Phenological mismatch with trees reduces wildflower carbon budgets

Abstract

Interacting species can respond differently to climate change, causing unexpected consequences. Many understorey wildflowers in deciduous forests leaf out and flower in the spring when light availability is the highest before overstorey canopy closure. Therefore, different phenological responses by understorey and overstorey species to increased spring temperature could have significant ecological implications. Pairing contemporary data with historical observations initiated by Henry David Thoreau (1850s), we found that overstorey tree leaf out is more responsive to increased spring temperature than understorey wildflower phenology, resulting in shorter periods of high light in the understorey before wildflowers are shaded by tree canopies. Because of this overstorey–understorey mismatch, we estimate that wildflower spring carbon budgets in the northeastern United States were 12–26% larger during Thoreau's era and project a 10–48% reduction during this century. This underappreciated phenomenon may have already reduced wildflower fitness and could lead to future population declines in these ecologically important species.

Low‐cost observations and experiments return a high value in plant phenology research

“…As environmental changes shift phenology, the effects ripple out across the ecosystem; however, the impacts of changes in phenology are not completely understood and often not incorporated into terrestrial biosphere models (Richardson et al., ; Viskari et al., ). For example, advancing spring phenology in temperate understory wildflowers is well documented (Miller‐Rushing and Primack, ; McDonough MacKenzie et al., ), but the concurrent and more rapid advance of canopy leaf‐out has shrunk the window of understory high light levels in early spring, such that carbon budgets for understory wildflowers are likely now smaller than in the 19th century and are predicted to continue to shrink (Heberling et al., ). In alpine plant communities, shifts in flowering phenology have shuffled coflowering patterns and redistributed floral abundance across the growing season (CaraDonna et al., ).…”

The Joint Effects of Precipitation Gradient and Afforestation on Soil Moisture across the Loess Plateau of China

“…Finally, the herbaceous layer of plantations obviously does not intensify moisture depletion in the upper soil layer, which has been confirmed by understory removal experiments in the Loess Plateau [42]. This is because plantations can greatly decrease herbaceous layer growth and diversity by altering the availability of light [43,44]. These opposing effects contribute to inconspicuous differences in the upper layer soil moisture between plantations and the grassland control.…”

“Estimating abundance and phenology from transect count data with GLMs”

“…Of course, sometimes data limitations constrain analysis to only use first or last metrics, especially when comparing with historic data sets (e.g. Heberling et al 2019). However, in many cases ecologists have much more complete data, and should not be limited to using problematic phenological metrics.…”