Effect of salinity on the decomposition of soil organic carbon in a tidal wetland

Abstract

Purpose Climate warming and sea level rise have the potential to change the salt level of soil in tidal wetlands. And it is important to clarify the process and the mechanism of decomposition of soil organic carbon in a tidal wetland under varying salinities. The aim of this study was to evaluate the impacts of soil salinity on the decomposition rate of organic carbon (DROC) and dissolved organic carbon (DOC) in a tidal wetland. Materials and methods Two types of soil (surface soil in Suaeda salsa and bare tidal flat) were collected, air-dried, and homogenized. After adding different content of salt (0 g/L, 3 g/L, 6 g/L, 9 g/L, and 12 g/L), the soils were incubated for 28 days at stable room temperature (25 ± 2°C) and added by deionized water to maintain the stability of soil moisture. The gases (CO 2 and CH 4 ) emission rates of each salt treatment were measured during 28-day incubation. DROC was determined by the sum of daily CO 2 -C emission rates and daily CH 4 -C emission rates in this study.Results and discussion Salt addition inhibited the process of gas emissions and DROC. Gases emission rates and DROC of two types of soil showed similar temporal trends, with distinctive drop in the beginning of experiment and no significant decrease followed. Significant difference of DOC among salt treatments was found in the bare tidal flat soil. Variations of partial correlation between DROC and soil salinity and DOC showed similar trends (e.g., in days 9-18, the positive effect of DOC on DROC was greatly promoted (R 2 = 0.80, p < 0.001), and the negative effect of soil salinity was highly improved (R 2 = 0.93, p < 0.001)). Soil properties, in particular DOC, may be primary factors accounting for the discrepancy of gases emission rates and DROC of two types of soil. Conclusions Increased soil salinity had a negative effect on DROC during 28-day incubation. The impact of soil salinity and DOC on DROC were varied in different phases of laboratory experiment (soil salinity generally had increasingly negative relationship with DROC, but DOC showed most significantly positive relationship in the middle stage of incubation). Both the formation and consumption of DOC may be valuable for more detail research regarding to decomposition of soil organic carbon.Keywords Dissolved organic carbon (DOC) . CH 4 . CO 2 . Salinity . Tidal wetlands

The integrated effect of salinity, organic amendments, phosphorus fertilizers, and deficit irrigation on soil properties, phosphorus fractionation and wheat productivity

“…N, P and K), due to higher salinity caused by less irrigation than evapotranspiration, particularly in the highly saline soil. Consequently, highly saline soils occur frequently in combination with DI and drought, thus causing negative impacts on microbial activity 23 , organic matter decomposition 24 , and decreased availability of N, P and K in soil. Application of P fertilizers combined with organic amendments is considered a successful management tool, improving the availability of soil macronutrients, especially under salinity or drought stress.…”

Distribution, sources, and decomposition of soil organic matter along a salinity gradient in estuarine wetlands characterized by C:N ratio, δ13C‐δ15N, and lignin biomarker

“…Salinity is a prevalent environmental stressor with a great potential to affect C source and sink functions in coasts and estuaries (Morrissey et al., 2014; Qu et al., 2019; Stagg et al., 2017). Previous studies have revealed that SOM contents depend mainly on plant functional traits (Han et al., 2020; Jobbagy & Jackson, 2000).…”

“…Response patterns of organic C accumulation to increasing salinity may be increased, decreased, or unchanged (e.g., Chambers et al., 2013; Liu, Li, et al., 2017; Liu, Ruecker, et al., 2017; Liu, Zheng, et al., 2017; Neubauer et al., 2013; Qu et al., 2019; Zhao et al., 2017), which is attributed to varying spatial and temporal scales of exposure to salinity. On a small scale, the factors regulating C accumulation under a salinity gradient mainly include vegetation type/coverage, soil texture, pH, and bulk density (BD; Chambers et al., 2011; Zhao et al., 2018).…”

“…The effect of salinity and vegetation on SOC stability is rather complex. For example, some studies observed the highest decomposition rates in most saline wetlands (e.g., Chambers et al., 2011; Marton et al., 2012), whereas others reported the highest decomposition rates in freshwater tidal wetlands (e.g., Qu et al., 2019) or no direct salinity effects (e.g., Liu, et al., 2017; Mendelssohn et al., 1999). Thus, information about differentiating numerous confounding variables affecting in situ SOC decomposition rates is necessary while isolating the effect of salinity on SOC turnover may be better discerned.…”

Effects of Drying-Rewetting Frequency on Vertical and Lateral Loss of Soil Organic Carbon in a Tidal Salt Marsh

“…Dissolved organic carbon (DOC) is recognized as one of the dominant forms of lateral carbon loss from terrestrial ecosystems to aquatic ecosystems (Billett et al 2010;D'Amore et al 2015). Besides, as a labile component of SOC, DOC is still found to have a close correlation with soil carbonic greenhouse gas formations (Fellman et al 2017;Liu et al 2017;Lee et al 2018;Qu et al 2018). Thus, both lateral and vertical carbon loss from tidal salt marshes soil to ocean and atmosphere, respectively, should be considered into "blue carbon" loss of salt marshes.…”