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

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.”

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

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

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

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

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

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

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

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

Photosynthesis 6 CO2 + 6 H2O C6H12O6 + 6 O2 SUNLIGHT

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

Photosynthate C6H12O6 “Stuff” Energy

Respiration C6H12O6 CO2 + H2O + O2 (Not balanced) ENERGY