The recovery process of a Sasa tsuboiana population after a mass flowering and death in 1977 was investigated by 15 years of observation in the Hira Mountains, Kinki district, western Japan. Seed production was high (6600-13 800 seeds m -2 in Sasa plots and 3900 seeds m -2 in a forest plot) but m ), probably because of seed predation by Microtus emergent seedling density was low (14-21 seedlings -2 montebelli occurring between seed shedding and the next spring. The seedling density had decreased further by the next year and the S. tsuboiana population recovered from only a limited number of seedlings. In spite of such a low initial density, the S. tsuboiana population was able to regenerate successfully and attained the previous full stand height in 7-16 years. Miscanthus sinensis invaded and delayed the recovery of S. tsuboiana in one plot, but S. tsuboiana became dominant as it caught up with the height of M. sinensis.Seedling growth patterns, such as frequent tillering, the onset of rhizome extension in the early stage of seedling growth and frequent culm production from rhizomes, played important roles in the successful regeneration of S. tsuboiana.

Whole‐lake areal distribution of submerged macrophyte growth in Lake Biwa was surveyed using aerial photographs in 1994 and 2000, when unusual declines in the water level of approximately 1 m occurred in the dry summers. The estimated total areas of the submerged macrophyte communities were 1441 ha for 1994 and 2825 ha for 2000. In the shallow and eutrophic southern basin, the bottom area covered by vegetation gradually increased year by year after 1994, and the ratio of this area to the total surface area of the basin in 2000 amounted to 52%. The dominant species were two natives, Hydrilla verticillata and Myriophyllum spicatum, and one exotic, Egeria densa. Changes in physical conditions and water quality associated with the decline in the water level, as well as the reactions of submerged plants to aquatic environments and ecosystem dynamics, are discussed.

Water quality and flow rates at a weir installed on the end of Aburahi-S Experimental Watershed (3.34 ha) were measured once a week from 2001 to 2003 and in appropriate intervals from 30 min to 6 h during five storm runoff events caused by each rainfall from 8 mm to 417 mm. The average annual loads of total nitrogen (TN) and total phosphorus (TP) were calculated to be 19.0 and 0.339 kg ha(-1) y(-1) from the periodical data by using the integration interval-loads method (ILM), which did not properly account for storm runoff loads. Three types of L(Q) equations (L = aQ(b)) were derived from correlations between loading rates L and flow rates Q obtained from the periodic observation and from storm runoff observation. L(Q) equation method (LQM), which was derived from the storm runoff observation and allowed for the hysteresis of discharge of materials, gave 9.68 and 0.159 kg ha(-1) y(-1), respectively, by substitution of the sequential hourly data of flow rates. L(R) equation (L = c(R - r)d) was derived from the correlations between the loads and the effective rainfall depth (R - r) measured during the storm runoff events, and L(R) equation method (LRM) calculated 9.83 +/- 1.68 and 0.175 +/- 0.0761 kg ha(-1) y(-1), respectively, by using the rainfall data for the past 16 years. The atmospheric input-fluxes of TN and TP were 16.5 and 0.791 kg ha(-1) y(-1).

The budgets of nutrients and major ions between the input flux from atmospheric deposition and the output flux to streams were measured on three forested small mountain watersheds, Aburahi-N (23.8 ha), Aburahi-S (3.8 ha, 2 km south from Aburahi-N) and Myokoji (1.77 ha, 28 km northwest from Aburahi-N), located at 34-35 N and 136 E around the central part of Japan. The bedrock of the watersheds is granite. The main vegetation of Aburahi-N and Aburahi-S was planted with Japanese cypress (Chamaecyparis obtusa Sieb. et Zucc), and Myokoji was a secondary forest growing deciduous broadleaf trees and Japanese red pine. The chemical analysis of the stream waters was carried out once a week at Aburahi-N from 1987 to 1991, at Aburahi-S from 1995 to 1998, and at Myokoji from 1991 to 1993. Wet and dry depositions were collected every month at Aburahi-N. The annual mean concentrations of total nitrogen (TN) of the stream water of Aburahi-N, Aburahi-S and Myokoji were 0.408, 0.614 and 0.349 mg/l, respectively, total phosphorus (TP) contents were 0.0074, 0.0046 and 0.0096 mg/l, and the potassium ion (K+) contents were 0.83, 0.49 and 0.77 mg/l. The average annual output fluxes of TN from the watersheds of Aburahi-N, Aburahi-S and Myokoji were calculated to be 5.85, 4.10 and 12.7 kg/ha/y, TP 0.131, 0.045 and 0.280 kg/ha/y, K+ 9.63, 3.23 and 9.70 kg/ha/y, and discharge 1062, 508 and 1265 mm/y, respectively. The annual outputs tended to increase as the annual precipitation increased. The average annual input fluxes of TN, TP and K+ for six years from 1990-1998 were 12.5, 1.31 and 7.64 kg/ha/y, respectively, and the precipitation averaged 1449 (1019-1947) mm/y.