Contrasting warming responses of photosynthesis in early- and late-successional tropical trees

Author:

Mujawamariya Myriam123ORCID,Wittemann Maria3,Dusenge Mirindi E45ORCID,Manishimwe Aloysie123ORCID,Ntirugulirwa Bonaventure136,Zibera Etienne7,Nsabimana Donat27,Wallin Göran38ORCID,Uddling Johan3ORCID

Affiliation:

1. University of Rwanda Department of Biology, College of Science and Technology, , Avenue de l’Armée, PO Box 3900, Kigali, Rwanda

2. University of Rwanda Center of Excellence in Biodiversity Conservation and Natural Resources Management, College of Science and Technology, , Avenue de l’Armée, PO Box 3900, Kigali, Rwanda

3. University of Gothenburg Department of Biological and Environmental Sciences, , PO Box 461, SE-405 30 Gothenburg, Sweden

4. The University of Western Ontario Western Center for Climate Change, Sustainable Livelihoods and Health, Department of Geography, , London, Ontario, Canada

5. University of Exeter College of Life and Environmental Sciences, , Exeter EX4 4RJ, UK

6. Rwanda Forestry Authority , PO Box 46, Muhanga, Rwanda

7. University of Rwanda School of Forestry and Biodiversity, College of Agriculture, Animal Sciences and Veterinary Medicine, , PO Box 210, Musanze, Rwanda

8. University of Oxford Environmental Change Institute, School of Geography and the Environment, , Oxford OX1 3QY, UK

Abstract

Abstract The productivity and climate feedbacks of tropical forests depend on tree physiological responses to warmer and, over large areas, seasonally drier conditions. However, knowledge regarding such responses is limited due to data scarcity. We studied the impact of growth temperature on net photosynthesis (An), maximum rates of Rubisco carboxylation at 25 °C (Vcmax25), stomatal conductance (gs) and the slope parameter of the stomatal conductance-photosynthesis model (g1), in 10 early successional (ES) and 8 late-successional (LS) tropical tree species grown at three sites along an elevation gradient in Rwanda, differing by 6.8 °C in daytime ambient air temperature. The effect of seasonal drought on An was also investigated. We found that warm climate decreased wet-season An in LS species, but not in ES species. Values of Vcmax25 were lower at the warmest site across both successional groups, and An and Vcmax25 were higher in ES compared with LS species. Stomatal conductance exhibited no significant site differences and g1 was similar across both sites and successional groups. Drought strongly reduced An at warmer sites but not at the coolest montane site and this response was similar in both ES and LS species. Our results suggest that warming has negative effects on leaf-level photosynthesis in LS species, while both LS and ES species suffer photosynthesis declines in a warmer climate with more pronounced droughts. The contrasting responses of An between successional groups may lead to shifts in species’ competitive balance in a warmer world, to the disadvantage of LS trees.

Funder

European Commission

University of Rwanda—Sweden

Swedish Research Council for Environmental, Agricultural Science and Spatial Planning

Publisher

Oxford University Press (OUP)

Subject

Plant Science,Physiology

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