海平面上升对红树林生态系统有机碳过程和碳预算的影响

Of all the climate change outcomes, sea level rise (SLR) may be the greatest threat to coastal mangrove ecosystems. However, except for those on vegetation succession, the related studies were focused on mangrove seedlings from laboratory simulated experiments in which tidal action was neglected, and the effects of SLR on the functions of mangrove ecosystems have been unknown. The processes of organic carbon are the important linkage of many functions of mangrove ecosystems. Therefore, in this project, a study will be carried out on the effects of SLR on organic carbon processes and carbon budgets of mangrove ecosystems by using the constructed control mangrove forest as well as SLRs of 40 cm and 80 cm (similar to the values of SLR in the future 100 and 200 years) mangrove forests with similar sediment background. Through field and laboratory experiments, we will study the effects of SLR on the stocks of organic carbon in both vegetation and sediment of mangrove ecosystems, estimate the effects of SLR on carbon fluxes between vegetation/sediment of mangrove forests and their adjacent waters/atmosphere, and explore the effects of SLR on the main ecological processes of organic carbon within mangrove ecosystems including organic carbon processes of litter fall, organic carbon processes of below-ground roots, and mineralization processes of sediment organic carbon. Under the background of global changes, the above studies on the effects of SLR on the processes of organic carbon of mangrove ecosystems will be useful in forecasting the changes in carbon budget of mangrove ecosystems in the future, and giving basis to the scientific management of mangrove forests.

气候变化的所有后果中，海平面上升对海岸带红树林生态系统影响最大。但因研究方法的原因，除植被演替外，已有相关研究集中于幼苗，且多为忽视潮汐作用的室内模拟实验，而基于生态系统功能的影响所知甚少。有机碳生态过程是红树林生态系统多种功能的重要纽带。因此，本项目通过在厦门海岸潮间带构建的具有相同底质背景的对照红树林以及海平面上升40 cm和80 cm（约相当于未来100年和200年的海平面上升值）的红树林，采用现场试验和室内模拟试验相结合的手段，研究红树林生态系统（包括植被和底质）有机碳储量、与毗邻系统（包括水域和大气）的碳通量（系统内外的碳交换）以及生态系统内部主要有机碳生态过程（包括凋落物有机碳过程、地下根系有机碳过程、底质有机碳矿化过程）对海平面上升的功能响应。在全球变化背景下，关于海平面上升对红树林有机碳过程影响的研究有助于预测未来红树林生态系统碳预算的变化，并为红树林的科学管理提供依据。

气候变化的所有后果中，海平面上升对海岸带红树林生态系统影响最大。但因研究方法的原因，除植被演替外，已有相关研究集中于幼苗，且多为忽视潮汐作用的室内模拟实验，而基于生态系统功能的影响所知甚少。有机碳生态过程是红树林生态系统多种功能的重要纽带。通过在厦门海岸潮间带构建的具有相同底质背景的对照红树林(海平面上升0 cm，SLR 0 cm)以及海平面上升40 cm (SLR 40 cm) 和80 cm (SLR 80 cm) (约相当于未来100年和200年的海平面上升值)的红树林，开展了海平面上升对红树林有机碳过程的影响的研究。结果表明：海平面上升将增加红树林底质碳储量和红树植被对底质有机碳的贡献比；地下根系总生物量会随着海平面上升而减少，但细根生物量对总根生物量的贡献比会随着海平面上升而增加；死细根分解速率和养分释放速率也会随着海平面上升而变快。对于地上有机碳过程而言，随着海平面上升80 cm, 植被生物量和有机碳储量分别降低了8.97 kg m-2 和3.85 kg C m-2；凋落物年产量也随着海平面上升而降低，但凋落花和凋落果对总凋落物的贡献量将随海平面上升而增加。对于凋落物的微生物分解而言，海平面上升将不利于凋落物的分解和养分的释放循环。各样地全年的林地现存凋落叶碳和蟹类摄食碳都呈现出SLR 0 cm>SLR 40 cm>SLR 80 cm的规律，且差异显著;随着海平面上升，底质温室气体通量也会随着减少; 底质沉积速率和有机碳沉积速率均呈现SLR 0 cm > SLR 40 cm > SLR 80 cm的规律。海平面上升对秋茄红树林生态系统主要有机碳过程有显著影响，会明显削弱红树林生态系统的固碳能力。