National Forestry and Grassland Administration Key Laboratory of Forest Resources Conservation and Ecological Safety on the Upper Reaches of the Yangtze River, Sichuan Province Key Laboratory of Ecological Forestry Engineering on the Upper Reaches of the Yangtze River, Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology & Forestry, Sichuan Agricultural University, Chengdu 611130, China.
Key Laboratory of Southwest China Wildlife Resources Conservation, China West Normal University, Ministry of Education, Nanchong, Sichuan 637009, China.
Sci Total Environ. 2021 Jan 20;753:142287. doi: 10.1016/j.scitotenv.2020.142287. Epub 2020 Sep 8.
The decomposition of litter carbon (C) fraction is a major determinant of soil organic matter pool and nutrient cycling. However, knowledge of litter chemical traits regulate C fractions release is still relatively limited. A litterbag experiment was conducted using six plant functional litter types at two vegetation type (coniferous forest and alpine shrubland) in a treeline ecotone. We evaluated the relative importance of litter chemistry (i.e. Nutrient, C quality, and stoichiometry) on the loss of litter mass, non-polar extractables (NPE), water-soluble extractables (WSE), acid-hydrolyzable carbohydrates (ACID), and acid-unhydrolyzable residue (AUR) during decomposition. Litter nutrients contain nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), aluminium (Al), manganese (Mn), zinc (Zn), iron (Fe) and copper (Cu), litter C quality contains C, WSE, NPE, ACID, and AUR, and stoichiometry was defined by C:N, C:P; N:P, ACID:N, and AUR:N. The results showed single exponential model fitted decomposition rates of litter mass and C fractions better than double exponential or asymptotic decomposition, and the decomposition rates of C fractions were strongly correlated with initial litter nutrients, especially K, Na, Ca. Furthermore, the temporal dynamics of litter nutrients (Ca, Mg, Na, K, Zn, and Fe) strongly regulated C fractions loss during the decomposition process. Changes in litter C quality had an evident effect on the degradation of ACID and AUR, supporting the concept of "priming effect" of soluble carbon fraction. The significant differences were found in the release of NPE, WSE, and ACID rather than AUR among coniferous forest and alpine shrubland, and the vegetation type effects largely depend on the changes in litter stoichiometry, which is an important implication for the change in plant community abundance regulate decay. Collectively, elucidating the hierarchical drivers of litter chemistry on decomposition is critical to soil C sequestration in alpine ecosystems.
凋落物碳（C）组分的分解是土壤有机质库和养分循环的主要决定因素。然而，关于凋落物化学特性如何调节 C 组分释放的知识仍然相对有限。本研究采用 6 种植物功能型凋落物，在山地林线交错带的两种植被类型（针叶林和高山灌丛）中进行了凋落物袋实验。我们评估了凋落物化学特性（即养分、C 质量和化学计量）对凋落物质量损失、非极性可提取物（NPE）、水溶性可提取物（WSE）、酸水解性碳水化合物（ACID）和酸不溶残余物（AUR）在分解过程中损失的相对重要性。凋落物养分包括氮（N）、磷（P）、钾（K）、钙（Ca）、钠（Na）、镁（Mg）、铝（Al）、锰（Mn）、锌（Zn）、铁（Fe）和铜（Cu），凋落物 C 质量包括 C、WSE、NPE、ACID 和 AUR，化学计量由 C:N、C:P；N:P、ACID:N 和 AUR:N 定义。结果表明，单指数模型比双指数或渐近分解更能拟合凋落物质量和 C 组分的分解速率，C 组分的分解速率与初始凋落物养分强烈相关，特别是 K、Na、Ca。此外，凋落物养分（Ca、Mg、Na、K、Zn 和 Fe）的时间动态强烈调节了分解过程中 C 组分的损失。凋落物 C 质量的变化对 ACID 和 AUR 的降解有明显影响，支持可溶性碳组分“激发效应”的概念。在针叶林和高山灌丛之间，NPE、WSE 和 ACID 的释放存在显著差异，而 AUR 则没有，植被类型的影响主要取决于凋落物化学计量的变化，这对植物群落丰度变化对分解的调节具有重要意义。总的来说，阐明凋落物化学特性对分解的层次驱动因素对于理解高山生态系统中土壤 C 固存至关重要。
