A systematic review of the ecological literature on cushion plants

Cushion-forming plant species are found in alpine and polar environments around the world. They modify the microclimate, thereby facilitating other plant species. Similar to the effectiveness of shrubs as a means to study facilitation in arid and semi-arid environments, we explore the potential for cushion plant species to expand the general- ity of research on this contemporary ecological interaction. A systematic review was conducted to determine the number of publications and citation frequency on relevant ecological topics whilst using shrub literature as a baseline to assess relative importance of cushions as a focal point for future ecological research. Although, there are forty times more shrub articles, mean citations per paper is comparable between cushion and shrub literature. Furthermore, the scope of ecological research topics studied us- ing cushions is broad including facilitation, competition, environmental gradients, life history, genetics, reproduction, community, ecosystem and evolution. The preliminary ecological evidence to date also strongly suggests that cushion plants can be keystone species in their ecosystems. Hence, ecological research on net interactions including facilitation and patterns of diversity can be successfully examined using cushion plants, and this is particularly timely given expectations associated with a changing climate in these regions.

垫状植物（Cushion-forming plant species）广泛分布于全球的高山与极地环境中。它们可改善微生境，进而促进其他植物物种的生长。与灌木作为干旱、半干旱环境中种间促进作用研究的经典研究载体的有效性相仿，本研究探讨了垫状植物拓展这类当代生态相互作用研究普适性的潜力。本研究通过系统综述，统计了相关生态主题的文献总量与被引频次，并以灌木相关文献作为基准，评估垫状植物作为未来生态研究核心议题的相对重要性。尽管灌木相关文献的数量是垫状植物相关文献的40倍，但二者的篇均被引频次相当。此外，以垫状植物为研究对象的生态研究主题覆盖范围极广，涵盖种间促进、种间竞争、环境梯度、生活史、遗传学、繁殖生态学、群落生态学、生态系统与进化生物学等多个研究方向。截至目前的初步生态学证据也充分证实，垫状植物可作为关键物种（keystone species）在其所在生态系统中发挥核心功能。因此，以垫状植物为研究对象，可有效开展包括种间促进在内的净相互作用以及多样性模式相关的生态学研究；考虑到这些区域正面临气候变化带来的诸多影响，该研究方向恰逢其时。