Negative Feedback by Vegetation on Soil Organic Matter Decomposition in a Coastal Wetland
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DEGRADATION AND ECOLOGICAL RESTORATION OF ESTUARINE WETLANDS IN CHINA
Negative Feedback by Vegetation on Soil Organic Matter Decomposition in a Coastal Wetland Qingyuan Lu 1 & Lixin Pei 2,3 & Siyuan Ye 2,3
&
Edward A. Laws 4 & Hans Brix 5
Received: 5 May 2020 / Accepted: 28 July 2020 # Society of Wetland Scientists 2020
Abstract There has been much debate about the external drivers that affect the decomposition of soil organic matter (SOM). Particularly, the feedback mechanisms between SOM and mineral weathering are poorly understood. We used the cotton strip assay combined with measurements of water table, pore water salinity, and soil properties along a landscape-scale gradient to study these mechanisms. The results revealed that cotton tensile strength loss (CTSL) rates ranged from 2.0% day−1 to 4.6% day−1 and varied significantly among sites and depths. A multiple regression model revealed that the corelation between the CTSL and submersion duration (SD) was positive when the chemical index of alteration (CIA) was ~65% and negative over most of the range of SD when the CIA was ~45%. The results suggest that the hydrological conditions induced by tidal effects endanger the stocks of carbon sequestered in coastal wetland soils. However, sites with CTSL rates as high as 4.0–5.0% day−1 tended to gain more nutrients than sites with lower CTSL rates. The fixation of atmospheric CO2 via plant growth may therefore be stimulated in coastal wetland soils by the recycling of mineral nutrients via enhanced weathering. The result is a negative feedback of the ecotone on SOM decomposition. Keywords Soils . Mineral weathering . Sea level rise . Coastal wetlands
Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13157-020-01350-0) contains supplementary material, which is available to authorized users. * Siyuan Ye [email protected] 1
Institute of Environmental and Biogeochemistry (eBig), School of Earth Sciences, Zhejiang University, Hangzhou 310027, China
2
Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, People’s Republic of China
3
Key Laboratory of Coastal Wetlands Biogeosciences, Qingdao Institute of Marine Geology, China Geologic Survey, Qingdao, People’s Republic of China
4
Department of Environmental Sciences, College of the Coast & Environment, Louisiana State University, Baton Rouge, LA 70803-4110, USA
5
Department of Bioscience, Aarhus University, 8000C Aarhus, Denmark
Coastal wetlands are ecotones impacted by the tides. They sequester organic carbon at remarkably high rates that average of 245 g carbon m−2 year−1 (Ouyang and Lee 2014) because of their high rates of plant production and low rates of organic matter decomposition (Craft 2008). The carbon they sequester has recently been known as “blue carbon” (McLeod et al. 2011). Coastal wetlands are important carbon sinks, and changes in the rates at which they decompose carbon could have large impacts on the global carbon cycle a
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