海南岛甘什岭低地次生雨林土壤有机碳及影响因素

热带雨林是世界上最复杂的森林生态系统,在全球碳循环中发挥着重要作用。热带低地次生雨林是受人类干扰较为严重的雨林类型,而关于其土壤有机碳库的研究甚少。以海南岛甘什岭热带低地次生雨林为研究对象,通过野外调查采样与室内分析相结合等方法,研究了经人为采伐干扰后自然更新恢复形成的3种林分类型(Ⅰ为较大采伐强度下恢复的灌丛与低矮乔木,Ⅱ为经中等采伐强度恢复成林分密度较大的次生雨林,Ⅲ为因交通条件不便,受采伐干扰较小的次生雨林)的土壤有机碳含量、碳密度的垂直分布特征及其影响因素,旨在为热带低地次生雨林恢复与土壤固碳能力研究提供科学依据。研究结果表明:(1)3种类型低地次生雨林的土壤有机碳含量均随土层深度的增加而降低,垂直分布特征为0—20 cm土层有机碳含量最高(3.07—4.49 g·kg^?1),在类型Ⅲ的变异系数最大为5.60%;(2)土壤有机碳密度的分布特征与有机碳含量基本一致,0—100 cm土层土壤有机碳密度为4.14—6.42 kg·m^?2,仅为全国平均水平的50.8%;(3)土壤有机碳与土壤全氮、碱解氮、有效磷均呈极显著正相关性(P<0.01),与林分凋落物厚度和物种丰富度呈显著正相关性(P<0.05)。热带雨林特有的水热条件、物种丰富度、土壤质地和极度缺磷现象的综合作用是形成其土壤有机碳积累特征的主要因素,加强受干扰破坏热带雨林的保护与修复,有助于土壤有机碳的积累。

Soil Organic Carbon Distribution and the Influencing Factors in the TropicalLowland Secondary Rainforest of Ganshiling,Hainan Island

Tropical rainforest is the most complex forest ecosystem in the world,which plays an important role in the global carbon cycle.The tropical lowland secondary rainforest is a type of rainforest seriously disturbed by human beings,but there is little research on its soil organic carbon pool.In this paper,the tropical lowland secondary rainforest in Ganshiling,Hainan Island,was taken as the research object.To provide scientific basis for the restoration of tropical lowland secondary rainforest and soil carbon sequestration capacity,the soil organic carbon content and carbon density of three forest stand types(I.Shrubs and low trees type restored from serious damage,Ⅱ.Secondary rainforest restored from medium damage,Ⅲ.Secondary rainforest far away from roads with less disturbance)were studied by field investigation and sample analysis.The results showed that:(1)The soil organic carbon content decreased with the increase of soil depth.The vertical distribution characteristics of soil organic carbon content in 0?20 cm soil layer was the highest(3.07?4.49 g·kg^?1),and the coefficient of variation in type Ⅲ was the largest(5.60%).(2)The distribution characteristics of soil organic carbon density were basically consistent with the content of organic carbon.The soil organic carbon density in 0?100 cm soil layer was 4.14?6.42 kg·m^?2 and 50.8%of the national average.(3)There was a significant positive correlation between soil organic carbon and soil total nitrogen,available nitrogen and available phosphorus(P<0.01),and a positive correlation between litter thickness and species richness(P<0.05).The characteristics of soil organic carbon accumulation in tropical rainforest are mainly caused by the combined effects of water and heat conditions,species richness,soil texture and extreme phosphorus deficiency.Strengthening the protection and restoration of disturbed tropical rain forest will contribute to the accumulation of soil organic carbon.