Nitrogen leaching is enhanced after a winter warm spell but mainly controlled by vegetation composition in temperate zone mesocosms
Background and aims
Leaching of nitrogen (N) from natural ecosystems poses serious environmental problems. Extreme events such as winter warm spells could exacerbate N leaching by disrupting biogeochemical cycles and will become more frequent with the projected climate change.
We used lysimeters to investigate N leaching in response to a 12-day winter warm spell at two field sites with contrasting winter climate and in seven different vegetation covers in 140 well established mesocosms.
Mean rates of N leaching reached 3.4 ± 0.4 mg N m−2 d−1 over the 49 days of observations in late winter/ early spring. The winter warm spell resulted in an 82 % increase of N leaching after the warm spell (up to 18 mg N l−1). Stronger leaching occurred at the colder site which can be explained by plants becoming photosynthetically active with subsequent frost damaging their above-ground tissue due to missing insulation by snow and/or dehardening, resulting in reduced N uptake. N leaching differed by >600 % among contrasting vegetation composition with almost no leaching from grassland types and strongest leaching from shrubland types that even surpassed leaching from bare ground controls.
Winter warm spells can affect the biogeochemistry of temperate ecosystems with plant performance and vegetation composition controlling the amount of N leaching.
KeywordsWinter ecology Freezing-thawing Frost Warming pulse Heat wave Nitrogen loss
This study was funded by the German Science Foundation (DFG JE 282/5-1). We thank Elke and Stefan König for installing the field experiment.
Compliance with ethical standards
Accepted principles of ethical and professional conduct have been followed, no conflicts of interest occurred, neither humans nor animals were studied.
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