%0 Research articles
%T Immediate and long-term change in the dimensions and vegetation of maintained forest ditches in Finland
%A Anttila, Tarja
%A Hökkä, Hannu
%A Ronkainen, Tiina
%A Joensuu, Samuli
%D 2024
%J Suo - Mires and peat
%V 75
%N 1-2
%U http://suo.fi/article/10836
%X <p>Deterioration of ditches in peatland forests is influenced mostly by peat subsidence, erosion, sedimentation, and vegetation development. In this study, forest ditch shallowing and the growth of vegetation was observed in two separate datasets: 0–3 years (two sites) follow-up data and remeasurement of 35 sites 20 years after ditch network maintenance. Over the 20-year period, the ditches were on average 33,4 cm shallower, and the average depth was 65 cm. In the mixed linear model, the most important variable explaining the shallowing of ditch depth was the original depth of the ditch. Also increasing temperature sum and increasing peat thickness when the peat layer was thicker than 70 cm increased the shallowing. Vegetation coverage in the ditches was ca 88 % after 20 years. In the three-year follow-up data, ditches dug to a deeper than 90 cm became 17–20 cm shallower. The biggest ditch shallowing was observed in ditches dug to a depth of 90 cm with a fine silt subsoil (ca 70 cm ditch depth after three years). More vegetation grew in the shallower ditches. The results support the new, shallower ditch depth guidelines for ditch network maintenance, that were introduced in 2022 in Best Practices for Sustainable Forest Management in Finland.</p>