芒萁对退化红壤碳积累的贡献及关键影响机制

Mechanisms of carbon accumulation in degraded soil have been highly focused for it's great Carbon sequestration potential. Soil organic matter is an important driver for forest restoration in red soil region of southern China, our previous researches have showed that understory (Dicranopteris dichotoma) plays a key role during accumulation of soil organic matter, but the relative contributions to soil carbon accumulation between Dicranopteris dichotoma and upper forest, and influence mechanisms of Dicranopteris dichotoma on soil carbon accumulation is still unclear. The project will be implemented in typical eroded degradation mountain in Hetian town, Changting county, fujian province. Through the use of field control experiment combining with isotope and biomarker technology, we will make a comparison of differences of pools, fractions and biomarker macromolecular in soil organic carbon under Dicranopteris dichotoma cover and bare land in different recovery ages of pinus massoniana forest, to reveal the relative contribution of Dicranopteris dichotoma on soil organic carbon accumulation. Furthermore, through field and laboratory simulation experiment combined with organic carbon fractionation by soil structure, nuclear magnetic resonance (NMR) and phospholipid fatty acid technology, we will observed key factors of carbon accumulation such as the quantity and structure of dissoluble organic carbon leached from Dicranopteris dichotoma, microbial functional groups and stability of newly formed organic carbon, to clarify the mechanism of Dicranopteris dichotoma of the effects on carbon accumulation in degraded red soil. The results of the study has important scientific value to further understand the mechanism of degraded red soil carbon sequestration, and has important significance for ecological restoration and undergrowth management in the red soil erosion area of China.

退化土壤具有巨大的固碳潜力，其碳库积累机制已成为当前国际研究热点。中国南方侵蚀红壤区土壤有机质是森林植被恢复的重要驱动力，前期研究表明林下植被芒萁在土壤有机质积累过程中扮演着关键角色，但芒萁对土壤碳积累的相对贡献及其影响机制并不清楚。本项目拟以福建省长汀县河田镇典型侵蚀退化红壤山地为研究区，利用野外控制实验结合同位素与生物标志物技术，通过比较不同恢复年限的马尾松林中芒萁覆盖和林下裸地土壤有机碳的储量、组分及其生物标志大分子的差异，揭示芒萁对土壤有机碳积累的相对贡献；在此基础上利用野外和室内模拟实验结合有机碳分组、核磁共振与磷脂脂肪酸等技术，研究芒萁淋溶产生的可溶性有机碳数量及结构、微生物功能群以及新形成有机碳的稳定性等关键因素的变化，阐明芒萁对退化红壤碳积累的影响机制。研究结果对深入理解退化红壤固碳机理具有重要科学价值，对红壤侵蚀区生态恢复和林下植被管理具有重要意义。

退化土壤具有巨大的固碳潜力。芒萁是中国南方侵蚀退化红壤区马尾松林的重要伴生植物，但其对土壤碳积累的相对贡献及其影响机制并不清楚。本项目以福建省长汀县河田镇典型侵蚀退化红壤山地为研究区，利用野外控制实验结合同位素、生物标志物技术、有机碳分组、核磁共振与磷脂脂肪酸等技术，研究了不同恢复年限的马尾松林中芒萁覆盖和林下裸地土壤有机碳的储量及其生物标志大分子的差异，芒萁淋溶产生的可溶性有机碳数量及结构、微生物功能群以及有机碳的稳定性等关键因素的变化，得出了以下主要结论：.（1）发现芒萁覆盖显著增加了马尾松林土壤碳储量，芒萁覆盖的土壤有机碳同位素与芒萁叶片和根系的碳同位素比与马尾松的关系更密切；芒萁与马尾松的凋落物和细根中的生物标志物二羟基苯甲酸/酚类物质（DHA/V）具有显著差异，可用于计算芒萁与马尾松对土壤碳积累的相对贡献，并据此揭示了退化红壤马尾松林恢复早期土壤碳的积累50-70%来自于芒萁。.（2）发现芒萁覆盖除了增加枯落物输入量外，还增加了芒萁鲜叶淋溶的DOC输入，而且比马尾松鲜叶淋溶的DOC更容易进入深层土壤，有利于深层土壤碳的积累。.（3）发现芒萁覆盖显著增加了土壤各类群微生物数量，改变了群落结构组成，土壤生态系统变得更稳定，土壤的养分可利用性更高，有利于土壤碳的积累，而土壤C/N、pH和氮素水平是调控芒萁覆盖下土壤微生物生物量和群落结构的主要生态因子。.（4）植被恢复和芒萁覆盖均显著增加了土壤呼吸，同一恢复年限样地内芒萁覆盖改善了土壤呼吸与温度的关系，而不同恢复年限的样地间凋落物归还量是调控土壤呼吸的主导因子。.（5）基于土壤有机碳分解过程的同位素分馏模型，发现林下芒萁促进红壤侵蚀区土壤有机碳的稳定性。通过13C核磁共振分析发现，未治理地土壤有机碳的结构相对简单，随着恢复年限增加，土壤有机碳的结构变得更加复杂。.以上结果表明，侵蚀地的林下植被的恢复对土壤有机碳的积累具有重要作用，为侵蚀退化土壤碳管理提供了科学依据。