Although some of the studies indicated above
were in pots and some were on soil sterilized to
remove putative native mycorrhizal fungi, it is obvious
that very large increases in growth of trees to be
used in agroforestry are possible from inoculation
with either of the main types of mycorrhizal fungi,
depending on the mycorrhizal status of the field soil.
The extent of the response will depend on the plant
species, the fungus used (notice the significant differences
between fungi in Table 2) and the particular
soil used. Note also that different results can be
obtained with different isolates of the one fungus
species and therefore one must think in terms of
particular fungus strains rather than generalizing on
species. There are also some recorded cases in
forestry of inoculated seedlings in nurseries and
planted out to the field being smaller than uninoculated
(e.g. StenstriSm et al., 1990); this may have
been due to the inoculated fungi being of lesser
effectiveness than naturally occurring ones, or to the
particular mycorrhizal fungi used being an inordinate
drain on the plant's photosynthates (e.g. of Douglas
fir seedlings, Dosskey et ai., 1990).