Om fröproduktion, fröträdsval och plantuppslag i försök med naturlig föryngring

This work reports on some results from an investigation of the permanent experiments with shelterwood stands carried on by the department of regeneration. The results concern: 1. Yield of seed 2. Importance of seed tree choice for the intensity of seeding 3. Establishment of seedlings 4. Relationship between the amount of seed shed and the number of seedlings established. The location of the sample plots are shown in fig. 1. Table 1 presents some general data on the plots and on the yield of seeds per tree. Table 2 reports on an inventory showing the results of scarification and restocking. The yield of Scots pine (Pinus silvestris L.) seeds per tree (fig. 3) is strongly related to the location of the site. In the north on relatively high locations the shelterwood trees have produced only a few 100's of germinable seeds per tree and annum. In south Sweden the average yield is instead well over 5000 seeds (per tree and annum). Because of differences in the number of shelterwood trees per hectare, the superiority of the rate of pine seed dissemination per unit area on the southern plots is still higher, or according to an example of calculation, on the average about 17 times. Comparisons between the yield of h'orway spruce (Picea abies L.) seeds per tree have been carried out only for a number of plots on high elevation (fig. 4). The trees on the more southerly of these plots have produced 2-3 times as many seeds as trees from the northern plots. Relatively good cone setting in Norway spruce has occurred on these plots almost every other year (table 3). A considerable portion of the seed from one and the same crop of cones, on an average 19 per cent, was not shed until the second autumn after cone setting.