Tautenhahn Susanne, Lichstein Jeremy W, Jung Martin, Kattge Jens, Bohlman Stephanie A, Heilmeier Hermann, Prokushkin Anatoly, Kahl Anja, Wirth Christian
Max Planck Institute for Biogeochemistry, Hans-Knöll-Strasse 10, 07745, Jena, Germany.
Department of Biosciences, TU Bergakademie Freiberg, Leipziger Strasse 29, 09596, Freiberg, Germany.
Glob Chang Biol. 2016 Jun;22(6):2178-97. doi: 10.1111/gcb.13181. Epub 2016 Mar 8.
Fire is a primary driver of boreal forest dynamics. Intensifying fire regimes due to climate change may cause a shift in boreal forest composition toward reduced dominance of conifers and greater abundance of deciduous hardwoods, with potential biogeochemical and biophysical feedbacks to regional and global climate. This shift has already been observed in some North American boreal forests and has been attributed to changes in site conditions. However, it is unknown if the mechanisms controlling fire-induced changes in deciduous hardwood cover are similar among different boreal forests, which differ in the ecological traits of the dominant tree species. To better understand the consequences of intensifying fire regimes in boreal forests, we studied postfire regeneration in five burns in the Central Siberian dark taiga, a vast but poorly studied boreal region. We combined field measurements, dendrochronological analysis, and seed-source maps derived from high-resolution satellite images to quantify the importance of site conditions (e.g., organic layer depth) vs. seed availability in shaping postfire regeneration. We show that dispersal limitation of evergreen conifers was the main factor determining postfire regeneration composition and density. Site conditions had significant but weaker effects. We used information on postfire regeneration to develop a classification scheme for successional pathways, representing the dominance of deciduous hardwoods vs. evergreen conifers at different successional stages. We estimated the spatial distribution of different successional pathways under alternative fire regime scenarios. Under intensified fire regimes, dispersal limitation of evergreen conifers is predicted to become more severe, primarily due to reduced abundance of surviving seed sources within burned areas. Increased dispersal limitation of evergreen conifers, in turn, is predicted to increase the prevalence of successional pathways dominated by deciduous hardwoods. The likely fire-induced shift toward greater deciduous hardwood cover may affect climate-vegetation feedbacks via surface albedo, Bowen ratio, and carbon cycling.
火灾是北方森林动态变化的主要驱动因素。气候变化导致火灾发生频率增加，可能会使北方森林的组成发生变化，针叶树的优势地位下降，落叶阔叶树的数量增多，这可能会对区域和全球气候产生生物地球化学和生物物理反馈。这种变化已经在一些北美北方森林中观察到，并被归因于立地条件的改变。然而，尚不清楚控制落叶阔叶树覆盖面积因火灾而变化的机制在不同的北方森林中是否相似，这些森林在优势树种的生态特征方面存在差异。为了更好地理解北方森林火灾发生频率增加的后果，我们研究了中西伯利亚暗针叶林五处火烧迹地的火灾后更新情况，这是一个广阔但研究较少的北方地区。我们结合了实地测量、树木年代学分析以及从高分辨率卫星图像得出的种子源地图，以量化立地条件（如有机层深度）与种子可获得性在塑造火灾后更新中的重要性。我们发现，常绿针叶树的扩散限制是决定火灾后更新组成和密度的主要因素。立地条件有显著影响，但作用较弱。我们利用火灾后更新的信息制定了一个演替路径分类方案，该方案代表了落叶阔叶树与常绿针叶树在不同演替阶段的优势地位。我们估计了在不同火灾情景下不同演替路径的空间分布。在火灾发生频率增加的情况下，预计常绿针叶树的扩散限制将变得更加严重，主要原因是火烧区域内幸存种子源的数量减少。常绿针叶树扩散限制的增加，反过来预计会增加以落叶阔叶树为主的演替路径的普遍性。火灾可能导致的落叶阔叶树覆盖面积增加，可能会通过地表反照率、鲍文比和碳循环影响气候 - 植被反馈。
