The duration of high spring light for understory plants: contrasting responses to spatial and temporal temperature variation

This dataset contains leaf phenology observations of canopy and two understory spring herbs (Trillium erectum and Erythronium americanum) derived from automated camera imagery collected between 2017 and 2023 from 10 sites in Mont St. Joseph, Québec, Canada. Additionally, it contains mean monthly temperatures estimated for each site-year combination using data from in situ climate stations at the base of the mountain. The data were used to investigate how spatial and inter-annual climate variation affect the duration of the high light period for spring understory herbaceous plants. For both understory species and the tree canopy, leaf phenology was sensitive to spatial and temporal variation in spring temperature; earlier leaf expansion occurred at warmer sites and in warmer years. Temporal variation in spring temperature had a stronger effect on understory than canopy phenology, such that warmer temperatures were associated with an increase in the duration of high spring light, especially at high elevation. Across the spatial (elevational) temperature gradient, temperature sensitivity of one understory species (T. erectum) was weaker than for the canopy. Thus, the combination of warmer conditions and different canopy tree species at low elevation was associated with a shorter duration of high spring light.