岷江流域海拔梯度上土壤动物对凋落叶腐殖化的作用

Litter humification is an essential process in soil carbon sequestration and organic matter formation, but the actions of soil fauna on litter humification are still unclear. Based on the hypothesis that the moisture and temperature changes as affected by altitude could control the actions of soil fauna on litter humification, a field experiment will be conducted on the Minjiang River basin. The foliar litter of dominate species will be selected in seven ecosystems from a mid-subtropical evergreen broad-leaved forest with 442 m altitude to an alpine meadow with 3989 m altitude. Litterbag method with different mesh sizes will be used to exclude or include soil fauna. Traditional technologies will be combined with advanced technologies, such as GC-MS and NMR. The accumulations of humus components (humic acid, fulvic acid and humin) will be analyzed. The changes of water, organic and acid soluble components, and acid unhydrolysed residues will also be measured. Meanwhile, we will determine the optical characters and functional carbons during the accumulation of humus. The relationships of these parameters will be also explored in combining with the dynamics of litter mass loss, limit value, total organic carbon dynamics, soil fauna community dynamical pattern, and changes in temperature and moisture. The results could be expected to further understand the actions of soil fauna on litter humification, and be helpful to predict soil carbon sequestration and organic matter dynamics in the scenario of ongoing climate change.

凋落物腐殖化是土壤碳吸存和有机质形成的重要过程，但土壤动物对凋落物腐殖化的作用仍不清晰。基于“海拔梯度上水分和温度变化显著调控土壤动物对凋落物腐殖化的作用”的科学假设，沿岷江流域从海拔442m的中亚热带常绿阔叶林到3989m的高山草甸，选取具有明显水热环境差异的7个生态系统，以其优势物种凋落叶为研究对象，采用不同大小孔径凋落物网袋法进行土壤动物控制实验，通过传统实验技术与气相-质谱联用以及核磁共振技术等相结合的方法，研究凋落叶胡敏酸、富里酸、胡敏素等腐殖质组分累积特征，了解腐殖化过程中水溶性组分、有机溶性组分、酸溶性组分和酸不溶性组分的变化，探讨腐殖质物质光学特征、有机碳和功能碳动态，并分析失重率和Limit value，同步监测土壤动物群落组成及结构，结合海拔梯度上温度/湿度的变化格局，深入揭示土壤动物对凋落物腐殖化的作用过程，为认识气候变化情景下土壤碳吸存和有机质动态提供科学依据。

按照《资助项目计划书》的要求，依托前期工作基础，在2017年到2020年间，采用凋落叶网袋排除土壤动物的方法，以岷江流域典型生态系统中代表性物种高山草甸的黄花亚菊和黑褐苔草，高山森林的康定柳和方枝柏，亚高山森林的红桦和岷江冷杉，干旱河谷-山地森林交错带的橿子栎和岷江柏，干旱河谷的岷江柏和西南抗子梢，北亚热带常绿阔叶林的麻栎和柳杉，中亚热带常绿阔叶林的油樟和马尾松凋落叶为对象，研究了各生态系统中土壤动物对凋落叶分解过程中凋落叶失重(Mass)、质量(Quality)变化、腐殖质积累动态的影响。获得以下主要研究结果：(1) 土壤动物增加了黄花亚菊、黑褐苔草、方枝柏、岷江柏(MFE )、抗子梢、岷江柏(DV)、麻栎和马尾松凋落叶可提取腐殖质碳含量，减少了康定柳、红桦、岷江冷杉、橿子栎、柳杉和油樟凋落叶的腐殖质碳含量；(2) 土壤动物促进了黄花亚菊、岷江冷杉、岷江柏(MFE)、抗子梢、麻栎和马尾松凋落叶的腐殖化度；抑制了康定柳、方枝柏、红桦、橿子栎、岷江柏(DV)、柳杉和油樟凋落叶腐殖化度；(3) 土壤动物作用于凋落叶分解速率的贡献在物种和生态系统之间均存在显著的差异，具体表现为：马尾松(25.89%)>岷江冷杉(13.26%)>柳杉(10.61%)>方枝柏(8.37%)>黄花亚菊(7.02%)>橿子栎(5.43%)>红桦(4.56%)，康定柳(-0.49%)<麻栎(-4.86%)<黑褐苔草(-14.02%)<岷江柏(ET, -16.31%)<油樟(-23.10%)<岷江柏(DV, -34.53%)<抗子梢(-42.87%)；(4) 土壤动物的参与明显降低了多数凋落叶C/N、C/P、N/P，促进凋落叶中水溶性组分、可溶性有机碳和有机溶性组分的降分解，抑制酸不溶性组分降解。这些结果更加清晰地了解岷江流域典型生态系统凋落物腐殖化以及土壤有机质积累等关键生态学过程提供了理论依据，为从土壤肥力角度科学管理区域生态系统提供了科技支撑。基于这些工作，在Ecology Letters、Global Ecology and Biogeography和生态学报等主流杂志共发表科研论文20篇，出版专著1部，国家发明专利1项，培养博士生2名，硕士生4名，项目骨干获得优秀青年基金资助，形成了一支从事森林土壤学年轻有活力的研究团队。