untitled

succession, with “pioneer” mycorrhizal species colo-

nizing the youngest parts of the root system and being

replaced successively by other mycorrhizal species in

the older root regions.

These distribution patterns, in which mycorrhizas of

“pioneer” or “early” fungi are found at the periphery of

the root system, but are replaced by later colonizers

(characteristic of older trees) near the tree base, were

explained by two types of experiment.

First, basidiospores were collected from fruitbodies of

either “pioneer” or “later” mycorrhizal fungi and were

added to pots of nonsterile soil. Then aseptically

FUNGAL SPORES, SPORE DORMANCY, AND SPORE DISPERSAL 187

Fig. 10.3Rings of toadstools of mycorrhizal fungi (mainly Hebelomaand Lactariusspecies) around young birch trees in
late autumn in an experimental field plot.

(a) (b)

700

600

0

25 50 75 100

Distance from base of tree (cm)

500

400

300

200

100

Number of root tips

Hebeloma

Lactarius

Leccinum

Unknown

Others

Fig. 10.4The changing pattern of naturally occurr-

ing mycorrhizal fungi at different distances from the

bases of birch trees in an experimental field plot.

(Data from Deacon et al. 1983.)