Global changes can interact to affect photosynthesis and thus ecosystem carbon capture, yet few multi-factor field studies exist to examine such interactions. Here, we evaluate leaf gas exchange responses of five perennial grassland species from four functional groups to individual and interactive global changes in an open-air experiment in Minnesota, USA, including elevated CO2 (eCO2), warming, reduced rainfall and increased soil nitrogen supply. All four factors influenced leaf net photosynthesis and/or stomatal conductance, but almost all effects were context-dependent, i.e. they differed among species, varied with levels of other treatments and/or depended on environmental conditions. Firstly, the response of photosynthesis to eCO2 depended on species and nitrogen, became more positive as vapour pressure deficit increased and, for a C4 grass and a legume, was more positive under reduced rainfall. Secondly, reduced rainfall increased photosynthesis in three functionally distinct species, potentially via acclimation to low soil moisture. Thirdly, warming had positive, neutral or negative effects on photosynthesis depending on species and rainfall. Overall, our results show that interactions among global changes and environmental conditions may complicate predictions based on simple theoretical expectations of main effects, and that the factors and interactions influencing photosynthesis vary among herbaceous species.
Bibliographical noteFunding Information:
We greatly appreciate A. Coker and many other undergraduate interns for assistance with data collection and thank K. Worm, S. Barrott, K. Bohn and D. Bahauddin for help in the field. This work was supported by the National Science Foundation (NSF) Long-Term Ecological Research (LTER) grants DEB-0620652, DEB-1234162, and DEB-1831944, Long-Term Research in Environmental Biology (LTREB) grants DEB-1242531 and DEB-1753859, Ecosystem Sciences grant DEB-1120064, and Biocomplexity grant DEB-0322057, and by U.S. Department of Energy Programs for Ecosystem Research grant DE-FG02-96ER62291, the University of Minnesota, and the University of Wisconsin-Eau Claire's Blugold Commitment Differential Tuition funding, Summer Research Experience for Undergraduates (A. Coker).
- climate change
- functional groups
- global change
- photosynthesis: carbon reactions
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.
- Research Support, Non-U.S. Gov't