Dissolved elements of rain water, throughfall and stemflow in Japanese cedar (Cryptomeria japonica) and stands of four deciduous trees, Chinaberry (Melia azedarach), Tulip tree (Liriodendron tulipifera), Wild cherry tree (Purnus jamasakura) and Japanese zelkova (Zelkova serrat) stands were analyzed for 1 year. Analyzed elements were Cl^-, NO_3^-", SO_4^2-, NH_4^+, K^+, Ca^<2+>, Mg^<2+>, Na^+ and pH. The amount of dry deposition and canopy leaching were estimated by the material balance approach. Anoins and cations in dry deposition were almost in equilibrium in the five spices. This equilibrium between anions and cations was mostly maintained in dry deposition. The annual amounts of dry deposition in Japanese cedar were two to four times higher than in the deciduous trees. On the other hand, the annual amounts of canopy leaching in the four deciduous trees were much higher than in Japanese cedar, especially in the case of Tulip tree, where more than 80% of Mg^<2+>, Ca^<2+> was supplied the forest soil by can py leaching. In Japanese zelkova, throughfall and stemflow contained enriched Cl^-, which is believed to have derived from canopy leaching. It was found that some elements supplied to forest soil, especially cations were enriched by canopy leaching in deciduous stands.

View full abstract

To clarify the effects of different regeneration methods on plant species composition and regeneration density, investigations were conducted at three sites where different regeneration methods (artificial regeneration by Cryptomeria planting and weeding: PL, natural regeneration: NR, and natural regeneration with herbicide spraying: HS) were applied, comparing with the floor vegetation as control. The sites were set up in 1984, following clear cutting of a 65-year-old mixed forest consisting of artificial Cryptomeria and hardwoods and ground clearance. Investigations were conducted at the stands of age 8 and 13. The plant species diversity (d, H') was the highest in the site of PL and the regeneration density was higher at sites of PL and HS. The factors of high species diversity and regeneration density were improved in a light environment by clear cutting and soil disturbance and repression of Sasa kurilensis growth by tasks such as yarding, ground clearance, planting and weeding. On the other hand, thick growth of S. kurilensis and herbicide treatment were factors of low species diversity. Vertical stratification in the forest had developed during the 8 -13 year period with growth of trees and extinction of some pioneer species. However, no recovery of the herb species was observed in the site of HS. Afforestation such as planting and weeding were proven to be the most effective measures to gain high regeneration density without growing Sasa thickly or killing the herb species.

View full abstract

The purpose of this study was to establish the effects of tree species on microbial biomass and activity in top soil of each slope position (upper, middle, lower). Study sites were planted with Japanese cypress in parallel with Japanese cedar along a slope from ridge to stream. The numbers of fungi and actinomycetes, and the amount of microbial biomass carbon and microbial activity in the soil, at a depth of 0-10cm, in the cypress plantations were 1.1-3.9 times greater than in the cedar plantations, regardless of slope position. The quantity of bacteria in the soil on the lower slope was 2.6 times greater in the cypress plantation than in the cedar plantation. The residence time of litter (standing stock of litter / annual litterfall) correlated negatively with the quantity of bacteria in the top soil, and it was particularly low in the cypress plantation on the lower slope. On the lower slope, it was thought that decomposition of litter was faster among the cypresses than among the cedars due to the fungi and bacteria.

View full abstract

Natural broad-leaved forest and artificial larch (Larix keampferi) forests (40-yr-old) were compared in the amount of litter layer and its contents of C, N, P, K, Na, Ca and Mg, rate of litter decomposition, and some chemical properties of mineral soil horizons. There were no differences in average concentrations of total C, N and P of the litter layer between the two forest types. Average concentrations of total K, Na, Ca and Mg of the litter layer were lower in the larch forest than in the broad-leaved forest. However, there were no consistent differences in the amounts of those elements in litter layer between two forest types. The decomposition rates (Olson's k) were 0.19 and 0.29 at the larch forest and the board-leaved forest, respectively, and suggested the nutrient return to the mineral soil through litter decomposition may much smaller in the former than the latter. The concentrations of total C, N, P, exchangeable K, Na and Mg in the surface mineral soil (0-5cm depth) were 0.66, 0.64, 0.73, 0.34, 0.28 and 0.36 times lower in the larch forest than in the broad-leaved forest, respectively. It was presumed that the nutrients status in the surface mineral soil, especially in exchangeable K, Na and Mg concentrations declined due to the decreased nutrients return from litter layer with the forest conversion into the larch forest. However, the concentrations of exchangeable Ca in the lower soil layers were 1.9 times higher in the larch forest than in the board-leaved forest, though it did not differ in the upper soil layers between them. The NO_3-N contents in mineral soils were 1.4-2.4 times higher in the larch forest than in the natural broad-leaved forest. Those findings suggested that the conversion of broad-leaved forests into artificial larch forest might bring about increased NO_3-N flux in a litter-mineral soils-system, and accelerate leaching loss of basic cations from soil.

View full abstract

We examined sprouting traits, including sprouting ratio, seasonal changes, number and biomass size (dry weight), for three deciduous and two evergreen shrubs and six deciduous arborescences in a post-pine wilt disaster secondary forest. Among the surveyed species, 90% of the parental felled stumps made sprouts during early May and mid June, but the remaining stumps did not sprout. A positive relationship between the biomass of sprouts and diameter of the parental tree at ground level was detected for seven of the eleven examined species, whereas no such significant relationship was found for Acer rufinerve, a pioneer species. These result suggest that A. rufinerve might have a lower below-ground accumulation of resources than the other species. The number, size and branch/leaf ratio of the sprouts differed among the life forms and species. The relationship between sprout biomass and parental tree diameter at ground level can be used to predict the amount of sprouts, and this information can be applied to devise suitable ways of managing abandoned forests.

View full abstract

Physical characteristics and moisture conditions of the soil in an experimental Hinoki (Chamaecyparis obtusa) stand located at Mt. Tsubakuroyama, Ibaraki Prefecture were observed and analyzed. This study examined slash that remained after thinning, and its effects of the surface soil moisture conditions. Observations and soil samples were collected in two plots in the stand : one was named the "Slash Plot", in which the slash remained on the forest floor and covered the surface of the ground after thinning; the other was called the "Control Plot", where no slash and litter covered the surface of the ground. Surface conditions there were similar to those observed before thinning. The results of observations and analyses are as follows: 1) Solid phase contents of respective soils at 5-, 10- and 30-cm depths were less than 20%. Pore contents of soils at each depth were more than 80% in the experimental plot. These observations emphasize the character of this black soil, which is volcanic in origin. 2) Total pore contents of soils at 5-, 10-, and 30-cm depths did not differ. Significant differences of pore contents were not observed among Control and Slash plot soils. 3) Matric potential of the Control plot was slightly less than that of the Slash plot at 5-cm depth during the period without rainfall. In contrast, the matric potential of the Slash plot was markedly less than that of the Control plot at 30-cm depth. The matric potential of each plot was not different at 10-cm depth. 4) The Slash plot soil temperature was 1-2℃ higher than that of the Control plot in winter, and 1-2℃ lower than that of the Control plot in summer. Those differences were engendered by temperature change moderation that is attributable to slash. 5) Effects of slash on surface soil moisture are derived from rainfall interception above the ground and reduction of evaporation from the ground surface. 6) Effects of rainfall interception by slash engender a decline in the water content of sub-surface soil. On the other hand, effects of evaporation reduction by slash moderate the increases in surface temperature and retain surface-soil moisture.

View full abstract