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Analysis of the beech litterfall of the drought year 2018

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Background

2018 is expected to be a beech mast year whose full development might be hindered by the summer drought.
The impact of mast seed production on annual leaf biomass is unclear to this day. The following questions will
be investigated:

  • Did summer drought of 2018 have an impact on beech leaf production on the Long-term Forest Ecosystem Research (LWF) plots?
  • How is the production and the quality of beechnuts affected by summer drought?
 

Ongoing work

Beech litterfall from the vegetation year 2018/2019 from the LWF plots Bettlachstock, Lägern, Lausanne and Schänis have been sorted and the data has been pre-processed. For the statistical analysis years with high pollen freight but low fruit production are compared to years with high pollen freight and high fruit production.

 

First results

On the LWF plot Bettlachstock only low amounts of fruits were collected in 2018 which shows that although pollen freight was high, pollination did not succeed. On the LWF plot Schänis the amount of fruits in the litterfall collection was quite low and the cupule/beechnut ratio was higher compared to the mast years 2011 and 2016, which could be evidence for an impeded development of the beechnuts. Although on the LWF plots Lausanne and Lägern fruit production was as expected for a mast year, in Lausanne, 2018 was the year with the lowest leaf production in the last two decades.

In years with high pollen freight but low fruit production soil moisture was significantly lower than in mast years from mid-July to end of August. Fruit development seems to be stopped if soil conditions become too dry which could be a similar reaction as the observed slowdown in stem growth during drought events.