Concentration dynamics and biodegradability of dissolved organic matter in wetland soils subjected to experimental warming.
Dissolved organic matter (DOM) is the most bioavailable soil organic pool. Understanding how DOM responds to elevated temperature is important for forecasting soil carbon (C) dynamics under climate warming. Here a 4.5-year field microcosm experiment was carried out to examine temporal DOM concentration dynamics in soil pore-water from six different subtropical wetlands. Results are compared between control (ambient temperature) and warmed (+5°C) treatments. UV-visible and fluorescence spectroscopy was performed to reveal DOM structural complexity at the end of the warming incubation. Elevated temperature resulted in initially (1 to 2.5 years) high pore-water DOM concentrations in warmed samples. These effects gradually diminished over longer time periods. Of the spectral indices, specific UV absorbance at 280 nm and humification index were significantly higher, while the signal intensity ratio of the fulvic-like to humic-like fluorescence peak was lower in warmed samples, compared to the control. Fluorescence regional integration analysis further suggested that warming enhanced the contribution of humic-like substances to DOM composition for all tested wetlands. These spectral fingerprints implied a declined fraction of readily available substrates in DOM allocated to microbial utilization in response to 4.5 years of warming. As a negative feedback, decreased DOM biodegradability may have the potential to counteract initial DOM increases and alleviate C loss in water-saturated wetland soils.
College of Natural Resource and Environmental Sciences, China Academy of West Region Development, ZheJiang University, Yuhangtang Avenue 688, HangZhou, ZheJiang Province, 310058, China.
Hang
H
Wang
water@leeds, School of Geography, University of Leeds, Leeds LS2 9JT, UK.
Joseph
J
Holden
College of Natural Resource and Environmental Sciences, China Academy of West Region Development, ZheJiang University, Yuhangtang Avenue 688, HangZhou, ZheJiang Province, 310058, China. Electronic address: zhangzhijian@zju.edu.cn.
Zhijian
Z
Zhang
College of Natural Resource and Environmental Sciences, China Academy of West Region Development, ZheJiang University, Yuhangtang Avenue 688, HangZhou, ZheJiang Province, 310058, China.
Meng
M
Li
College of Natural Resource and Environmental Sciences, China Academy of West Region Development, ZheJiang University, Yuhangtang Avenue 688, HangZhou, ZheJiang Province, 310058, China.
Xia
X
Li
D001673:Biodegradation, Environmental; D004784:Environmental Monitoring; D006358:Hot Temperature; D006812:Humic Substances / Q000032:analysis*; D012987:Soil / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
D006812:Humic Substances; D012987:Soil; D014874:Water Pollutants, Chemical
Dissolved organic matter; Fluorescence; Microbial utilization; Soil carbon; Soil warming; Wetland