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.
Photosynthesis of a tree canopy is driven or influenced by
air temperature (T).
photosynthetically active solar radiation (PAR).
air humidity (VPD).
soil moisture (REW).
the total leaf area (LAI).
What is the source of carbon that is assimilated in photosynthesis?
Almost half of the total biomass of a tree may be allocated to the roots.
In general, the more carbon dioxide that is available to the plant, the faster the rate of photosynthesis - if other factors are favourable.
Early spring is a tricky time for plants due to the combination of sunny but still quite cold days.
High soil moisture leads to decreased photosynthesis.
In boreal upland forests, low soil moisture decreases the rate of photosynthesis.
The annual cycle of photosynthesis mainly follows
the changes in CO2 concentration.
the changes in air temperature.
the changes in soil temperature.
the changes in light.
The rate of respiration decreases with temperature.
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.
A complex microbiota lives belowground, releasing carbon dioxide to the soil.
De-hardening in spring involves gradual re-hydration of the cells, recovery of photosynthetic capacity and a tight control of water loss.
As plants respire, they release
Photosynthesis releases oxygen whereas respiration releases CO2.
Carbon becomes locked as part of the accumulating plant biomass as plants grow.
Transpiration decreases as air becomes drier.