热带海岸典型森林类型土壤有机碳储量和碳氮垂直分布特征

热带海岸森林是重要的碳库,很容易受到人类活动的干扰,包括森林砍伐和气候变化。因此,迫切需要探明森林土壤有机碳储量,为热带海岸森林的保护和恢复提供理论依据。以热带海岸4种典型森林类型为研究对象,研究土壤中有机碳和全氮垂直分布特征及其与其他土壤理化性状关系。结果表明:不同林型土壤有机碳和全氮在土壤剖面中的垂直变化规律一致,表层含量较高,随着剖面深度增加含量逐渐降低,且不同土壤层次间呈现显著性差异。不同森林类型土壤有机碳和全氮含量平均值分别为1.35~7.06、0.08~0.61 g/kg,其中椰子人工林的土壤有机碳和全氮含量平均值最高,分别为7.06、0.61 g/kg,其次是香蒲桃天然次生林(6.07、0.44 g/kg)。各森林类型土壤碳氮比平均值依次为大叶相思人工林﹥木麻黄人工林﹥香蒲桃天然次生林﹥椰子人工林。各森林类型0~100 cm土层土壤有机碳储量从大到小依次为椰子人工林、香蒲桃天然次生林、大叶相思人工林和木麻黄人工林。相关分析结果表明,各个森林类型土壤有机碳与土壤容重呈显著负相关,与全氮呈显著正相关。说明椰子人工林和香蒲桃天然次生林森林生态系统达到平衡稳定状态,其碳汇效益较木麻黄人工林和大叶相思人工林显著,对热带海岸森林生态系统健康的经营与维护具有重要意义。

Soil Organic Carbon Storage and Vertical Distribution of Carbon and Nitrogen Under Different Typical Forest Types in the Coastal Tropical Area

Tropical coastal forests are an important carbon pool and are easily disturbed by human activities,including deforestation and climate change.Therefore,it is urgent to explore the organic carbon storage of forest soil,which provides a theoretical basis for the protection and restoration of tropical coastal forests.We estimated the soil organic carbon (SOC) storage and its vertical distribution under typical forest types,including secondary natural forest of S.odoratum,Coconut plantation,Acacia plantation,Casuarina plantation in the coastal tropical zone.The results showed the vertical variation of soil organic carbon and total nitrogen in the soil profile was consistent with the vertical variation of soil organic carbon and total nitrogen,the content of SOC and total nitrogen (TN) decreased with increasing soil depth on all of the four soil profiles,and the content of SOC and TN showed significant differences among layers.The content of SOC and TN in Coconut plantation was the highest among the four forest types (7.06 g/kg and 0.61 g/kg,respectively),followed by the natural secondary forest of S.odoratum (6.07 g/kg and 0.44 g/kg).The mean C/N was in the descending order of Acacia plantation (19.7),Casuarina plantation (19.3),secondary natural forest of S.odoratum (14.8),and Coconut plantation (11.5).The content of SOC and TN in the four forest soils ranged from 1.35 to 7.06 g/kg and from 0.08 to 0.61 g/kg.The descending order of SOC storage of 0-100 cm soil layer was Coconut plantation (48.09 t/hm2),secondary natural forest of S.odoratum (41.98 t/hm2),Acacia plantation (14.28 t/hm2),and Casuarina plantation (12.06 t/hm2).Correlation analysis showed significantly negative correlations between SOC and soil bulk density,and positive correlation between TN,but no significant correlations between soil water content.Coconut plantation and secondary natural forest of S.odoratum were the ecosystem equilibrium,and the carbon sequestration benefits than Casuarina plantation and Acacia plantation significantly.Our research has important significance for the management and maintenance of the tropical coastal forest.