What is the window of food production and storage for a typical deciduous tree?  It really is quite short.  It is done in about 5-6 months and depending on the availability of sun, about 8 hours a day.  That is a pretty short time for the tree to prepare for the winter and next years growth.

On the graph, one can see that the carbohydrates produced in the summer months must carry the tree for an extended period of time.  Question. What are the implications of this process for bonsai enthusiasts?

There is a seasonal pattern of carbohydrate “deposition and mobilization”.  Review the chart below and see, perhaps even better, the implications for the bonsai enthusiast.
        

Beginning with tree no. 4, one can see a tree is fully satiated with carbohydrates. The carbs are stored in the roots and trunk (#5) and are then available in early spring for the tree to pull up the carbs (#1) and prepare for the emergence of leaves. With spring comes leaf emergence and the carbs become quite depleted. By mid-summer, the tree is replenishing the depleted carbs. Again, what are the implications of this process for the bonsai enthusiast for fertilization and pruning.?

What happens when the rate of tree respiration (using the carbs and this goes on throughout the year) exceeds the rate of photosynthesis?  Yep, the tree vigor declines and tree mortality eventually occurs. Have you ever had a tree die because of this occurence?  What happens when you remove healthy photosynthesizing limbs (particularly during the growing season)?  What does this tell you about pruning? How does root pruning (a regular bonsai task) affect the livelihood (physiology) of the tree?

Questions are being asked but answers not provided.  The answers to the questions should be obvious to the bonsai enthusiast. Perhaps there should be discussion about these matters at a meeting of the Memphis Bonsai Society.

There is another bit of information to cause you to think about the above processes and their implications. Trees allocate their carbs to support five different processes, in priority order (Oliver and Larson 1996.

•    Maintenance of living tissue (staying alive-respiration)
•    Production of fine roots and leaves
•    Flower and seed production
•    Primary growth (elongation of branches and roots)
•    Secondary growth (diameter growth, i.e. wood)

In a healthy tree, each of these processes is sufficiently “fueled” by carbohydrates.  “Life is good.”  Gradual mortality of a tree can be observed by examining these processes in reverse order.

Charts and most materials are from Dr. David Mercker, University of Tennessee Extension, West Tennessee Forester; presentations by Jim Volgas, Master Gardener and ISA Certified Arborist and others at the Shelby County Urban Forester Training Program 2008.