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.