内蒙古典型草原物种竞争能力及其对氮沉降和刈割的响应

Competitive ability has been suggested to include two components: competitive effect (CE), the ability of one plant to suppress the growth of another, and competitive response (CR), the ability of a species to resist suppression from its neighbours. Competitive ability is of great importance for community structure and dynamics, however, our understanding of the relationship between CE and CR, and its response to abiotic factors is inconsistent. Comprehensive consideration of species functional groups, dominant species, photosynthetic pathways and the frequency in the field, this study select 15 species (i.e. Leymus chinensis, Stipa grandis, Cleistogenes squarrosa, Achnatherum sibiricum, Agropyron cristatum, Carex korshinskyi, Potentilla bifurca, Allium bidentatum, Thalictrum aquilegifolium, Saposhnikovia divaricate, Melissitus ruthenica, Artemisia frigida, Caragana stenophylla, Chenopodium glaucum, Salsola collina ) in the typical steppe as the focal species, and Leymus chinensis and Cleistogenes squarrosa as phytometer. This study explore the dominant plant-plant interaction, relative competition ability of species and its response to nitrogen deposition and mowing based on the removal of aboveground biomass of all neighboring plants and field controlled experiment. CE and CR are measured and compared for focal species at four nitrogen deposition treatments and two mowing treatments through control experiment, greenhouse pot experiment and pairwise competition experiment. The relationship between species competition ability and functional traits was explored through measuring factors such as biomass allocation, leaf traits, root traits and relative growth rate, which had important influence on interspecific competition. Finally, on the basis of the above study, the correlation between the competitive ability of species and its distribution position on the environmental gradient is discussed. This study can provide a scientific basis for understanding the succession mechanism of typical steppe communities in Inner Mongolia under the background of nitrogen deposition, and provide theoretical support for the adaptive management of typical steppe in Inner Mongolia.

物种竞争能力是影响群落结构和动态的重要因素，然而关于物种竞争影响和竞争响应之间的关系及其对非生物环境响应的理解尚缺乏一致的认识。本研究综合考虑物种功能群类型、优势物种类型、光合作用途径及物种在野外实验样地的频度，选择典型草原15个物种作为目标物种，以羊草和糙隐子草作为参考物种。基于物种移除实验研究了内蒙古典型草原种间相互作用的主导类型；基于控制实验、温室盆栽实验和配对竞争实验等途径，研究了目标物种的竞争能力及其对氮沉降和刈割干扰的响应；通过对生物量配置、叶性状、根系性状及相对生长速率等对种间竞争具有重要影响参数的测定，探究了物种竞争能力与功能性状之间的关系；最后，在上述研究的基础上探讨物种竞争能力与其环境梯度上分布位置的相关性。本研究可为深入理解氮沉降背景下内蒙古典型草原群落演替机制提供科学依据，为内蒙古典型草原的适应性管理提供理论支撑。

种间竞争在调控群落结构和生态系统功能方面起着重要的作用。本项目研究了典型草原物种的竞争能力及其对氮沉降和刈割干扰的响应，研究能够为理解氮沉降背景下内蒙古典型草原群落结构和功能的变化提供了科学依据。研究结果显示临体植物移除显著提升了植物的高度和生物量，竞争是内蒙古典型草原植物-植物相互作用的主导类型。植物生长对施氮和刈割的响应受到竞争的调控，并且这种调控具有物种特异性。随着氮沉降的增加基尼系数呈显著增加的趋势，表明氮沉降会引起植株高度的不对称性增加，这种不对称性的增加将导致光竞争能力弱的物种逐渐丧失，从而降低了物种的丰富度。氮是限制内蒙古典型草原生产力的关键因子，随着氮沉降的增加地上生物量呈显著增加趋势。植物对光资源的竞争是调控物种丰富度和生物量对氮沉降响应的重要机制。以羊草和糙隐子草分别作为参考物种的竞争影响和竞争响应在对照和施氮处理间均具有显著的正相关关系，表明物种的竞争影响和竞争响应与参考物种无关，施氮没有改变物种的竞争影响和竞争响应格局。刈割会改变物种的竞争影响，氮添加可以削弱刈割对物种竞争影响的改变。群落中目标物种的平均位置与竞争响应不具有相关性，而与竞争影响具有显著的负相关关系，表明自然资源梯度上物种分布与它们的相对竞争行为相关，具有较高竞争影响能力的物种分布在养分较高的地方。