Utveckling av gran, Douglasgran, bok och tall under skärm av hybridlärk
?Development of Norway spruce, Douglas fir beech and Scots pine with a larch
shelter wood? is a report written by Per-Olof Magnusson. The thesis is a
compulsory part of forest engineer program at ?Skogsmästarskolan?, SLU,
Skinnskatteberg, Sweden.
The purpose of this report is to describe and evaluate an experiment with hybrid
larch (Larix x eurolepis) as shelter wood, and different tree species growth and
survival depending on the density of the shelter wood. The experiment is
conducted by southern Swedish forest research centre, faculty of forestry, SLU in
Alnarp.
The hybrid larch ought to be an interesting alternative to birch (Betula sp.) as
shelterwood on suitable sites in southern Sweden. It outgrows both grass and
other vegetation quickly and is regarded to be a good shelter tree to shadow
tolerant tree species as beech and spruce. The timber prices is approximately the
same as for spruce, but straight, knot free wood can have same prizes as pine.
About 2000 hybrid larches per ha were planted 1974. After four thinnings and one
storm there?s now standing 230 trees in the dense shelter and 145 in the sparse
shelter. Below the shelters and on one open area spruce (Picea abies) were
planted in 1990.
Due to heavy gracing a fence was built spring 1993. Beech (Fagus sylvatica),
douglas fir (Psedotsuga menziesii) and pine (Pinus sylvestris) and spruce were
planted in the tree areas, a dense shelter, a sparse shelter and an open area
adjacent to the shelters.
Since these results is based on only one experiment no final conclusions can be
made, but the results give a hint on how the different tree species react on the
shelterwood density. As expected the growth of all the different tree species
increase with lesser amount of shelter wood (Fig. 2-3).
The pines bellow the shelter woods were all killed by insects or by a combination
of competition from the shelter and insects, at an early stage.
The survival lies between 72 and 97 % for all the tree species except for the
Douglas-fir. The lowest survival for Douglas-fir was below the sparse shelter
wood (36 %). Overall it looks like the mortality is greater below the sparse shelter
wood but the most probable reason for this is that the fence on this location was
broken in a couple of places and roe deer and elk has got in and graced.
You could probably see more obvious trends of survival if the experiment had
been placed in a more frost affected area. One could also speculate if the spruce
and beech would have a greater mortality without the shelter wood since grass
grew thick amongst the plants.