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十分重要。 然而，植物促进作用的结果通常仅限于单一的营养水平效应，即植物-植物相互作用，而不是传粉者，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，这可能是决定社区复原力的一个关键因素。 直接的相互作用也主要研究。 这些研究空白可以扩展社区理论并为恢复提供信息。 因此，在旱地生态系统，如草地或退化的农业系统中提供便利，将调解物种的损失，并提供结构和功能上的复原力。 苗圃研究是旱地促进研究的主要内容。 保育植物是促进其他植物物种（通常是一年生植物）的建立和表现的灌木。 因此，灌木在干旱系统，退化的草地，或农业系统的降雨量低的管理是至关重要的，以维持生态系统的功能，这些文献是一个重要的途径，明确的研究准备适应。 在这个项目中，首要的假设是，苗圃植物是基础物种，为社区集会提供了一个锚。 因此，主要目的是通过扩展到其他营养级，多种相互作用途径和恢复来创新苗圃研究。 所有研究活动旨在测试以下三个广泛目标之一：（i）解开营养植物对传粉者，动物和节肢动物的营养作用，（ii）解决许多直接和间接的相互作用途径，包括种子库，以及（iii）探索灌木在这些生态系统中作为恢复剂的能力。新奇和预期的意义 * 该计划直接测试是否可以使用强大的，基础的积极相互作用来管理受干扰的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学文献的新贡献。 营养型苗圃对动物的影响很少得到研究，探讨对节肢动物或传粉者影响的研究也较少，即不到5项研究。 恢复灌木是相对较好的研究，但使用灌木作为恢复工具是罕见的，一个关键的范式转变。 重要的是，将这些不同的概念试验性地纳入一项研究方案，实际上是将旱地的各个部分重新组合在一起。 因此，与该项目相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基础物种和高度受影响的系统中的社区组装动态。 这与政策有关，因为全球传粉媒介减少，人类对这些生态系统的影响越来越大，越来越频繁，入侵物种和气候变化增加可能对物种多样性产生负面影响。 有效管理苗圃将是保持复原力的重要一步。 加拿大将受益于这项研究，因为以下发现：护士植物和节肢动物/授粉服务之间的联系，绘制新的生态网络，并确定最佳恢复做法。 加拿大的草地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，利用积极互动促进生态系统功能至关重要。

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.