The rising atmospheric CO2 concentration leads to a CO2 fertilization effect on plants—that is, increased photosynthetic uptake of CO2 by leaves1-3 and enhanced water-use efficiency (WUE)4,5. Yet, the resulting net impact of CO2 fertilization on plant growth and soil moisture (SM) savings at large scale is poorly understood. Arid lands provide a natural experimental setting to detect the CO2 fertilization effect on WUE since foliage amount, plant water-use and photosynthesis are all tightly coupled in water-limited ecosystems6. A long-term change in the sensitivity of leaf area index (LAI, a measure of foliage amount) to SM is likely to stem from changing water demand of primary productivity in water-limited ecosystems6-8 and is a proxy for changes in WUE. Using 30-year satellite observations of LAI and SM over tropical and subtropical arid lands, we identify that an equivalent increment in SM leads to a larger increase in LAI and has contributed 11.3% (±5.5%) to total arid land greening during 1997‒2011 compared to 1982‒1996. This finding is consistent with the CO2 fertilization effect on WUE, implying that a given amount of SM has sustained greater amounts of photosynthetic foliage over time due to decreasing transpiration per unit LAI with increasing CO2 concertation.

GONSAMO Alemu;  CIAIS P.;  MIRALLES Diego G.;  SITCH Stephen;  DORIGO W.;  LOMBARDOZZI Danica;  FRIEDLINGSTEIN P.;  NABEL Julia E.M.S;  GOLL Daniel;  O'SULLIVAN Michael;  ARNETH Almut;  ANTHONI Peter;  JAIN Atul;  WILTSHIRE Andy;  PEYLIN Philippe;  CESCATTI Alessandro; 

2022-03-15

WILEY

JRC121900

1354-1013 (online),   

https://onlinelibrary.wiley.com/doi/10.1111/gcb.15658,    https://publications.jrc.ec.europa.eu/repository/handle/JRC121900,   

10.1111/gcb.15658 (online),