Biazzo Ian N, Quintana-Ascencio Pedro F
Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816 USA.
Fire Ecol. 2022;18(1):24. doi: 10.1186/s42408-022-00148-1. Epub 2022 Oct 22.
Pine flatwoods of the southeastern United States were shaped by frequent fires. Land managers use prescribed fires to control fuels but also to restore historical fire dynamics. Broad outcomes of this practice are well-understood, but impacts on many organisms are still being explored. Frogs, for example, have upland and wetland requirements, limited mobility, and skin susceptible to desiccation. Treefrogs spend most of their lives in uplands away from water. When fire approaches, animals may escape to an unburned area, shelter in place, or be killed by the fire. We examined which of these mechanisms is the prevailing short-term response for a specialist treefrog in a pyrogenic flatwood system.
We assessed the short-term impacts of prescribed fire on the dynamics of an upland flatwood specialist, the pinewoods treefrog , using a replicated before-after-control-impact field experiment. We set pipes as treefrog refugia at 3 m, 6 m, 9 m, and 9 m in 12 pine trees spread evenly across two treatments: reference trees in units burned in 2020 and trees in units with 2021 prescribed fire. Prescribed fires occurred on 16 April and 21 July 2021. Every 2 weeks between 5 March and 5 September, we checked pipes for frogs and assigned them unique color marks. We observed 78 individuals with 199 additional recaptures. We modeled abundance (as raw counts), survival, and vertical movement using mark-recapture methods, multi-state, and mixed linear models with a Bayesian framework. Survival and recapture were comparable among prescribed fire treatments, but abundances and movement probability varied. Frogs in trees in areas burned during the study were more likely to stay in place and less likely to descend to lower heights. We observed more frogs in trees after a 2021 fire compared to reference trees.
The prevailing mechanism for resiliency to fire for pinewoods treefrogs was migration up large pines, then likely recolonization to lower vegetation layers when plants regreen post-fire. This substantiates conclusions from other works that the integrity of mature pines is key to sustaining native biodiversity. Future work and management should consider the three-dimensional structure of habitat when developing burn prescriptions and study designs.
美国东南部的松树低地受频繁火灾影响而形成。土地管理者利用规定火烧来控制燃料，同时恢复历史火灾动态。这种做法的广泛结果已为人熟知，但对许多生物的影响仍在探索中。例如，青蛙有高地和湿地的生存需求，行动能力有限，且皮肤易干燥。树蛙一生大部分时间生活在远离水源的高地上。当火灾临近时，动物可能逃到未燃烧区域、就地躲避或被火烧死。我们研究了在一个火成低地系统中，对于一种特化树蛙而言，这些机制中哪种是主要的短期应对方式。
我们通过一个重复的前后对照影响田间实验，评估了规定火烧对高地低地特化物种——松林树蛙动态的短期影响。我们在均匀分布于两种处理的12棵松树上，分别在3米、6米、9米和9米处设置管道作为树蛙避难所：2020年已燃烧单元中的参考树，以及2021年有规定火烧单元中的树。规定火烧于2021年4月16日和7月21日进行。在3月5日至9月5日期间，我们每两周检查一次管道中的青蛙，并给它们标记独特的颜色。我们观察到78只个体，另外还有199次重新捕获。我们使用标记重捕法、多状态模型以及贝叶斯框架下的混合线性模型，对丰度（以原始计数表示）、存活率和垂直移动进行建模。规定火烧处理之间的存活率和重新捕获率相当，但丰度和移动概率有所不同。在研究期间被烧毁区域的树中的青蛙更有可能原地不动，且下降到较低高度的可能性较小。与参考树相比，我们在2021年火灾后观察到树上有更多青蛙。
松林树蛙对火灾的主要适应机制是向上迁移到高大松树上，然后在火灾后植物重新变绿时，可能重新定殖到较低植被层。这证实了其他研究的结论，即成熟松树的完整性是维持本地生物多样性的关键。未来的工作和管理在制定火烧处方和研究设计时，应考虑栖息地的三维结构。
