3.1 Soil physical-chemical properties
PCA of the soil physical-chemical variables among the five forest states (n = 25) identified two principal components (PC) which together explained 87.8% and 69.2% of the total variance in the dry and rainy season, respectively (Fig. 2). Represented by cluster centroids (i.e., the average score on both PC1 and PC2 with standard errors), the forest states were aligned in the two-dimensional PC space along a gradient of ecosystem degradation from natural, semi-natural, simplified and shrub-dominated forests to arid land. In both seasons, natural and semi-natural forest were associated with high levels of C/N, TOC, TN and WSC as opposed to simplified forest, shrub-dominated forest and arid land, which were associated with low levels of these parameters. In general, these variables declined with ecosystem degradation. For example, TOC on average showed a significant reduction of 15, 37, 54, and 68% and TN decreased significantly by 11, 32, 47 and 55% from natural forest to semi-natural, simplified, shrub-dominated forests, and arid land, respectively (Table 1). Likewise, WSC decreased significantly by 3, 19, 29 and 42% along the same gradient. In contrast, SWC, pH, EC and C/N did not decrease significantly along the gradient although arid land was consistently and, in some cases, significantly lower than natural and/or semi-natural forest for these variables.
In terms of seasonal differences, in the rainy season, natural, semi-natural and simplified forest were clustered with overlapping standard errors while shrub-dominated forest and arid land were separated from this cluster (Fig 2). Variation in the PC1 and PC2 scores of each forest state, as measured by the size of the centroids, was generally greater in natural, semi-natural and simplified forest than shrub-dominated forest and arid land and during the rainy season compared to the dry season. The only soil properties that differed significantly between seasons were SWC and WSC, which, on average, increased by 42.2% ± 5.1 and decreased by 58.7% ± 1.4 across all forest states from the dry to the rainy season, respectively.