Water balance in afforestation chronosequences of common oak and Norway spruce on former arable land in Denmark and southern Sweden

Precipitation, throughfall and soil moisture were measured, and interception, transpiration and water recharge were estimated in four afforestation chronosequences on former arable land at two Danish locations (Vestskoven and Gejlvang) and at one southern Swedish location (Tönnersjöheden). Afforestation was performed using Norway spruce (Picea abies (Karst.) L.) and common oak (Quercus robur L.) at Vestskoven and only Norway spruce at Gejlvang and Tönnersjöheden. Four to five stands of different ages (5–92 years) were studied in each of these chronosequences. Hydrological fluxes were calculated using the soil hydrological model SWAP. Throughfall flux and soil water content were used for calibration of the model. The simulated water recharge decreased with increased stand age within 30–40 years of afforestation. This was mainly due to increased interception evaporation with age. The annual water recharge was higher below oak stands (149–192 mm yr−1) than below spruce stands (107–191 mm yr−1) of similar age. The relative water recharge was also considerably higher from the sandy glaciofluvial soils at Gejlvang and Tönnersjöheden than from the sandy loamy till soils at Vestskoven.