Linking plant spatial aggregation with reproductive traits and near-source seed dispersal: ecological adaptation to heavy grazing

Aims Ecological strategies related to the adaptation of plants to environmental stress have long been studied by ecologists,but few studies have systematically revealed the ecological process of plant adaptation to herbivores as a whole.Methods In this study,Stipa breviflora,the dominant species in the desert steppe of Inner Mongolia,was used to analyse its reproductive individual characteristics and seed traits as well as the soil seed bank and spatial patterns under heavy-grazing and no-grazing treatments.Important Findings The results showed that the number of reproductive branches positively affected the number of vegetative branches.The analysis of the soil seed bank showed that the density of S.breviflora seeds beneath reproductive S.breviflora individuals was significantly higher than that in bare land.The seed density was also significantly negatively correlated with the seed characteristics and the soil seed bank in bare land.The spatial distribution of S.breviflora was aggregated under heavy grazing.Our results suggest that under heavy grazing,reproductive activity plays a key role in resource allocation.Stipa breviflora evolved the ecological strategy of nearby diffusion by regulating the morphological characteristics of the seeds,which promotes a positive spatial correlation between the juvenile and adult populations at a small scale,thus leading to the formation of‘safe islands’.

植物的生态适应策略一直备受生态学者的关注,然而很少有研究能够整体地、系统地揭示植物适应草食动物的生态过程。本研究以内蒙古荒漠草原建群种短花针茅为研究对象,分析了重度放牧和不放牧处理下短花针茅的繁殖个体性状、种子性状以及土壤种子库和种群空间格局。研究结果表明,生殖个体性状方面,生殖枝数量对营养枝数量有正向影响;土壤种子库方面,短花针茅生殖个体基部的土壤种子库中短花针茅密度显著高于旁边裸地土壤种子库中短花针茅的密度,且与种子性状和裸地土壤种子库显著负相关;在种群空间格局方面,重度放牧下短花针茅种群空间聚集分布。我们的结果认为在重度放牧处理下,生殖活动在短花针茅的资源分配中处于主导地位;短花针茅植物种群通过调控种子形态特征,采用就近扩散的生态策略,促进了幼年种群与成年种群在较小的尺度上空间正关联,从而形成“安全岛”。