| Field investigation was made in 2013 at East Chongming Headland in order to explore the carbon sequestration and spatial distribution as well as key influencing factors for this young salt marsh through ArcGIS Kriging interpolation, SPSS correlation and path analyses. Based on our results, some main conclusions can be drawn:1) The spatial distribution of soil organic carbon was relatively high in the northern part and high tidal zone of East Chongming Headland, while soil salt content, biomass and elevation were the main factors that affecting soil organic carbon content.Soil organic carbon was ranged from 1.67 to 14.15 g·kg-1. Soil salt content was ranged from 1.00 to 15.75 g-kg-1. NDVI Index was ranged from 0.03 to 0.61. Elevation was ranged from 3.43 to 4.38 m. Soil bulk density was ranged from 0.69 to 1.44 g·cm-3. Soil moisture content was ranged from 38.70 to 133.19%, pH value was ranged from 7.90 to 8.37, median grain size was ranged from 4.71 to 46.33 μm.Soil organic carbon content, soil salt content, as well as NDVI index were all higher in the northern part than that in the southern part. Similar pattern was also observed along the elevation gradient, that the values in the high salt marsh was higher than those found in the low salt marsh. On the other hand, the median grain size and soil bulk density were higher in the southern part and low salt marsh than those in the northern part and the high salt marsh. The spatial distribution of elevation and pH showed no significant changing trends.All of the investigated environmental factors showed close relationships with the soil organic carbon content. Soil salt content was suggested to be the most important factor that affecting soil organic carbon content.2) The vertical distribution of soil organic carbon was also relatively high in the northern part and high tidal zone. Soil salt content, biomass, and 0-31 μm soil particles showed close relationships with the soil organic carbon content.Results showed that the soil organic carbon content decreases with depth. The soil organic carbon content for the northern part, the southern and different tidal flats of the middle part were 9.52 g·kg-1、3.88g·kg-1、4.17 g·kg-1、3.17g·kg-1、2.07 g·kg-1, respectively.Soil salt content, biomass and the content of 0-31 μm soil particles showed close relationships with the soil organic carbon content. Linear regression equations for soil organic carbon content was:SOC= 10.31 TN-1.65 (R2= 0.96).Different area showed different character of soil organic carbon accumulation:High tidal flat of the northern part and the middle part had more organic carbon input, high decomposition rate and soil organic carbon content. Middle and low tidal flat had less organic carbon input, low decomposition rate and soil organic carbon content. The character of high tidal flat of the southern part were medium.3) The soil organic carbon density and accumulation rate of East Chongming Headland were high, and the carbon sequestration rate decreased with vegetation establishment time.Results showed that the 0-30 cm soil organic carbon density of the study area was ranged from 1.03 kg·m-2 to 5.22 kg·m-2, with the average value of 2.32 ± 0.57 kg-m-2. The soil organic carbon storage of East Chongming Headland was 1.15×108 kg. The 0-100 cm soil organic carbon density of the study area was ranged from 3.74 kg·m-2 to 13.7 kg·m-2, with the average value of 6.38 ± 1.56 kg-m’2. The soil organic carbon storage of East Chongming Headland was 3.16×108 kg.Soil organic carbon content, soil organic carbon density, soil moisture content, soil salt content and elevation increased after the levee was buit in 1998 while soil bulk density, median grain size of particals decreased. There were significant difference beween Soil organic carbon density of 15 years old area and 5 years old area. The accumulation rate of soil organic carbon was 28.98 ± 7.25 g·m-2·a-1 in the first 5 years, and 27.01 ± 6.59 g·m-2·a-1 from 10 to 15 years. Therefore the carbon sequestration rate decreased with time.As mentioned aboved, the saltmarsh of East Chongming Headland showed very high carbon sequestration ability, though different areas showed different capacity of soil organic carbon accumulation, which were affected by physicochemical factors significantly. Protection of salt marshes was of great importance as a strategy for mitigating climate change. |
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