Relationship among water penetration, soil structure and understory vegetation according to the land conditions around the greenway in Kohoku New Town

Abstract

In the slope forest of suburban area, which is affected by the land development, rainwater is getting to be more difficult to be penetrated because of the long-term compaction of surface soil. In the slopes along the greenway in Kohoku New Town, we selected survey plots according to the land conditions and the existence of understory vegetation cover, comparing original slopes of tablelands, slopes of constructed fill and cut mud slopes. We investigated rainwater penetration capacity, soil softness, soil particle size composition, and cover and biomass of understory vegetation, and analyzed their relationships. As a result, soil softness and the hierarchical diversity of understory vegetation had positive correlation with water penetration capacity, and these relationships were found in the cut mud slopes, same as in the original slopes, although no such relation was confirmed in the filled slopes. In the filled slopes, the effect of the underground structure to water penetration is stronger than that of surface soil, but in the cut mud slopes, hierarchical vegetation and softened surface soil are distributed with higher water penetration capacity. It was suggested that it is important to utilize such cut mud slopes to recover rainwater penetration capacity, with conserving the developing vegetation, in the restructuring of the greenway.