Influences of fire-vegetation feedbacks and post-fire recovery rates on forest landscape vulnerability to altered fire regimes
Influences of fire-vegetation feedbacks and post-fire recovery rates on forest landscape vulnerability to altered fire regimes
复制标题
火灾植被反馈和火灾后恢复率对森林景观易受火灾状况影响的脆弱性的影响
DOI：
10.1111/1365-2745.12950
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发表时间：
2018
影响因子：
5.5
通讯作者：
Lines, ed., Emily
中科院分区：
文献类型：
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作者：
Tepley, Alan J.;Thomann, Enrique;Veblen, Thomas T.;Perry, George L. W.;Holz, Andrés;Paritsis, Juan;Kitzberger, Thomas;Anderson-Teixeira, Kristina J.;Lines, ed., Emily
在持续气候变暖的背景下，森林景观面临着通过改变其火灾状况和火灾后恢复动态而转化为非森林植被的风险越来越大。然而，这种压力可能会被放大或减弱，这取决于火驱动的植被变化如何反馈，以改变随后火灾的程度或行为。在这里，我们开发了一个数学模型，以正式理解火灾植被反馈和森林恢复的时间如何在高严重性（即林分替换）火灾后影响森林覆盖的范围和稳定性。我们评估增加燃烧率的反应，同时改变方向（负与正）的火灾植被反馈下的连续值的反馈强度和火灾后恢复时间。在此过程中，我们确定了这些变量之间的相互作用如何在景观对变化的火灾状况的响应中产生阈值和临界点。在早期演替的植被比老森林更不容易发生火灾的地方，负反馈限制了森林覆盖率的减少，以应对更高的火灾频率或更慢的森林恢复。相比之下，正反馈（更易燃的早期演替植被）产生了一个临界点，超过这个临界点，燃烧率的增加或森林恢复的减缓会导致大规模的森林损失。在负反馈的情况下，森林损失和扩张的速度对火灾频率的变化的反应是相似的。然而，在反馈是积极的情况下，随着火灾频率的增加，从主要森林到非森林条件的转换比恢复到初始燃烧率后森林覆盖率的重新扩大要快。加强正反馈增加了这种不对称性。我们的分析阐明了火灾植被反馈和火灾后恢复率如何相互作用，以影响改变火灾制度的景观响应的轨迹和速率。我们说明了生态系统的脆弱性与积极的火灾植被反馈气候变化驱动的火灾活动的增加，特别是在火灾后恢复缓慢。尽管负反馈最初通过增加燃烧率来提供对森林丧失的抵抗力，但这种抵抗力最终会被相对于恢复时间的燃烧率的足够增加所压倒。
In the context of ongoing climatic warming, forest landscapes face increasing risk of conversion to non‐forest vegetation through alteration of their fire regimes and their post‐fire recovery dynamics. However, this pressure could be amplified or dampened, depending on how fire‐driven changes to vegetation feed back to alter the extent or behaviour of subsequent fires.Here we develop a mathematical model to formalize understanding of how fire–vegetation feedbacks and the time to forest recovery following high‐severity (i.e. stand‐replacing) fire affect the extent and stability of forest cover across landscapes facing altered fire regimes. We evaluate responses to increasing burn rates while varying the direction (negative vs. positive) of fire–vegetation feedbacks under a continuum of values for feedback strength and post‐fire recovery time. In doing so, we determine how interactions among these variables produce thresholds and tipping points in landscape responses to changing fire regimes.Where the early‐seral vegetation was less fire‐prone than older forests, negative feedbacks limited the reductions in forest cover in response to higher fire frequency or slower forest recovery. By contrast, positive feedbacks (more flammable early‐seral vegetation) produced a tipping point beyond which increases in burn rates or a slowing of forest recovery drove extensive forest loss.With negative feedbacks, the rates of forest loss and expansion in response to variation in fire frequency were similar. However, where feedbacks were positive, the conversion from predominantly forested to non‐forested conditions in response to increasing fire frequency was faster than the re‐expansion of forest cover following a return to the initial burn rate. Strengthening the positive feedbacks increased this asymmetry.Synthesis. Our analyses elucidate how fire–vegetation feedbacks and post‐fire recovery rates interact to affect the trajectories and rates of landscape response to altered fire regimes. We illustrate the vulnerability of ecosystems with positive fire–vegetation feedbacks to climate change‐driven increases in fire activity, especially where post‐fire recovery is slow. Although negative feedbacks initially provide resistance to forest loss with increasing burn rates, this resistance is eventually overwhelmed with sufficient increases to burn rates relative to recovery times.