ABSTRACT
Clear cutting causes considerable change in the nitrate content of groundwater. The content keeps on increasing for at least five years. Although the changes were big compared to the control area and to the situation before clear cutting, the amount of nitrate nitrogen remains relatively low when compared to the risk limit, above which drinking water is regarded as hazardous to the health. On the other hand, the leaching of nitrate out of the site may decrease the forest yield if it continues for a long time.
Plot studies show that, if the waste wood is collected, the change of the content is similar to the plot where waste wood was left. Site preparation, too, had a similar effect if there was no surface run-off. On an area where surface run-off appeared the content remained low for four years after ploughing.
