Fire regimes and forest composition in Canadian mixedwood boreal forest

景观结构及其与干扰机制的相互作用是理解北方森林马赛克的关键因素。一些研究表明，频繁、大而严重的火灾可能会导致缺乏后期演替物种的林分的形成，因为这些物种不得不从未被烧毁的地区带着种子重新入侵。火灾严重程度通过控制苗床可利用性和生产力，也可能影响火灾后的成分和演替发展。我的长期目标是了解火灾制度如何控制北方森林的森林组成和生态过程。在未来5年，我建议通过3个互补项目来实现这一目标。第一个项目的目的是完成重建加拿大混合木材北方森林的长期火灾制度。以前的工作包括魁北克省和安大略省的一些地区。这个建议将弥补到BC的差额。火灾周期将根据火灾以来的时间地图和档案进行重建，航空照片（自20世纪30年代以来）将用于描绘20世纪发生的火灾。用树木年代学测量的林分形成年份来估计由老火产生的森林的比例。在第二个项目中，我将使用横跨加拿大东部到西部的一个样带的可比较的白杨林，来评估在区域和景观层面上，火灾制度是如何控制林分水平上的多样性和演替的。第三个项目将在白杨、云杉和冷杉丰富的东部北方地区进行。我将评估火灾严重程度如何控制火灾后的森林组成和演替途径。低严重程度的火灾将以云杉为主，有利于苔藓，排除白杨和冷杉。本研究提出了一种新的时空方法来解释北方森林植被嵌合现象。预期结果将有助于了解气候变化对植被变化的影响，通过确定生态系统对气候和干扰制度引起的变化的抵抗力。

Landscape structure and its interactions with disturbance regimes are key elements to consider in understanding boreal forest mosaics. Several studies have demonstrated that frequent, large and severe fires may contribute to the creation of stands lacking late successional species as these species have to reinvade by seeds from unburnt areas. Fire severity, via its control of seed-bed availability and productivity, could also influence post-fire composition and successional development. My long term objective is to understand how fire regimes control forest composition and ecological processes in the boreal forest. In the next 5 years I propose to address this objective through 3 complementary projects. The first project aims to complete the reconstruction of long-term fire regimes in the Canadian mixedwood boreal forest. Previous works included territories in Quebec and in some parts of Ontario. This proposal will cover the gap to BC. Fire cycles will be reconstructed using time since fires maps and archives, and aerial photographs (since the 1930s) will be used to delineate fires that occurred during the twentieth century. The proportion of forests originating from older fires will be estimated using year of stand initiation as measured by dendrochronology. In a second project, I will use comparable aspen stands across a transect from eastern to western Canada to assess how fire regimes, acting at the regional and landscape level, control diversity and succession at the stand level. The third project will be undertaken in the eastern boreal where aspen, spruce and fir are abundant. I will assess how fire severity controls post fire forest composition and successionnal pathways. Low severity fires would be dominated by spruce and would favour mosses and exclude aspen and fir. The proposed research introduces a new spatio-temporal approach to interpreting vegetation mosaics in the boreal forest. Anticipated results will contribute towards understanding the effects of climate change on vegetation changes by determining ecosystem resistance to changes due to climate and disturbance regimes.