In article ,
(Iris Cohen) wrote:
does anybody know how many leaves trees are supposed to have?

I hope this isn't a troll question, but serious curiosity. There is no specific
number. It depends on species, location, and many other factors. The larger the
tree, the more leaves it will have. Generally, a tree with large leaves, like a

I presume by "larger" you mean "wider"? A mature rainforest tree
probably has much the same number of active leaves throughout its life
because its canopy is in competition with its neighbours. So its
trunk and main branches will get bigger (mostly thicker hence
heavier), but its canopy probably won't change much over decades.

sycamore, will have fewer of them. The same species in shade will have fewer &
larger leaves than in sun.
At one extreme, Welwitschia mirabilis, a primitive conifer from Africa, has
only two leaves its entire life, which may be 2000 years. The same two leaves
keep growing from the base as they wear out on the end. At the other extreme,
there are trees that grow in the desert or the far north, both conifers and
flowering trees, like Junipers and Tamarisks, which have thousands of tiny
scale leaves or needles you couldn't begin to count. If a tree is healthy and
growing, you can assume it has as many leaves as it should.

Going back nearly 50 years we learnt about "leaf area index (LAI)" as
applied to herbage species (specifically, natural and sown pasture
plants). I seem to recall that there was an approximate limit to this
beyond which shading causes death of leaves at lower levels once
respiration exceeded photosynthesis. (Note: this limit will vary
somewhat depending on the typical attitude of the leaves on individual
species; but it can be made more consistent if the projected leaf
surface is used rather than one sided leaf area as such.)

Assuming such a "limit" it should be possible to work out the
approximate number of leaves by measuring the projected area of the
canopy of a mature tree and determining the average size of the
leaves. For example, if the maximum LAI is 4, the projected area is
30 square metres, and the average leaf single surface area is 20
square centimetres, then the estimated limit for leaf number would be
around 60,000. [Of course a "specimen tree" growing in the open would
be quite different because it's "canopy area" would effectively be
closer to a hemisphere -- at least here in the tropics. ]

Definition: LAI defines an important structural property of a plant
canopy as the one sided leaf area per unit ground area.
http://edcdaac.usgs.gov/modis/mod15a2.asp

Daffynition: Leaf Area Index A type of information worked out by
calculating the volume of the upper surface of leaves in relation to
the volume of ground that is directly below the plant.
http://www.biology-online.org/dictio...20Area%20Index

Ain't the World Wide Web marvellous! A "dictionary" no less. Sigh...

Cheers, Phred.

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LID