内蒙古草原大针茅群落关键种间竞争-促进作用对干旱胁迫和放牧干扰的响应机制研究

How the direction and the strength of species interactions varies with both stress and disturbance has been highlighted as a major gap in our ecological understanding, and is one of the main topics for plant ecologist. In the project, we will select the Stipa grandis communities and its key species (S. grandis, S. krylovii, Artemisia frigida, Cleistogenes squarrosa) to perform the studies.1) Neighbour-removed experiments (NRE) and spatial pattern analyses (SPA) will be carried out in the non-grazing plot and grazing plot in the natural S. grandis communities. We will examine how the joint effects of both seasonal rainfall and grazing pressure on the outcome of competitive – facilitative interaction and find the essential mechanism. Furthermore, we will examine the effects of competitive – facilitative interaction on population regeneration and on the community stability, and try to explain the relationships of environment gradients– species interaction – community dynamic process by plant traits. 2) In the control condition, we will set drought and mowing gradients, and investigate the outcome of competition – facilitation interaction for those four species and plant ecological adaptive strategies, and the relationship between plant traits(or trait trade-offs) and plant competitive ability along the environmental gradients. Therefore, this project will reveal the mechanisms of how water variability change and disturbance pressure determine the competition-facilitation interaction, and the role of species interaction in structuring plant communities. And it will find out the correlation of traits or trait trade-offs for competitive ability. Finally, it will provide the scientific explanation for the short-term community change and prediction for the long-term trajectory of S. grandis community dynamics.

近年来，揭示胁迫和干扰的交互作用是如何影响半干旱草原群落关键种间竞争-促进作用逐步成为植物生态学家的主要研究内容之一。本项目以大针茅群落及其群落关键种（大针茅、克氏针茅、冷蒿和糙隐子草）为研究对象，1）在野外原生生境中，通过邻体植物移除实验和空间格局分析，研究降水量季节（和年际）变化与放牧梯度对关键种间竞争-促进作用的影响及其内在机制，研究种间竞争-促进作用对种群更新和群落稳定性的影响；并将植物性状用于解释环境梯度-植物-植物相互作用-动态变化过程；2）在人工控制条件下，研究这4 种植物种间竞争-促进作用随干旱和刈割梯度的变化模式；并寻找环境梯度下植物生态适应策略和性状或性状权衡与植物竞争能力之间的关系。开展本研究能够揭示可利用水分变化和干扰如何影响大针茅群落关键种间竞争-促进作用及其对群落构建的重要性，确定植物性状或性状权衡与植物竞争能力的关系，对大针茅群落动态变化进行科学解释与预测。

近年来，揭示胁迫和干扰的交互作用是如何影响半干旱草原群落关键种间竞争-促进作用逐步成为植物生态学家的主要研究内容之一。本项目以大针茅群落及其群落关键种（大针茅、克氏针茅、冷蒿和糙隐子草）为研究对象，1）在野外原生生境中，通过邻体植物移除实验和空间格局分析，研究降水量季节（和年际）变化与放牧梯度对关键种间竞争-促进作用的影响及其内在机制，经过数据综合及分析，结果表明：（a）大针茅的相对竞争指数（RII）主要受利用方式和邻居物种的交互作用的影响；而羊草的RII均不受利用方式、年际气候及其交互作用的显著影响。（b）在极端干旱和高温的年份，放牧和刈割两种利用方式下群落植物间相互作用的值或方向发生了很多变化，其中，放牧利用加剧植物间的竞争，而刈割利用方式下植物间相互作用为促进。（c）物种性状值与其SRA之间有很高比例的显著相关，而围封群落的功能丰富度高于放牧/割草群落，功能分化程度低于放牧/割草群落，且围封群落的株高与SRA呈显著正相关。2）在人工控制条件下，研究这4 种植物种间竞争-促进作用随干旱和刈割梯度的变化模式，结果表明：（d）刈割干扰是大针茅、克氏针茅和冷蒿种群变化的原因，干旱胁迫是糙隐子草种群退化演替的原因。（e）冷蒿和糙隐子草对不同的环境变化有不同的适应策略，冷蒿增加生物量以应对割草干扰，而糙隐子草增加分蘖以应对干旱胁迫。开展本研究揭示了可利用水分变化和干扰如何影响大针茅群落关键种间竞争-促进作用及其对群落构建的重要性，确定植物性状或性状权衡与植物竞争能力的关系，对大针茅群落动态变化进行科学解释与预测。