黄河源区（玛曲）沙化草地褐鳞苔草阻固沙机理研究

Maqu is the important water conservation area in the source area of the Yellow River, the environmental degradation in this area has seriously affected the ecological environment and economic development of the Yellow River basin in recent years. Carex brunnescens（Carex）,a perennial herb with the characteristics of underground stem vegetative reproduction，is an excellent sand-fixing plant in Maqu alpine grassland, It plays an important role in maintaining biodiversity and ecosystem stability in Maqu Alpine pastoral. This study used a combined methods of computeriized virtual plant simulation (geometry structural modeling) and field experiments observation to establish the static model of morphological charactiristics of Carex brunnescens through observing morphological features and spatial distribution of Carex brunnescens (underground stems and roots), which aims at revealing its biological characteristics and evolution law to adapt to the wind-sand environment. Second, through establishing the quantitative relationship between vegetation coverage, population density, biomass, numbers, structure of the underground stems (roots) and wind prevention and sand resistance to discuss the prerequisite and the critical thresholds of sand-fixing of Carex brunnescens, reveal the establishment process of community and thus illustrate the formation mechanism of resistance and sand fixing effect. Finally, establishing the artificial sand-fixing test areas to verify, supplement and perfect the sand-fixing static model, critical threshold and the degreefitting of the model and the real effect in moving sand dune. The project will provide a theoretical basis and technological support for the technique of biological sand -fixing to Maqu alpinegrassland.

玛曲是黄河源涵养水源的重要区域，近年来该地区环境退化影响整个黄河流域生态环境与经济发展。褐鳞苔草为苔草属多年生草本植物，地下茎营养繁殖，是玛曲当地固沙的先锋植物，对维护玛曲高寒草地生物多样性和生态系统稳定性有重要作用。本项目采用虚拟植物技术与野外实验观测相结合的方法，首先从褐鳞苔草地下茎（根系）形态特征及生长分布特征入手，应用几何结构建模方法，构建褐鳞苔草形态学静态模型，揭示其适应风沙环境的生物学特性及演变规律；其次，建立褐鳞苔草植被覆盖度、种群密度、生物量、地下茎(根系)数量及结构与防风阻沙效果的数量化关系，探讨其阻固沙效能的必备条件和安全维持阈值，揭示高寒风沙生境下褐鳞苔草群落的建植过程，进而阐明其阻固沙作用的形成机理；最后，在流动沙丘建立人工固沙试验区，验证、补充和完善褐鳞苔草固沙静态模型、临界阈值以及模型与现实效果的拟合度，为玛曲高寒草地生物防沙治沙提供理论依据和科技支撑。

褐鳞苔草 (Carex brunnescens) 是黄河源区 (玛曲) 沙漠化草地发现的固沙能力强、且唯一能够形成“草本植物沙堆”的先锋植物，对维护玛曲高寒草地生物多样性和生态系统稳定性有重要作用。本研究通过对高寒风沙环境下褐鳞苔草的物候学特征，生物学（地下器官）特性及演变规律、繁殖特征及阻固沙特性进行系统研究，确定了褐鳞苔草阻固沙效能的必备条件和安全维持阈值，揭示了群落的固沙原理，并探索出阻固沙的生物防沙治沙技术。另外，本研究增加了玛曲沙漠化草地粗壮嵩草种子生物学及萌发特性研究，取得以下研究成果：⑴ 褐鳞苔草返青早，生育期较长，具有二次开花和结果的生长特性，且单株和群落性状表现出明显的季节变化特征。⑵ 地下茎和根系适宜生存的沙层深度为0-60cm，垂直茎能穿透沙埋的最大深度为50 cm，且可以成活并形成新的植株。⑶ 不同沙层深度均以直径为0.02～0.05 cm的中根数量最多，在20～40 cm沙层内细根、中根和粗根的根系总长度最大；在10-30 cm 沙层内，水平茎、垂直茎和主根长度、鲜重和干重均最大。⑷ 种群密度为145-156株.m-2、植被盖度为31.2%-39.3%、地下茎长度为11223 cm.m-2、一级根系长度为9161cm.m-2以及地上部和地下部鲜重分别为198.5-212.6 g.m-2和578.8-612.4 g.m-2时是衡量褐鳞苔草能否固沙的临界阈值。⑸ 褐鳞苔草适应风沙环境的适应策略在于高度发达地下茎不断延长产生垂直茎并向上生长迅速穿透沙面形成新的植株，周而复始使形成多层网状结构起到固沙作用。随着其它优良牧草迅速蔓延入浸占据优势，褐鳞苔草逐渐退化至其它半固定或流动沙丘上以保持种群的稳定。⑹ 沙丘布设草方格移植地下茎有效提高了土壤养分含量，增强褐鳞苔草地下茎的生长和繁殖能力，促进了群落的建植并快速起到阻固沙作用。⑺ 粗壮嵩草种子在变温处理25/5℃（12/12h）下，种皮划破后，放置于98%的浓H2SO4中浸泡6min，经300mg.L-1赤霉素（GA3）浸泡48h后，14天内种子的萌发率达到64%，但仍有36%的种子处于休眠状态，表明粗壮嵩草种子存在综合休眠的生理机制，并且种皮的机械阻碍是抑制种子萌发的主要原因。