while in the H horizon it was higher in August. The content of total
and bacteria-specific PLFA was found to significantly correlate with
soil moisture content in both horizons and at both sampling times
(Table 2). Although the content of fungi-specific PLFA was not significantly
affected by soil moisture in the H horizon in August, the
other marker of fungal biomass content, ergosterol, was affected.
The differences in soil or litter moisture content explained a substantial
portion of the total variability, typically above 10% and, in
some cases, even more than 50% (Table 2). Despite higher variation,
the content of most of the individual PLFA molecules also significantly
decreased with decreasing soil moisture content in both
horizons (data not shown).
The activity of all enzymes in all treatments also tended to
decrease with decreasing soil moisture content, but due to higher
variability of enzyme activities and their lognormal rather than normal
distribution, fewer correlations were statistically significant.
Acid phosphatase activity significantly correlated with soil moisture
content in both soil horizons at both sampling times while
the other enzyme activities only showed significant response to
soil moisture content in particular cases (Table 2). The responses of
other enzymes were more season- and horizon-specific, but all of
them were affected in at least one season and horizon. The effect of
soil moisture was more pronounced in the L horizon in May and in
the H horizon in August, seasons when F/B ratio in these horizons
was higher. Up to 29% of total variability of enzyme activity could
be explained in individual cases by the differences in soil moisture
content.
Activity of some enzymes also exhibited significant correlations
with the amount of microbial biomass in soils (Table 3). In all cases,
the content of fungi-specific PLFA correlated more closely with
enzyme activity than the content of bacteria-specific PLFA. Fungispecific
PLFA content was an especially good predictor of enzyme
activities in the H horizon in August.
The above results show that there is a significant effect of soil
moisture content on soil microbial biomass and enzymatic processes.
Linear regression models were used to calculate the extent
of these effects on individual parameters. The results demonstrated
that the total and bacteria-specific PLFA content in the dry patches
of soil may represent only 17–63% of the values in the moist soil
patches (Table 4), and the difference between dry and moist samples
was at least 15–69% at a 95% probability level. The effect of
soil moisture content on enzyme activities is more seasonal, as
stated above, but the effect of soil moisture content may result
in great differences in enzyme activities, often greater than 50%
when comparing the dry and moist patches. Since the quantitative
response of fungi-specific and bacteria-specific PLFA to moisture
content was different, the quantitative composition of microbial
community was also affected by soil moisture content: the F/B ratio
significantly increased with soil moisture content in the L horizon
sampled in May (Table 2, Fig. 1).