Eating is an agricultural act - Wendell Berry

Thursday, December 24, 2009

learning from leaves

i heard about this intricate design of nature at a workshop over 2 months ago.
it was about what was the difference between green biomass (fresh leaves/grass) and brown biomass (leaf litter).
the leaf, as it prepares to fall from the stem/branch, gives back much of its nutrients to the stem/branch in a true display of low wastage.
this link explains the process very beautifully.
But why do trees (and of course shrubs) drop their leaves in winter? Surely this is terrible waste of resources as the plant then has to replace them all – plus a few extra – during the following spring?

The winter season is always guaranteed to bring two things. The first is far lower light levels while the second is terrible weather.
With the lower light levels leaves will become increasingly unproductive, but with a drop in temperatures the plants metabolic rate is also reduced and so photosynthesis can effectively stop.

With regards to poor weather conditions, a combination of strong winds, snowfall and freezing temperatures would provide any large broad leaved tree a serious risk from damage if they kept their leaves in place. Firstly, heavy snowfall would remain in the canopy placing huge stress on the branch framework, and if you combined that with strong winds you’ll definitely have a recipe for disaster. Of course, the leaves of deciduous plants are particularly sensitive to freezing temperatures anyway as internal cells are easily ruptured when exposed to large enough ice crystals.

The lesser of two evils is to absorb as much of the available and usable nutrients that are within the leaf structures as possible and then lose the remaining ‘leaf husk’ before snow appears. Of course – as with many things in nature – nothing is wasted as the following leave litter is broken down further by bacterial activity to create a humus rich mulch.
there is much to learn from leaves.
to leave one's life richer than one found it is what the leaves do. it is what we must also do.

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