植硅体作为植被演化重要指标，在草本植物中产量大、对禾本科植物指示性好等特点使其在草原生态系统的研究中具有优势，不同功能类群植物植硅体形态的差异为研究草原植物功能类群C3、C4植物提供可能性。本研究拟以植被对气候变化敏感的黄旗海流域为研究区域，通过植被调查和草本种植硅体形态数据的收集，并分析现代植物和表土中植硅体的形态，建立指示C3/C4植物植硅体形态组合指标；通过对比现代表土、河道、湖表沉积物的植硅体形态组成，揭示风力和水力作用对植硅体迁移的影响，提出基于湖泊沉积物植硅体复原流域植物功能类群组成的方案；基于以上研究结果，利用黄旗海沉积物中植硅体形态组合、沉积物碳同位素，结合已有测年结果和孢粉记录，重建近2000年以来林草交错带草原C3/C4植物的动态演变过程。为今后利用植硅体重建过去草原植物演化奠定基础，为研究未来气候变化和人类活动影响下草原生态系统植被变化提供参考。

Phytoliths, as an important vegetation evolution index, have significant advantages (e.g., high content; a good index for Gramineae) in studying grassland ecosystems, which will provide potentials to explore the grassland vegetation functional groups (e.g., C3/C4 plants). In this project, we will investigate the vegetation and collect phytolith morphology data of the areas surrounding the Huangqihai. Simultaneously, we will analyze the phytolith morphology of modern plant and surface soils to establish phytolith morphology combination index of different C3/C4 plants. Besides, we plan to reveal the transport processes of phytoliths under the force of wind and water by analyzing the phytolith morphology of modern surface soils, riverway surface sediments and lake surface sediments. This will ensure the phytolith composition of the lake sediments could reflect the surrounding vegetation. Based on the above results, we could reconstruct the C3/C4 plants dynamic of forest-steppe ecotone during the last 2000 years based on the phytolith morphology of the Huangqihai lake sediments, combining with the existing pollen record and chronology results. The aim of this study is to enrich our understanding about the role of phytoliths in reconstructing the grassland vegetation evolution. This study will also help to recover vegetation dynamic of grassland ecosystem under the impact of the future climate changes and anthropogenic activities.