海南岛东部热带雨林次生林土壤有机碳分布特征及其影响因素

Distribution Characteristics and Influencing Factors of Soil Organic Carbon in Secondary Forests of Tropical Rain Forests in the Eastern Part of Hainan Island

热带雨林次生林碳循环对全球碳平衡具有重要意义,森林土壤有机碳分布特征及影响因素已成为研究热点。土壤粒径组成与pH值是影响土壤有机碳碳库稳定性的重要物理化学因子。在海南岛东部的吊罗山、七仙岭以及五指山选取10个热带雨林次生林典型样地,分层采集距地表0~10 cm、11~30 cm、31~50 cm的土样,利用有机元素分析仪测定土壤有机碳质量分数,采用电位法测定pH值,使用马尔文激光粒度仪测定土壤粒径。结果表明:在空间上,平均有机碳质量分数由大到小依次为五指山、七仙岭、吊罗山;在垂直方向上,3个区域表层土壤有机碳质量分数随着剖面深度的增加而递减,呈表聚性特征;3个区域土壤有机碳质量分数与p H值、粉粒含量无显著相关性,与黏粒含量呈显著(P <0.05)或极显著(P <0.01)正相关,砂粒含量与五指山、吊罗山土壤有机碳质量分数呈显著负相关(P <0.05);黏粒含量是海南岛东部热带雨林次生林土壤有机碳质量分数的主控因子,后续可考虑研究固碳微生物对土壤有机碳分布的影响,进一步探讨热带雨林次生林土壤有机碳的分布特征与累积规律。

The carbon cycle of secondary forests in tropical rainforests is essential for global carbon balance.The distribu⁃tion characteristics and influencing factors of soil organic carbon in forests have become a research hotspot.The composi⁃tion of soil particle size and pH are significant physicochemical parameters influencing the stability of soil organic carbon pool.In this study,10 typical sample sites were selected in the secondary forests of tropical rainforests at Diaoluo Mountain,Qixianling Mountain,and Wuzhishan Mountain on the eastern part of Hainan Island.Soil samples were collected at three depths of 0~10 cm,11~30 cm,31~50 cm.The mass fraction of soil organic carbon(SOC)was determined by an organic element analyzer,pH was measured by a potential method,and soil particle size was determined by a Malvern laser particle size analyzer.The results showed that the average mass fraction of SOC was highest in Wuzhishan,followed by Qixianling and Diaoluo Mountain.Vertically,the mass fraction of SOC in the topsoil of the three regions decreased with the increase of profile depth,indicating aggregation characteristics.The mass fractions of SOC in the three areas had no significant correla⁃tion with pH and silt content but had a significant(P<0.05)or extremely significant positive correlation(P<0.01)with clay content.Sand content were significantly negatively correlated(P<0.05)with the mass fraction of SOC in Wuzhi Moun⁃tain and Diaoluo Mountain.Clay content was identified as the main controlling factor affecting the distribution of soil organic carbon in the secondary forests of tropical rainforests in the eastern part of Hainan Island.Future studies should be considered to explore the impact of carbon-fixing microorganisms on the distribution characteristics and accumulation rules of soil organic carbon pools in secondary forests of tropical rainforests.