Effect of Thinning Method and Nitrogen Fertilization on the Growth of Scots Pine and Norway Spruce Stands

1989

20 S.

5 Abb., 5 Tab., 4 Anh., 25 Lit. Ang.

Bandaufführung

37196

Preliminary results concerning the effect of different thinning methods and nitrogen fertilization on the growth of middle-aged stands are presented in this paper. The experiments were established in 1980 in Norway spruce (Picea abies Karst.) and Scots pine (Pinus sylvestris L.) stands situated in southern Finland (Table 1). The study period covers the first five years after thinning and fertilization. The material consists of 4 stands and 80 permanent sample plots. The site type of both pine stands is the Vaccinium vitis-idaea type (dryish site). The spruce experiments were located on the most fertile site types. The site type of experiment 543 is Oxalis acetosella-Maianthemum bifolium type (grove). Experiment 544 extends over two different site types. Part of the experiment is on a drained, grove-like spruce swamp and the rest on mineral soil (grove). Except for experiment 544, where earlier thinnings had been selection thinnings, the stands had been thinned from below before the experiments were established. Three selective types of thinning were compared: thinning from above and selection thinning. The trees of the dominant crown class were removed on the sample plots thinned from below. In thinning from above the trees of the dominated crown class and also some dominant trees were removed. Only those dominant trees with adjacent trees in good condition were removed. In selection thinning most of the drain consisted of the dominant trees, although some dominated trees with no development potential were also removed. The same basal area was left after thinning in all types of thinning, except for experiment 544 where thinning from above and selection thinning were heavier than thinning from below. All the thinning treatments were done on the fertilized and unfertilized sample plots. Fertilization was carried out at the time the experiments were established. Experiments 541-543 were fertilized with ammonium nitrate with lime (180 kg N/ha). Experiment 544 was fertilized with urea (232 kg N/ha) and super phosphate (62 kg P/ha). According to the results for the unfertilized sample plots, thinning from above and selection thinning usually resulted in a greater diameter growth than thinning from below, especially in the case of trees belonging to the thickest diameter classes (Fig. 2). Fertilization increased the diameter growth in the pine stands. There was no diameter growth response after fertilization in the spruce stands. The dominant height was not changed by thinning from below. Thinning from above and selection thinning decreased the dominant height on the average by 40 cm and 80 cm respectively. The thinning method had no influence on the increment of the dominant height after thinning. In the pine stands fertilization increased the increment of the dominant height.