Day length regulates seasonal patterns of stomatal conductance in Quercus species

Abstract

Vapour pressure deficit is a major driver of seasonal changes in transpiration, but photoperiod also modulates leaf responses. Climate warming might enhance transpiration by increasing atmospheric water demand and the length of the growing season, but photoperiod‐sensitive species could show dampened responses. Here, we document that day length is a significant driver of the seasonal variation in stomatal conductance. We performed weekly gas exchange measurements across a common garden experiment with 12 oak species from contrasting geographical origins, and we observed that the influence of day length was of similar strength to that of vapour pressure deficit in driving the seasonal pattern. We then examined the generality of our findings by incorporating day‐length regulation into well‐known stomatal models. For both angiosperm and gymnosperm species, the models improved significantly when adding day‐length dependences. Photoperiod control over stomatal conductance could play a large yet underexplored role on the plant and ecosystem water balances.

Climate and stomatal traits drive covariation in nighttime stomatal conductance and daytime gas exchange rates in a widespread C4 grass

“…Predawn measurements were taken in darkness (0 μmol m −2 s −1 photosynthetic photon flux density (PPFD)) while all daytime measurements were made at a saturating, fixed light intensity (1800 μmol m −2 s −1 PPFD) using the Li‐Cor red‐blue light source. We note that prevailing light conditions under which the genotypes were grown could affect leaf gas exchange among other physiological traits; however, we did not have access to a sensor to continuously monitor light and were not able to assess the potential impacts of prevailing light conditions (Granda et al ., 2020). Daytime measurements included steady state measurements of light‐saturated net photosynthesis ( A sat , μmol m −2 s −1 ), daytime stomatal conductance to water vapor ( g s , mol m −2 s −1 ), and the ratio A sat : g s (i.e.…”

Seasonal trends in leaf‐level photosynthetic capacity and water use efficiency in a North American Eastern deciduous forest and their impact on canopy‐scale gas exchange

“…Consistent precipitation and SMC over the growth season (Fig. 2d,e) may also contribute to the lack of a seasonal decline in V cmax.25 as has been observed in studies of drought‐prone ecosystems (Bauerle et al ., 2012; Zhou et al ., 2014; Gourlez de la Motte et al ., 2020; Granda et al ., 2020). Of the five meteorological variables investigated here, mean daytime air temperature best explained seasonal progression of V cmax.25 and R dark.25 (Fig.…”

“…Leaf ontogenetic changes may influence the patterns of g 0 we observed, which have been observed in other studies of oak species (Granda et al ., 2020). During the first measurement period, all four groups had a markedly higher g 0 (up to 8×) than their respective midseason average.…”

Stand structure of Central European forests matters more than climate for transpiration sensitivity to VPD

“…As a consequence, the vapour pressure deficit (VPD) of the atmosphere has increased globally (e.g. Ficklin & Novick, 2017), which might lead to higher forest transpiration (Granda, Baumgarten, et al, 2020; Grossiord et al, 2020). At the same time, changes in precipitation patterns, including more frequent droughts, may limit forest transpiration (Grossiord et al, 2019; Liu et al, 2020) and increase the risk of drought‐induced forest decline (McDowell et al, 2022).…”

“…As a consequence, the vapour pressure deficit (VPD) of the atmosphere has increased globally (e.g. Ficklin & Novick, 2017), which might lead to higher forest transpiration (Granda, Baumgarten, et al, 2020;Grossiord et al, 2020).…”