Almost half of the total biomass of a tree may be allocated to the roots.
In some part of the stems, some photosynthesis may also occur.
When there is low soil moisture, plants close its stomata pores which then decreases photosynthesis.
Carbon becomes locked as part of the accumulating plant biomass as plants grow.
Photosynthesis of a tree canopy is driven or influenced by
air temperature (T).
the total leaf area (LAI).
air humidity (VPD).
photosynthetically active solar radiation (PAR).
soil moisture (REW).
Early spring is a tricky time for plants due to the combination of sunny but still quite cold days.
At low air humidity, a plant closes its stomata to prevent transpiration. The action also decreases photosynthesis
Transpiration decreases as air becomes drier.
Plant respiration captures CO2.
Unlike photosynhesis, plant respiration captures atmospheric oxygen and releases carbon dioxide.
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.
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.
Photoinhibition means the decrease in photosynthesis due to
exposure to excess of light.
exposure to high temperature.
exposure to shortage of soil moisture.
exposure to excess of CO2.
High soil moisture leads to decreased photosynthesis.
In boreal upland forests, low soil moisture decreases the rate of photosynthesis.
In general, the more carbon dioxide that is available to the plant, the faster the rate of photosynthesis - if other factors are favourable.
De-hardening in spring involves gradual re-hydration of the cells, recovery of photosynthetic capacity and a tight control of water loss.