Timescale effects on the driving mechanisms of post-fire recruitment in Larix gmelinii population

Abstract

Post-fire recruitment plays a crucial role in enhancing forest resilience. While previous research highlights the importance of early post-fire forest recovery in determining future forest structure, little has breen reported on whether this relationship exists in the boreal coniferous forests of Eastern Siberia. Additionally, there is a lack of research on whether there are differences in the driving mechanisms that affect juvenile recruitment across different timescales. This study compared key biophysical factors affecting recruitment across short-term and long-term timescales. Leveraging field data and dendrochronological techniques, we determined the germination years of saplings and seedlings in 73 plots across eight fire times. We quantified annual recruitment and cumulative recruitment rates post-fire for each plot, examining the correlation between the time to achieve 75% cumulative recruitment post-fire and the number of recruits, thereby assessing the importance of initial recruitment. Utilizing spatial Generalized Linear Mixed Models (GLMMs), we inferred the impact of biophysical factors on recruitment across short- and long-term timescales. Subsequently, we visualized the relationship patterns between predictor variables and recruitment. The findings revealed that plots with a faster post-fire recruitment pace exhibited a greater quantity of recruitment. On long-term timescales, growing-season mean temperature (GSMT) exhibited a positive correlation with Larix gmelinii recruitment. Basal area demonstrated a robust positive effect on Larix gmelinii recruitment, displaying significance at long-term timescales. The stand age between 60 to 150 years, representing the middle-mature stage of Larix gmelinii, is conducive to post-fire recruitment. Downed dead wood (DDW) exhibited a highly significant boost to recruitment at both timescales, albeit with a relatively weaker effect observed at the long-term scale. Our findings provide some confirmation of the critical role of immediate post-fire recruitment in forest resilience, while also unveiling timescale effects that influence the mechanisms of post-fire recruitment. The findings furnish timely new perspectives on integrating temporal scales into model predictions of the recovery process and adaptive forest management strategies.