Black locust can produce two types of new sprouts from horizontal roots. One is the sprouts for vegetative reproduction which occur from apical meristem every year, and the other is injury-induced sprout that emerges after the stem or root system is damaged by natural disturbance or logging. Among 124 sprouts investigated at bank of Akagawa river, 74 (59.7%) belonged to the former type and 50 (40.3%) the latter. Further, all the injury-induced sprouts emerged from dormant buds accumulated on the surface of root and no sprout derived from adventitious bud. Since most of the horizontal roots were less than four-years-old at the age when they emerged sprouts, the dormant buds seem to have rather short lifespan, even though they distribute at high density on root surface. No sprout emerged on the root of seven-years-old or more. This suggests young and narrow roots should be thoroughly removed to prevent regrowth of Black locust stand. However it will be difficult to completely extinct the root systems, since they might remained underground. In such a case, it is effective to pull up newly grown sprouts with human power until several years when a dormant bud loses ability to emerge.

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Leaf water relations in seedlings of Aesculus turbinata, a riparian-specific tree species, were studied under various soil water conditions. Current-year seedlings were grown in a greenhouse under wet, moist, and dry conditions, mimicking spatial variation in soil water conditions within forests. At the end of the first growing season, leaf water relations were estimated by leaf pressure-volume curve and compared among the water conditions and with other species distributing drier habitats in forests. The leaf water potentials at full turgor (Ψ_s^sat) and at the turgor loss point (Ψ_s^tlp) were much greater, and the modulus of tissue elasticity was much lower than other species specific to drier habitat. The Ψ_s^sat and Ψ_s^tlp were significantly greater under the dry condition than wet and moist conditions, suggesting that acclimation to drought was unlikely for current-year A. turbinata seedlings. These results were partly concordant with distribution of this species within a forest community.

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[in Japanese]

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