Implications of applied best management practice for peatland forest harvesting

• Two forest catchments were studied to assess efficacy of best management practices.
• Concentrations of nitrogen and phosphorus were examined before and after harvesting.
• Harvesting impacted phosphorus and nitrogen concentrations.
• Forest operations should use best management practices where possible.
• Concentrations of nutrients in stream were below threshold limits within 15 months.

Elevated levels of nutrients and suspended sediment (SS), and changes to other environmental parameters, are frequently associated with forestry harvesting (clearfelling) operations, and are indicative of the potentially complex changing environment associated with clearfelling. Current and future recommended best management practices (BMPs) for forestry clearfelling on upland peat catchments must provide for a healthy soil and good water quality. The aim of this study was to quantify the effects of implementation, or violation, of BMPs in the clearfelling of an upland peat conifer forest. Over periods of 12 months prior to clearfelling and 15 months after clearfelling, two peatland forests, comprising a study control (no clearfelling) and a study site (clearfelling), were monitored for the release of phosphorus (P) and nitrogen (N) species (dissolved reactive phosphorus (DRP), total phosphorus (TP), total oxidised nitrogen (TON) and ammonium nitrogen (NH4+-N)), SS, dissolved oxygen (DO), electrical conductivity (EC), pH and stream water temperature. Clearfelling was conducted during poor weather conditions and a watercourse, which drained the study site, was not protected. The maximum recorded concentration exported from the study site after clearfelling was 471 μg L−1 for DRP, 611 μg L−1 for TP, 1336 μg L−1 for NH4+-N, and 194 μg L−1 for TON. Concentrations of SS exiting the study site increased in one of the two samples taken during clearfelling (maximum release of 481 mg L−1, with 68% of this organic) and returned to pre-clearfelling levels, or below, within 6 months of the commencement of clearfelling. Exports of TP and DRP from the study site were 0.9 and 0.4 kg ha−1 yr−1, which were greater than the study control (0.6 and 0.2 kg ha−1 yr−1, respectively). This indicated that the mitigation practices employed on site were not effective in phosphorus retention.