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Summary Increasing atmospheric CO2is changing the dynamics of tropical savanna vegetation. C3trees and grasses are known to experience CO2fertilization, whereas responses to CO2by C4grasses are more ambiguous.Here, we sample stable carbon isotope trends in herbarium collections of South African C4and C3grasses to reconstruct13C discrimination.We found that C3grasses showed no trends in13C discrimination over the past century but that C4grasses increased their13C discrimination through time, especially since 1950. These changes were most strongly linked to changes in atmospheric CO2rather than to trends in rainfall climatology or temperature.Combined with previously published evidence that grass biomass has increased in C4‐dominated savannas, these trends suggest that increasing water‐use efficiency due to CO2fertilization may be changing C4plant–water relations. CO2fertilization of C4grasses may thus be a neglected pathway for anthropogenic global change in tropical savanna ecosystems.
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C 3 plant carbon isotope discrimination does not respond to CO 2 concentration on decadal to centennial timescales
Summary Plant carbon isotope discrimination is complex, and could be driven by climate, evolution and/or edaphic factors. We tested the climate drivers of carbon isotope discrimination in modern and historical plant chemistry, and focus in particular on the relationship between rising [CO2] over Industrialization and carbon isotope discrimination.We generated temporal records of plant carbon isotopes from museum specimens collected over a climo‐sequence to test plant responses to climate and atmospheric change over the past 200 yr (includingPinus strobus,Platycladus orientalis,Populus tremuloides,Thuja koraiensis,Thuja occidentalis,Thuja plicata,Thuja standishiiandThuja sutchuenensis). We aggregated our results with a meta‐analysis of a wide range of C3plants to make a comprehensive study of the distribution of carbon isotope discrimination and values among different plant types.We show that climate variables (e.g. mean annual precipitation, temperature and, key to this study, CO2in the atmosphere) do not drive carbon isotope discrimination.Plant isotope discrimination is intrinsic to each taxon, and could link phylogenetic relationships and adaptation to climate quantitatively and over ecological to geological time scales.
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- Award ID(s):
- 1812949
- PAR ID:
- 10398589
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 229
- Issue:
- 5
- ISSN:
- 0028-646X
- Page Range / eLocation ID:
- p. 2576-2585
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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