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Chanjuan Guo

Seasonal effects of drought stress on nitrogen uptake and partitionig in European beech

 

Ecosystem internal N cycling is of particular significance in N-limited forests. It seems that for the establishment of high growth rates on N poor calcareous soil beech trees need to acquire N from leaf and root litter in addition to degrading microbial biomass. My PhD research investigates the effects of drought and litter type on beech (Fagus sylvatica L.) and its competitiveness for nitrogen with soil microorganisms.

In a field experiment at the research station Tuttlingen, Germany, natural regeneration of beech was exposed to 15N-labeled beech litter to the soil surface. In this experiment, the accumulation of 15N in different below- (fine roots, coarse roots) and aboveground fractions (leaves, stems) of beech is studied to provide information on the different sink strength of beech natural regeneration for inorganic and organic N sources. Furthermore, to characterize the significance of leaf versus root litter as N sources for beech and soil microorganisms, 15N-labelled leaf and / or root litter was applied to microcosms at sufficient and limiting water supply. The results will be compared with microbial N uptake and 15N accumulation in microbial biomass. In another experiment under controlled conditions, I will quantify the uptake of inorganic and organic nitrogen sources by beech fine roots during spring and / or  summer drought followed by recovery phases.

 

Supervisors: Heinz Rennenberg; Judy Simon; Hans Papen (KIT)

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