Recovery Across a Gradient of Disturbance Novelties: Patterns and Drivers of Understory Plant Community Dynamics in Northern Lodgepole Pine Forests

每年有数百万公顷的加拿大北部森林受到自然和人为干扰因素的影响。新的干扰正在推动北方森林超越其历史上的自然变化范围；这些森林正在经历前所未有的类型和严重的干扰。干扰制度的变化反过来又导致森林结构、功能和长期演替轨迹的变化，并带来未知的生态后果。这些干扰对林冠、林下植物群落和地下特征的相对影响将在决定这些森林的演替、生物多样性和保护方面发挥重要作用。鉴于林下植物群落是森林生态功能和生物多样性的组成部分，了解干扰对这些植物群落的影响及其与其他生态系统特性和过程的联系将有助于我们更好地理解森林对变化干扰制度的复杂反应。黑松（Pinus contorta）林为评估不同新奇干扰对林下植物群落的影响提供了天然实验室。在加拿大西部，气候变化导致了前所未有的山松甲虫（MPB）爆发，而MPB持续扩展到新栖息地对林下植物群落的影响尚不清楚。MPB选择性地杀死较大和较老的树木，使林下植被保持完整，而对被攻击树木的抢救采伐对林下植被有直接的影响。直接影响在随后用于石油和天然气开采，然后重新开垦为新森林的砍伐地区更为显著。当松树被引进到世界其他地区时，它们本身可能被认为是主要的干扰因子。我的研究项目侧重于了解林下植物群落对这些干扰的反应与历史干扰因子（林分替代火）之间的差异。我提出的研究考察了单一森林生态系统类型，黑松的植物群落结构和功能响应，跨越了新干扰类型的梯度。我的研究活动将为一个框架的发展奠定基础，使我们能够更好地预测：i)各种干扰对植物生物多样性和功能的长期影响，以及ii)变化干扰制度下松林的演替轨迹。此外，它将为北部森林的保护和恢复实践提供经验基础，包括推进省级长期监测计划的发展，以评估阿尔伯塔省再生森林的生态恢复。它同时为11名下一代UG、MSc、PhD和PDF科学家提供变革性的研究经验和培训。

Millions of hectares of Canada's northern forests are impacted each year by both natural and anthropogenic disturbance agents. Novel disturbances are pushing northern forests beyond their historical natural ranges of variability; these forests are experiencing unprecedented types and severities of disturbance. The changes in disturbance regimes are in turn are leading to changes in forest structure, function, and long-term successional trajectories, with unknown ecological consequences. The relative impacts of these disturbances on the forest canopy, understory plant community, and below-ground properties will play an important role in determining succession, biodiversity and conservation of these forests. Given that understory plant communities are integral to the ecological functioning and biodiversity of forests, gaining an understanding of impacts of disturbance on these plant communities and their linkages with other ecosystem properties and processes will help us to better understand the complex responses that forests may have to shifting disturbance regimes. Lodgepole pine (Pinus contorta) forests provide natural laboratories for assessing the effects of varying novelties of disturbance on understory plant communities. In western Canada, climate change has contributed to an unprecedented mountain pine beetle (MPB) outbreak, and the impacts of ongoing range expansion of MPB into new habitats on understory plant communities remain unknown. MPB selectively kills larger and older trees, leaving the understory intact, whereas salvage harvest of attacked trees has immediate direct effects on the understory. Direct effects are even more dramatic in logged areas that are subsequently used for oil and gas extraction, and then reclaimed to new forest. When pine trees are introduced to other regions of the world, they may themselves be considered as the primary disturbance agent. My research program focuses on understanding both how and why understory plant community responses differ among these disturbances compared with historical disturbance agents (stand-replacing fire). My proposed research examines plant community structural and functional responses of a single forest ecosystem type, lodgepole pine, across a gradient of novelties of disturbance types. My research activities will set the stage for development of a framework that will allow us to better predict: i) long-term impacts of varied disturbances on plant biodiversity and function, and ii) the successional trajectories of pine forests under changing disturbance regimes. Further, it will provide the empirical basis to inform conservation and restoration practices in northern forests, including advancing development of a provincial long-term monitoring program to assess ecological recovery of reclaimed forests in Alberta. It simultaneously provides transformative research experience and training for 11 next generation UG, MSc, PhD and PDF scientists in an inclusive brave space.