中国科学院重庆绿色智能技术研究院机构知识库

Understanding how P enrichment alters the quantity and quality of dissolved organic carbon (DOC) is important, because of their role in regulating the C cycle. Here, we established a four-level P addition experiment (0, 1.2,4.8, and 9.6 g Pm-2 year(-1)) in a N-limited freshwater wetland in the Sanjiang Plain, Northeast China. The aim of this study was to examine the effects of eight years of P addition on DOC concentration, SUVA(254) (Abs(254)/DOC concentration, indicating the aromaticity of DOC), C:C ratio (Abs(400)/DOC concentration, indicating the proportion of colored humic substances in DOC), and E4:E6 ratio (Abs(465)/Abs(665), indicating the molecular size of humic substances) in surface water and soil pore water (0-15 cm depth) during the growing season (June through September). Our results showed similar changing trends in concentration and optical properties of DOC following eight years of P addition in the both surface water and soil pore water across the sampling dates. Generally, P addition decreased DOC concentration, SUVA254, and C:C ratio, and increased E4:E6 ratio, irrespective of P addition levels. These altered optical properties of DOC indicated that P addition decreased the molecular weight and aromaticity of DOC, and thus increased the quality of DOC. These results suggest P enrichment substantially reduces the quantity of DOC in N-limited temperate freshwater wetlands, and imply that increased DOC quality following P addition can further provide a positive feedback to decreased DOC pool. (C) 2017 Elsevier B.V. All rights reserved.