水保所知识产出(1956---)知识库

The effects of cropland abandonment on soil enzyme activity and soil organic carbon (SOC) stability, along with
the driving factors, are poorly understood. Here, we aimed to systematically and comprehensively evaluate soil
enzyme activity, SOC stability, and the associated driving factors in different vegetation zones after cropland
abandonment on the Loess Plateau, China. We selected grasslands with different recovery times along a rainfall
gradient encompassing the steppe zone (SZ), forest-steppe zone (FSZ), and forest zone (FZ). We measured and
compared the changes in soil enzyme activity (saccharase, polyphenol oxidase, urease, phosphatase, and cata-
lase) and SOC stability as a function of recovery time; we also evaluated the relationships between these two
parameters. In SZ and FSZ, soil enzyme activity, fractions of oxidizable carbon (including very labile [C1], labile
[C2], and less labile [C3]), and the carbon management index (CMI) increased with recovery time, whereas the
SOC stability index (SI) decreased. Conversely, in FZ, polyphenol oxidase activity increased linearly, urease and
catalase activities decreased linearly, and the change in saccharase activity was represented by a cubic equation
regression. SI showed no obvious changes with recovery time, whereas C1, C2, and C3 initially decreased and
then increased. Redundancy analysis showed that, in FSZ and FZ, soil enzyme activity, C1, C2, C3, and SI were
influenced by vegetation diversity, coverage, and soil nutrient levels. In comparison, in SZ, these parameters
were mainly influenced by soil nutrient levels. Soil enzyme activity was strongly correlated with C1 and C3 in SZ
and FSZ, but not in FZ. Overall, in SZ and FSZ, soil enzyme activity increased with recovery time, whereas SOC
stability decreased. In contrast, both parameters were relatively stable in FZ, which had higher mean annual
precipitation and mean annual temperature.