Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
Department of Macroecology and Landscape Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland.
Glob Chang Biol. 2018 Oct;24(10):4929-4945. doi: 10.1111/gcb.14380. Epub 2018 Jul 20.
The influence of different drivers on changes in North American and European boreal forests biomass burning (BB) during the Holocene was investigated based on the following hypotheses: land use was important only in the southernmost regions, while elsewhere climate was the main driver modulated by changes in fuel type. BB was reconstructed by means of 88 sedimentary charcoal records divided into six different site clusters. A statistical approach was used to explore the relative contribution of (a) pollen-based mean July/summer temperature and mean annual precipitation reconstructions, (b) an independent model-based scenario of past land use (LU), and (c) pollen-based reconstructions of plant functional types (PFTs) on BB. Our hypotheses were tested with: (a) a west-east northern boreal sector with changing climatic conditions and a homogeneous vegetation, and (b) a north-south European boreal sector characterized by gradual variation in both climate and vegetation composition. The processes driving BB in boreal forests varied from one region to another during the Holocene. However, general trends in boreal biomass burning were primarily controlled by changes in climate (mean annual precipitation in Alaska, northern Quebec, and northern Fennoscandia, and mean July/summer temperature in central Canada and central Fennoscandia) and, secondarily, by fuel composition (BB positively correlated with the presence of boreal needleleaf evergreen trees in Alaska and in central and southern Fennoscandia). Land use played only a marginal role. A modification towards less flammable tree species (by promoting deciduous stands over fire-prone conifers) could contribute to reduce circumboreal wildfire risk in future warmer periods.
本研究基于以下假设，调查了不同驱动因素对全新世北美和欧洲北方森林生物质燃烧（BB）变化的影响：土地利用仅在最南端的地区重要，而在其他地区，气候是主要的驱动因素，受燃料类型变化的调节。通过 88 个沉积木炭记录，将 BB 分为六个不同的站点群进行重建。采用统计方法，探讨了以下因素对 BB 的相对贡献：（a）花粉基 7 月/夏季平均温度和年平均降水重建，（b）过去土地利用（LU）的独立模型基情景，以及（c）花粉基植物功能型（PFT）重建。我们用以下两种情况检验了我们的假设：（a）一个气候条件不断变化、植被单一的北方森林西部-东部地区，（b）一个气候和植被组成逐渐变化的北方森林北部-南部欧洲地区。在全新世，北方森林 BB 的驱动过程因地区而异。然而，北方森林生物质燃烧的总体趋势主要受气候变化（阿拉斯加、魁北克北部和北芬诺斯堪的亚的年平均降水，加拿大中部和北芬诺斯堪的亚的 7 月/夏季平均温度）和燃料组成变化（BB 与阿拉斯加和中南部芬诺斯堪的亚的北方针叶常绿树种的存在呈正相关）的控制。土地利用仅起次要作用。向不易燃树种的转变（通过促进落叶林取代易着火的针叶林）可能有助于降低未来温暖时期的环北极野火风险。
