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、大火和严重的火灾可能会导致缺乏后期演替物种的林分的形成，因为这些物种必须通过来自未烧毁地区的种子重新入侵。火灾的严重程度，通过控制苗床的可用性和生产力，也可能影响火灾后的组成和演替发展。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。在接下来的5年里，我建议通过3个相辅相成的项目实现这一目标。第一个项目旨在完成加拿大北方混交林长期火灾制度的重建。之前的作品包括魁北克和安大略省部分地区的领土。这项提案将弥补BC的缺口。将使用自火灾地图和档案以来的时间重建火灾周期，并将使用航空照片(自1930年代以来)来描绘发生在20世纪的火灾。将使用树木年代学测量的林分起始年份来估计源自较旧火灾的森林的比例。在第二个项目中，我将使用从加拿大东部到西部的样带上的可比杨树林分来评估火灾制度是如何在区域和景观水平上发挥作用，在林分水平上控制多样性和演替的。第三个项目将在东部北方地区进行，那里有大量的白杨、云杉和冷杉。我将评估火灾严重程度如何控制火灾后的森林组成和后续路径。低强度的火灾将以云杉为主，有利于苔藓，不包括白杨和冷杉。这项拟议的研究引入了一种新的时空方法来解释北方森林中的植被马赛克。预期成果将通过确定生态系统对气候和干扰制度变化的抵抗力，有助于理解气候变化对植被变化的影响。

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.