Photosynthate-C-13 allocation in the plant-soil system after C-13-pulse labeling of Phragmites australis in different salt marshes

摘要

Photosynthetic carbon is an integral part of carbon cycle in plant-soil system, also is an important source of soil organic carbon. In this study, C-13 labeling was used for exploring allocation of photosynthate-C-13 in Phragmites australis -soil system undergoing the salt marsh restoration project by freshwater pumping in Yellow River Estuary (YRE), China. Samples were collected from T-0 (before labeling) to 90 days after labeling (T-4), in natural salt marsh, 5-, 10- and 15-year freshwater pumping areas, respectively. The photosynthate-C-13 contents of soil were gradually decreased to 0 mg/g at T-4 in most areas, while it was 2.21 mg/g in 15-year pumping area, higher than other areas at the last sampling time (T-4). And the allocation of photosynthate-C-13 in soil was increased from 3.58% at T-2 to 44.46% at T-3 in natural salt marsh, while no significant change was found in other areas from T-2 to T-3, followed by the significantly higher photosynthate-C-13 proportion in soils of 15-year pumping area at T-4. EC (R-2 = 0.5972) and small macro-aggregates proportion of soil (R-2 = 0.4829) had positive correlations with A photosynthate-C-13 (the value of photosynthate-C-13 in underground part minus that in soil); silt and clay fractions proportion of soil (R-2 = 0.7044) had negative correlation with Delta photosynthate-C-13. Distribution and transportation of photosynthetic carbon in the underground were affected by soil physical and chemical properties.