MODEL COMPUTATIONS ON THE EFFECT OF RISING TEMPERATURE ON SOIL-MOISTURE AND WATER AVAILABILITY IN FOREST ECOSYSTEMS DOMINATED BY SCOTS PINEIN THE BOREAL ZONE IN FINLAND

Based on model calculations, the moisture of soil for sites with and w ithout a cover of trees under the current and rising temperature was s tudied assuming a 5 degrees C increase in annual mean temperature over a period of 100 years. The calculation for southern Finland (61 degre es N) showed that the soil moisture under elevated temperature could b e reduced compared to that under current temperature conditions. This was also true for northern Finland (66 degrees N), but there the reduc tion in soil moisture was less substantial. In particular, when trees were present, the soil moisture during the growing season was reduced due to enhanced evapotranspiration. In the presence of trees, the mois ture content of the surface soil was only half that under the current temperature. In these conditions, reduced accumulation of snow and a t hin humus layer allowed the soil tc freeze to deep layers, thereby cau sing further reduction in soil moisture due to poor transfer of water deeper in the soil.