Biodiversity and composition of understory plant communities in the boreal mixedwood forest

林下植物群落(生长在树冠下的灌木和非木本植物)是森林生物多样性的重要组成部分。它为各种生物提供了栖息地，也是生态系统进程的驱动力。在森林中，树冠树通过直接竞争和对林下植物重要的环境条件(例如，建立的微型地点、土壤pH值和养分有效性、小气候)的影响来影响林下植物。树木还可以影响火灾干扰的严重程度，进而影响火灾后林下植被的重新开发。在加拿大西部北部平原的中生地，森林主要是颤抖的白杨和白云杉的不同组合。这两个树种对火灾严重程度和林下环境条件的影响不同。因此，它们的相对丰度对混交林景观中林下植物群落的组成和生物多样性具有重要的意义。本研究旨在探索混交林景观中白云杉的存在对林下植物群落组成和生物多样性的影响。在接下来的五年里，我们将：1)记录森林组成对火灾严重程度的影响，进而对火灾后林下重建的影响；2)研究白云杉在火灾后演替过程中对林下植物群落的长期影响；3)量化在杨树为主的林分中添加白云杉对环境条件和林下群落的影响；4)评估大型郁闭型白云杉对森林环境、白云杉更新和混交林中林下群落的影响。通过这项研究，将培养三名硕士和两名博士生。研究结果将有助于我们了解影响北方针叶林植物群落的因素。此外，这项工作将有助于我们了解操纵混交林组成的森林管理做法的潜在影响，从而为努力管理这些森林以维护生物多样性提供重要的知识基础。

The understory plant community (shrubs and non-woody plants growing under canopy trees) is an important component of forest biodiversity. It provides habitat for a diversity of living organisms and is a driver of ecosystem processes. In forests, canopy trees influence the understory through direct competition and also through effects on environmental conditions important for understory plants (e.g., microsites for establishment, soil pH and nutrient availability, microclimate). Trees can also influence the severity of disturbance by fire, which in turn affects post-fire redevelopment of the understory. On mesic sites in the boreal plain of western Canada forests are dominated by varying combinations of trembling aspen and white spruce. These two tree species differ in their effects on fire severity and on environmental conditions for the understory. Their relative abundance, therefore, has important implications for the composition and biodiversity of understory plant communities in mixedwood landscapes.My research is exploring the influence of the presence of white spruce in mixedwood forest landscapes on understory plant community composition and biodiversity. Over the next five years we will: 1) Document the influence of forest composition on fire severity and, in turn, effects on post-fire understory redevelopment; 2) Examine the influence of white spruce on understory plant communities over the long term during post-fire succession; 3) Quantify the effects of the addition of white spruce to aspen-dominated stands on environmental conditions and the understory community; 4) Assess the effects of large, canopy-emergent white spruce on forest environment, white spruce regeneration, and understory communities in mixedwood stands. Three MSc and two PhD students will be trained through this research. The results will contribute to our understanding of factors influencing plant communities in the boreal forest.  Further, this work will help us to understand the potential impacts of forest management practices that manipulate the composition of mixedwood forest, thus providing an important knowledge base for efforts to manage these forests to maintain biodiversity.