Speaking of deciduous trees...

Let me make some guesses.

Chlorophyl works with sunlight, water, and gases in the air to produce a sugar, so that's it. Sugar maple do such a good job of it, we mine them for maple syrup - sith a little processing

Maybe some trees count of the winds that are common in spring to disperse the seeds, and spring rains to get them started. I guess peaches are ready to seed in the fall because it takes longer to make a peach than a tuft of cottonwood seed.

Leaf mulch also inhibits competition by blocking light from other plants. Walnut husks get into chemical warfare, by poisoning other plants. Russian knapweed does the same, though it's hardly a tree.

Hey, I said I was guessing.

Thanks, Roger, for the guesses.

I especially appreciate the one about the mulch.

I have grandchildren, hence questions arise. It just struck me that up here in the northern US tier, trees are pretty-much dormant and then they explode with leaves.

So then I'm thinking--hey--if some don't have a tap root, where do they store their sap? and What are they doing with all those leaves? and so forth.

And, boy that must be a huge generating factory outside my window while just see leaves.

-Sal

http://www.fw.vt.edu/dendro/dendrology/doctor/doctor.cfm

Around here it doesn't seem to matter whether it is wet or dry--it is a lot more often dry than wet--the leaves come out on the different trees in the same order that they do every year. The mimosa first; the cottonwood last; everything else in between. And they turn and lose their leaves in the fall in the same order. I'm not sure that it is possible to regulate that artificially, but heck, I'm guessing too. The apple trees and elms seem to sprout lots of babies each spring; the oaks and cotton woods almost never do. The poplars put out long runners under the ground and pop up new trees from a common tap root.

We don't do anything at all with our big trees--don't even water them though we are in the desert--and they do just fine. So they're seeking out and finding water on their own. I'm sure that people who have commercial orchards and stuff do treat theirs a lot better though.

Mimosa? You sure it's not tamarisk, also called salt cedar? That's what we've got here. They're pretty, but they are also an invasive weed.

I honestly don't know. These are gorgeous trees--don't get really big, but they are beautifully naturally mushroom shaped and are pretty in the winter even after they have lost their leaves. We have some friends from Juarez--they participate in Christian men's work with hubby-who we asked what they were. They said they didn't know what the Americanos called them, but in Mexico they called them Mimosa. There's one down the street from us. I'll try to get a picture and post it tomorrow. Or maybe the next day--going to the theater tomorrow and won't have much time between church and departure time.

Plants need more than sugar for a balanced diet. They take in water and dissolved nutrients from the ground via their roots. The dead leaves that fall keep the ground damp as you guessed, but they also restore to the ground the nutrients that went into making them (trees recycle!). So, when you clean up your leaves in twigs in the fall, you need to replenish the system by adding mulch in the spring.

Leaves also help trees cool cool themselves when they need it - they can emit water to cool which has a cooling effect when it evaporates (like human sweat).

Sally, what do you mean by 'whole-organismic'?

Thanks for the question, Littlek. Good to get specific

I was searching for words in using "whole organismic" --for a meaning that included activities and benefits to trees-as-entire organisms. Benefits not mainly associated with leaves and potentially extending into the environment--such as shading the ground below to keep roots cooler and presumably damper.

People have brought up some fine examples in response to my question. I'm grateful for the mind-opening and connecting of "known" fragments--respiration, shade, etc. (I don't think self-mulching would support the tree much nutritionally, since it already took energy to make the leaves and whatever came back from the tree's own leaves would not support it without imported matter. Lucky leaves blow in from afar. )

I am still wondering where sap gets stored and how stored sap gets used precisely. I've been told and read it's store in roots and "other" places. I doubt my grandkids would find this topic as interesting as I do at the moment.

The "fact" that sap contains sugar--useful for other purposes than our pancakes seemed to me to get undertold. So are weeds and flowers out there making sugar too? It seems sugar is the product of photosynthesis and trees making it so furiously and storing it allows them to survive winter when marigolds go down and instead make seed in fall.

So life forms need sugar to burn and bind into their needed fluids and parts, along with certain gases in the air. This would extend into my idea of whole-organismic. Whatever side chemicals get made with sap or sugars.

I found one site on the web that contained less information than I hoped within a plethora of words and evaluations. But it may have been stabbing at part of what interested me in this subject. I may edit that page into an unimbellished few paragraphs and see what it yields. It did have some info, but there was room for more of what you folks brought up and also room for follow-through in a systems and ecological sense. Personally, I didn't care for the fluff.

http://www.apples4theteacher.com/holidays/arbor-day/what-leaves-do.html

-Sal