title: Contrasting effects of elevated CO2 and warming on temperature sensitivity of soil organic matter decomposition in a Chinese paddy field.
abstract: Climate changes including elevated CO2 and temperature have been known to affect soil carbon (C) storage, while the effects of climate changes on the temperature sensitivity of soil organic matter (SOM) are unclear. A 365-day laboratory incubation was used to investigate the temperature sensitivity for decomposition of labile (Q 10-L) and recalcitrant (Q 10-R) SOMs by comparing the time required to decompose a given amount of C at 25 and 35 °C. Soils were collected from a paddy field that was subjected to four treatments: ambient CO2 and temperature, elevated CO2 (500 μmol/mol), enhanced temperature (+2 °C), and their combination. The results showed that the temperature sensitivity of SOM decomposition increased with increasing SOM recalcitrance in this paddy soil (Q 10-L = 2.21 ± 0.16 vs. Q 10-R = 2.78 ± 0.42; mean ± SD). Elevated CO2 and enhanced temperature showed contrasting effects on the temperature sensitivity of SOM decomposition. Elevated CO2 stimulated Q 10-R but had no effect on Q 10-L; in contrast, enhanced temperature increased Q 10-L but had no effect on Q 10-R. Furthermore, the elevated CO2 combined with enhanced temperature treatment significantly increased Q 10-L and Q 10-R by 18.9 and 10.2 %, respectively, compared to the ambient conditions. Results suggested that the responses of SOM to temperature, especially for the recalcitrant SOM pool, were altered by climate changes. The greatly enhanced temperature sensitivity of SOM decomposition by elevated CO2 and temperature indicates that more CO2 will be released to the atmosphere and losses of soil C may be even greater than that previously expected in paddy field.
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Zhaozhi
authors: Z
authors: Chen
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Bingyu
authors: B
authors: Wang
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Jinyang
authors: J
authors: Wang
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Genxing
authors: G
authors: Pan
authors: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China. zqxiong@njau.edu.cn.
authors: Zhengqin
authors: Z
authors: Xiong
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis*; D057965:Carbon Sequestration; D002681:China; D057231:Climate Change; D004784:Environmental Monitoring; D006358:Hot Temperature; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D012987:Soil; D002245:Carbon Dioxide
keywords: Global change; Paddy field; Soil organic matter decomposition; Soil organic matter quality; Temperature sensitivity