Carbon sequestration along vegetation coverage gradient in the Suaeda salsa marsh from the Liaohe Delta

Carbon storage or sequestration is important in studying the global carbon cycle and budget. To evaluate carbon accumulation rate of S. salsa marsh along the vegetation coverage gradient, the authors collected 7 core samples from Liaohe Delta in May, 2010. The sediment accretion rate was calculated by 210Pb dating method. The laboratory analyses focused on water content, bulk density, nutrient contents, Mehlich III extractable nutrients and carbon concentration. Remarkably, carbon concentration is significantly related to nutrient contents（p<0.01）, implying that organic matters can effectively accumulate nutrient elements and support the growth of wetland vegetation, which favors carbon sequestration in the wetland soils. The results showed that total carbon concentration, about 83% of which is organic carbon, varies within 10.5- 14.6 g/kg and carbon accumulation rates are in the ranges of 98.02-260.37 g/m2/a（for total carbon）and 81.17-229.98 g/m2/a（for organic carbon）respectively with the average accumulation rate of 171.84 g/m2/a for TC and 141.29 g/m2/a for Corg. Carbon accumulation rates are likely affected by sediment accretion rate which is significantly related to the elevation of each wetland（p<0.01）. The implication is that not every wetland in different geological conditions and vegetation coverages is equally effective in sequestering carbon; it is important to address differences in wetland elevation, geological conditions and vegetation coverages when assessing the role of wetlands as carbon sinks in global carbon budgets.