Abstract
Evolutionary adaptation to variation in resource supply has resulted in plant strategies that are based on trade-offs in functional traits. Here, we investigate, for the first time across multiple species, whether such trade-offs are also apparent in growth and morphology responses to past low, current ambient, and future high CO 2 concentrations. We grew freshly germinated seedlings of up to 28 C3 species (16 forbs, 6 woody, and 6 grasses) in climate chambers at 160ppm, 450ppm, and 750ppm CO 2. We determined biomass, allocation, SLA (specific leaf area), LAR (leaf area ratio), and RGR (relative growth rate), thereby doubling the available data on these plant responses to low CO 2. High CO 2 increased RGR by 8%; low CO 2 decreased RGR by 23%. Fast growers at ambient CO 2 had the greatest reduction in RGR at low CO 2 as they lost the benefits of a fast-growth morphology (decoupling of RGR and LAR [leaf area ratio]). Despite these shifts species ranking on biomass and RGR was unaffected by CO 2, winners continued to win, regardless of CO 2. Unlike for other plant resources we found no trade-offs in morphological and growth responses to CO 2 variation, changes in morphological traits were unrelated to changes in growth at low or high CO 2. Thus, changes in physiology may be more important than morphological changes in response to CO 2 variation.
Highlights
From slow-growing cypresses to prolific kudzu vines, plants employ a wide variety of different growth strategies depending on environmental resource availability (Bloom and Mooney 1985)
Ecology and Evolution published by John Wiley & Sons Ltd
This study is novel in that we investigated 19 plant species belonging to different functional types in their performance across the whole range of Pleistocene low, via ambient to future high CO2 levels, and 25 species for their performance at low CO2, thereby doubling the available data on plants’ low CO2 response (Temme et al 2013)
Summary
From slow-growing cypresses to prolific kudzu vines, plants employ a wide variety of different growth strategies depending on environmental resource availability (Bloom and Mooney 1985). Trait combinations that result in high growth rates in one environment may preclude good performance in another environment Such trade-offs are widespread in the plant kingdom, and for light, nutrients, and water, they have been analyzed in great detail (e.g., Aerts and Chapin 2000; Diaz et al 2004; Wright et al 2004; Feschet et al 2010; Reich 2014). These trade-offs underpin the current understanding of plant strategy theory (Grime 2006).
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