Armillaria species in coniferous stands

Identification of the Armillaria species in selected coniferous stands (Scots pine stands, Norway spruce stands and fir stands) was the aim of the work carried out on the basis of mating tests and consideration of macroscopic traits of fruit bodies. One species of Armillaria [ A. ostoyae (Romagnesi) Herink] was found in Scots pine stands, three species [ A. ostoyae, A. cepistipes Velenovský and A. borealis Marxmüller et Korhonen] were found in Norway spruce stands and two species [ A. ostoyae and A. cepistipes ] were found in fir stands.

The objectives of the present study were to identify Armillaria species in selected coniferous stands: Scots pine stands, Norway spruce stands and fir stands in Poland and to determine the occurrence of Armillaria species considering forest habitat (according to Polish forest site typology) and stand age classes.

MATERIALS AND METHODS
Material (samples) consisted of fruit bodies of Armillaria, fragments of wood colonized by mycelium of Armillaria and rhizomorphs. Samples were taken from experimental one-time-sampled plots of 500 m 2 each (20x25 m) established in production stands: Scots pine stands, Norway spruce stands and fir stands. The stands were ACTA MYCOLOGICA Vol. 42 (2): 211-217 2007 Dedicated to Professor Alina Skirgiełło on the occasion of her ninety-fifth birthday chosen on the basis of data obtained from questionnaires of the annual forest state assessments informing about the area of stands infested by root rot of Armillaria, inventory documents and the author's own observations.
One hundred and five plots were established in the Scots pine stands, situated within the territory of 52 Forest Districts (Fig. 1A). On each plot 1 to 10 samples were taken in 1985, 1989-94 and 1996-1998. Fifty plots were established in the Norway spruce stands, situated within the territory of 17 Forest Districts, 1 -in Gorce National Park and 1 -in Krynica Experimental Forest. On each plot 1 to 15 samples were taken in 1981, 1989, 1991, 1994, 1996-98 and 2001-03. Fifteen plots were establish in the fir stands, situated within the territory of 5 Forest District, 1 -in Gorce National Park and 1 -in Rotocze National Park. On each plot 1-12 samples were taken in 1991, 1994, 1996 and 1998. Characterization of the stands and samples is presented in table 1.
The identification of Armillaria isolates was performed by using mating tests (K o r h o n e n 1978). Fruit bodies of Armillaria were identified on the basis of the macro-and microscopic features (Ro m a g n e s i , M a r x m ü l l e r 1983).    -Only one species of Armillaria -A. ostoyae was found in the Scots pine stands, three species: A. ostoyae, A. cepistipes and A. borealis were found in the Norway spruce stands and two species: A. ostoyae and A. cepistipes were found in the fir stands (Fig. 1B). In the Norway spruce stands, among the identified isolates and fruit bodies belonging to genus Armillaria, the species A. ostoyae attained the highest proportion -85,5%. The remaining ones were less frequent: A. borealis -11,4% and A. cepistipes -3,1%. In the fir stands share of A. ostoyae was 51,2% and share of A. cepistipes was 48,8%. In the Scots pine stands the species A. ostoyae was found in six forest site types, mainly in fresh mixed coniferous forest (Tab. 4). In the Norway spruce stands all the three identified species were found in fresh mixed broadleaved forest site type. The species A. ostoyae was recorded in six investigated site types. A. borealis was found in fresh broadleaved forest site type and fresh mixed broadleaved forest site type. A. cepistipes was found in fresh mixed broadleaved forest site type, mixed mountain forest site type, and mountain forest site type. In the fir stands A. ostoyae was noticed on three forest site types: upland forest, mountain forest and mixed mountain forest, A. cepistipes -in fresh broadleaved forest, upland forest, and mountain forest. A. ostoyae was found most frequently in the 1-20-year-old Scots pine stands (84,8%), in the 61-80-year-old Norway spruce stands (75,4%) and in the 101-120year-old fir stands (31,3%; Tab. 5). A. borealis and A. cepistipes were noticed mainly in the 41-60-year-old Norway spruce stands. A. cepistipes was collected particularly in the 101-120-year-old fir stands.

CONCLUSIONS
A. ostoyae seems to be the most frequent species of Armillaria in coniferous stands in Poland. It was found in the all investigated stands (100% in pine, 85,5% in Norway spruce and 51,2% in fir stands), in all types of forest habitat and in all stand age classes. It is in concordance with findings of many authors that A. ostoyae is responsible for most cases of A. borealis was found only in the older (41-100-years-old) Norway spruce stands in fertile forest site types (FBF, FMBF). A. cepistipes was noticed in the older Norway spruce and fir stands and in many forest site types except for weak coniferous ones. Over 50% of samples of that species were collected in the mountain sites.