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Widiyatno,Gadjah Mada University | Widiyatno,Tokyo Metroplitan University | Indrioko S.,Gadjah Mada University | Na'iem M.,Gadjah Mada University | And 5 more authors.
Tree Genetics and Genomes | Year: 2016

Selective logging systems have been used to prevent the rapid decline of forest resources in Southeast Asia, but little is known about the impacts of selective logging on the genetic diversity of Southeast Asian rainforests. We evaluated the effects of silvicultural systems with differing cutting rotations and enrichment planting regimes on the genetic diversity of Shorea parvifolia, an abundant and ecologically important tree in Southeast Asian rainforests. Our result showed that in most respects the genetic diversity is not significantly different between primary forest and the other silvicultural systems; however, the proportion of private alleles is significantly different between them. Intensive second-rotation (L3) harvesting of individuals >40 cm in diameter at breast height (dbh) resulted in a sizable reduction in the number of reproductive trees and a dramatic decrease in the numbers of rare and private alleles, suggesting a negative impact on the genetic diversity of the remaining tree population. Enrichment planting with S. parvifolia in the logged forest improved some genetic parameters, significantly increasing the number of rare alleles in L3 in particular. We conclude that the genetic diversity of logged tropical forests gradually decreases depending on logging rotation times, especially with respect to sensitive genetic parameters such as the numbers of rare and private alleles, and that enrichment planting with native dipterocarps can maintain or even increase the genetic diversity of logged tropical forests in Southeast Asia. © 2016, Springer-Verlag Berlin Heidelberg. Source

Kitamura S.,The Museum of Nature and Human Activities
Acta Oecologica | Year: 2011

I summarize the current knowledge of frugivory and seed dispersal by hornbills in tropical forests. Many studies report on frugivory by hornbills but few specifically identify hornbills as effective dispersers. Hornbills are able to disperse a diverse array of fruits in tropical forests (748 plant species from 252 genera and 79 families) and move many of the seeds far from the parent trees. They digest only the fleshy parts of fruits that they swallow and then regurgitate/defecate the seeds intact. The relatively long seed retention times (>1 h) and propensity for depositing seeds away from the parent trees while foraging suggest high-quality dispersal. Some seeds might be aggregated at nest and roost sites, but hornbills are capable of dispersing seeds over several kilometers, resulting in a relatively even spread of seeds throughout the forest. Based on the results summarized here, hornbills provide excellent seed dispersal services to tropical plants in their respective habitats. © 2011 Elsevier Masson SAS. Source

Osawa T.,Japan National Institute for Agro - Environmental Sciences | Kohyama K.,Japan National Institute for Agro - Environmental Sciences | Mitsuhashi H.,The Museum of Nature and Human Activities
Science of the Total Environment | Year: 2016

An understanding of land-use change and its drivers in agroecosystems is important when developing adaptations to future environmental and socioeconomic pressures. Agricultural abandonment occurs worldwide with multiple potentially positive and negative consequences; however, the main factors causing agricultural abandonment in a country i.e., at the macro scale, have not been identified. We hypothesized that socio-environmental factors driving agricultural abandonment could be summarized comprehensively into two, namely "natural" and "social", and the relative importance of these differs among regions. To test this postulate, we analyzed the factors currently leading to agricultural abandonment considering ten natural environment variables (e.g., temperature) and five social variables (e.g., number of farmers) using the random forest machine learning method after dividing Japan into eight regions. Our results showed that agricultural abandonment was driven by various socio-environmental factors, and the main factors leading to agricultural abandonment differed among regions, especially in Hokkaido in northern Japan. Hokkaido has a relatively large area of concentrated farmland, and abandonment might have resulted from the effectiveness of cultivation under specific climate factors, whereas the other regions have relatively small areas of farmland with many elderly part-time farmers. In such regions, abandonment might have been caused by the decreasing numbers of potential farmers. Thus, two different drivers of agricultural abandonment were found: inefficient cultivation and decreasing numbers of farmers. Therefore, agricultural abandonment cannot be prevented by adopting a single method or policy. Agricultural abandonment is a significant problem not only for food production but also for several ecosystem services. Governments and decision-makers should develop effective strategies to prevent further abandonment to ensure sustainable future management of agro-ecosystems. © 2015 Elsevier B.V. Source

Osawa T.,The Museum of Nature and Human Activities | Mitsuhashi H.,Kyoto University | Niwa H.,Kobe University | Ushimaru A.,Japan National Institute for Agro - Environmental Sciences
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2011

While flooding creates diverse habitats for plants and animals in riparian ecosystems, it presents a nuisance to human settlement. Thus, such areas that are frequently disturbed by flooding are more likely to experience strong artificial control measures. This hypothesis was tested and a method was developed to identify these areas using river maps. The effects of two terrain components that could potentially influence flooding frequency (the number of confluences and the degree of meandering per unit area) on both the distribution of threatened species and the degree of artificial modification were examined at two different scales (grid sizes) using two riparian data sources. The numbers of threatened plant species and artificial constructions increased with the number of confluences and the degree of meandering per unit area. The number of threatened plant species was not correlated with the number of artificial constructions. In addition, the results suggest that confluences and meanderings provide different habitat conditions for threatened plant species. Confluences may provide more frequently disturbed habitats, whereas meanderings may provide relatively stable habitats. Based on these results, through flooding, both confluences and meanderings are important for creating and maintaining the diverse habitats used by threatened species, but these habitats are also currently threatened by artificial controls. We suggest that a per-unit-area confluence density and river length map is a helpful tool for locating local biodiversity hot spots. The identification of major reservoirs of biodiversity that are currently threatened can improve conservation and management planning. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd. 21 4 June 2011 10.1002/aqc.1194 Research Article Research Articles Copyright © 2011 John Wiley & Sons, Ltd.. Source

Osawa T.,Japan National Institute for Agro - Environmental Sciences | Kohyama K.,Japan National Institute for Agro - Environmental Sciences | Mitsuhashi H.,The Museum of Nature and Human Activities
Land Use Policy | Year: 2016

Human-driven land-use changes often cause a decline in biodiversity. Although traditional agricultural practices maintained biodiversity at high levels, recent land-use changes may have negative consequences on species composition. In this study, we examined the hypothesis that land consolidation, which is a major recent land-use change in agricultural areas, decreases plant species diversity over the long term (the so-called negative legacy). To test this hypothesis, we examined the relationships between consolidated areas and the occurrence of threatened plant species across Japan and at the prefecture scale. Twenty-three threatened plant species were selected, all of which were formerly common. Our results show that areas containing records of threatened plant species rarely experienced consolidation at whole-country and prefectural scales. Breakdown analysis showed that unconsolidated agricultural areas contained significantly more threatened species than consolidated agricultural areas. These results suggest that threatened plant species require unconsolidated agricultural areas (i.e., these species could not grow in consolidated areas). Thus, we propose that consolidation history could be used as an indicator of the potential for biodiversity recovery. We also suggest that consolidated agricultural areas should be used for food production rather than for the restoration of biodiversity, for reasons of cost efficiency. © 2016 Elsevier Ltd. Source

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