Global CO ₂ rise leads to reduced maximum stomatal conductance in Florida vegetation

Abstract

A principle response of C3 plants to increasing concentrations of atmospheric CO 2 (CO 2 ) is to reduce transpirational water loss by decreasing stomatal conductance (g s ) and simultaneously increase assimilation rates. Via this adaptation, vegetation has the ability to alter hydrology and climate. Therefore, it is important to determine the adaptation of vegetation to the expected anthropogenic rise in CO 2 . Short-term stomatal opening-closing responses of vegetation to increasing CO 2 are described by free-air carbon enrichments growth experiments, and evolutionary adaptations are known from the geological record. However, to date the effects of decadal to centennial CO 2 perturbations on stomatal conductance are still largely unknown. Here we reconstruct a 34% (±12%) reduction in maximum stomatal conductance (g smax ) per 100 ppm CO 2 increase as a result of the adaptation in stomatal density (D) and pore size at maximal stomatal opening (a max ) of nine common species from Florida over the past 150 y. The species-specific g smax values are determined by different evolutionary development, whereby the angiosperms sampled generally have numerous small stomata and high g smax , and the conifers and fern have few large stomata and lower g smax . Although angiosperms and conifers use different D and a max adaptation strategies, our data show a coherent response in g smax to CO 2 rise of the past century. Understanding these adaptations of C3 plants to rising CO 2 after decadal to centennial environmental changes is essential for quantification of plant physiological forcing at timescales relevant for global warming, and they are likely to continue until the limits of their phenotypic plasticity are reached. cuticular analysis | subtropical vegetation L and plants play a crucial role in regulating our planet's hydrological and energy balance by transpiring water through the stomatal pores on their leaf surfaces. A fundamental response of C3 plants to increasing atmospheric CO 2 concentration (CO 2 ) is to minimize transpirational water loss by reducing diffusive stomatal conductance (g s ) and simultaneously increasing assimilation rates (1). The resulting increased intrinsic water-use efficiency (iWUE: the ratio of assimilation to g s ) improves the vegetation's drought resistance and reduces the cost associated with the leaf's water transport system like leaf venation (2, 3). On a regional to global scale, decreasing rates of transpiration concurrently affect climate through reduced cloud formation and precipitation (4) and with this exert a physiological feedback on climate and hydrology on top of the radiative forcing of increasing CO 2 (5-7). In the light of continuing anthropogenic climate change, it is therefore imperative to determine how plants adapt to rising atmospheric CO 2 .During their 400 million year history, land plants have been exposed to large variations in environmental conditions that prompted genetic adaptations toward mechanisms that optimize individual fitness. Over this period, plant ad...

Responses of Legume Versus Nonlegume Tropical Tree Seedlings to Elevated CO2 Concentration

“…The p i /p a of tropical trees also appears to have remained approximately constant in response to variation in p a from preindustrial times to the present, as inferred from tree-ring D 13 C (Hietz et al, 2005;Nock et al, 2010;Brienen et al, 2011). A similar pattern was inferred for subtropical vegetation from preindustrial times to the present, based on changes in SD and morphology Lammertsma et al, 2011). Together, these observations suggest that W P of tropical trees has increased in response to increasing p a over the past 200 years and will continue to increase in the future as p a continues to increase.…”

Land-use and climate change risks in the Amazon and the need of a novel sustainable development paradigm

“…In a CO 2 -enriched environment, the plants can respond with stomatal closure to capture the same amount of CO 2 required for photosynthesis (129). As a consequence, transpiration rates could decrease, potentially returning a lower amount of vapor to the atmosphere, or, in other words, altering ET rates (130). Ultimately, this behavior could impact precipitation in the Amazon, which, as shown above, plays an important role in generating dry season precipitation.…”

Evolutionary context for understanding and manipulating plant responses to past, present and future atmospheric [CO 2 ]

“…In addition, biological responses to global environmental change are detectable in both natural and agricultural ecosystems [51][52][53][54]. Included in these biological responses are evolutionary changes across a range of taxa in response to air pollutants, drought and temperature [55][56][57][58] 2 ] has risen from 290 to 390 ppm [51].…”