Understorey vegetation as an indicator of water content in till soils in Finnish Lapland

Artificial regeneration of Scots pine (Pinus sylvestris L.) has been applie d to a variety of forest site in Lapland. Occasional failures in regenerati on have been observed on sites with high soil moisture contents and origina lly dominated by Norway spruce (Picea abies (L.) Karst). Understorey vegeta tion was studied on four naturally pine-dominated and eight spruce-dominate d sites to determine suitable indicator plants for assessing soil moisture regimes. Soil moisture contents were estimated using the in situ dielectric measurements with radar surface arrival detection targeted to a depth of 0 -50 cm. The abundance and frequence of plant species were analysed using lo gistic regression. The most reliable indicators were found to be Stereocaul on and Cladonia lichens for the dry regime (theta upsilon < 25%), and Polyt richum commune Hedw. and Carex globularis L. for the wet regime (theta upsi lon > 25%). It was concluded that the indicator plants found in this study provide an alternative to the traditional Finnish forest site type approach in recognizing high soil moisture regimes.