The
direct and legacy effects of drying-rewetting cycles on active and
relatively resistant soil carbon decomposition
Shuai Zhanga,b, Junjie Lina*, Peng
Wangc, Biao Zhud*
- Chongqing
Key Laboratory of Water Environment Evolution and Pollution Control in
Three Gorges Reservoir,
Chongqing Three Gorges
University, Chongqing 404100, China
- College of environmental and resource sciences, Zhejiang University,
Hangzhou, Zhejiang 310058, China
- Key Laboratory of Forest Ecology and Management, Institute of Applied
Ecology, Chinese Academy of Sciences, Shenyang 110016, China
- Institute of Ecology, College of Urban and Environmental Sciences, and
Key Laboratory for Earth Surface Processes of the Ministry of
Education, Peking University, Beijing 100871, China
*Corresponding authors: Dr. Junjie Lin and Dr. Biao Zhu
E-mail addresses:junjielin@sanxiau.edu.cn(J. Lin) and biaozhu@pku.edu.cn(B. Zhu)
Abstract: Global climate change is expected to increase the
frequency of drought and heavy precipitation, which could create more
frequent drying-rewetting cycles (DWC) in the soils. Although the DWC
effects on soil organic carbon (SOC) decomposition has been widely
studied, the effect of DWC and the
subsequent legacy effect on the decomposition of different SOC pools is
still unclear. We conducted a
128-d laboratory incubation to investigate the DWC effects by using
soils from old-field for 15 years (OF, representing active SOC),
bare-fallow for 15 years (BF), and bare-fallow for 23 years plus extra
815-d incubation (BF+, representing relatively resistant SOC). The
experiment included nine 10-d DWC of three treatments: 1) one mean
constant-moisture at 60% water-holding capacity (WHC), 2) a mild DWC
with 10-d drying to 40% WHC and immediately rewetting to 80% WHC, and
3) a strong DWC with 10-d drying to 20% WHC and immediately rewetting
to 100% WHC. Following the DWC period (0-90 d), there was a 10-d
stabilization period (adjusting all treatments to 60% WHC), and then a
28-d extended incubation under the constant moisture of 60% WHC. During
the DWC period, the strong DWC had
a strong effect on CO2 release compared with the
constant-moisture control, reducing the SOC decomposition from OF by 8%
and BF by 10%, while increasing the SOC decomposition of BF+ by 16%.
In addition, during the extended period, both mild and strong DWC
significantly increased SOC mineralization of OF, but decreased that of
BF and BF+. This legacy effect induced by DWC compensated the changes in
CO2 release during the DWC period, resulting in the
minor response of SOC decomposition of OF and BF+ to the DWC during the
entire incubation. Together, DWC could create both direct and legacy
effects, and these effects vary with DWC intensity and SOC pools.
Keywords : Drying-rewetting; Soil carbon pool; Soil organic
matter; Soil respiration; Legacy effect
Abbreviations : DWC – drying-rewetting cycles; OF – old-field;
BF – bare-fallow; BF+ – bare-fallow + incubation; C – carbon;
CO2 – carbon dioxide; SOC – soil organic carbon; MBC
– microbial biomass carbon; DOC – dissolved organic carbon; TC –
total carbon; TN – total nitrogen; C/N – the ratio of carbon to
nitrogen; F:B – the ratio of fungi to bacteria.