Vertical and Horizontal Structure of the Urban Park Ponds as Habitat for Aquatic Plants

Abstract

The authors investigated the effect of vertical and horizontal pond structure on aquatic plant diversity in nine urban parks in eastern part of Honshu, Japan. The structural parameters that we measured were coverage of each plant species, water depth and bottom material. Water quality parameters such as water temperature, pH, electric conductivity, dissolved oxygen, suspended solid, COD, total nitrogen and total phosphorus were also measured. We performed multivariate correlation analysis to examine the effect of these parameters on the diversity of aquatic plants.The results were as follows:(1) Most of investigated ponds were eutrophicated.(2) The number of emergent plant species was positively correlated with the pond figure index and the size of pond, and negatively correlated with the slope of the bottom near shoreline.Generally, each aquatic plant appeared in a particular set of habitat type expressed as the combination of the water depth and the bottom material. Technical suggestions for constructing and/or managing urban park ponds to make them better as the habitats of aquatic plants are as follows:(1) The figure of the pond should be complex, rather than being simple figures like circle.(2) The size of the pond should be as large as possible.(3) Suitable bottom materials are coarse sand, fine sand, silt and clay. Each material should be used in an appropriate part of the pond.(4) The slope of the bottom near the shore should be less than 10% and should never exceed 15%.