Fire legacies, heterogeneity, and the importance of mixed-severity fire in ponderosa pine savannas
Fire legacies, heterogeneity, and the importance of mixed-severity fire in ponderosa pine savannas
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黄松稀树草原火灾遗产、异质性和混合严重程度火灾的重要性
DOI：
10.1016/j.foreco.2019.117853
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发表时间：
2020
影响因子：
3.7
通讯作者：
Twidwell, Dirac
中科院分区：
文献类型：
--
作者：
Roberts, Caleb P.;Donovan, Victoria M.;Nodskov, Sarah M.;Keele, Emma B.;Allen, Craig R.;Wedin, David A.;Twidwell, Dirac
在全球范围内，热带稀树草原生态系统正在转移到“安全运行空间”之外，这是由于它们主要的自我强化反馈-火灾-以及随后的干扰遗产侵蚀的消除。恢复稀树草原需要恢复火灾反馈。但是，在历史火灾制度的性质以及火灾后时间和火灾严重程度等机制如何相互作用以产生干扰遗产方面的知识空白阻碍了与生态相关的恢复目标的发展。一个基于理论的方法来确定恢复目标是比较结构产生的时间，因为火灾/火灾严重程度的相互作用，以培育动物群落，历史上居住在稀树草原的结构。在这里，我们使用一个空间的时间替代，以量化的互动影响的时间，因为火灾和火灾的严重程度对植被结构相关的已知的动物群落栖息地的偏好调查网站在10岁和27岁的混合严重程度火灾发生在东部黄松（黄松）稀树草原火灾被排除在欧洲人定居。我们的具体目标是1），量化的相对强度和互动效果的时间，因为火灾和完整的火灾严重度梯度的多变量植被结构景观斑块和2），评估多变量植被结构和时间，因为火灾/火灾严重度类景观斑块之间的关系。我们使用了分层随机设计，分布112个抽样地块火灾的严重程度（未燃烧，低，中，高）和时间，因为火灾（10年和27年），并测量了林分结构，树腔特征，粗木质残体。火灾发生后的时间和火灾严重程度的相互作用驱动了火灾后27年的结构复杂性，但火灾严重程度解释的结构变化量是火灾发生后时间的14倍以上。一个完整的火灾严重度梯度（低，中，高严重度）和结构变化的补丁，经历了不同的火灾严重度产生足够的补丁级异质性，以促进动物群落历史上本土东部黄松稀树草原。结构产生的火灾严重程度低，这是一个共同的目标，在最东端的黄松稀树草原火灾管理，并没有反映足够的结构复杂性，以支持特有动物物种的多样性。这表示信息遗留（即，由群落中物种特征的分布表示）是由混合严重度火制度形成的，这进一步支持了寻求最小化火制度变化的管理目标（例如，低强度和低严重程度的火灾）支持各种生物多样性的能力较低。相反，混合严重性火灾是结构异质性的重要驱动力，促进了不同的信息遗产，并提高了黄松稀树草原对极端火灾的抵御能力。
Globally, savanna ecosystems are shifting outside of “safe operating spaces” due to removal of their primary self-reinforcing feedback—fire—and subsequent erosion of disturbance legacies. Restoring savannas will require reinstating fire feedbacks. But knowledge gaps in the nature of historic fire regimes and how mechanisms such as time-since-fire and fire severity interact to produce disturbance legacies hinders development of ecologically relevant restoration targets. A theory-based approach for determining restoration targets is to compare structures produced by time-since-fire/fire severity interactions to structures that fostered animal communities that historically inhabited savannas. Here, we use a space-for-time substitution to quantify interactive effects of time-since-fire and fire severity on vegetation structures related to known animal community habitat preferences by surveying sites in 10-year-old and 27-year-old mixed-severity fires that occurred in an eastern ponderosa pine (Pinus ponderosa) savanna where fire was excluded since European settlement. Our specific objectives are to 1), quantify the relative strengths and interactive effects of time-since-fire and a full fire severity gradient on multivariate vegetation structure across landscape patches and 2), assess relationships between multivariate vegetation structures and time-since-fire/fire severity classes across landscape patches. We used a stratified random design to distribute 112 sampling plots by fire severity (unburned, low, moderate, and high) and time-since-fire (10 years and 27 years) and measured stand structure, tree cavity characteristics, and coarse woody debris. The interaction of time-since-fire and fire severity drove structure complexity for 27 years post-fire, but fire severity explained > 14 times the amount of variation in structure than time-since-fire alone. A full fire severity gradient (low-, moderate-, and high-severities) and structural changes within patches that experienced different fire severities generated sufficient patch-level heterogeneity to foster animal communities historically native to eastern ponderosa pine savannas. Structures generated by low fire severity alone, which is a common goal of fire management in easternmost ponderosa pine savannas, did not reflect sufficient structural complexity to support the diversity of endemic animal species. This indicates information legacies (i.e., represented by the distribution of species traits in a community) were shaped by mixed severity fire regimes, which provides further support for the scientific premise that management goals seeking to minimize variation in fire regimes (e.g., low intensity and low-severity fires only) is less able to support a full array of biodiversity. Rather, mixed-severity fire is an important driver of structural heterogeneity, fosters diverse information legacies, and enhances ponderosa pine savanna resilience to extreme fire.
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