Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, China.
Tianjin Key Laboratory of Earth Critical Zone Science and Sustainable Development in Bohai Rim, Tianjin University, Tianjin, China.
Glob Chang Biol. 2021 Apr;27(8):1627-1644. doi: 10.1111/gcb.15516. Epub 2021 Jan 28.
Coastal wetlands are among the most productive ecosystems and store large amounts of organic carbon (C)-the so termed "blue carbon." However, wetlands in the tropics and subtropics have been invaded by smooth cordgrass (Spartina alterniflora) affecting storage of blue C. To understand how S. alterniflora affects soil organic carbon (SOC) stocks, sources, stability, and their spatial distribution, we sampled soils along a 2500 km coastal transect encompassing tropical to subtropical climate zones. This included 216 samplings within three coastal wetland types: a marsh (Phragmites australis) and two mangroves (Kandelia candel and Avicennia marina). Using δ C, C:nitrogen (N) ratios, and lignin biomarker composition, we traced changes in the sources, stability, and storage of SOC in response to S. alterniflora invasion. The contribution of S. alterniflora-derived C up to 40 cm accounts for 5.6%, 23%, and 12% in the P. australis, K. candel, and A. marina communities, respectively, with a corresponding change in SOC storage of +3.5, -14, and -3.9 t C ha . SOC storage did not follow the trend in aboveground biomass from the native to invasive species, or with vegetation types and invasion duration (7-15 years). SOC storage decreased with increasing mean annual precipitation (1000-1900 mm) and temperature (15.3-23.4℃). Edaphic variables in P. australis marshes remained stable after S. alterniflora invasion, and hence, their effects on SOC content were absent. In mangrove wetlands, however, electrical conductivity, total N and phosphorus, pH, and active silicon were the main factors controlling SOC stocks. Mangrove wetlands were most strongly impacted by S. alterniflora invasion and efforts are needed to focus on restoring native vegetation. By understanding the mechanisms and consequences of invasion by S. alterniflora, changes in blue C sequestration can be predicted to optimize storage can be developed.
滨海湿地是生产力最高的生态系统之一，储存了大量的有机碳（C），即所谓的“蓝碳”。然而，热带和亚热带的湿地已被互花米草（Spartina alterniflora）入侵，影响了蓝碳的储存。为了了解互花米草如何影响土壤有机碳（SOC）储量、来源、稳定性及其空间分布，我们沿着 2500 公里的沿海地带采集了土壤样本，该地带涵盖了热带到亚热带气候带。这包括在三种滨海湿地类型内进行的 216 次采样：一个沼泽（荻）和两个红树林（秋茄和白骨壤）。我们利用 δC、C：氮（N）比和木质素生物标志物组成来追踪 SOC 来源、稳定性和储存的变化，以响应互花米草的入侵。互花米草衍生的 C 在 40cm 深度内的贡献分别占荻、秋茄和白骨壤群落的 5.6%、23%和 12%，SOC 储量相应增加 3.5、-14 和-3.9 t C ha。SOC 储量与从本地物种到入侵物种的地上生物量趋势不符，也与植被类型和入侵时间（7-15 年）不符。SOC 储量随年平均降水量（1000-1900mm）和温度（15.3-23.4℃）的增加而减少。在互花米草入侵后，荻沼泽的土壤变量保持稳定，因此它们对 SOC 含量的影响不存在。然而，在红树林湿地中，电导率、总氮和磷、pH 值和活性硅是控制 SOC 储量的主要因素。红树林湿地受互花米草入侵的影响最大，需要努力关注恢复本地植被。通过了解互花米草入侵的机制和后果，可以预测蓝碳封存的变化，以优化储存。
