Evaluation of community gradients on environmental gradients at different topographical spaces in poor fen under nutrient and mineral loading via groundwater

Abstract

To clarify the relationship between hydrochemical variables and community gradients in poor fen under nutrient and mineral loading via groundwater, we set up loaded and control sites in poor fen and investigated plant community and pH, electrical conductivity (EC) and inorganic ions of peat water in both sites. Poor fen consists of mosaic topographies with raised hummocks and depressed hollows and non-mosaic topographies without hummocks and hollows. We expected that groundwater (saturated peat water) would have different effects on plants growing in each topography, because the distance from the water table to the surface of each topography is different. In this study, as a result of the plant community analysis in different topographical spaces, two community gradients were extracted from the mosaic-non-mosaic and one community gradient from the hummock, and one end of each community gradient consisted of a community type dominated by Sphagnum species. These three community gradients were accompanied by changes in concentrations of inorganic ions. On the other hand, no community gradient was extracted from the hollow along changes in concentrations of inorganic ions. As a result of comparing peat water in hummocks (unsaturated peat water) and hollows (saturated peat water) between loaded site and control site, concentration of most inorganic ions was generally higher in loaded site for both hummocks and hollows. From this result, it can be suggested that ion concentrations in hummocks increased due to the loading of nutrients and minerals via groundwater, and reduced in coverage of Sphagnum species, which arose community gradient on hummocks through loaded and control sites.