Interannual variation in spring weather conditions as a driver of spring wildflower coverage: a 15-year perspective from an old-growth temperate forest

Abstract

Spring ephemerals are wildflowers found in temperate deciduous forests that typically display aboveground shoots for a period of two months or less. Early spring, before canopy leaf-out, marks the beginning of the aboveground growth period where ephemerals acquire nutrients and resources via aboveground tissues. Several studies have shown that spring ephemeral reproduction is affected by spring temperature, but few have looked at how weather conditions of the current and previous season, including precipitation and temperature, influence aboveground growth. Here we examine the response of a spring ephemeral community in a temperate hardwood forest to weather conditions during their current and previous growing seasons. For 15 years we estimated percent cover of each species within our community. We highlighted five dominant spring ephemerals within this community: wild leek (Allium tricoccum), cutleaf toothwort (Cardamine concatenata), spring beauty (Claytonia virginica), squirrel corn (Dicentra canadensis), and trout lily (Erythronium americanum). We compared changes in cover on both a community and species level from one year to the next with average precipitation and temperature of the year of measurement as well as the year prior. We found precipitation and temperature influence a change in cover at the community and species level, but the strength of that influence varies by species. There were few significant correlations between plant cover in the current year and temperature and precipitation in the 30 days preceding measurement. However, we found significant correlations between plant cover and precipitation and temperature during the previous spring; precipitation and cover change were positively correlated, while temperature and cover change were negatively correlated. Overall, cooler, wetter springs lead to an increase in aboveground cover the next year. Learning how individual species within a forest plant community respond to weather conditions is a crucial part of understanding how plant communities will respond to climate change.

Understanding the effects of weather parameters on the population dynamics of an endangered geophyte supports monitoring efficiency

“…The weather parameters of the actual spring expressed stronger effects, than the assimilation periods of the previous years. Especially the effects of temperature-related parameters were important, similarly to the ndings of other studies, which found that temperature has a superior role compared to precipitation (Eppich et al 2009;Jahn et al 2023).…”

“…A negative effect of shading on tness was also found in Erythronium japonicum (Kim et al 2015) and in six other species as well (Augspurger and Salk 2017), while other species, like Gagea lutea, can be insensitive to light conditions (Sunmonu and Kudo 2015). The results published so far are controversial and highlight that mechanisms underlying the observable changes are affected both by light-and temperature, so their effects cannot be separated (Jahn et al 2023). The effect of litter cover was opposite to that of understorey plant cover, as the presence of litter layer affected positively the number of detectable individuals.…”