3.1. SWC variability with landcover types
SWC data collected from 10 sampling plots across different landcover
types are shown in Fig. 3 and Table 2. Data for each plot conform to
normal distribution, with the absolute value of Skewness andKurtosis of < 1. There were some differences (from 9.01
to 16.55 cm3 cm-3) in surface SWC
corresponding to various landcover types, but most were not significant.
For example, brushland (15.81 cm3cm-3) exhibited significant differences compared with
planted forest (12.28 cm3 cm-3) and
grassland (13.30 cm3 cm-3) (plot #6
in Fig. 3), and grassland (13.35 cm3cm-3) also exhibited unnoteworthy compared with
planted and mixed forests (10.53 cm3cm-3) (plot #9 in Fig. 3). The differences between
natural (16.5 cm3 cm-3) and planted
forests (11.82 cm3 cm-3) were
notable (mean value between plot #10 and plot #2).
To further quantify SWC differences among the landcover types, SWC was
summarized using SPSS by landcover type (Fig. 4). Results showed a
decreasing trend from natural forest, brushland, grassland and planted
forest to mixed forest, representing changes in SWC over several decades
of plantation succession in this semi- and arid region. SWC in planted
forest and mixed planted forest was lower than that in the brush and
grass areas, with the only significant difference found between the
natural forest and other landcover types.
Furthermore, standard deviations in natural forest (plot #10) and
planted forest (plot #1) were 6.16 cm3cm-3and 3.5 cm3cm-3, respectively; while in brushland and grassland
(plot #8 and #3), they were 1.18 cm3cm-3 and 2.62 cm3cm-3, respectively (Table 2). A larger standard
deviation indicated that the forest had greater water storage capacity
compared to other two landcover types.