1. How Do Trees and Stands Grow?
Lecture 9
How Do Trees and Stands Grow?

2. Blog Question for the Week of September 25:
“Labels on UBC waste management trucks read ‘powered by natural gas: a renewable resource’. Do you think natural gas is a renewable resource? Cite two references that you have read on the topic.”

3. Even-Aged vs. Uneven-Aged Stands
Even-aged stands are comprised of trees that are predominantly the same age
Such stands generally originate following a stand-replacing disturbance
Uneven-aged stands are comprised of trees of several (or multiple) ages
Such stands generally originate following small-stage disturbances that kill some, but not all, of the trees

4. Even-Aged Stand Dynamics
Yield
Volume
(m3/ha)
Inflection Point
Culmination Age
Age
Growth
Current Annual Increment (CAI)
Volume Growth
(m3/ha/yr)
Mean Annual Increment (MAI)
Age

5. Current Annual Increment (CAI) = yearly growth at some point in time
E.g., if a stand has a volume of 170 m3/ha at age 33 and 177 m3/ha at age 34, then its CAI at that point in time is 7 m3/ha/year
Mean Annual Increment (MAI) = average growth up to some point in time
Volume at some point in time divided by age
E.g., If a stand has a volume of 200 m3/ha at age 40, its MAI would be 200m3/ha /40 years = 5 m3/ha/year

6. Dynamics of a Balanced Uneven-Aged Stand
Yield
Cutting Cycle
DBH Growth
Volume
(m3/ha))
Current Distribution (Inverse-J Shaped)
Future Distribution
Stems per Ha
Time
Growth
Volume Growth
(m3/ha/yr)
DBH (Diameter at Breast Height)
Time

7. Factors Affecting Stand Dynamics
Site Quality
Species (species mixtures) and genetics
Density
Age (stand structure)
Disturbance (e.g., diseases, insects, wind, fire, animals)
Treatment

8. Growing Space
The integration of all the factors that trees need to grow
Sunlight, water, nutrients, physical space

9. What is the ‘food” for trees?
Water
Nutrients
Sunlight
Insects

10. Photosynthesis How the ecosystem captures energy
Photosynthetic mechanism
Foliage
Chloroplasts (chlorophyll)

11. Photosynthesis
6 CO2 + 6 H2O C6H12O6 + 6 O2
SUNLIGHT

12. What happens if the CO2 levels go up?
Trees grow faster
Trees grow slower
Trees die

13. Photosynthate
C6H12O6
“Stuff”
Energy

14. Respiration
C6H12O CO2 + H2O + O2
(Not balanced)
ENERGY