Shoot litter outweighs root inputs in building soil organic carbon during Spartina alterniflora invasion in a coastal wetland

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S0038071726000234

Authors: Yamin Chen, Yanghui He, Lingyan Zhou, Peter M. Homyak, Guiyao Zhou, Kaiyan Zhai, Diandian Wei, Boyun Tian, Xuhui Zhou 

27 January 2026

https://doi.org/10.1016/j.soilbio.2026.110104

Highlights

•The contribution of aboveground litter to SOC pool was greater than plant roots.

•Litter C input increased invasive-C pool in macro-aggregates by 10 %.

•C input from plant litter induced priming effects on mineral-associated C.

Abstract

Coastal salt marsh wetlands are highly productive ecosystems with carbon (C) sequestration rates up to 40–50 times higher than forests, making them a major biome for climate change mitigation. However, plant invasions driven by human activities are altering vegetation composition, C allocation, decomposition dynamics, and ultimately the fate of soil organic C (SOC). Here we conducted a 4-year field-based mesocosm experiment to simulate the invasion of the C4 plant, Spartina alterniflora Loisel, into C3 plant-dominated coastal wetland soils and to quantify the relative contributions of above- and below-ground litter inputs to SOC formation. Taking advantage of the δ13C contrast between C3 and C4 plants, we showed that S. alterniflora-derived SOC increased by 9 % after four years, with aboveground litter contributing 12 times more C to the SOC pool than belowground root litter. Litter addition preferentially enriched S. alterniflora-derived C in macro-aggregate fractions by 10 %, while slightly reducing its contribution in the clay fractions, indicative of accelerated decomposition of native mineral-associated organic matter (“priming”). Litter inputs also enhanced soil CO2 efflux, and its close correlation with soil δ13C signatures indicates that the decomposition of the added plant litter was the primary source of the newly cycled C. These findings challenge terrestrial paradigm that belowground inputs dominate long-term SOC sequestration, highlighting the pivotal role of aboveground litter in governing C cycling and storage at the terrestrial-aquatic interface.

Source: ScienceDirect