Norway spruce needles were sampled from two series of stand
areas located in southern Finland. Both series consisted of five
sampling areas in mature managed stands and one in a mature virgin stand.
The proportion of spruce varied from 8 to 100% of the
basal tree area and the major other species were pubescent birch and Scots
pine.
From each sampling area (some of which consisted
of several sites) 40 mature spruces were randomly chosen and healthy looking
needles of the third age class were sampled from
heights of 5–8 m and incubated on water agar for isolation of endophytic
fungi.
The majority of isolates were identified by their combined fatty acid
and sterol profiles (FAST-profiles) as Lophodermium piceae.
Tiarasporella parca was less common and Rhizosphaera kalkhoffii,
Sclerophoma pythiophila, Lirula macrospora and Thysanophora
penicillioides occurred occasionally. For calculations of fungal diversity
all isolates were classified by their FAST-profiles into 81
groups (=operational chemotaxonomic units) according to a defined upper
variation limit, i.e. an upper FAST-profile mismatch limit.
The highest percentage of endophytically infected needles was found
in
pure spruce stands and dense virgin stands. Location of
the stand, its proportion of spruce and total basal area of trees (i.e.
tree density) explained 82% of the variation of the overall
infection rate. The effect of location was probably a consequence of
differences in air quality between the various sampling areas.
The endophyte diversity, expressed as the number of FAST-groups per
40 spruces of each sampling area, correlated positively
and statistically significantly with the percentage of needles infected
or with the proportion of spruce in the stand. The highest
endophytic diversity, expressed as FAST-groups per tree, was found in
pure spruce and mixed virgin stands.