Science chasing industry: Is this novel technique as good as it seems?

Water quality can be negatively impacted by tree felling operations and peatland restoration. This research considers how different and innovative brash (a by-product of felling trees - their tops and branches) management techniques might impact water quality following forest felling and subsequent peatland restoration.

The research design consisted of a Before-After Control-Impact experiment, wherein three different management techniques on three paired sites were compared. Two of these techniques are standard for the industry: conventional felling of trees, and the mulching of trees in-situ followed by ground smoothing. The third technique (felling multiple drifts of trees into one followed by ground smoothing) is novel and endorsed by the Scottish Government but it has not been studied previously.

Every four weeks (for 32 months) water samples and water table depths have been taken in and around treated sites. Water samples are tested for a range of water quality parameters in the laboratory. These quality indicators included: phosphate, ammonium, nitrate + nitrite, dissolved organic carbon, heavy metals, suspended solids, pH, conductivity, turbidity, etc.

Findings show that the novel technique resulted in little water quality impact (i.e., on suspended solids and nitrate + nitrite) in impacted watercourses. A spike (4.0 - 8.7 fold, mean 35.1) in ammonium occurred around one year after works were completed, and phosphate and potassium showed an elevated pulse soon after the works. Dissolved organic carbon showed strong seasonality which mirrored the control sites.

The novel technique considered here is an understudied method that is being recommended by Scottish Government agencies, and as such, science is chasing industry practice. This research aimed to sense check the impact of this technique on water quality and consider how it may impact the effectiveness of peatland restoration.