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

林下植物群落（灌木和生长在树冠下的非木本植物）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，是生态系统进程的驱动力。在森林中，冠层树木通过直接竞争和对林下植物重要的环境条件的影响（例如，微型基地的建立，土壤pH值和养分供应，小气候）。树木也可以影响火灾干扰的严重程度，这反过来又会影响火灾后重建的林下植物。在加拿大西部北方平原的梅西奇地区，森林主要由颤抖的白杨和白色云杉的不同组合组成。这两个树种不同的影响火灾的严重程度和林下环境条件。因此，它们的相对丰富度对混交林景观林下植物群落的组成和生物多样性具有重要意义。本研究旨在探讨混交林景观中白色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，并反过来影响火灾后林下重建; 2）研究火灾后演替过程中白色云杉对林下植物群落的长期影响; 3）量化白色云杉对环境条件和林下群落的影响; 4）评估大型、顶出白色云杉对森林环境、白色云杉更新和混交林林下群落的影响。三个硕士和两个博士生将通过这项研究进行培训。研究结果将有助于我们了解影响北方森林植物群落的因素。 此外，这项工作将帮助我们了解操纵混交林组成的森林管理做法的潜在影响，从而为管理这些森林以保持生物多样性的努力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.