lundi 14 décembre 2015

Dressed for the winter

Even if the sun is still there, the autumn is coming to an end and the deciduous trees have lost their leaves, all of them except marcescent trees.

Marcescence, the term used to describe leaf retention, i.e. when dead leaves stay on the tree after autumn until the following spring at the latest, is most common with many of the oak species (pictured here), American beech, witch hazel, hornbeam (musclewood) and hophornbeam (ironwood). It is often young trees or branches close to the soil when those on the top have lost their leaves already.
 

Several reasons could explain this modification in the abscission process, where the cell layer allowing the decay of the leaves is not formed: genetic variation related to the hydric regime of the plant, biomass cycle or even protection against predators because those leaves are less appetent.  
http://extension.psu.edu/natural-resources/forests/news/2012/winter-leaves-that-hang-on

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