<Fig. 5>
The spatial patterns of the SOC changes during the three time periods
were presented in Fig. 5. In the first two decades (1980-2000), the
areas with relatively large SOC increments (> 5 g
kg-1) were mainly distributed in the north (along the
Yangtze River) and southwest of the study area, while the areas with
relatively large SOC decrements (> 5 g
kg-1) were scattered in the northeastern parts (brown
areas in Fig. 5a). Changes in the SOC contents in the major croplands of
the study area varied from -12.4 to 15.1 g kg-1. In
contrast, the SOC contents for most of the study area decreased during
the period of 2000-2015; in particular, the areas with SOC decrements
> 5 g kg-1 expanded significantly (mainly
located in the east, Fig. 5b). A slight decrease in the SOC contents
(decrement< 3 g kg-1) across the study area
could be intuitively observed (yellow areas), while the increases in SOC
mainly occurred in the northeastern, northwestern, and southeastern
parts of study area (green areas in Fig. 5b), with a small increment of
less than 5 g kg-1. Over the entire 35 years (Fig.
5c), changes in the SOC contents in the topsoil of the major croplands
varied from -21.3 to 10.2 g kg-1, and the SOC for most
parts of the study area increased, except for that in the southeastern
parts (close to Changshu city), where SOC declined significantly (with
SOC decrement > 5 g kg-1).
3.4 Probability of SOC increase/decrease