nutrient uptake; stable isotopes; assimilate transport; carbon starvation; drought
Joseph Jobin, Külls Christoph, Arend Matthias, Schaub Marcus, Hagedorn Frank, Gessler Arthur, Weiler Markus (2019), Application of a laser-based spectrometer for continuous in situ measurements of stable isotopes of soil CO<sub>2</sub> in calcareous and acidic soils, in SOIL
, 5(1), 49-62.
Grossiord Charlotte, Gessler Arthur, Reed Sasha C., Borrego Isaac, Collins Adam D., Dickman Lee T., Ryan Max, Schönbeck Leonie, Sevanto Sanna, Vilagrosa Alberto, McDowell Nate G. (2018), Reductions in tree performance during hotter droughts are mitigated by shifts in nitrogen cycling, in Plant, Cell & Environment
, 41(11), 2627-2637.
Simon Judy, Dannenmann Michael, Pena Rodica, Gessler Arthur, Rennenberg Heinz (2017), Nitrogen nutrition of beech forests in a changing climate: importance of plant-soil-microbe water, carbon, and nitrogen interactions, in Plant and Soil
, 418(1-2), 89-114.
Gessler Arthur, Schaub Marcus, McDowell Nate G. (2017), The role of nutrients in drought-induced tree mortality and recovery, in New Phytologist
, 214(2), 513-520.
The Global Climate Change is projected to increase the frequency and intensity of weather extremes in Central Europe. As one consequence extreme drought events will occur more often with potential negative effects on the growth and performance of trees and forest ecosystems. Mainly two complementing mechanisms leading to growth impairment, reduction of physiological performance and mortality upon drought are discussed at present, namely hydraulic failure (as a result of xylem embolisms) and carbon starvation (due to insufficient photosynthetic carbon assimilation). In addition, the negative impacts of drought on nutrient uptake may lead to disturbed nutrient balance of trees and ecosystems. Hence, nutrient uptake is an additional important parameter affecting tree performance under drought and there is only little information available on the underlying mechanisms.The research proposed here will thus shed light on the effects of drought and recovery from drought on the nitrogen uptake of trees. Nitrogen is the major growth limiting nutrient in natural temperate terrestrial ecosystems and has thus been chosen as model nutrient. The proposed project consists of three modules: in module 1 we will screen the importance of physiological restrictions of nitrogen uptake capacity (Jmax (maximum ammonium and nitrate net uptake capacity) and C50 (nitrate or ammonium concentration where 50% of the maximum net uptake is observed)) under drought for seven different tree species. Module 1 will also assess the plasticity of tree species to compensate for a decreased soil nitrogen availability with biomass allocation to the mycorrhizal fine roots. Module 2 will build upon this screening and consist of an in-depth analysis of the mechanisms that control the nitrogen uptake capacity under restricted water supply, with a particular focus on the interplay between transport of recent assimilates belowground and nitrogen uptake. In module 3, we will extend the mechanistic analysis of module 2 to the phase of recovery from drought and will focus on the re-establishment of transport of recent assimilates and nitrogen uptake capacity. By linking nutrient uptake with the carbon and water balance this work will complement and extend the existing conceptual models on drought effects on tree physiology