The influence of drought and rewetting on plant and soil nutrient dynamics
Lenaerts, B . 2020. University of Antwerp
Abstract
Global climate change is currently already impacting the world as we know it and will do so even more
in the future. An increase in the frequency of extreme weather events and intensification of the global
hydrological cycle are among the expected consequences. Changes in precipitation patterns and
altered evapotranspiration will lead to prolonged droughts in many regions.
In soils, when droughts come to an end, rewetting will typically cause a temporary pulse of numerous
microbial processes, known as the Birch effect. A prominent result is an elevated CO2 flux, which has
been studied extensively. Effects of these mineralization and soil processes on nutrients other than
carbon (to a lesser extent N and P) have been left aside. However, these other nutrients may play an
important role for plants that have been subjected to drought and their recovery after rewetting.
We examined the effect of rewetting on several relevant nutrients (N, P, K, Mg and Ca) in a mesocosm
environment with controlled irrigation and no natural precipitation. Eight different irrigation regimes
were imposed, varying between 1 and 60 days. Soil nutrient supply rates were measured with PRS
probes. Plant aboveground biomass was sampled right before the major rewetting event at day 60, a
week after and one month after this event. Nutrient supply rates in the soil and nutrient concentrations
in the plant aboveground biomass were compared.
We found a positive trend with drought length in both the nutrient supply rates and the plant biomass,
indicating that post-drought recovery of plants might be mediated by nutrient release upon rewetting.
However, we did not find a significant difference between nutrient supply rates, or pre and post
rewetting in the plant aboveground biomass nutrients. We confirmed the Birch effect, but more
research remains necessary to disclose its exact impacts and underlying mechanisms.
