The decrease in the number of pines in drained middle-aged and older swamp site types varies in non-fertilized, once-fertilized and repeatedly fertilized stands (table 1). In fertilized and intensively drained stands a large number of trees are died compared with the stands of moderate drainage. In addition to the decrease in the number of trees of smaller diameter on account of differentiation, the number of trees of medium and thicker diameter also decrease on account of sudden changes in nutritional environment subsequent to fertilization (Fig.). In case of once-fertilized stands the decrease in more fertilized stands is similar to that of unfertilized stands. One of the reasons for greater decrease could be a deficiency of phosphorus and potassium in peat on account of excessive nitrogen fertilization (table 2).
