Invasive grasses increase fire occurrence and frequency across US ecoregions
Invasive grasses increase fire occurrence and frequency across US ecoregions
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DOI：
10.1073/pnas.1908253116
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发表时间：
2019-11-19
影响因子：
11.1
通讯作者：
Bradley, Bethany A.
中科院分区：
文献类型：
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作者：
Fusco, Emily J.;Finn, John T.;Bradley, Bethany A.
容易着火的入侵草通过增加精细燃料负荷和连续性而造成新的生态系统威胁，这可能会改变火灾状况。虽然侵入性草地火灾循环的存在是众所周知的，但火势改变的证据通常基于当地规模的研究或专家知识。在这里，我们量化了 12 种外来入侵草对美国 29 个生态区（涵盖美国领土三分之一以上）火灾发生、规模和频率的影响。这 12 种草种会在当地引发火灾，并且有大量大量侵扰的空间记录。我们将机构和卫星火灾数据与大量草丛入侵的记录结合起来，以测试被入侵和附近“未入侵”栖息地之间的火势差异。此外，除了与火灾相关的人为和生态协变量之外，我们还通过将火灾的发生、规模和频率建模为草入侵的函数，评估了入侵草的存在是否是改变火灾的重要预测因素。八个物种的火灾发生率明显较高，其中 Schismus barbatus 和 Pennisetum ciliare 的火灾发生率增加了两倍多。有六个物种表现出明显更高的平均火灾频率，其中 Neyraudia reynaudiana 和 Pennisetum ciliare 的平均火灾频率增加了一倍多。草丛入侵在火灾发生和频率模型中显着，但在火灾规模模型中不显着。火灾状况的显着差异，加上草类入侵在模拟这些差异时的重要性，表明入侵草类在区域范围内改变了美国的火灾状况。随着人们对美国野火的担忧日益加剧，为了有效管理生态系统，必须考虑助火入侵草类。
Fire-prone invasive grasses create novel ecosystem threats by increasing fine-fuel loads and continuity, which can alter fire regimes. While the existence of an invasive grass-fire cycle is well known, evidence of altered fire regimes is typically based on local-scale studies or expert knowledge. Here, we quantify the effects of 12 nonnative, invasive grasses on fire occurrence, size, and frequency across 29 US ecoregions encompassing more than one third of the conterminous United States. These 12 grass species promote fire locally and have extensive spatial records of abundant infestations. We combined agency and satellite fire data with records of abundant grass invasion to test for differences in fire regimes between invaded and nearby "uninvaded" habitat. Additionally, we assessed whether invasive grass presence is a significant predictor of altered fire by modeling fire occurrence, size, and frequency as a function of grass invasion, in addition to anthropogenic and ecological covariates relevant to fire. Eight species showed significantly higher fire-occurrence rates, which more than tripled for Schismus barbatus and Pennisetum ciliare. Six species demonstrated significantly higher mean fire frequency, which more than doubled for Neyraudia reynaudiana and Pennisetum ciliare. Grass invasion was significant in fire occurrence and frequency models, but not in fire-size models. The significant differences in fire regimes, coupled with the importance of grass invasion in modeling these differences, suggest that invasive grasses alter US fire regimes at regional scales. As concern about US wildfires grows, accounting for fire-promoting invasive grasses will be imperative for effectively managing ecosystems.