17:15 〜 18:30
[MIS11-P02] Physical and chemical properties of soils controlling vegetation in Renkoji mire : Impacts of sediment influx as a source of nutrients
The Renkoji-Wakabadai Satoyama Conservation Area, which is located at the boundary of Tama City and Inagi City in Tokyo, was designated as an environmental conservation area by the Tokyo Metropolitan City in 2014 because of the presence of rare plants and animals such as Vertigo hirasei and Asarum tamaense. However, in recent years, the vegetation in the mire within the conservation area has been changing, and there are concerns that the habitat may be changing or disappearing, which could lead to the extinction of the species. In order to establish a management policy, it is essential to elucidate the factors controlling the distribution of vegetation in Renkoji mire. Therefore, the purpose of this study was to clarify the factors that determine the vegetation of the mire by focusing on the physical and chemical properties of soil.
A vegetation survey was conducted in August 2020 and the dominant species within the area were determined using the quadrat method. Pore-waters at a soil depth of 5cm were sampled at 18 sites using the depressurized porous cup method. Soil samples were collected from 0-10 cm and 10-20 cm. Pore-waters concentrations of cations (Na+, K+, Ca2+, Mg2+, NH4+) and anions (Cl-, NO3-, SO42-) were measured by ion chromatography, and PO43- concentration was measured by the molybdenum blue method. Soil moisture content, ash content, C/N ratio, soil NH4+ (KCl extraction), and total Phosphorus content were also measured.
A remarkable difference in the mean total phosphorus content in 10-20 cm of subsoil differed was found among vegetation types. In the reed community that occupied the uppermost part of the mire, the total P content in the subsoil was significantly higher than that of other vegetations. The biomass and grass height of each vegetation tended to increase with the total P content in the subsoil 10-20 cm (p<0.05), with the highest for the reed. Since other pore waters and soil components did not show clear differences among communities, it was most likely that the differences in total P content determined the distribution of plant communities.
In the upper reaches of the mire, where reeds were dominant, the upper soil layer (0-10 cm) had a lower moisture content and a higher ash content. In addition, the C/P ratios of soil at the reed sites were significantly lower than those in the central part of the mire. This suggests that the reed community in the upper part of the mire is influenced by the influx of sediment and accompanied with phosphorus which results in the establishment of a reed community with a high growth rate.
These results indicate that phosphorus, one of the physical and chemical factors of soil, is affecting the distribution of vegetation in Renkoji mire.
A vegetation survey was conducted in August 2020 and the dominant species within the area were determined using the quadrat method. Pore-waters at a soil depth of 5cm were sampled at 18 sites using the depressurized porous cup method. Soil samples were collected from 0-10 cm and 10-20 cm. Pore-waters concentrations of cations (Na+, K+, Ca2+, Mg2+, NH4+) and anions (Cl-, NO3-, SO42-) were measured by ion chromatography, and PO43- concentration was measured by the molybdenum blue method. Soil moisture content, ash content, C/N ratio, soil NH4+ (KCl extraction), and total Phosphorus content were also measured.
A remarkable difference in the mean total phosphorus content in 10-20 cm of subsoil differed was found among vegetation types. In the reed community that occupied the uppermost part of the mire, the total P content in the subsoil was significantly higher than that of other vegetations. The biomass and grass height of each vegetation tended to increase with the total P content in the subsoil 10-20 cm (p<0.05), with the highest for the reed. Since other pore waters and soil components did not show clear differences among communities, it was most likely that the differences in total P content determined the distribution of plant communities.
In the upper reaches of the mire, where reeds were dominant, the upper soil layer (0-10 cm) had a lower moisture content and a higher ash content. In addition, the C/P ratios of soil at the reed sites were significantly lower than those in the central part of the mire. This suggests that the reed community in the upper part of the mire is influenced by the influx of sediment and accompanied with phosphorus which results in the establishment of a reed community with a high growth rate.
These results indicate that phosphorus, one of the physical and chemical factors of soil, is affecting the distribution of vegetation in Renkoji mire.