A bark beetle attack caused elevated nitrate concentrations and acidification of soil water in a Norway spruce stand

A bark beetle attack in a Norway spruce forest in southwestern Sweden killed most trees, which however mostly remained standing, and caused elevated nitrate concentrations and subsequent acidification in the soil water. Long-term monitoring showed very low nitrate concentrations in the soil water before the bark beetle attack. High nitrate concentrations remained throughout five years after the initiation of the bark beetle attack until the monitoring was terminated. The increased nitrate concentrations in the soil water were accompanied by a decrease in both pH and the acid neutralizing capacity, ANC. The significance for future nitrogen and acidity leakage to ground- and surface waters is discussed in relation to the expected future increase in the frequencies of bark beetle attacks in boreal and northern temperate forests.