Impact of high daytime air humidity on nutrient uptake and night-time water flux in silver birch, a boreal forest tree species
2017
At northern latitudes, a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We investigated the impact of high (H) and moderate (M) daytime air relative humidity (RH) on water relation parameters and foliar nutrient status in saplings of silver birch, to elucidate the interactions between water and nutrient uptake. A ~40% lower daytime vapour pressure difference between the leaf interior and atmosphere caused significantly (P < 0.05) higher canopy conductance to water vapour in daytime, but also at night. The linearized regression slopes of the relationships between dependent variable (daytime cumulative sap flow (Q ᶜ), night-time Q ᶜ, total leaf area, total leaf biomass) and week of study were significantly higher in the H treatment than in the M treatment (P < 0.05), indicating greater increase in these variables under high RH during the study period. Although the foliar phosphorous (P) content was significantly (P < 0.05) higher in the H than in the M treatment, the total foliar nitrogen (N) content did not differ (P > 0.05) between the treatments. Our results suggest that the 32.3% higher total foliar P in the H treatment could be partly induced by 28.2% greater transpiration-driven mass flow of water-soluble P and/or by 25.4% higher number of absorptive root tips. Our results confirm that elevated daytime atmospheric humidity increases the potential for night-time water flux and might also facilitate the uptake of mineral nutrients in silver birch, a dominating deciduous tree species in boreal forests.
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