It takes a few to tango: changing climate and fire regimes can cause regeneration failure of two subalpine conifers
It takes a few to tango: changing climate and fire regimes can cause regeneration failure of two subalpine conifers
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DOI：
10.1002/ecy.2181
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发表时间：
2018-04-01
期刊：
影响因子：
4.8
通讯作者：
Turner, Monica G.
中科院分区：
文献类型：
--
作者：
Hansen, Winslow D.;Braziunas, Kristin H.;Turner, Monica G.
在21世纪，环境变化正在加速，但多个驱动因素如何相互作用以改变森林的弹性仍不确定。在受大型高强度干扰影响的森林中，树木再生是数十年来形成演替轨迹的弹性关键。我们模拟了美国西部两种分布广泛的针叶树--道格拉斯冷杉(Pseudotsuga menziesii var.)Gluca)和小叶松(Pinus trorta var.)美国怀俄明州黄石国家公园(Yellowstone National Park，美国怀俄明州)进行了一项调查，询问(1)距离种子源的距离、火灾返回间隔和升温干燥条件的什么组合会导致火灾后树木再生失败？(2)如果火灾后树木再生成功，那么未来气候下的早期树木密度与历史气候相比有何不同？我们使用基于个体的森林过程模型iLand进行了林分水平(1ha)因子模拟实验，以确定火回归间隔(11-100yr)、到种子源的距离(50-1000m)和气候(历史上的、21世纪中叶、21世纪末)的组合，其中树木在火灾后30年无法再生。如果更新成功，我们比较了不同气候时期的林分密度。模拟的火灾后再生令人惊讶地对不断变化的气候和火灾驱动因素具有弹性。道格拉斯冷杉更新失败的频率(55%)高于小叶松(非5粘质和5粘质林分别为28%和16%)。离种源的距离是导致道格拉斯冷杉和无浆液性小落叶松更新失败的一个重要因素；当林分距离种源50m时，更新从未失败，而当林分距离种源1公里时，更新几乎总是失败。只有当退火间隔为20年且林分距离种源较远(1公里)时，5-羟基松的更新才会失败。气候变暖增加了道格拉斯冷杉的更新成功率，但不影响樟子松的更新。如果更新成功，则火后密度会因气候而异。在21世纪的气候下，道格拉斯冷杉和5-羟基松的更新密度都有所增加，但对不同的气候变量(生长季节长度与寒冷限制)的反应不同。结果表明，考虑到未来更温暖、更大和更频繁的火灾，火灾后未能更多更新的林分数量增加，再加上更新成功的林分密度增加，可能会产生更粗粒度的森林景观。
Environmental change is accelerating in the 21st century, but how multiple drivers may interact to alter forest resilience remains uncertain. In forests affected by large high-severity disturbances, tree regeneration is a resilience linchpin that shapes successional trajectories for decades. We modeled stands of two widespread western U.S. conifers, Douglas-fir (Pseudotsuga menziesii var. glauca), and lodgepole pine (Pinus contorta var. latifolia), in Yellowstone National Park (Wyoming, USA) to ask (1) What combinations of distance to seed source, fire return interval, and warming-drying conditions cause postfire tree-regeneration failure? (2) If postfire tree regeneration was successful, how does early tree density differ under future climate relative to historical climate? We conducted a stand-level (1ha) factorial simulation experiment using the individual-based forest process model iLand to identify combinations of fire return interval (11-100yr), distance to seed source (50-1,000m), and climate (historical, mid-21st century, late-21st century) where trees failed to regenerate by 30-yr postfire. If regeneration was successful, we compared stand densities between climate periods. Simulated postfire regeneration were surprisingly resilient to changing climate and fire drivers. Douglas-fir regeneration failed more frequently (55%) than lodgepole pine (28% and 16% for non-serotinous and serotinous stands, respectively). Distance to seed source was an important driver of regeneration failure for Douglas-fir and non-serotinous lodgepole pine; regeneration never failed when stands were 50m from a seed source and nearly always failed when stands were 1km away. Regeneration of serotinous lodgepole pine only failed when fire return intervals were 20yr and stands were far (1km) from a seed source. Warming climate increased regeneration success for Douglas-fir but did not affect lodgepole pine. If regeneration was successful, postfire density varied with climate. Douglas-fir and serotinous lodgepole pine regeneration density both increased under 21st-century climate but in response to different climate variables (growing season length vs. cold limitation). Results suggest that, given a warmer future with larger and more frequent fires, a greater number of stands that fail to regenerate after fires combined with increasing density in stands where regeneration is successful could produce a more coarse-grained forest landscape.