Oak leaves vs. Maple leaves - Part II

["William Vannerson" <William_Vannerson@ama-assn.org>]

Continuing my reading of "The Vegetation of Wisconsin, an Ordination of Plant Communities," John T. Cutris, 1959, University Wisconsin Press, I have found additional information regarding the differences between oak and maple leaves.  These differences may help explain why oak leaves are more favorable to hobbyists in creating soft, acidic water and leaf litter habitats for our fish.

"[Xeric forest soils] show a greater acidity and lower nutrient content than comparable figures for mesic forest soils.  The acidity is apparently the result of organic compounds, especially tannic acids, produced by the oak leaves.  The ash content of leaves of various species of oaks varies from 4.5 to 7 percent, in contrast to levels of 10 to 12 percent in sugar maple and basswood.  Of this amount of ash, only about 1/3 is in the form of calcium and magnesium oxides, compared to 2/3 in the mesic trees.  The low lime content is associated with low palatability by millipedes and other soil fauna and may be partially responsible for the low rate of decay, induced by other soil biota."

So oak leaves have more tannins, which makes them more acid than maple leaves.  But they also have less ash composition, which means they cannot release chemicals that would make the water more alkaline, or at lease neutral.  The lower ash content also may make the leaves less tasty (palatable) and slower to decay, assuming that the aquatic biota that's responsible for leaf decay have similar tastes to forest millipedes!

Again, I must caution that this material is forty years old.  But it would stand to reason that these simple statements have remained basically true.


Bill Vannerson
McHenry, IL
http://vannerson.home.att.net/



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