海南清澜港红树林湿地土壤有机碳分布及其与pH的关系

Soil Carbon Sequestration and Its Relationship with Soil pH in Qinglangang Mangrove Wetlands in Hainan Island

基于野外实地调查,研究我国海南清澜港红树林湿地离文昌河河口和海洋的距离对红树林土壤有机碳分布的影响及土壤有机碳与pH的关系。结果表明:在取样区域内,清澜港红树林土壤有机碳含量高、分布深;近河口各样地土壤pH为4.9~6.2,远河口各样地土壤pH为7.9~8.5;近河口红树林土壤厚度在85 cm以上,取样区内土壤有机碳含量为(9.1±1.08)^(66.2±5.17)g·kg-1,且随土壤深度增加先升高后降低,在60~70 cm处有机碳含量达到最高;在水平方向上,近河口红树林土壤有机碳平均含量(0~80 cm)随离海洋距离的增加而降低,近海、中间、近陆区域的土壤有机碳平均含量依次为(36.76±3.04),(35.12±3.78)和(17.20±1.56)g·kg-1;近河口红树林近海和近陆区域的土壤有机碳平均含量差异显著(P<0.05);近河口红树林土壤有机碳含量的分布特征与密克罗尼西亚的雅浦和帕劳地区的红树林一致;远河口红树林湿地土壤平均厚度约60 cm,其土壤有机碳含量为(8.35±0.94)^(38.3±2.53)g·kg-1,表层土壤有机碳含量最高,且有机碳含量随土壤深度的增加呈双峰递减型,在40 cm处有另一峰值;在水平方向上,远河口红树林土壤有机碳平均含量(0~60 cm)随离海洋距离的增加而降低;远河口红树林在近海、中间、近陆区域的土壤有机碳含量依次为22.12±2.57,14.83±1.01和13.18±1.20 g·kg-1,且近海和近陆区域的土壤有机碳含量差异显著(P<0.05);各样地土壤有机碳含量与其pH均显著负相关(P<0.05),其原因有待进一步研究。

Mangrove ecosystems play an important role in carbon sequestration. A survey was carried out along two transects of mangroves in Qinglangang, Hainan Island, where the most typical mangrove community in China is distributed. This study aimed at evaluating site effect on carbon sequestration and its relationship with pH. One of the transects was located in a site far away from the sea（ more than 500 m）,the other near the sea（ less than 100 m）. Along each transect,three soil columns（ seaward,interior,landward） were withdrawn using a PVC pipe. Each soil column was separated into sections of 5 cm interval. Soil samples from each section were analyzed for carbon content and pH. The main results are as follows. The pH of mangrove soil far from sea ranged from 4. 9 to 6. 2,compared with a much higher pH of around 8. 0 near sea. The SOC content in the soil far from sea ranged from（ 9. 1 ± 1. 08） g·kg^- 1to（ 66. 2 ± 5. 17）g·kg^- 1,with an average soil depth of about 85 cm. The SOC content increased with soil depth until 60-70 cm,then the SOC decreased. Along each transect,the SOC content decreased with the distance away from sea. The SOC contents of seaward,interior,landward were（ 36. 76 ± 3. 04） g·kg^- 1,（ 35. 12 ± 3. 78） g·kg^- 1,（ 17. 20 ± 1. 56） g·kg^- 1,respectively. There was significant difference in SOC content between seaward site and landward site. The change patterns of the mangrove SOC far from sea in Qinglangang were consistent with that of Yap and Palau mangrove in Micronesia. The SOC content of transect near sea ranged from 8. 35 ± 0. 94 g·kg^- 1to（ 38. 3 ± 2. 53） g·kg^- 1,with an average depth ofabout 60 cm. The SOC content generally decreased with depth but with a small peak at 40 cm. Average SOC contents of seaward,interior,landward were（ 22. 12 ± 2. 57） g·kg^- 1,（ 14. 83 ± 1. 01） g·kg^- 1,（ 13. 18 ± 1. 20） g·kg^- 1,respectively. The SOC content was significantly different between seaward and landward sites. The SOC content of all samples had significant negative relationship with the soil pH.