Landscape Change Affects Soil Organic Carbon Mineralization and Greenhouse Gas Production in Coastal Wetlands

Abstract

Plant invasion and aquaculture activities have drastically modified the landscape of coastal wetlands in many countries, but their impacts on soil organic carbon (SOC) mineralization and greenhouse gas production remain poorly understood. We measured SOC mineralization rate and soil CO2 and CH4 production rates in three habitat types from 21 coastal sites across the tropical and subtropical zones in China: native mudflats (MFs), Spartina alterniflora marshes (SAs), and aquaculture ponds (APs). Landscape change from MFs to SAs or APs increased total and labile fraction of SOC, as well as carbon mineralization rate and greenhouse gas production, but there were no discernible differences in SOC source‐sink dynamics between SAs and APs. SOC mineralization rate was highest in SAs (20.4 μg g−1 d−1), followed by APs (16.9 μg g−1 d−1) and MFs (11.9 μg g−1 d−1), with CO2 as the dominant by‐product. Bioavailable SOC was less than 2% and was turned over within 60 days in all three habitat types. Proliferation of S. alterniflora marshes and expansion of AP construction had resulted in a net increase in soil CO2‐eq production of 0.4–4.3 Tg yr−1 in the last three decades. Future studies will benefit from better census and monitoring of coastal habitats in China, complementary in situ measurements of greenhouse gas emissions, and more sampling in the southern provinces to improve spatial resolution.

Latitudinal responses of wetland soil nitrogen pools to plant invasion and subsequent aquaculture reclamation along the southeastern coast of China

“…Earlier studies showed that landscape transformation may impact the organic and inorganic pools of the soil differently, and that the soil greenhouse gas production and emission may respond in an unexpected way. For example, invasion of mudflats by S. alterniflora has been shown to increase soil organic carbon concentration but decrease inorganic carbon concentration, whereas subsequent removal of S. alterniflora to create aquaculture ponds caused the opposite changes (Duan et al, 2023;Yang et al, 2022a;Hong et al, 2023). Similar changes were also observed in soil organic carbon mineralization rate (Yang et al, 2022a;Hong et al, 2023).…”

“…For example, invasion of mudflats by S. alterniflora has been shown to increase soil organic carbon concentration but decrease inorganic carbon concentration, whereas subsequent removal of S. alterniflora to create aquaculture ponds caused the opposite changes (Duan et al, 2023;Yang et al, 2022a;Hong et al, 2023). Similar changes were also observed in soil organic carbon mineralization rate (Yang et al, 2022a;Hong et al, 2023).…”

“…Descriptions of the wetland areas, local climate and history of habitat modification (mudflats to S. alterniflora marshes, then to earthen aquaculture ponds) can be found in (Hong et al, 2023;Lin et al, 2023;Yang et al, 2022a and.…”

“…Different lowercase letters along the same row indicate significant differences at p < 0.05 between habitat types. Data are taken from Yang et al (2022) for reference and review only. See main text for explanation of the abbreviations.…”

“…During the past century, over 21% natural coastal wetlands have been lost or degraded globally as a result of land use change to support population growth and economic development (Davidson and Finlyson, 2018;Han et al, 2014;Fluet-Chouinard et al, 2023). Alteration of plant community through invasion or de-vegetation would change the primary production and the rate of organic deposition into the soil (Ge et al, 2015;Wang et al, 2023b), while corresponding changes to the soil microbial community would affect organic remineralization rate (Bahram et al, 2022;Yang et al, 2022a;Yang et al, 2023). Land conversion to aquaculture ponds also changes soil particle size and creates a continuously water-logged environment, and the aquaculture operation itself may introduce additional disturbances to soil chemistry, e.g.…”