Nobukazu Nakagoshi

Urbanization and green space dynamics in Greater Dhaka, Bangladesh

Green space is particularly indispensable for proper functioning of the ecosystem in an urban environment. This study was an attempt to dynamically map and monitor green spaces in Greater Dhaka of Bangladesh. Both primary and secondary data were acquired to document the spatial–temporal dynamics of green spaces in the study area. Using a supervised classification algorithm, multi-temporal land use/cover data were extracted from a set of satellite images. A number of spatial metrics were employed to understand the landscape condition in a multi-temporal manner. In addition, 50 key informants along with focus group discussion and observation techniques were used to document existing management aspects of green spaces and their conservation policies. The analysis revealed that green spaces in Greater Dhaka are rapidly disappearing over the course of time even though they provide a number of natural, economic and social benefits. The disappearance of green spaces was primarily attributed to a rapid increase in the urban population, mainly driven by rural–urban migration. As a result, the landscape became highly fragmented and less connected. A substantial reduction of green patches is also leading to deterioration of the ecological condition of the landscape. The drastic reduction of green spaces in Greater Dhaka has been attributed to a lack of policy, low political motivation, and poor management. In order to ensure sustainability of green spaces and proper functioning of the city’s ecosystem, there is an urgent need for strategic green space planning.

Buried Viable Seeds in Temperate Forests

The buried seed population has great significance for plant demography, since it is regarded as the potential or initial coenopopulation. Buried seeds in the diverse communities in the temperate forest in Japan were analyzed. The density of buried seeds increases in the early stage of secondary succession, comes to a maximum in the secondary forest and decreases later in the climax forest. This fluctuation of densities is caused by a high seed production of the species in the felling site and secondary forest, and a low seed production in the climax forest. The seed banks of the main species consist of three types: no reserve of seeds in the growth season (Type A), reduced seed bank (Type B) and permanent seed bank (Type C). The main species are classified into nine groups based principally on their seed bank type and life form. Each of these nine functional groups has its own reproductive pattern. Each functional group is present at a particular stage during the process of vegetation change. It is suggested that these diverse patterns were evolved in forest vegetation with a mosaic structure having cyclic vegetation changes: forest vegetation is a complex association consisting of species which have diverse life history patterns.

Riparian Landscape changes over a period of 46 years, on the Azusa River in Central Japan

Abstract Change in a riparian landscape was studied for the Azusa River of Central Japan, where Chosenia arbutifolia A. Skav. and Robinia pseudo-acacia L. grow. The objectives were: 1) to describe the dynamics of plant communities over a 46-year period (1948–1994) by using air photographs; and 2) to evaluate the effects of C. arbutifolia and R. pseudo-acacia on riparian landscape diversity. Both species could colonize throughout the study period because their ecological niches differ, i.e. C. arbutifolia grows mainly on the islands and terraces along streams newly formed by channel-changing, whereas R. pseudo-acacia establishes itself primarily on the terraces supporting the revetment. After R. pseudo-acacia scrubs established near the revetment, they invaded the land which different vegetation types, such as native Salicaceous and Pinus densiflora forests, already occupied. In particular, the stability of beaches promoted the succession of beaches in various forest types during the period 1975–1989 and contributed to the increase in riparian landscape diversity. The rapid increase and wide ecological niche of R. pseudo-acacia patches, however, may bring about a decline in the landscape diversity and biodiversity in the near future.

Landscape structure and the disturbance regime at three rural regions in Hiroshima Prefecture, Japan

Using the vegetation maps of island, inland and mountainous rural regions in Hiroshima Prefecture in western Japan, landscape structures in terms of the size and number of patches are compared, and the characteristics of the disturbance regimes creating each landscape are discussed. Landscape structure in the island rural region is the most heterogeneous, because factors which alter the landscape structure are the most complex. This heterogeneity is established and kept by the agricultural land uses and natural disturbances such as forest fire and pine-disease. At the mountainous rural region, the landscape mosaic is characterized by the relatively large patches composed of conifer plantations and secondary deciduous oak forests. This is the result of the forestry. The inland region landscape is the most homogeneous, because factors which alter landscape structure are now absent. The complex of the physical, biological and anthropogenic forces makes the landscape unique to each region.

Gnawing damage by rodents to the seedlings ofFagus crenata andQuercus mongolica var.grosseserrata in a temperateSasa grassland-deciduous forest series in southwestern Japan

The effects of dwarf bamboo,Sasa, cover on the initial morrality of hardwood seedlings were investigated by transplanting 1-year-old beech (Fagus crenata) and current-year oak (Quercus mongolica var.grosseserrata) seedling to three different stands; old-growth beech and secondary oak forests withSasa undergrowth, and aSasa grassland in a grassland-forest series near the top of Mt Jippo, southwestern Japan. The most frequent cause of seedling morrality was gnawing of the stems by rodents. In the beech forest, the gnawing was more likely to occur underSasa cover, suggesting that it provides a good habitat for rodents on the beech forest floor. TheSasa under growth may thus play an imporrant role in regeneration of beech forest. In the oak floor, mortality of both species was low and only a little gnawing occurred during a year. However, no natural oak seedling were found in the forest even after a mast year. This may be because most of the acorns disappeated before establishment. The early-stage demography of hardwood seedling as oak may thus play an imporrant role in regeneration of oak forest. In theSasa grassland where the seed supply is small, almost all of the seedlings died fromo gnawing regardless of the presence ofSasa cover. These factors prevent the recruitment of a sizable seedling bank. Rodents may thus play an imporrant role in maintenance of theSasa grassland.

Regional landscape change as a consequence of plantation forestry expansion: an example in the Nelson region, New Zealand

Abstract Forestry is expanding in New Zealand and increasingly contributing to the economy. The expansion has also altered the landscape and will continue to do so. In addition, the implementation of the district plan under the Resource Management Act (RMA) 1991 also directly influences the expansion of forestry and the future land-use. Using Nelson region as a case study, the difference in land-use distribution patterns between the mid-1970s and 1990s, and the land-use changes over the 20 years were interpreted. The factors influencing the changes were also examined. Because landscape is mainly changed by human activity, land-use change was considered from an economic perspective. Thus, the productivity, the land-use capability (LUC), and the distance from the city center were considered as well as the physical attributes of the land. The objective was to establish a data set from which future land-use could be predicted. Forest expansion over the period was mainly from shrub or pasture, and horticulture expansion from pasture. Both changes probably were related to the higher returns from forestry and horticulture than from sheep grazing or dairy farming. Based on discriminant analysis, the distance from the city was always the main factor determining the land-use change, which reflects costs and ease of transportation. Conversion to plantation over the 20-year period was closer to the city than conversion to pasture. Since more intensive and higher demand land-use tends to be closer to the city, this means that forestry had priority over pasture during this period. If this tendency continues, it will probably change the regions land-use distribution pattern in the future. The large conversion of shrub to other land-uses over the period is of concern because of risk of reduction in biodiversity and loss of habitat for threatened species. Based on discriminant analysis, the data set in this study was useful for predicting the future land-use.

Patterns and levels of gene flow in Rhododendron metternichii var. hondoense revealed by microsatellite analysis

Parentage analysis was conducted to elucidate the patterns and levels of gene flow in Rhododendron metternichii Sieb. et Zucc. var. hondoense Nakai in a 150 × 70 m quadrat in Hiroshima Prefecture, western Japan. The population of R. metternichii occurred as three subpopulations at the study site. Seventy seedlings were randomly collected from each of three 10 × 10 m plots (S1, S2, and S3) on the forest floor of each subpopulation (A1, A2, and A3). Almost all parents (93.8%) of the 70 seedlings were unambiguously identified by using 12 pairs of microsatellite markers. Within the quadrat, adult trees less than 5 m from the centre of the seedling bank (plots S1, S2, and S3) produced large numbers of seedlings. The effects of tree height and distance from the seedling bank on the relative fertilities of adult trees were highly variable among subpopulations because of the differences in population structure near the seedling bank: neither distance nor tree height had any significant effect in subpopulation A1; distance from the seedling bank had a significant effect in subpopulation A2; and tree height had a significant effect in subpopulation A3. Although gene flow within each subpopulation was highly restricted to less than 25 m and gene flow among the three subpopulations was extremely small (0–2%), long‐distance gene flow from outside the quadrat reached 50%. This long‐distance gene flow may be caused by a combination of topographical and vegetational heterogeneity, differences in flowering phenology, and genetic substructuring within subpopulations.

Human impacts on pine-dominated vegetation in rural landscapes in Korea and western Japan

To understand the human influence on the successional process of vegetation, structures of the pine forest as a dominant vegetation were compared between in Yanghwa-ri of rural Korea and Miwa-cho of rural Japan. The secondary pine forests are well developed around the villages in both regions. In rural Korea, pine forests are still used intensively for several traditional purposes. The pine forests in Yanghwa-ri of Korea, therefore, are stayed in the early stage of the succession. The floristic composition in pine forests of Yanghwa-ri was similar to that in the secondary grasslands. The fertilizer trees such as Robinia and Alnus contributed to develop the stratification of the forest. On the other hand, in Japan, almost all pine forests in rural regions had been abandoned due to the changing of traditional use because of the economic growth and the development of alternative energy sources since 1960s. In the case of pine forests of Miwa-cho, those in the early successional stage were few in number and small in patch size. Several woody plants covered under the pine canopy. The shade-tolerant shrub invaded into pine forest floor, because the undergrowth as a traditional energy source had no longer used. Pine forests were partly succeeded by deciduous oaks in Miwa-cho corresponding to the social changes. On the contrary in Yanghwa-ri, the vegetation replacement will not present because traditional management such as collecting fuels and making graveyards will be remained as a Korean ideology in the rural landscape.

Microbial biomass and abundance after forest fire in pine forests in Japan

Microbial characteristics of soil are being evaluated increasingly as sensitive indicators of soil health because of the clear relationship between microbial diversity, soil and plant quality and ecosystem sustainability. This study aimed to determine microbial carbon biomass and microbial abundance after fire to estimate the degree of damage, including the rate of recovery of micro-organisms, in each area. The study also aimed to establish relationships between microbial biomass and microbial abundance and the physico-chemical properties of the soil. The study was conducted in three different study areas in Hiroshima prefecture, one unburned area and two burnt areas (one immediately after and one 2 years after fire). anova showed a significant difference in microbial carbon biomass and microbial abundance among the study areas. Microbial carbon biomass and microbial abundance were highest in the unburned area, followed by the area burnt 2 years ago and lastly by the area studied immediately after fire. Carbon biomass was highly correlated with microbial abundance (r2 = 0.950). Carbon biomass and microbial abundance were shown to be significantly correlated to the soil’s physico-chemical properties, such as pH, moisture content, water-holding capacity and carbon : nitrogen (C : N) ratio. However, the C : N ratio was closely correlated to both carbon biomass and microbial abundance with r2 = 0.705 (P < 0.01) and r2 = 0.560 (P < 0.01), respectively.

Simultaneous spectrophotometric determination of phosphate and silicate ions in river water by using ion-exclusion chromatographic separation and post-column derivatization

The simultaneous spectrophotometric determination of phosphate and silicate ions in river water was examined by using ion-exclusion chromatography and post-column derivatization. Phosphate and silicate ions were separated by the ion-exclusion column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the H(+)-form (TSKgel Super IC-A/C) by using ultra pure water as an eluent. After the post-column derivatization with molybdate and ascorbic acid, so-called molybdenum-blue, both ions were determined simultaneously by spectrophotometry. The effects of sulfuric acid, sodium molybdate and ascorbic acid concentrations and reaction coil length, which have relation to form the reduced complexes of molybdate and ions, on the detector response for phosphate and silicate ions were investigated. Under the optimized conditions (color-forming reactant, 50 mM sulfuric acid-10 mM sodium molybdate; reducing agent, 50 mM ascorbic acid; reaction coil length, 6 m), the calibration curves of phosphate and silicate ions were linear in the range of 50-2000 microg L(-1) as P and 250-10,000 microg L(-1) as Si. This method was successfully applied to water quality monitoring of Kurose-river watershed and it suggested that the effluent from a biological sewage treatment plant was significant source of phosphate ion in Kurose-river water.