Genetic response of tree populations to aridification
on the
Csaba Mátyás*,
Imre Berki*, Attila Borovicsº, Gábor Veperdi*
*
Abstract
Genetically set tolerance limits at
the xeric (lower) end of distributional ranges are attracting growing interest,
but have been insufficiently studied in the past. Insect, pathogen calamities
and mass mortality events are obviously linked to an increased frequency of dry
summers, when the genetically set tolerance is exhausted.
According to the working hypothesis,
increasing climate aridity should be reflected in growth decline of tree
populations. The comparison of historic (40-50 years old) and present growth
trends however did not verify the hypothesis.
On the other hand the same concept
was used in common garden (provenance) tests of model species Scots pine,
Norway spruce and beech. Results indicate that response to warming climate
depends strongly on test location conditions. Strongest increment losses are
expected at locations close to the xeric (lower) limit of distribution, while
cooler regions might profit from warming. For the two conifer species, the calculated
increment loss response to a 2° C mean annual temperature increase will be
around 10-15%, with anticipated mass mortality events at the present southern
(xeric) limits of cultivation.
The forecasts are supported by the
analysis of health condition and mortality at monitored grid points. Growing
selection pressure results also in loss of genetic diversity. Both the decline
of allelic numbers and the loss of heterozygotes were
detected. The results should be implemented in the strategy of mitigation and
adaptation to climate change effects. The most important task is the
improvement of adaptability and plasticity both on the community (species) and
on the genetic level.
Keywords: drought
tolerance, genetic diversity, forest decline, adaptation, plasticity.
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Contact
information: Csaba MÁTYÁS, Prof.,