Photosynthesis of a tree canopy is driven or influenced by
the total leaf area (LAI).
air temperature (T).
air humidity (VPD).
soil moisture (REW).
photosynthetically active solar radiation (PAR).
The rate of respiration decreases with temperature.
As plants respire, they release
Carbon becomes locked as part of the accumulating plant biomass as plants grow.
Plant respiration captures CO2.
Unlike photosynhesis, plant respiration captures atmospheric oxygen and releases carbon dioxide.
De-hardening in spring involves gradual re-hydration of the cells, recovery of photosynthetic capacity and a tight control of water loss.
Early spring is a tricky time for plants due to the combination of sunny but still quite cold days.
Photoinhibition means the decrease in photosynthesis due to
exposure to excess of light.
exposure to shortage of soil moisture.
exposure to excess of CO2.
exposure to high temperature.
Almost half of the total biomass of a tree may be allocated to the roots.
At low air humidity, a plant closes its stomata to prevent transpiration. The action also decreases photosynthesis
High soil moisture leads to decreased photosynthesis.
In boreal upland forests, low soil moisture decreases the rate of photosynthesis.
Leaf area increases with stand age, resulting in a decreasing rate of photosynthesis in the stand.
An increment in leaf area increases also the photosynthesis of a tree stand. However, the relationship is saturating.
What is the source of carbon that is assimilated in photosynthesis?
The effect of light on photosynthesis has a clear saturating pattern: more light results in more photosynthesis but eventually leaves cannot take full advantage of all the extra light.
In general, the more carbon dioxide that is available to the plant, the faster the rate of photosynthesis - if other factors are favourable.