Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA.
Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado, USA.
Glob Chang Biol. 2023 Aug;29(15):4342-4353. doi: 10.1111/gcb.16764. Epub 2023 May 21.
The western United States is projected to experience more frequent and severe wildfires in the future due to drier and hotter climate conditions, exacerbating destructive wildfire impacts on forest ecosystems such as tree mortality and unsuccessful post-fire regeneration. While empirical studies have revealed strong relationships between topographical information and plant regeneration, ecological processes in ecosystem models have either not fully addressed topography-mediated effects on the probability of plant regeneration, or the probability is only controlled by climate-related factors, for example, water and light stresses. In this study, we incorporated seedling survival data based on a planting experiment in the footprint of the 2011 Las Conchas Fire into the Photosynthesis and EvapoTranspiration (PnET) extension of the LANDIS-II model by adding topographic and an additional climatic variable to the probability of regeneration. The modified algorithm included topographic parameters such as heat load index and ground slope and spring precipitation. We ran simulations on the Las Conchas Fire landscape for 2012-2099 using observed and projected climate data (i.e., Representative Concentration Pathway 4.5 and 8.5). Our modification significantly reduced the number of regeneration events of three common southwestern conifer tree species (piñon, ponderosa pine, and Douglas-fir), leading to decreases in aboveground biomass, regardless of climate scenario. The modified algorithm decreased regeneration at higher elevations and increased regeneration at lower elevations relative to the original algorithm. Regenerations of three species also decreased in eastern aspects. Our findings suggest that ecosystem models may overestimate post-fire regeneration events in the southwest United States. To better represent regeneration processes following wildfire, ecosystem models need refinement to better account for the range of factors that influence tree seedling establishment. This will improve model utility for projecting the combined effects of climate and wildfire on tree species distributions.
由于气候条件更加干燥和炎热，未来美国西部预计将经历更频繁和更严重的野火，从而加剧破坏性野火对森林生态系统的影响，如树木死亡和野火后不成功的再生。虽然实证研究已经揭示了地形信息与植物再生之间的强烈关系，但生态系统模型中的生态过程要么没有充分考虑地形对植物再生概率的影响，要么概率仅受气候相关因素控制，例如水和光胁迫。在这项研究中，我们将基于 2011 年 Las Conchas 火灾足迹内种植实验的幼苗生存数据纳入 Photosynthesis and EvapoTranspiration (PnET) 扩展的 LANDIS-II 模型中，通过向再生概率中添加地形和额外的气候变量来改进算法。修改后的算法包括热负荷指数和地面坡度以及春季降水等地形参数。我们使用观测到的和预测的气候数据（即代表性浓度路径 4.5 和 8.5），对 2012 年至 2099 年的 Las Conchas 火灾景观进行了模拟。我们的改进显著减少了三种常见的西南针叶树树种（矮松、黄松和花旗松）的再生事件数量，导致地上生物量减少，无论气候情景如何。与原始算法相比，修改后的算法减少了高海拔地区的再生，增加了低海拔地区的再生。三种物种的再生也减少了东向。我们的研究结果表明，生态系统模型可能高估了美国西南部火灾后的再生事件。为了更好地代表野火后再生过程，生态系统模型需要改进，以更好地考虑影响树木幼苗建立的一系列因素。这将提高模型用于预测气候和野火对树种分布的综合影响的实用性。
