Data from: Complementary responses of morphology and physiology enhance the stand-scale production of a model invasive species under elevated CO2 and nitrogen

1. Elevated atmospheric carbon dioxide (eCO2) concentrations and nitrogen
(N) enrichment are known to enhance plant productivity and invasion.
However, the implications of their interactive effects for plant
productivity are not well understood, especially at the stand scale,
presumably because morphological and physiological responses to these
global change factors are rarely studied together in the field or assessed
at the stand-level. 2. We first determined how leaf-level morphological
and physiological traits responded to factorial combinations of ambient
and elevated CO2 and N. We collected trait data from the model invasive
species Phragmites australis (common reed) that were measured over three
years in a long-term global change field experiment. We then combined the
trait data and additional descriptions of P. australis canopies in a
simulation model of carbon assimilation to determine how morphology and
physiology contribute to P. australis’ stand scale productivity. 3. At the
leaf level, we found that light-saturated rates of photosynthesis were
strongly stimulated by eCO2 (37%) and that this effect was enhanced by
increasing salinity. N had a smaller effect (17% stimulation) on
physiological responses than eCO2, but leaf morphological traits responded
primarily to N; plant height increased by 27% and leaf area increased by
47%. 4. Stand scale simulations demonstrated that that morphological and
physiological adjustments induced approximately additive responses when P.
australis experienced both eCO2 and N enrichment. The simulations also
indicated that morphological changes (which were primarily associated with
canopy size) influenced stand scale carbon assimilation more than
physiological changes. Moreover, 97% of the N response was due to changes
in morphology, whereas 62% of the eCO2 response was caused by
physiological shifts. 5. Our analysis indicates that morphological and
physiological trait responses to elevated CO2 and nitrogen are likely to
enhance the productivity of P. australis in complementary ways,
potentially accelerating its invasion in North America. Furthermore, our
data suggest that changes in morphological traits may have a greater
influence on carbon gain than leaf-level physiology under near-future
environmental conditions. Our study also highlights the importance of
accounting for both morphological and physiological responses when
attempting to infer global change responses from leaf-level data.