环境条件和放牧干扰对肃南草地物种多样性影响机制的研究

Sunan County Grassland is an important functional area which supplies water for Heihe River. Due to overgrazing and unreasonable utilization, across Sunan County Grassland there rise crises of the degeneration of vegetation, and the proper gramineous forage germplasm in the local grassland communities reduced year by year while population density decrease year by year. In addition, the change process and mechanism of its plant diversity after degradation and restoration of grassland are still unclear, especially to the diversity change process and mechanism of gramineous germplasm in the climate change and environmental disturbances. Based on previous study and selected 10 kinds of common gramineous forage germplasm across Sunan County Grassland as research object, this project utilizing field monitoring and indoor analysis method research the morphological plasticity and resource allocation pattern and life history strategies of the grass under the environmental factor changes and grazing disturbance; it also analyzes the relationship between species and community dynamics across Sunan County Grassland under livestock grazing, climate change and environmental factors.change, and it compares the inner connection between the change of the characteristics of individual plant and species diversity changes, and explores the reason and mechanism of diversity changes of gramineous germplasm across Sunan County Grassland so as to solve the key ecological problems of grassland vegetation restoration. In theory this research can provide basis for the development and perfection of the plants diversity change model of grassland ecosystem, and in practice which provides theoretical support for the grassland recovery and rational utilization at present and in future.

肃南草地是黑河重要水源补给功能区，由于过渡放牧和不合理利用，植被严重退化，适牧的禾本科牧草在当地草地群落中多样性逐年减少，种群密度逐年降低。在退化及恢复后的草地中植物多样性变化过程及其机理尚有许多不清楚的地方，尤其是对禾本科牧草在气候变化和环境扰动下的多样性变化机理认识明显不足。本项目在我们前期研究的基础上，以肃南草地常见的禾本科牧草为研究对象，通过野外监测、室内分析等方法，研究牧草在环境因子变化和放牧干扰下的形态可塑性、资源分配格局和生活史对策；分析肃南草地在牲畜放牧利用、气候变化、环境因子变化下的物种间相互关系及群落动态；对比研究植物个体特征变化和物种多样性变化的内在联系，探明肃南湿地禾本科牧草多样性变化的原因和机理，解决草地植被恢复的关键生态问题。理论上可为草地生态系统中植物多样性变化模型的完善和发展提供依据，实践上可为目前和今后进行的草地恢复和合理利用提供理论支持。

肃南草地由于过渡放牧和不合理利用，植被严重退化，适牧的禾本科牧草在草地群落中多样性逐年减少，种群密度逐年降低。在退化及恢复后的草地中植物多样性变化过程及其机理尚有许多不清楚的地方，尤其是对禾草在气候变化和环境扰动下的多样性变化机理认识明显不足。本项目以肃南草地常见的禾本科牧草和豆科植物为研究对象，通过研究放牧干扰、温度变化、环境条件变化、干旱胁迫、盐份胁迫对植物生长的影响以及植物之间的竞争、化感作用，对比研究植物个体特征变化和物种多样性变化的内在联系，探明肃南草地牧草多样性变化的原因和机理。研究结果表明：①在肃南草地，土壤含水量是决定植物群落分布的关键因子；②放牧压力的大小会直接影响草地植物的生长，再生能力弱和补偿能力差的草种被排挤，导致草地物种多样性降低；③全球温度变化导致草地物种多样性变化并未出现一致性结果，温度升高利于一些物种生长，而不利于另一些物种的生长，结果是适应性高、抗逆性强、对环境温度变化反应速度快的物种生存了下来，导致草地物种多样性发生变化;④草地植物竞争和化感作用可能促进草地良性发展，草地豆科毒杂草的存在，对禾本科牧草有积极的作用，而并非绝对的竞争作用。草地杂草可通过释放化学物质，影响草地禾草的生长，主要是通过影响禾草膜透性及内容物丙二酫、脯氨酸、叶绿素的含量实现的；⑤草地水份过多过少都是对植物生长不利的，水份变化可通过影响植物的生长，直接影响草地物种的多样性。对干旱胁迫适应性强的物种可在多变的环境中存活下来，而适应性低的物种，可能在多变的环境中逐渐减少，以至在草地中消失。草地土壤中盐份含量过多不利于草地植物生长，但不同禾草对盐胁迫的适应能力不同；⑥光照和肥力均可对草地植物生长造成影响；海拔梯度影响植物的资源分配、结实和空间分布。草地物种多样性是环境多因子共同作用的结果，放牧压力和温度变化伴随的水份变化互作，是导致肃南草地物种多样性变化的主要因素。