Long-term influence of site preparation on water-retention characteristics of forest soil in Finnish Lapland

Site preparation is commonly used with reforestation in Lapland, but environmental aspects of site preparation, such as visual impacts and possible changes in runoff, soil density and aeration, often raise questions. The present study investigated, 21 years after site preparation and reforestation with Scots pine, how ploughed ridges affect water-retention characteristics of till soils compared with untreated intermediate areas, and whether these characteristics differ on untreated intermediate areas when different site-preparation techinques have been applied.It was found that in ploughed ridges the water retention at saturation and air-filled porosity at field capacity (−10 kPa) were significantly higher and the bulk density lower than in the untreated intermediate areas. No long-term differences were found in the water-retention characteristics between untreated intermediate areas of the patch-scarified, disc-trenched and ploughed plots (scarified by a bulldozer) and prescribed-burned plots (scarified manually). The results suggest that the changes found in the soil physical properties and organic matter content may still affect the soil–water regime and thus prerequisites for forest growth over two decades after site preparation in Lapland.