海南儋州不同林龄橡胶林土壤碳和全氮特征

Characteristics of soil carbon and tatal nitrogen contents of rubber plantations at different age stages in Danzhou,Hainan island

为研究热带人工林巴西橡胶树(Hevea brasiliensis)生态系统不同林龄土壤碳、全氮特征,对热带地区种植橡胶及其更新进行生态效益评估,文章分析了海南儋州地区幼林早期(2龄)、幼林晚期(7龄)、开割树(16龄)和老龄即将更新树(30龄)4种不同林龄的橡胶林土壤碳、氮质量分数垂直分布特征。结果如下,(1)不同林龄橡胶林胶园土壤有机碳质量分数存在极显著差异,其大小排列顺序为幼林晚期(7龄)>老龄即将更新树(30龄)>幼林早期(2龄)>开割树(16龄),各土壤层次土壤有机碳质量分数的空间垂直分布大体随着土层的深入而降低,其垂直分布的变异系数由大到小排列顺序为7龄幼林晚期(37.54%)>16龄开割树(26.48%)>30龄老龄即将更新树(24.44%)>2龄幼林早期(18.99%);(2)不同林龄橡胶林胶园土壤全氮质量分数存在显著差异,其大小排列顺序为幼林晚期(7龄)>幼林早期(2龄)>老龄即将更新树(30龄)>开割树(16龄),各土壤层次土壤全氮质量分数的空间垂直分布大体随着土层的深入而降低,其垂直分布的变异系数由大到小排列顺序为16龄开割树(34.32%)>7龄幼林晚期(30.98%)>30龄老龄即将更新树(21.09%)>2龄幼林早期(14.37%);(3)不同林龄胶林土壤碳氮(C/N)比存在极显著差异,其大小排列顺序为开割树(16龄)>老龄即将更新树(30龄)>幼林晚期(7龄)>幼林早期(2龄),各胶林土壤有机碳质量分数与土壤全氮质量分数之间均存在极显著线性正相关关系(R2≥0.5839,p<0.01)。本研究可为研究热带土地利用与覆盖变化对全球碳循环及橡胶林生长碳氮耦合提供基础数据,为我国热区进行天然橡胶种植提供理论依据。

Assessment of ecological benefits of rubber （Hevea brasiliensis） plantations and replanted rubber plantations in the tropical area necessitates understanding of distribution of soil organic carbon （SOC） and total nitrogen （TN） in the tropical rubber plantation ecosystem. Soil profiles were sampled in rubber plantations at 4 different ages, 2 years, 7 years, 16 years and 30 years, in Dan- zhou, Hainan Island, and the SOC and TN contents in different soil layers and their vertical distribution were analyzed. The SOC content was found highly significantly different between rubber plantations at different ages, and was in the order of rubber plantations at the age of 7 years 〉 30 years 〉 2 years 〉 6 years; the SOC content decreased gradually with the soil depth in the rubber plantations at the 4 different age stages, and coefficient of variance （CV） of SOC contents on soil profile in the rubber plantations were in the descending order of the rubber plantations at the age of 7 years （37.54%） 〉 16 years （26.48%） 〉30 years （24.44%） 〉 2 years （18.99%）. Significant difference was observed in the TN content between rubber plantations at different ages, and the TN content was in the order of rubber plantations at the age of 7 years 〉 2 years 〉 30 years 〉 16 years; the TN content decreased gradually with the soil depth in the rubber plantations at 4 different ages, and the spatial vertical distribution of the TN content tended to show a decrease in TN content in each soil layer with the soil depth, and the variation coefficient of vertical distribution of the TN content was in the order of rubber plantations at the age of 16 years （34.32%） 〉 7 years （30.98%） 〉 30 years （21.09%） 〉 2 years （14.37%）. C/N ratios in rubber plantations at different ages were highly significantly different and they were in the order of rubber plantations at age 16 years 〉 30 years 〉 7 years 〉 2 years. A highly significant positive correlation （R^2≥0.5839, p〈0.01） was observed between the SOC and TN contents in the rubber plantations at 4 different ages. This study might provide benchmark for the study of tropical land utilization and cover change affecting the global carbon cycle and the carbon-nitrogen coupling of rubber tree growth in the rubber plantations, and theoretical grounds for cultivating natural rubber trees in Tropical China.