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).