科尔沁沙地草原入侵植物少花蒺藜草种子异型性生态适应研究

Cenchrus Pauciflorus Benth., an annual Poaceae weed, is an alien invasive species distributed widely in Horqin sandy grassland. In our previous study, seed heteromorphic was found in Cenchrus Pauciflorus Benth. with ecological characters germination and dormancy of significant temporal heterogeneity. However, whether these are keys of adjustment accommodation effect in its life-history strategy led to successful invasion and details of ecological law and mechanism are still unknown. Therefore, based on results of last project, targeting on seed heteromorphism of Cenchrus Pauciflorus Benth.,an adaptation adjustment accommodation study will be focused on effects of special environmental factors in local drought / half-drought sandy surroundings by using a comparison experiment of natural population and experimental population to trace their multiple life history generations between two settings: originally environmental field and inner control condition. Comprehensive study of 3-level "heteromorphism traits - effects of key ecological factors - adaptive adjustment accommodation reaction" will be conducted 1) to survey performance of seed heteromorphism of Cenchrus Pauciflorus Benth. and which factors have leading effects; 2) to answer ecological regular pattern of adaptation on seed heteromorphism of Cenchrus Pauciflorus Benth. to drought / half-drought sandy environment and its function in life-history strategy adjustment accommodation. Hence, importance of ecological adaptation on seed heteromorphism of Cenchrus Pauciflorus Benth. will be revealed furthermore plant ecology theoretical research will be enhanced and contributed meanwhile theoretical basis will be available to Horqin grassland management practice.

少花蒺藜草是科尔沁沙地草原广泛分布的一年生禾本科入侵植物。我们前一项目研究中发现，该植物具有异型种子，且存在显著时间异质性的萌发和休眠等生态特征。但对其成功入侵的生活史策略是否起关键调节作用，以及具体的生态学规律和机制尚不清楚。因此，本研究在结题项目基础上，拟以少花蒺藜草异型种子为研究对象，通过野外原位条件和室内受控条件下追踪多个生活史世代的天然种群和实验种群对比实验，开展异型种子受当地干旱半干旱沙地生境较为特殊的生态因子影响的适应调节研究。从"异型性特征--关键影响因素作用--适应性调节反应"三个层面综合研究以下内容：1）少花蒺藜草种子异型性如何表现，哪些影响因子起主导作用；2）少花蒺藜草异型种子适应干旱半干旱沙地生境的生态学规律是什么，以何方式在生活史策略调节中起作用。从而揭示少花蒺藜草种子异型生态适应意义，为深化生态学理论研究做贡献，同时也为科尔沁草原管理等生产实践提供理论依据。

本项目以少花蒺藜草异型种子为研究对象，开展异型型种子受干旱半干旱科尔沁沙地生境生态因子影响的适应性调节研究。主要完成了入侵地原位土壤环境因子变化特征、群落背景综合分析实验，土壤种子库中种子数量变化、种子生活力结构特征实验，室内人工种群变温恒温、盐碱浓度、pH值、光照和覆土深度单因子环境控制实验，刺苞机械处理和其它因子结合条件下的双因子环境控制实验，异型性种子解剖结构差异、种子生理生化特征差异和种子苗期差异表现等工作。主要研究结论：少花蒺藜草同一刺苞内的2粒种子在大小、重量、解剖结构、生理生化特征及萌发、休眠等存在着显著差异，是典型的异型性种子，具异型性生态行为。科尔沁沙地影响少花蒺藜草种子萌发与休眠异时性行为的关键因子是温度和水分条件，而土壤pH值和盐碱浓度是影响其分布的主要因子。在关键因子及其组合作用下少花蒺藜草种子异时输出行为有利于在异质性较强的科尔沁沙地生境中成功定居，一年生的少花蒺藜草采取了“类二年生”跨生长季异时萌发策略，有利于种群适应新生境，稳定占据、保持和扩大分布区。