Abstract:
BACKGROUND : Atmospheric CO2 may double by the year 2100, thereby altering plant growth, photosynthesis, leaf
nutrient contents and water relations. Specifcally, atmospheric CO2 is currently 50% higher than pre-industrial levels
and is projected to rise as high as 936 μmol mol−1
under worst-case scenario in 2100. The objective of the study was
to investigate the efects of elevated CO2 on woody plant growth, production, photosynthetic characteristics, leaf N
and water relations.
METHODS : A meta-analysis of 611 observations from 100 peer-reviewed articles published from 1985 to 2021
was conducted. We selected articles in which elevated CO2 and ambient CO2 range from 600–1000 and 300–
400 μmol mol−1
, respectively. Elevated CO2 was categorized into <700, 700 and >700 μmol mol−1
concentrations.
RESULTS : Total biomass increased similarly across the three elevated CO2 concentrations, with leguminous trees
(LTs) investing more biomass to shoot, whereas non-leguminous trees (NLTs) invested to root production. Leaf area
index, shoot height, and light-saturated photosynthesis (Amax) were unresponsive at <700 μmol mol−1
, but increased
signifcantly at 700 and >700 μmol mol−1
. However, shoot biomass and Amax acclimatized as the duration of woody
plants exposure to elevated CO2 increased. Maximum rate of photosynthetic Rubisco carboxylation (Vcmax) and appar ent maximum rate of photosynthetic electron transport (Jmax) were downregulated. Elevated CO2 reduced stoma tal conductance (gs) by 32% on average and increased water use efciency by 34, 43 and 63% for <700, 700 and
>700 μmol mol−1
, respectively. Leaf N content decreased two times more in NLTs than LTs growing at elevated CO2
than ambient CO2.
CONCLUSIONS : Our results suggest that woody plants will beneft from elevated CO2 through increased photosyn thetic rate, productivity and improved water status, but the responses will vary by woody plant traits and length of
exposure to elevated CO2.
