Unpacking the trophic effects of shrubs in arid and semi-arid systems to inform restoration and management.

积极的植物相互作用对包括草原在内的旱地的多样性和生产力至关重要。然而，植物促进作用的结果通常局限于单一的营养水平效应，即植物与植物之间的相互作用，而不是传粉媒介、节肢动物或动物。植物相互作用对种子库的影响往往被忽视，而这可能是决定群落恢复力的关键因素。直接的相互作用也主要被检查。这些研究空白可以扩展社区理论并为修复提供信息。因此，旱地生态系统（如草地或退化的农业系统）的促进作用将调节物种损失，并提供结构和功能上的恢复能力。护理植物研究占旱地便利化研究的大部分。护理植物是灌木，它们有助于其他植物物种的建立和生长，通常是一年生植物。因此，在干旱系统、退化草原或降雨量少的农业系统中，灌木的管理对维持生态系统功能至关重要，这一文献是为适应做好准备的清晰研究的重要途径。在这个项目中，研究的首要假设是护理植物是基础物种，为群落聚集提供了一个锚点。因此，主要目的是通过扩展到其他营养水平，多种相互作用途径和恢复来创新护理植物研究。所有的研究活动都旨在测试以下三个主要目标之一：(i)揭示护理植物对传粉者、动物和节肢动物的营养效应；（ii）解决护理植物对群落动态（包括种子库）的许多直接和间接相互作用途径；（iii）探索灌木在这些生态系统中作为恢复剂的能力。新颖性和预期意义该项目直接测试了强的、基础的正相互作用是否可以用于管理受干扰生态系统中的生物多样性。每个目标都是对基础和应用生态文献的新贡献。营养护理植物对动物的影响很少被研究，对节肢动物或传粉媒介影响的研究较少，即少于5项研究。灌木的恢复研究相对较好，但使用灌木作为恢复工具的情况很少，而且是一个关键的范式转变。重要的是，将这些不同的实验概念整合到一个研究项目中，实际上是将旱地的碎片重新拼凑在一起。因此，与该项目有关的学员将在理论和应用方面获得坚实的基础。相互作用的整合将定义高影响系统中的基础物种和群落组装动态。鉴于传粉媒介的全球减少，人类对这些生态系统影响的规模和频率不断增加，以及入侵物种和气候变异性增加可能对物种多样性产生负面影响，这与政策有关。有效管理护理植物将是维持恢复力的重要一步。加拿大将从这项研究中受益，因为有以下发现：护理植物与节肢动物/传粉者服务之间的联系，绘制新的生态网络，以及确定最佳恢复措施。加拿大的草原和农业系统与所提出的模式系统非常相似。不幸的是，加拿大也面临上述所有挑战，利用积极的相互作用来促进生态系统功能将是至关重要的。

Objectives & nature of work Positive plant interactions are important to diversity and productivity in drylands including grasslands. The consequences of plant facilitation are however generally restricted to single trophic-level effects, i.e. to plant-plant interactions, and not to pollinators, arthropods, or animals. Plant interaction impacts on seedbanks are often overlooked and can be a critical factor in determining community resilience. Direct interactions are also predominantly examined. These research gaps can expand community theory and inform restoration. Accordingly, facilitation in dryland ecosystems such as grasslands or degraded agricultural systems will mediate species loss and provide structural and functional resilience. Nurse-plant studies comprise the majority of research on facilitation in drylands. Nurse plants are shrubs that facilitate the establishment and performance of other plant species, typically annuals. Hence, the management of shrubs in arid systems, degraded grasslands, or agricultural systems with low rainfall in general is vital to maintaining ecosystem function, and this literature is an important avenue of well-articulated research ready for adaptation. In this programme, the overarching hypothesis examined is that nurse-plants are foundation species that provide an anchor for community assembly. The primary purpose is thus to innovate the nurse-plant research by extending to other trophic levels, multiple interaction pathways, and restoration. All research activities are designed to test one of following three broad objectives: (i) to unpack the trophic effects of nurse plants on pollinators, animals, and arthropods, (ii) to resolve many of the direct and indirect interaction pathways of nurse-plants on community dynamics including seedbanks, and (iii) to explore the capacity for shrubs to act as restoration agents in these ecosystems. Novelty & expected significance This program directly tests whether strong, basal positive interactions can be used to manage biodiversity in disturbed ecosystems. Each objective is a novel contribution to the fundamental and applied ecological literature. Trophic nurse-plant effects on animals are rarely examined, and there are fewer studies exploring impacts on arthropods or pollinators, i.e. less than 5 studies. Restoration of shrubs is relatively well studied, however using shrubs as the restoration tool is infrequent and a critical paradigm shift. Importantly, the implication of integrating these different concepts experimentally into a research programme is in effect putting the pieces back together for drylands. Trainees associated with the project will thus receive a solid grounding in both theory and application. Integration of interactions will define the foundation species and the community-assembly dynamics in highly impacted systems. This is relevant to policy given global declines of pollinators, the increasing scale and frequency of impacts by humans on these ecosystems, and the likelihood that both invasive species and increased climatic variability will negatively impact species diversity. Effective management of nurse plants will be an important step in maintaining resilience. Canada will benefit from this research because of the following discoveries: linkages between nurse plants and arthropod/pollinator services, mapping novel ecological networks, and identification of best restoration practices. Canadian grasslands and agricultural systems are very similar to the model system proposed. Unfortunately, Canada also shares all of the challenges described above and capitalizing on positive interactions to promote ecosystem function will be critical.