Hydrologic controls on water chemistry, vegetation and ecological patterns in two mires in the South-Eastern Alps (Italy).

We examined how hydrology influenced water chemistry, vegetation, nutrient status, aboveground net primary production (ANPP) and litter decomposition rates in two peatlands on the South-Eastern Alps of Italy. One of the peatlands had a modest hydraulic gradient and prevalently acted as a recharge system, although there were short phases of vertical flow reversal during dry periods. This peatland was, therefore, prevalently fed by rainwater and was covered by bog-like vegetation, mainly hummocks and scrubs with a ground layer rich in Sphagnum mosses. The other peatland presented a steeper hydraulic gradient, with the surface being fed by mineral water either by surface runoff and by vertical, upwards directed ground-water flow. Compared to the bog-dominated peatland, the pore water was less acidic and richer in telluric cations. More than half of the peatland surface was covered by fen meadows. Nitrogen (N) content in the vegetation was very similar in the two peatlands, while phosphorus (P) concentration was lower in the fen-dominated site. Contrary to our expectations, ANPP did not differ significantly between the two sites while litter decomposition rates were significantly lower in the fen-dominated peatland, presumably because of P limitation of decomposers. This suggests that the development of ombrogenous peatlands in this region need not be due to increased accumulation of peat during succession from mineralwater-fed to rainwater-fed conditions.