Effects of drought on nitrogen uptake and carbon dynamics in trees

Abstract

Research on drought impact on tree functioning is focused primarily on water and carbon (C) dynamics. Changes in nutrient uptake might also affect tree performance under drought and there is a need to explore underlying mechanisms. We investigated effects of drought on a) in-situ nitrogen (N)-uptake accounting for both, N availability to fine-roots in soil and actual N-uptake, b) physiological N-uptake capacity of roots, and c) the availability of new assimilates to fine roots influencing the N-uptake capacity using 15N and 13C labelling. We assessed saplings of six different tree species (Acer peudoplatanus, Fagus sylvatica, Quercus petraea, Abies alba, Picea abies, Pinus sylvestris). Drought resulted in significant reduction of in-situ soil N-uptake in deciduous trees accompanied by reduced carbon allocation to roots and by a reduction in root biomass available for N-uptake. While physiological root N-uptake capacity was not affected by drought in deciduous saplings, reduced maximum ammonium but not nitrate uptake was observed for A.alba and P.abies. Our results indicate that drought has species-specific effects on N-uptake. Even water limitations of only 5 weeks as assessed here can decrease whole plant inorganic N-uptake independent of whether the physiological N-uptake capacity is affected or not.

Drought legacies and ecosystem responses to subsequent drought

“…Furthermore, drought-induced effects on roots as well as leaf senescence can affect nutrient status and nutrient demand post-drought (Schlesinger et al, 2016). For example, N uptake under drought can be reduced (Joseph et al, 2021) and detrimental impacts of drought on K availability can reduce tree resistance to subsequent drought (Touche et al, 2022).…”

Substrate and adenylate limit subtropical tree fine‐root respiration under soil warming

“…In our study, warming reduced soil inorganic N concentrations, which was consistent with some previous studies (Durán et al, 2016; Zhang et al, 2005). This might be due to reduced organic matter decomposition, limited ion mobility in drier soils (Jarvi & Burton, 2018; Joseph et al, 2021), and/or increased N leaching loss under warming (Wu et al, 2022). However, soil N availability is relatively higher in subtropical areas and warming can also increase root N uptake capacity (Cao et al, 2020; Jiang et al, 2023).…”

Coordination of leaf functional traits under climatic warming in an arid ecosystem

“…However, the present findings indicated close relationships between functional traits under AM and MW conditions, but this relationship almost disappeared under SW, implying a shift in the relationship direction under a more stressful environment. The underlying mechanisms can be explained as follows: i) severe drought induced by SW could constrain the change in the photosynthetic rate at a low level by damaging mesophyll cell ultrastructure and enhancing lipid peroxidation, consequently weakening the relationship (e.g., less change in A sat with SLA [ 75 ]; ii) plant growth and carbon allocation could be severely affected by severe stress, inhibiting leaf carbon investment and slowing the change in SLA [e.g., [ 42 ]]; and iii) plant N absorption, transport and allocation could also be constrained [ 14 , 76 ], lessening flexible changes in leaf N concentration. Together, this may explain why severe warming diminishes the trade-off between plant functional traits.…”