Effects of environmental variation on stable isotope abundances during typical seasonal floodplain dry season litter decomposition

Guangshuai Zhang; Xiubo Yu; Jun Xu; Houlang Duan; Loretta Rafay; Quanjun Zhang; Ya Li; Yu Liu; Shaoxia Xia

doi:10.1016/j.scitotenv.2018.02.298

Effects of environmental variation on stable isotope abundances during typical seasonal floodplain dry season litter decomposition

Sci Total Environ. 2018 Jul 15:630:1205-1215. doi: 10.1016/j.scitotenv.2018.02.298. Epub 2018 Mar 7.

Authors

Guangshuai Zhang¹, Xiubo Yu², Jun Xu³, Houlang Duan¹, Loretta Rafay⁴, Quanjun Zhang¹, Ya Li¹, Yu Liu⁵, Shaoxia Xia⁵

Affiliations

¹ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: yuxb@igsnrr.ac.cn.
³ Donghu Experimental Station of Lake Ecosystem, State Key Lab of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.
⁴ School of Environmental and Forest Sciences, University of Washington, Seattle, Washington 98195, USA.
⁵ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.

PMID: 29554742
DOI: 10.1016/j.scitotenv.2018.02.298

Abstract

Unique hydrological characteristics and complex topography can create wide-ranging dry season environmental heterogeneity in response to groundwater level across China's Jiangxi Province Poyang Lake wetland. Soil traits are one of several fluctuating environmental variables. To determine the effects of soil variables on stable isotope (δ¹³C and δ¹⁵N) abundances during decomposition, we performed a field experiment using Carex cinerascens along a groundwater level gradient (GT-L: -25 to -50cm, GT-LM: -15 to -25cm, GT-MH: -5 to -15cm, GT-H: 5 to -5cm) in a shallow lake. Twelve soil properties-including total organic carbon (TOC), nitrogen (N), pH, moisture, bulk density, clay, silt, sand, peroxidase, cellulase, microbial biomass carbon (MBC), and microbial biomass nitrogen-were measured in surface soil samples to assess soil environmental conditions. Analyses were performed to determine the effects of soil traits and lignin degradation on changes in stable isotope abundances. This study revealed that stable isotope abundances were significantly lower at high groundwater levels than at low groundwater levels. Lignin degradation was associated with a decrease in both δ¹³C and δ¹⁵N abundances. These two stable isotopes were positively related with soil N and bulk density, but negatively with pH and microbial quotient (MBC/TOC). Variation partitioning analysis (VPA) showed that soil variables and lignin decay rates explained 80.1% of the δ¹³C variation and 42.8% of the δ¹⁵N variation. Soil chemical and biological variables exhibited significant interactions with lignin decay rates, indicating they may affect stable isotope abundances via complex mechanisms. Our results indicate that the change in stable isotope abundances during decomposition may be affected directly by soil variables or indirectly through lignin degradation. Our results provide useful insight for understanding the roles of litter decomposition and soil traits in changing environmental conditions of seasonal floodplain wetlands.

Keywords: Isotopic variation; Lignin degradation; Litter decomposition; Poyang Lake Wetland; Variation partitioning analysis.