冷蒿在羊草草原放牧退化过程中的生态适应机制研究

Grassland degradation in China is largely due to overgrazing. Therefore, understanding the impact of grazing on the degradation process of community succession is crucial for the restoration and management of degraded grassland. Artemisia frigida has been considered as the indicator species of grassland degradation caused by overgrazing for temperate grassland in China. However, the specific ecological adaptation strategies used by A. frigida during the degradation process are still unclear, which constricts our understanding of the community degradation process caused by overgrazing. This study focuses on the formation mechanism of the dominant status of A. frigida in grazing Leymus chinense grassland. Based on the field sampling experiment, GC-MS method will be used to quantify the allelochemicals accumulated in A. frigida under different grazing intensities. Meanwhile, the phenotypic plasticity and photosynthesis allocation pattern of A. frigida along grazing gradients will be investigated. Furthermore, the specific impact of allelopathy of A. frigida, interspecific competition and their coupling effects on the growth of vegetative propagation and seed germination of the community dominant species during the degradation process will be separated based on field control experiment. By comparing the results of allelopathy, interspecific competition and their coupling effects, phenotypic plasticity and photosynthesis allocation pattern of A. frigida between field sampling experiment and control experiment, this study aims to reveal the specific ecological adaption strategies used by A. frigida during the community succession process in degraded L. chinense grassland. Results from the proposed study will provide scientific strategies and suggestions for the restoration and management of degraded grassland.

过度放牧是导致我国草地退化的重要因素，理解放牧驱动下草地群落的退化演替进程是退化草地恢复和管理的关键。冷蒿是我国温带草原放牧退化的指示种，但当前对冷蒿随草原退化过程所采取的生态适应对策尚不明确。本项目以放牧退化羊草草原的群落优势种冷蒿为研究对象，基于野外观测实验，应用气相色谱-质谱联用仪(GC-MS)分析方法，研究冷蒿植株包含的化感物质成分和含量、冷蒿的表型可塑性和光合产物分配格局随放牧梯度的响应规律；利用野外控制实验，区分冷蒿化感作用和种间竞争对群落物种组成的具体影响，阐明冷蒿化感作用、种间竞争及其耦合效应对不同退化演替阶段群落优势种的营养繁殖和有性繁殖过程的影响。对比分析冷蒿的化感作用、种间竞争、表型可塑性及光合产物分配格局随退化演替进程的动态变化，揭示冷蒿在放牧驱动的典型草原退化过程中所采取的生态适应对策，为退化草地的恢复和放牧草原的管理提供科学依据。

理解放牧驱动下草地群落的退化演替进程及控制机制是退化草地恢复的关键。冷蒿是放牧退化草原群落的重要指示种，但对其如何占据群落的优势地位还缺乏深入的了解。. 本项目探究不同放牧梯度冷蒿茎叶水浸提液对4种牧草种子萌发、胚根和幼苗生长的影响，并采用气相色谱与质谱(GC-MS)联用技术测定了不同放牧梯度样地冷蒿茎叶水浸提液和生长季冷蒿挥发性有机化合物的主要化学成分和含量。在内蒙古呼伦贝尔草原辉河野外实验站开展了冷蒿的化感作用和种间竞争区分和耦合作用的野外控制实验，得出以下结论：.（1）不同放牧梯度样地获得的冷蒿茎叶水浸提液对紫花苜蓿、黄花草木樨、芨芨草和克氏针茅的胚根生长存在显著影响，对黄花草木樨和羊草苗高的影响在实验后期较为显著，对紫花苜蓿的单株地上及地下生物量、黄花草木樨的单株地上生物量也存在显著影响。.（2）不同放牧梯度样地获得的冷蒿茎叶水浸提液所包含的化合物含量和成分存在较大的差异，其中桉树脑的相对含量随放牧强度的增加而升高。在挥发性有机物组成中相对含量较高的为α-蒎烯（α-pinene，8.28%～14.73%），桉树脑（eucalyptol，7.69％～12.12％）、樟脑（camphor，5.75%～7.70%）和-4-萜品醇[(-)-terpinen-4-ol，5.14%～6.68%]等4种化合物。.（3）冷蒿的化感作用在典型草原放牧退化演替过程中起到关键的调控作用。冷蒿化感作用和种间竞争的耦合效应对羊草和糙隐子草的生长均起到显著的抑制效应，但对星毛委陵菜的生长无显著影响。因此本研究表明在放牧退化羊草草原，冷蒿的化感作用会抑制演替前一阶段物种的生长，加速群落的演替进程，并在其成为群落优势种的过程中发挥着重要的作用。. 本研究从化学生态学的角度解释了放牧退化羊草草原的群落演替过程，为放牧退化草原的恢复和管理提供了研究基础和参考。