Pine and Spruce Yield After the 1753 Forest Fire at Umgransele in Northern Sweden

1987

S. 15-29

9 Abb., 3 Tab., 18 Lit. Ang.

Unselbständiges Werk

200054427

In a pine stand located a few kilometers south of Umgransele village in the parish of Lycksele two forest fires have occurred in the lifetime of the current stand. The first fire was in 1843 and probably extinguished by a heavy rain when half of the stand had burned. In 1893, the entire area was again in flames. These events provide us with the possibility of studying the long-term effects on yield of an "extra" forest fire (1843) in this 230- year-old stand - the aim of this investigation. The field work was carried out during May-June, 1983. The following results were obtained: 1. Between 1694 and 1983, the stand burned at least 4 times, which gives a mean fire interval of 66 years. At least two of these fires were probably related to human activity in the area. 2. The area can be divided into two plots - that which burned once, in 1893, referred to here as plot I, and that which was burned in both 1893 and in 1843 - plot II. The mechanical composition of the bleached horizon is identical for the two plots. Plot II has a bleached horizon thickness of 5.2 cm. The corresponding value for Plot I is 6.5 cm. Even if the difference is not significant, there is a tendeny toward a lesser thickness on plot II, which can either be traced back to a lower natural fertility or be an effect of the difference in stand history after 1843. 3. The thickness of the humus layer is 4.2 cm on plot I and 3.7 cm on plot II. This difference is significant. Both plots had a humus-layer pH value of 3.9. The levels of stored nitrogen were also fairly similar, through there is a marked tendency towards a higher amount in the humus layer on plot I. 4. On plot I, which burned in 1893 only, the coverage of bilberry and lingonberry is higher than on plot II. The opposite is true in the case of black crowberry and heather. The number of herbs and grasses and their degree of coverage is higher on plot II. The most-marked difference in vegetation occurs in the bottom layer. Plot I is here dominated by red- stemmed feather moss and glittering feather moss, with some fork moss also present. Red-stemmed feather moss and reindeer lichen are dominant on plot II. 5. The standing volume of vegetation on plot I in the spring of 1983 amounted to 257.0 forest m3/ha. The corresponding value for plot II was 238.3 for m3/ha, or 7% less. An estimate of the total volume yield between 1753 and 1982, which is unreliable for several reasons, increases the difference to 11%. 6. An examination of bore samples from 49 pines indicates that the trees on plot II were mildly favoured by the fire of 1843 (see Figures 6 & 7). This positive effect lasted for 30 years. After the 1893 fire, the positive effects on plot II were considerably greater, and can be traced for 60 years. 7. The undergrowth of spruce, which was first established after 1893, is relatively the same, numerically speaking, on both.....