3.2 Enzymatic activity
Enzymatic activity generally declined with ecosystem degradation
although differences among forest states were more exacerbated during
the dry season (Fig. 3). Dehydrogenase and β-glucosidase in both seasons
declined significantly and at a near constant rate with increasing
degradation from natural forest to arid land. Relative to natural
forest, dehydrogenase activity decreased by 33, 64 and 70% on average
in simplified forest, shrub-dominated forest and arid land, respectively
for the dry season whereas for the rainy season this enzyme activity was
reduced by 11, 22, 28 and 62% from the natural forest compared to
semi-natural, simplified, shrub-dominated forests and arid land
respectively (Fig. 3a). β-glucosidase activity declined by 12, 41, 62
and 72% on average for both seasons among the natural forest and the
gradient of forest degradation (Fig. 3b). In each case, the difference
between natural and semi-natural forest was not significant. Urease
activity followed the same trend, although the only significant
difference was in arid land, where the activity was approximately 63 and
72% less on average compared to the other states for the dry and the
rainy seasons respectively (Fig. 3c).
Overall, the rainy season entailed both a reduction in soil enzymatic
activity and a weakening of the association between enzymatic activity
and most soil properties compared to the dry season. Dehydrogenase and
urease activity declined significantly by 63% and 33% in the rainy
season relative to the dry season across all forest states, respectively
(Fig. 3). β-glucosidase activity also decreased in the rainy season but
this difference (12%) was not significant. During the dry season, the
activity of the three enzymes was significantly and positively
correlated with all soil properties except the POC/MAOC ratio, which
showed a significant negative correlation, and pH, which was not
significantly correlated with urease activity (Fig. S1a). During the
rainy season, the correlation between both dehydrogenase and
β-glucosidase activity and SWC, pH, EC and POC/MAOC was no longer
significant, while the correlation between urease activity and most
properties remained significant but less so (Fig. S1b).