Hydrology, groundwater chemistry and peat chemistry in relation to habitat conditions in a mire on the South – eastern Alps of Italy

Abstract

The habitat conditions in a mire on the southern Alps of Italy were defined based on data on topography, hydrology, water chemistry, peat chemistry and floristic composition. Water flowed along the main longitudinal axis from the eastern dry sector to the western wet sector of the mire. Along the transverse axes the water table assumed a convex shape during dry periods, which resulted in water flowing towards the margins of the mire. During wet periods the water table assumed a concave shape, determining a flow of water from the margins towards the mire centre. The absence of any vertical groundwater flows enhanced habitat acidification, particularly in the eastern sector of the mire characterised by a smaller peat thickness. Surface water in the central portion of the mire had low calcium concentration and low electrical conductivity, comparable to those found in ombrotrophic bogs. Calcium concentration and electrical conductivity in surface water were higher along the margins, indicating a certain degree of mineral soil water inflow. Total contents of major nutrients (N, P and K) in the peat were rather homogeneous over the mire, while calcium concentrations were slightly higher in the peat layers of the wet portion of the mire. Species distribution was strongly influenced, rather than by surface water chemistry, by water table position and rate of surface water flow.