Assimilation Efficiencies and Gas Exchange Responses of Four Salix Species in Elevated CO2 under Soil Moisture Stress and Fertilization Treatments

Assimilation to the internal CO2 (ACi) response curve and gas exchange parameters were quantified for four North American willows ((Salix cordata (COR), S. discolor (DIS), eriocephala (ERI), interior (INT)) grown in a 2 × factorial of atmospheric soil moisture treatments see how they would respond climate change factors. After first year greenhouse growth under said treatments, we saw no difference aboveground stem biomass between treatments. Thus, second year, experiment on subset well-watered, coppiced was conducted fertilization (FERT) In both experiments, maximum rate carboxylation (Vcmax) significantly declined all species elevated (eCO2). drought treatment (DRT), Vcmax declined, except INT, which increased Vcmax. INT had greatest Vcmax, electron transport (Jmax), triose phosphate utilization, followed by COR ERI, with DIS having lowest values. FERT resulted strong increase assimilation (A) stomatal conductance (Gwv) 92 119%, respectively. Gwv is primary driver A minor water use efficiency (WUE) DRT. mitigated downregulation eCO2, but eCO2 did not mitigate DRT effect. Differences other three number adaptive traits responses related may reflect evolutionary origins taxonomic group Longifoliae arid southwest USA Mexico.