Norra Hörken is a lake situated between Ludvika and Ljusnarsberg Municipalities in central Sweden. This page shows some ecological aspects of a small wild fire in a rather typical Scandinavian forest. This wildfire occurred in summer 2006 (probably July), according to dendrochronological analysis. A search in the local newspaper for the actual period did not give any further information.
Over wiew of the wildfire area on a ridge between a road and the lake Norra Hörken
Coring dead Picea abies for dendrochronological analysis
The same woodsample now prepared and measured. It contained growth rings from 1910 to the summer 2006. The outermost ring shows that this spruce was killed by the fire sometime at midsummer, or not too long after, 2006. While the core was taken at breast height and the pitch was not hit, the tree was at least 100 years old when died. So this dates the fire to high-summer 2006 and the forest than was around 100 years. (Measurements available in the image description file)
All the Picea abies were killed by fire, while some (but not all) Pinus sylvestris survived with scars and severe foliage reduction.
The damaged bark of Pinus sylvestris falling down, leaving an open scar
At the downwind side of the tree the temperature become so high that the cambium does not survive. This will invite some insects causing the bark falling of, and leaving a scar. If enough bark will remain alive the tree will survive and a fire scar will be possible to see for hundreds of years (if the tree is not cut down before that).
Increased resin production according to fire damage without visible scar in Pinus sylvestris. This pine standing just at the border or the wild fire area, so the temperature was less high.
The ground covered with Pinus sylvestris foliage. Most of the foliage was damaged by the fire, and fall down afterwards, when the fire was already over. The roots of Populus tremula did survive and new plants now grows rapidly.
After the wild-fire new plants of Pinus sylvestris grows. This first year only a few plants, but soon the surviving pines will put a lot of cones and seed the ground. So in a few years we will assume many more young pine tree plants.
Prepared wood sample of wild fire damaged Pinus sylvestris. Growth rings from 1914-2009 (and the very beginning of 2010 years early wood). The pine was cored from bark to bark with a Haglöf's 5 mm*400 mm increment borer. The pine was damaged by the fire in high summer (midsummer or early? July) 2006. One side died, but the other one is still alive. In the dead side the sap wood is affected by blue stain. The the heavily increasing growth rate already from late summer 2004 (late wood but not early wood that year), indicates that the trees around were cut at least two years before the fire. The growth rate in the healthy side of the tree seem not being very much affected by the fire event. The pith was missed with about 10 mm or 1-4 rings.
Ring width diagram for two radii of a partial fire damaged pine (Pinus sylvestris). from latewood 2004 the growth rate increase strongly indicating removal of neighbor trees. 2005 is the last complete ring for the dead side but there are also a early wood ring for 2006 not measured.
The living side of the cored pine, early summer four years after the fire. The wood inside seems not affected at all by the heat that killed almost half of the tree. The surrounding stumps was trees cut at least two years before the fire.
The dead side of the cored pine. Note that the bark is still present but the wood inside is dead. Resin flow is only present at the sides where the heat was not that strong, and the xylem survived.