Bond-Lamberty Ben, Peckham Scott D, Ahl Douglas E, Gower Stith T
Department of Forest and Wildlife Ecology, University of Wisconsin, 1630 Linden Drive, Madison, Wisconsin 53706, USA.
Nature. 2007 Nov 1;450(7166):89-92. doi: 10.1038/nature06272.
Changes in climate, atmospheric carbon dioxide concentration and fire regimes have been occurring for decades in the global boreal forest, with future climate change likely to increase fire frequency--the primary disturbance agent in most boreal forests. Previous attempts to assess quantitatively the effect of changing environmental conditions on the net boreal forest carbon balance have not taken into account the competition between different vegetation types on a large scale. Here we use a process model with three competing vascular and non-vascular vegetation types to examine the effects of climate, carbon dioxide concentrations and fire disturbance on net biome production, net primary production and vegetation dominance in 100 Mha of Canadian boreal forest. We find that the carbon balance of this region was driven by changes in fire disturbance from 1948 to 2005. Climate changes affected the variability, but not the mean, of the landscape carbon balance, with precipitation exerting a more significant effect than temperature. We show that more frequent and larger fires in the late twentieth century resulted in deciduous trees and mosses increasing production at the expense of coniferous trees. Our model did not however exhibit the increases in total forest net primary production that have been inferred from satellite data. We find that poor soil drainage decreased the variability of the landscape carbon balance, which suggests that increased climate and hydrological changes have the potential to affect disproportionately the carbon dynamics of these areas. Overall, we conclude that direct ecophysiological changes resulting from global climate change have not yet been felt in this large boreal region. Variations in the landscape carbon balance and vegetation dominance have so far been driven largely by increases in fire frequency.
在全球北方森林地区，气候、大气二氧化碳浓度和火灾模式的变化已经持续了数十年，未来气候变化可能会增加火灾发生频率，而火灾是大多数北方森林的主要干扰因素。此前定量评估环境条件变化对北方森林净碳平衡影响的尝试，并未充分考虑大规模不同植被类型之间的竞争。在此，我们使用一个包含三种相互竞争的维管植物和非维管植物类型的过程模型，来研究气候、二氧化碳浓度和火灾干扰对加拿大10000万公顷北方森林的净生物群系生产、净初级生产和植被优势度的影响。我们发现，1948年至2005年期间，该地区的碳平衡受火灾干扰变化的驱动。气候变化影响了景观碳平衡的变异性，但未影响其平均值，其中降水的影响比温度更为显著。我们发现，20世纪后期更频繁、规模更大的火灾导致落叶树和苔藓的产量增加，而针叶树的产量则相应减少。然而，我们的模型并未呈现出卫星数据所推断的森林总净初级生产的增加。我们发现，土壤排水不畅降低了景观碳平衡的变异性，这表明气候和水文变化加剧有可能对这些地区的碳动态产生不成比例的影响。总体而言，我们得出结论，在这个广袤的北方地区，尚未感受到全球气候变化所导致的直接生态生理变化。迄今为止，景观碳平衡和植被优势度的变化主要是由火灾频率增加所驱动的。
