Buffering of microclimate extremes in the understory and its consequences for tree seedling survival

Forest canopies provide shade and generally buffer summer extremes in the understory. However, the wind attenuation and water consumption of large trees can sometimes make the understory hotter and drier than an open field. To maintain forest regeneration and biodiversity, it is crucial to identify the factors that cause forest canopies to transition from buffering to amplifying climate extremes. Structural factors such as leaf area index, crown aggregation, and canopy height are important and well-known factors that influence canopy density and understory microclimate. However, other local factors, such as the species composition and vertical complexity of the canopy, topographic convergence and water availability also influence the ability of forest canopies to attenuate summer climate extremes. In this talk, I will present an overview of how these factors influence the buffering or amplification of climate extremes individually and collectively using examples from experimental and physics-based modelling studies. I will also discuss how this influence translates to heat and water stress for understory species and tree seedlings.