%0 Articles
%T Dynamics of vegetation, nitrogen and carbon as indicators of the operation of peatland buffers
%A Saari, Päivi
%D 2014
%J Dissertationes Forestales
%V 2014
%N 173
%R doi:10.14214/df.173
%U http://dissertationesforestales.fi/article/1957
%X Forestry in peatlands may result in an increased release of inorganic nitrogen (N), phosphate phosphorus (PO4-P), dissolved organic matter (DOM) and solids. Peatland buffers with sedimentation ponds have been constructed in order to prevent leaching of solids and nutrients to the watercourses. Results of peatland buffer functionality have been contradictory probably because the potential nutrient retention capacity of the peat, the biomass of nutrient binding microorganisms and vegetation, and the amount of N liberated in a gaseous form to the atmosphere varies between buffers. Therefore, a detailed knowledge of N cycling in peatland buffers is crucial. In addition, the possible impact of the quality of DOM on nitrous oxide (N2O) dynamics is unknown.

Three buffers were constructed in eastern Finland: a spruce swamp and a brook margin meadow (constructed prior to our study in 1997) and a spruce-pine mire with lake margin fen during the research period in 2005. Fluxes of N2O were measured in buffers and a clearcut area in the catchment of the spruce-pine mire
with lake margin fen and the rate of N2O accumulation was determined for peat profiles cored in the spruce swamp. In addition, the production capacity of N2O-N under different fertilization levels was measured from peat samples cored from the spruce swamp in the laboratory. Nutrient concentrations were measured and DOM characterized by means of DOC from the surface waters entering the buffer and from the vadose water. The quality of DOC was characterized in terms of molecular size fractions and aromaticity indexes. The dynamics of DOM characteristics were related to those of N2O by evaluating the significance of DOC quality on the N2O flux. Vegetation cover was monitored temporally and spatially over a three year period in order to evaluate possible
vegetation change following buffer construction.

In the buffers and the sedimentation pond, N2O emissions were low, although fluxes from the sedimentation pond were higher than those from N loaded humic lakes. The rate of N2O accumulation and N2O emissions after fertilization were high in the peat samples cored from the spruce swamp indicating a high capacity to produce N2O if free nitrate (NO3-) enters the buffer. However, the observed concentrations of N inflow to the buffers were low; supporting low N2O emissions even near the water inflow. The presence of low molecular weight DOC seems to be a significant controller for N2O efflux between the soil and the atmosphere after forestry operations.

Concentrations of PO4-P were occasionally higher in the water outflow than those in the inflow in the buffers indicating a possible nutrient leak. Thus, the changes in vegetation cover reflected an area of effective water flow paths within the buffer rather than eutrophication. Changes in above-ground biomass or its N content did not indicate an increased nutrient binding capacity in the buffer vegetation. Small buffers on organic soils may often have more importance in preventing the flow of solids rather than nutrients. The significance of buffers as a source of the greenhouse gas N2O was negligible, both because of the low flux rates, and the small area used for water protection.