Abstract
This study examined the effects on bird assemblages of replacing deciduous broadleaf forest with larch Larix leptolepis plantations in the Chikuma Highland in Nagano Prefecture, Japan. Birds were sampled by the plot census method within deciduous forests and plantations in the winter and also during the breeding season. Sample sites were selected to cover a range of deciduous forest areas surrounding the study site. Redundancy analysis revealed that bird communities within deciduous forests were not associated with the loss of deciduous forests strongly in both seasons. Surprisingly, the occurrence of evergreen-conifer associated species decreased with the loss of deciduous forests, while canopy gleaners increased with the loss of deciduous forests. Hierarchical partitioning showed that the decrease of evergreen-conifer associates was actually caused by a reduction of hemlock and fir within deciduous forests rather than by loss of deciduous forest itself. Species that occurred less frequently within plantations tended to decrease as deciduous forests were lost. The results of this study suggest that the effects of deciduous forest loss on birds, resulting from the planting of larches, are weak unless loss of deciduous forest proceeds strongly. Species tending to decrease as deciduous forests are reduced may depend on resources eliminated during habitat replacement and habitat modification. Therefore, restoration of such resources in modified remnant habitats and the introduction of such resources into the matrix replacing original habitats may be effective in tempering and preventing species loss.
