家畜消化道传播影响荒漠草原种子更新潜力的机制研究

The natural renewal of grasslands is a vital process to maintain plant diversity and sustainable performance of the grazed ecosystems. The dispersal of seeds via livestock’s digestive system is one of the main dispersal vectors for many plant species. As yet, we have known little about the influence mechanism of endozoochorous seed dispersal by herbivores on seed regeneration potential of desert steppe. Therefore, in this study desert steppe of four different types are treated as an object of study in Yanmenguan Ecological and Animal Husbandry Economic Zone in Shanxi Province. Grazing is used to identify the spatial-temporal patterns of seed dispersal by investigating and quantifying the species composition and the number of the ingested seeds in sheep dung in grazed ecosystems. Meanwhile, the main stages after seed ingestion, namely seed recovery, seed germination, seedling emergence and early seedling establishment are studied by feeding known quantities of seeds of component species to four captive sheep. Besides, the project also further analyses the main ways that dispersal process and the survival of ingested seeds are affected by seed traits and compares the change of seed persistence between ingested and non-ingested seeds based on dormancy release and seedling complement during a period of time. The research results will be helpful for us to determine the impacts of endozoochorous seed dispersal by herbivores on seed regeneration potential of desert steppe, and will help understand the relationship between species diversity maintenance and herbivores grazing. The study will provide solution strategies for grassland adaptive management and sustainable operation of semi-arid grasslands.

促进放牧草地天然更新是实现草地植物多样性维持与可持续经营的重要途径。放牧家畜消化道传播是草地植物种子传播的重要途径之一，而关于消化道传播对种子更新潜力的影响机制目前还不清楚，这将对深刻认识放牧草地更新过程产生影响。本项目以山西雁门关生态畜牧区短花针茅荒漠草原和放牧家畜—绵羊为研究对象，通过野外放牧和室内定量饲喂种子，明确放牧家畜消化道传播种子的时空格局及群落常见组分种的消化道传播潜力；在种子性状多样性中筛选影响消化道传播过程，及之后随粪便排泄种子存活、萌发和幼苗生长的主要因子，揭示其直接和间接作用途径；并从种子持久性角度，基于种子的休眠释放和幼苗补充，阐明消化道作用前后持久种子库随时间的变化规律。通过以上研究，解析消化道传播对放牧草地种子更新潜力的影响机制。研究结果为深入理解草地植物多样性与草食动物放牧之间的关系、实现草原适应性管理与可持续经营提供重要理论参考。

草地生态系统中放牧动物通过牧食行为将植物种子扩散到更大的空间范围的作用，是草地植物和家畜协同进化的重要内容之一。为了查明荒漠草原植物种子通过绵羊采食、消化作用后的消失、排出以及萌发等情况，本项目基于种子饲喂和全粪收集相结合的方法，研究了荒漠草原常见植物种子通过绵羊消化道进行传播的模式。主要结论如下：（1）供试植物种子都一定的数量从绵羊粪中排出，种子回收率（16.7%）与种子长度（r=-0.66）和种子形状（r=-0.73）呈负相关，平均滞留时间（56.9 h）与种子长度（r=0.62）、种子厚度（r=0.50）和种子体积（r=0.64）呈正相关；（2）种子排放高峰集中在采食后的24~48 h时间段内，但不同植物种子排放时间节点有差别；（3）放牧绵羊的消化作用对荒漠草原植物种子萌发格局产生影响，不同科属种子萌发能力对消化作用的反应表现不尽相同，但所有植物种子的存活率都有不同程度的下降；（4）绵羊消化作用造成禾本科植物种子的巨大损耗，但仍有部分莎草科和杂类草种子成功“逃逸”，这为家畜对其进行消化道传播提供了可能；（5）围封改变荒漠草原草地群落物种多度分布格局和土壤种子库结构，促使赖草单顶级群落趋于稳定，并通过改变植被-土壤互作关系驱动植被异化演替。研究结果为实现基于草地植物多样性与草食动物放牧之间关系的草原适应性管理提供重要依据。