ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

CLEAR- CUT
THOUSAND
3 YEARS AFTER HARVEST. 2 YEARS AFTER BURN
Figure 18.-- Based on average numbers of ectomycorrhizai! root tips (per
acre), caZcuZuted porn same swllpZes as in figure 17, ectornporrhizae
are divided by the basaZ area of the Zive tree stms (per acre) re-
maining on the site. *Increase not signif$cant at p = 0.05.
As was the case in a partial cut situation, clear-cutting reduced ectornycorrhizal
tips in direct proportion to the loss of trees. When all the trees were removed,
active ectomycorrhizae were eliminated. However, low numbers of active ectomyc-
orrhizal tips persisted on residual roots until July following a fall harvest
(fig. 19). Similarly, the number of active ectomycorrhizal tips dropped when we
sampled from an undisturbed stand into an adjacent cl ear-cut-broadcast burn two
years after treatment (fig. 20). In fact, the presence of the clear-cut burn
appeared to reduce ectomycorrhital tips in the bordering uncut stand. This finding
agrees with the previously noted suppression effect of broadcast burns in partial
cuts.
How long this reduction of ectomycorrhizal tips on burned sites may be is not
known. However, we suspect that the burn-related reduction is caused by the
increase in soil reaction following fire (Jurgensen and others 1980). This shift
in soil reaction was as much as a full pH unit and on one experimental site values
were higher than the control even after four years.