Vapor pressure deficit in broadleaf forest understory: landscape-scale variability, its drivers and effects on vegetation.

Vapor pressure deficit (VPD) represents the drying power of the air and strongly affects plant growth and survival. Although experiments have shown that VPD impacts plant physiology, few studies have mapped its fine-scale variability or studied its impact on plant communities. To fill this gap, I am developing a spatial model of VPD. I chose the forest understory because it is less studied and its conditions differ from those in open areas.

I use point measurements of temperature and relative humidity from a network of sensors in a forest understory to calculate VPD. I apply a generalized additive model (GAM) to predict VPD across space, using topographic and canopy structure variables to capture the main drivers of microclimatic variation.

I will present how VPD varies within the area and identify its main predictors. Next, I will show the model’s performance across years and evaluate how much variation in understory plant communities it explains.

This work provides a practical framework for studying the spatial variability of vapor pressure deficit and a basis for further research on vegetation responses to increasing VPD.