Effects of plantation forest clearfelling on stream temperatures in the Plynlimon experimental catchments, mid-Wales

Abstract

Hourly stream temperatures monitored over 28 months, which spanned a 3 month period of environmentally sensitive plot-scale harvesting of 20 ha. (20%) of the Nant Tanllwyth catchment (0.89 km2) on the south side of the main stream in early 1996, resulted in a 0.58°C (pMonthly mean maximum stream temperatures, also highest in July and August in the year before and the year after the clearfelling, showed a marked increase of 7.0°C: in July and 5.3°C in August from the pre- to the post-clearfelling years, while monthly mean minimum air temperatures actually showed a slight decrease for the same months. The likely effects on stream fauna are discussed, as are suggestions for, and likely effects of, buffer strips alongside the streams. Keywords: stream temperature; air temperature; ground surface temperature; clearfelling; Plynlimon