Nighttime stomatal conductance differs with nutrient availability in two temperate floodplain tree species

Abstract

Nighttime water flow varies between plant species and is a phenomenon for which the magnitude, purpose and consequences are widely discussed. A potential benefit of nighttime stomata opening may be increased nutrient availability during the night since transpiration affects the mass flow of soil water towards plant roots. We investigated how nitrogen (N) and phosphorus (P) fertilization, and short-term drought affected stomatal conductance of Fraxinus excelsior L. and Ulmus laevis Pallas during the day (gs) and night (gn), and how these factors affected growth for a period of 18 weeks. Both species were found to open their stomata during the night, and gn responded to nutrients and water in a different manner than gs. Under N-deficiency, F. excelsior had higher gn, especially when P was sufficient, and lower pre-dawn leaf water potential (Ψpd), supporting our assumption that nutrient limitation leads to increases in nighttime water uptake. Under P-deficiency, F. excelsior had higher relative root production and, thus, adjusted its biomass allocation under P shortage, while sufficient N but not P contributed to overall higher biomasses. In contrast, U. laevis had higher gn and lower root:shoot ratio under high nutrient (especially N) availability, whereas both sufficient N and P produced higher biomasses. Compared with well-watered trees, the drought treatment did not affect any growth parameter but it resulted in lower gn, minimum stomatal conductance and Ψpd of F. excelsior. For U. laevis, only gs during July was lower when drought-treated. In summary, the responses of gs and gn to nutrients and drought depended on the species and its nutrient uptake strategy, and also the timing of measurement during the growing season. Eutrophication of floodplain forests dominated by F. excelsior and U. laevis may, therefore, considerably change nighttime transpiration rates, leading to ecosystem-level changes in plant-water dynamics. Such changes may have more severe consequences in the future as a higher frequency of drought events is predicted under climate change.

Drivers of nocturnal water flux in a tallgrass prairie

“…However, other studies have reported negligible relationships of E night with VPD (Barbour et al., ; Resco de Dios et al., ), or stronger relationships of E night with other environmental variables such as wind speed (Karpul & West, ; Phillips et al., ) or atmospheric CO 2 concentration (Zeppel et al., ). Further complicating our understanding of the mechanisms controlling E night may be interactions among environmental factors (Zeppel et al., ), leaf age (Phillips et al., ), responses to nutrient availability (Eller, Jensen, & Reisdorff, ; Kupper et al., ; Rohula, Kupper, Räim, Sellin, & Sõber, ; Scholz et al., ), differential diurnal and nocturnal stomatal behavior (Ogle et al., ), species‐specific effects of hydraulic architecture on water loss (Sack & Holbrook, ), positive relationships of g snight with VPD (Howard & Donovan, ), or effects of endogenous circadian rhythm (Caldeira, Jeanguenin, Chaumont, & Tardieu, ; Resco de Dios, Loik, Smith, Aspinwall, & Tissue, ; Resco de Dios et al., , ).…”

Night and daytime water relations in five fast‐growing tree species: Effects of environmental and endogenous variables

“…This result brings about the idea that low nightly water flux in these two nitrogen‐fixing Alnus species is related to their specific nutritional strategy. Recent findings suggest that species' preferences for soil fertility are also involved in determining the ability to open stomata and lose water at night (Eller, Jensen, & Reisdorff, ; Rohula et al, ; Zeppel et al, ). In our previous study (Rohula et al, ), we indicated that species characterized by low leaf nitrogen concentration demonstrate higher nightly water‐use percentage from daily water use than the species with high leaf nitrogen concentration.…”

“…The forecasted increase in the number of warm nights in the future (Sillmann, Kharin, Zwiers, Zhang, & Bronaugh, ) will probably increase the intensity of night‐time water flux in fast‐growing tree species, whereas the impact of rising temperature is likely to reflect the effects of VPD (Zeppel et al, ). Therefore, global or regional changes in night‐time environmental conditions may impact the competition, and the distribution of broadleaved tree species, depending on their water‐use strategies and as a consequence, may affect the hydrological regime of forest ecosystems (Eller et al, ; Zeppel et al, ). The current results support the idea that different mechanisms underlie the day and night‐time stomatal conductance and regulation of water fluxes (Eller et al, ; Ogle et al, ; Rohula et al, ).…”

“…Therefore, global or regional changes in night‐time environmental conditions may impact the competition, and the distribution of broadleaved tree species, depending on their water‐use strategies and as a consequence, may affect the hydrological regime of forest ecosystems (Eller et al, ; Zeppel et al, ). The current results support the idea that different mechanisms underlie the day and night‐time stomatal conductance and regulation of water fluxes (Eller et al, ; Ogle et al, ; Rohula et al, ). Thus, trees' ability to open stomata and lose water at night does not depend directly on their daily water‐use strategy but is probably governed by their photosynthetic capacity, growth potential, nitrogen‐use strategy, and competition capability.…”

Quantification and Prediction of Nighttime Evapotranspiration for Two Distinct Grassland Ecosystems

“…Eddy‐covariance observations for three distinct ecosystems showed that the ratios of nighttime ET ( ET N ) to daytime ET ( ET D ) were dependent not only on the vegetation type but also on the seasonal environmental conditions (Novick et al, ). Leaf gas exchange, nocturnal stomatal conductance, or sap flow, which are associated with ET N , was found to respond to exogenous atmospheric drivers like wind speed (Karpul & West, ), air temperature (Fisher et al, ), and vapor pressure deficit (Doronila & Forster, ; Fisher et al, ; Novick et al, ) and to depend on soil water (Howard & Donovan, ) and nutrient availability (Eller et al, ). But counteracting effects of different drivers prevented some authors from observing clear effects from single drivers (Fisher et al, ; Howard & Donovan, ).…”