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We investigated seasonal fluctuation patterns in species and individuals of adult butterflies and flowering plants providing nectar in a semi-natural grassland in central Japan. We considered their interrelationships and implications for conservation. The seminatural grassland included different vegetation structures and management regimes, including: (1) firebreaks where the grass was mowed and removed, (2) plantation areas that were mowed, (3) unpaved roads with mowed banks, (4) abandoned grassland, (5) scattered scrub forest, and (6) the surrounding forest. The sites with management (e.g., firebreaks), plantations and banks of the unpaved road sustained a larger number of butterflies and flowers than sites without management, such as the abandoned grassland, scrub forest and surrounding forest. The number of butterflies increased in the firebreak in June and at all sites in August and September. The firebreak sustained flowers in the spring, and the plantation area and banks of the unpaved road sustained flowers primarily in August and September, which was correlated with the distribution of butterflies. The different treatments such as mowing or mowing with removal of grass induced different numbers of flowers of each species affecting the habitat of adult butterflies through a season. On the other hand, the shrub tree species composing the scrub forest were host plants for the larvae of certain butterfly species. Our results suggest that heterogeneous environments with different human management or different vegetation structure or both could support habitat for various butterfly species, depending on the season and the seral stage.

We investigated the factors that encourage sprouting by Cercidiphyllum japonicum, as well as its ability to sprout after cutting, by analyzing the age structure, distribution, and growth of sprouts in one stool of this species. C. japonicum produced numerous sprouts in various age classes, ranging from 7-92 years old; the main stem was 226 years old.Sprouts that were relatively close in age (e.g., 30 or 80 years old) tended to form clusters.Based on an increase in the width of annual growth rings, we estimated that gap formation occurred about 30 years ago. This encouraged existing sprouts to grow more, and many sprouts were produced on the periphery of the stand to take advantage of the improved light conditions. After cutting, larger stems produced more simultaneous sprouts; therefore, sprout occurrence probably depends on the biomass of parent stems, although smaller stems were also able to produce some simultaneous sprouts. In the absence of physical damage, C. japonicum produced more sprouts as a function of increased age as a means of self-maintenance. C. japonicum sprouted simultaneously in response to external disturbances, such as gap formation and cutting, and it sprouted sequentially with increasing age. Therefore, although C. japonicum seedlings are rarely found in forests, C. japonicum can maintain its populations over long periods by sprouting, which compensates for sparse seedling regeneration.

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