by F. mandshurica var. japonica. U. davidiana var. japonica occurred at drier sites than those occupied by A. japonica and F. mandshurica var. japonica. Occurrence of U. davidiana var. japonica showed some relationship to the presence of flood deposits. It was assumed that the occurrence of tree species in lowlands was related to the presence-absence of flooding as well as moisture conditions.
Community-level spatial structure and its developmental pattern are reviewed for hardwood forests on the basis of individual-tree-based studies. Many studies suggest that a tree species shows a specific form of behavior in which it occupies space by a crown according to its successional status ; e.g., a greater height growth rate may be advantageous for competing with adjacent trees at earlier stages of succession, whereas this may discourage stem-diameter growth and horizontal expansion of crowns which would be advantageous for persistence and survival at later stages of succession. The behavior of securing space with a crown seems to be an important factor affecting the growth and survival of a species in a community. Furthermore, there can be intraspecific differences in crown development pattern, resulting from interaction among neighboring trees of different species differing in behavior and size. This will cause structural variation among local sites within a community. The spatial structure of canopies and its developmental pattern in a hardwood forest cannot be explained without considering the behavior of the component species and individual trees. When predicting succession in a forest, it is important to simulate the forest dynamics by taking into account the behavior of species and individuals.
Natural abundance of 15N (δ15N) in nitrogen compounds in forest ecosystems is a useful parameter for analyzing the nitrogen cycle in forests. The δ15N value for nitrogen compounds is determined mainly by input of N (N-fixation and precipitation) originating from atmospheric N2 less enrichment with 15N and output of N through denitrification and nitrate leaching, which leads to preferential 15N enrichment in ecosystems. Temporal and spatial variation in δ15N can provide useful information on changes in nitrogen cycling in terrestrial ecosystems. Some case studies using this technique are reviewed.