Appraising soil carbon storage potential under perennial and annual Chenopodiaceae in salt marsh of NE Spain

The work was conducted at La Pletera salt marsh (NE Spain) to investigate the potential for atmospheric carbon capture of perennial Sarcocornia fruticosa (L.) Scott and annual Salicornia patula Duval Jouve and subsequent carbon integration and storage into S. fruticosa and S. patula soils respectively, at 0–5 and 5–20 cm depth. S. fruticosa amounts of aboveground (aC), belowground (bC) and litter (lC) carbon were 2300%, 350% and 3000% higher than S. patula according to the respective plant, root and litter biomass. This dramatic difference was reflected in soil organic carbon (SOC) values, much higher in S. fruticosa soil at 0–5 cm depth with 17.07 ± 5.83 g kg−1 than S. patula soil with 5.89 ± 1.68 g kg−1, namely 189% increase. Similarly, SOC increased by 109% in S. fruticosa soil at 5–20 cm depth. This perennial species can accumulate great amount of decaying debris at surface, which would gradually decompose by microbial activity to increase the soil organic carbon stock. Furthermore, the organic carbon incorporated is of better quality because contains higher fractions of glomalin, a stable organic compound known for its important role in soil aggregate stability. In fact, glomalin related soil protein (GRSP) was 292% and 182% higher in S. fruticosa than S. patula at the two depths respectively. By contrast, the low amount and nature of decaying debris produced in S. patula are easily mineralized and lesser organic carbon is consequently incorporated into soil. Lower SOC and GRSP affected the soil aggregate stability (WSA) in the 0.25–2 mm and 2–5.6 mm aggregate fractions, considerably more detachable in S. patula soil. Moreover, this soil exhibited the highest mineralization coefficient (Qm) at both depths, 125% and 175% higher than S. fruticosa soil respectively, and a major sensitivity to carbon loss. The PCA further highlighted the ability of S. fruticosa habitat to act as a carbon sink. Results may be valuable for salt marsh vegetation management addressed to mitigate climate change and increase ecosystem services.