Creation and functioning of a buffer zone in an upland peat forested catchment

Abstract

Buffer zones can be used to reduce nutrient and suspended sediment export following forest clearfelling by directing runoff over a vegetated area. This study demonstrates the achievability of constructing a buffer zone by initially clearfelling the standing forest, seeding with two native grass species and directing the water from a semi-natural stream draining an upstream 10 ha forested peatland site through it. Following the clearfelling of the upstream study site this study tested the efficacy of this management practice in reducing nutrient and suspended sediment concentration in the receiving water. The buffer zone reduced total reactive phosphorus (TRP) and suspended sediment (SS) loads by 18% and 33%, respectively. Phosphorus (P) retention efficiency was dependent on inlet concentrations, loading and hydraulic loading rates. In storm events with a loading rate of >28 g P ha-1, a flow rate higher than 88.5 L s-1 and an inlet concentration of <17 µg L-1 the buffer zone became a TRP release source. The maximum P concentration in the buffer zone did not exceed 40 µg L-1 during this study demonstrating that the buffer zone method could be used efficiently in peatland forestry to moderate the high P concentrations and assist in protecting salmonids and freshwater pearl mussels.