干扰-胁迫-竞争条件下羊草种群的空间拓展策略及机制

Degradation, salinization and alkalization caused by overgrazing utilization seriously threaten the meadow ecosystem safety and the healthy development of livestock husbandry. The spatial expansion traits of dominant forage populations have the potential utilization values to the degraded meadows restoration. In this project, both the field and pot-culture experiments were combined and considered to study the spatial expansion strategies of clonal Leymus Chinensis population and its eco-physiological mechanisms under grazing/mowing disturbance, saline-alkali stress and competition conditions in Songnen saline and degraded meadow, northeast of China. By analyzing responses regularity of the morphology and ramets distribution patterns of L. Chinensis populations to disturbance, stress and competition conditions, we revealed its spatial expansion strategies under grazing utilization pressure in degraded meadow; by studying the variations of the leaves gas exchanges parameters, the antioxidant enzyme activity and osmotic regulators concentrations, we analyzed the physiological responses to disturbance-stress-competition, and elucidated the internal physiological regulation mechanisms of L. Chinensis clones’ spatial expansion. Allometric growth analysis was also conducted among different modules’ biomass of L. Chinensis populations, and revealed its biomass allocation strategies in different environments. Finally, we elucidated the spatial expansion strategies of clonal L. Chinensis populations and its eco-physiological adaptive mechanisms under the interactions of disturbance, stress and competition. This project provides a theoretical basis for the use of clonal plants spatial expansion to restore the degraded meadows, and also helps to enrich the study of the life history strategies of L. Chinensis populations.

过度放牧利用引起的草地退化、盐碱化严重威胁到草地生态系统安全和畜牧业的健康发展。优势植物种群的空间拓展特性对退化草地的修复具有潜在利用价值。本项目在松嫩平原盐碱斑块化退化草地，以原位观测和控制实验相结合的方法，开展放牧/刈割干扰、盐碱胁迫与邻体竞争条件下优势物种-羊草种群的空间拓展策略及生理生态适应机制的研究。通过分析羊草形态和分株放置格局对干扰-胁迫-竞争的响应规律，揭示放牧利用条件下羊草在退化草地的空间拓展策略；通过研究叶片气体交换参数、抗氧化酶活性及渗透调节物质变化，解析羊草应对干扰-胁迫-竞争的生理响应，阐明羊草空间拓展的内在生理调控机制；同时开展羊草不同构件生物量异速生长分析，揭示不同环境压力下羊草的生物量分配对策。最终阐释干扰-胁迫-竞争互作下羊草的空间拓展策略及相应的生理生态机制。本项目可为利用克隆植物的空间拓展特性修复退化草地提供理论依据，也可丰富羊草生活史对策的研究内容。

过度放牧利用引起的草地退化、盐碱化严重威胁到草地生态系统安全和畜牧业的健康发展。优势植物种群的空间拓展特性对退化草地的修复具有潜在利用价值。本项目在松嫩平原盐碱斑块化退化草地，以原位观测和控制实验相结合的方法，对放牧/刈割干扰、盐碱胁迫与邻体竞争条件下羊草种群的空间拓展策略及生理生态适应机制开展了如下研究：（1）通过野外原位试验，开展了模拟采食和N添加对克隆植物羊草种群从正常生境向盐碱斑块拓展影响的研究。结果表明，模拟采食和N添加均可提高羊草种群向盐碱斑块的空间拓展能力，且提高了羊草分株在盐碱斑块上的潜在繁殖能力。模拟采食和N添加均增加了盐碱斑块羊草根茎总长度和根茎芽密度，N添加使羊草根茎总长度和芽密度分别提高88%和98%，模拟采食使羊草根茎总长度和芽密度分别提高59%和52%。（2）通过对全球已发表的198篇有关克隆植物（包含108个物种，分属35科）克隆整合的研究性论文进行数据提取整理，建立数据库，开展meta分析研究。从生理、形态及生物量分配三大方面对克隆植物克隆整合的特性和生态学意义进行了系统性归纳与总结。总体看来，无论在同质性还是异质性条件下，生理整合均能显著克隆植物的整体表现。在异质性生境下生理整合对供体分株无显著影响，但在同质性生境下，生理整合却显著影响了供体分株的生长。（3）盆栽模拟实验表明，适度刈割或种间竞争均可显著促进羊草向中度盐碱胁迫土壤斑块的拓展。适度刈割和种间竞争能够使羊草分配更多生物量至地下部分以提高空间拓展能力。从生理学角度看，刈割处理还可通过提高光合速率有效地诱导补偿性生长。羊草在空间拓展过程中采取了不同的适应策略以应对刈割和种间竞争。本项目的开展，对克隆植物的生态适应性有了更全面的认识。对我们下一步利用克隆植物的克隆性进行退化草地生态系统修复具有重要的指导和借鉴价值。