Published papers

The objectie of this study is to propose a method for evaluating ecological network. We propose to consider two classes of spatial scales for evaluation. In the macro-scale research, we classified land use types by satellite data, and extracted two areas of heterogeneous or homogeneous land use in the object region In these areas, we performed micro-scale researches through field survey and geographical information based topographical maps. Throughout these researches of different spatial scales, we evaluated present ecological network and discussed the availability of this method.

The influence of the vegetation and surrounding land use on the bird distribution in the wintering season was analyzed in order to develop a method of ecological network planning in urban area. The bird distributions were surveyed by line transects method with mapping observed points from December 2002 to February 2003 in the west part of Nishinomiya City, Hyogo Prefecture, Central Japan. The relationship between species and surrounding land uses of observed points was analyzed by Geographic Information Systems (GIS). The result showed it is necessary for the appearance of forest species that forest is the most dominant land use (over 50 %) in the surrounding area. Shrub and herb layers are also impotant for the appearence of some species.

都市近郊に残存する樹林地において,ダミーの卵を入れた人工巣を設置して卵が捕食される状況を調査し,樹林地における捕食圧の空間的なパターンを明らかにすることを試みた.調査は,東京都と埼玉県の境に位置する狭山丘陵の比較的大規模な樹林地とその周辺の孤立樹林地5ヵ所の計6ヵ所で行った.樹林地では,周囲から侵入してくる捕食者によって,林縁付近においては被捕食率が高くなることが予測されたが,林縁からの距離と被捕食率の間には統計的に有意な相関は認められなかった.また,面積の小さな樹林地では被捕食率が高いことが予測されたが,比較的大規模な樹林地でもっとも被捕食率が高く,その他の孤立樹林地と有意な差を示した.最も面積の小さい樹林地で捕食率は最低であった.生息密度の高さからハシブトガラスが主な巣の捕食者であると考えられるが,ハシブトガラスの密度は狭山丘陵の樹林地で最も高く,またハシブトガラスは樹林地周辺に限らず樹林地内部でも多数観察された.このことから,鳥類の巣における捕食は,主な捕食者の樹林地内外の分布状況によって大きな影響を受けていることが示唆される.

Agricultural reservoirs are now regarded as important habitats for some aquatic organisms, though their value as habitats of algae has clarified little. Diatom is often the most dominant component of freshwater algal communities and its contribution to species diversity can not be negligible. We studied periphytic diatom assemblages in 24 agricultural reservoirs in Awajishima Island, Japan to find major factors controlling diatom species composition. As it has often been reported and discussed, influence of eutrophication to species composition was detected. However, surrounding land cover was estimated to be the most important factor: some dystrophic or soil diatoms characterized diatom assemblages in reservoirs surrounded by woodland. Compositional difference caused by substrate was not detected. It is concluded that water quality management considering eutrophication and land use management where conservation priority is put on woodlands surrounding reservoirs are possible means to conserve diatom assemblages in agricultural reservoirs.

  Dragonfly and damselfly (Odonata) species were surveyed from May to October 2002 on 38 small irrigation ponds in the north part of Awaji Island. The investigation was conducted nine times on each pond. Totally 1568 individuals of 28 species were recorded for six months. We selected nine species recorded more than 40 individuals and analyzed the relationships of individual number of these species with environmental factors, including conductivity, NO2-, NO3-, NH4-, PO43-, COD, surrounding land uses within 50 meters from the edge of pond, the number of aquatic water plant species, and autocovariates explaining spatial autocorrelation, using Generalized Linear Models (GLM). The result showed that NO3-, COD, surrounding grassland, woodland and the number of water plant species were critical factors for the distribution of some Odonata species.

We digitized land uses in the latter Edo era in Awaji Island, central Japan, using old maps called Bugengunzu. Bugengunzu is one of the oldest map by a modern measurement method in Japan, which was drawn by Okazaki family working for the domain of Tokushima from 1802 to 1847. Two maps (approximately 1/18000) covered whole Awaji Island. A total area of woodland was 34,916 ha at that time. Compared with the area in 1980's, which was 34,729 ha, only 0.5 % of woodland disappeared in 150 years. Some woodlands changed into fields and plantations in 1960's in north and middle parts of the Island. On the other hand, some fields on the steep slop and at high altitude in south part were abandoned, then these areas changed into woodlands.

This survey monitored the quantity and distribution of egg clutches of Tohoku salamander (Hynobius lichenatus) in the tsunami inundated lowland area from the period 2012 to 2015, looking at the case of Moune district, Kesennuma city, Miyagi prefecture, Japan. After the 2011 Tohoku Earthquake, lowland area almost changed into wetlands by erosion and land subsidence, and seawater ran into a part of the lowland. Lots of egg clutches were found in the whole area in 2012. However several egg clutches deposited in brackish-water were dead. After 2013, the number of egg clutches declined, and the distribution moved inland. The number of egg clutches roughly increased in 2015, indicating the meta-population of Tohoku salamander's resilience against temporary disturbance caused by the tsunami. Models of relations analyzed between the numbers of egg clutches in each year showed larger population had higher resilience and the numbers of dead egg clutches had negative correlation to the total numbers of egg clutches in late years. Results indicated that the environmental changes after the tsunami had more severe impacts on the population's survival. However the population of Tohoku salamander had resilience under the natural state. This resilience may be weakened by man-made induced environmental changes and habitat loss from the tsunami recovery and reconstruction works. Hence, the need for conservation and monitoring was suggested.

The reed is a wetland vegetation which has ecological and economical values. Development of large-scale monitoring method of the reed is needed for effective habitat management. This research studies the reed of Xianghai wetland in China, and aims to construct four models to predict occurrence of the reed, height, stem diameter, and density, using the field measurement and satellite data. Based on predictive models and GIS, habitat conditions of reed in Xianghai Wetland at northeast China in 2010 was evaluated spatially. Habitat condition of reed and its important environmental variables are discussed.