PS 34-229 - Increasing post-wildfire planted seedling survival in the South West; From DIY data loggers to machine learning;

Abstract: Across the southwestern United States, high-severity wildfire is causing increasingly large areas of tree mortality and removing the seed sources required for the natural regeneration of these formerly conifer-dominated landscapes. Planting tree seedlings can accelerate reforestation, but in the semi-arid southwestern US, the survival of planted conifer seedlings is typically low (~25%). Our research examines how post-fire planting success is influenced by climate, topographic, biotic, and microclimate factors. We present data from multiple seedling planting experiments within the 2011 Las Conchas Fire footprint in northern New Mexico and initial data from “DIY” microclimate data loggers. Our results show tree seedling survival in high-severity burn patches is largely determined by microclimatic refugia, or areas that are consistently wetter and cooler than those of the surrounding landscape. These refugia are formed by both topographic variation and existing vegetation. Our microclimate modeling work shows that existing vegetation can alter the maximum temperature by ∼12 °C, increase relative humidity by ∼20% and reduce vapor pressure deficit by 0.3mbar relative to open areas during the hottest parts of the year. Our “DIY” data logger results show that there is a high degree of soil moisture variability across sloped areas only 25m apart. We also found that microtopography shapes microclimate in a predictable manner, allowing the identification of favorable areas across large areas using a machine learning framework, resulting in a straightforward index of seedling survival probability that can be mapped for efficient reforestation planning. By combing these findings, success rates of reforestation efforts in post-wildfire landscapes could be substantially increased.