Stomatal Development and Conductance of a Tropical Forage Legume Are Regulated by Elevated [CO2] Under Moderate Warming

The opening and closing of stomata are controlled by the integration of environmental and endogenous signals. Here, we show the effects of combining elevated atmospheric carbon dioxide concentration (eCO2; 600 μmol mol-1) and warming (+2°C) on stomatal properties and their consequence to plant function in a Stylosanthes capitata Vogel (C3) tropical pasture. The eCO2 treatment alone reduced stomatal density, stomatal index, and stomatal conductance (gs), resulting in reduced transpiration, increased leaf temperature, and leading to maintenance of soil moisture during the growing season. Increased CO2 concentration inside leaves stimulated photosynthesis, starch content levels, water use efficiency, and PSII photochemistry. Under warming, plants developed leaves with smaller stomata on both leaf surfaces; however, we did not see effects of warming on stomatal conductance, transpiration, or leaf water status. Warming alone enhanced PSII photochemistry and photosynthesis, and likely starch exports from chloroplasts. Under the combination of warming and eCO2, leaf temperature was higher than that of leaves from the warming or eCO2 treatments. Thus, warming counterbalanced the effects of CO2 on transpiration and soil water content but not on stomatal functioning, which was independent of temperature treatment. Under warming, and in combination with eCO2, leaves also produced more carotenoids and a more efficient heat and fluorescence dissipation. Our combined results suggest that control on stomatal opening under eCO2 was not changed by a warmer environment; however, their combination significantly improved whole-plant functioning

Earth System Model Needs for Including the Interactive Representation of Nitrogen Deposition and Drought Effects on Forested Ecosystems

One of the biggest uncertainties of climate change is determining the response of vegetation to many co-occurring stressors. In particular, many forests are experiencing increased nitrogen deposition and are expected to suffer in the future from increased drought frequency and intensity. Interactions between drought and nitrogen deposition are antagonistic and non-additive, which makes predictions of vegetation response dependent on multiple factors. The tools we use (Earth system models) to evaluate the impact of climate change on the carbon cycle are ill equipped to capture the physiological feedbacks and dynamic responses of ecosystems to these types of stressors. In this manuscript, we review the observed effects of nitrogen deposition and drought on vegetation as they relate to productivity, particularly focusing on carbon uptake and partitioning. We conclude there are several areas of model development that can improve the predicted carbon uptake under increasing nitrogen deposition and drought. This includes a more flexible framework for carbon and nitrogen partitioning, dynamic carbon allocation, better representation of root form and function, age and succession dynamics, competition, and plant modeling using trait-based approaches. These areas of model development have the potential to improve the forecasting ability and reduce the uncertainty of climate models

Poulsenia armata seedling biomass

Data on Poulsenia armata seedling biomass allocation at a growing house at the Los Tuxtlas Biological Station, Mexico, from 2012. Data includes soil source and maternal habitat as well as total dry mass, root mass fraction, stem mass fraction, leaf mass fraction, specific leaf area, leaf area ratio, stem length, root-to-shoot ratio and number of leaves

Seed quality parameters

Data on Poulsenia armata seed quality data at Los Tuxtlas forest, Mexico. Seeds were collected in 2012 and sent to the University of Illinois at Chicago to determine the carbon and nitrogen stable isotope ratios (13C12C and 15N14N, respectively), carbon and nitrogen concentrations (% dry mass) and carbon-to-nitrogen ratios. Data also includes seed dry mass, amount of nitrogen per seed and seed relative water conten

Poulsenia armata seedling survival

Data on Poulsenia armata seedling survival from a growing house at the Los Tuxtlas Biological Station, Mexico, in 2012. Data includes soil source, maternal habitat and survival (0 = no survival, 1 = survival

Seed germination of Poulsenia armata

Data on germination of Poulsenia armata seeds from a growing house at the Los Tuxtlas Biological Station, Mexico, in 2010. Data soil source, maternal habitat and germination (0 = no germination, 1 = germination

Fruit production of Poulsenia armata

Data on annual fruit and seed production for Poulsenia armata at Los Tuxtlas forest, Mexico, from 2010 to 2012. Data includes tree tag, name of the plot and habitat type

Soil parameters

Data on soil quality data from Los Tuxtlas forest, Mexico. Soil samples were collected in 2012 and sent to the University of Illinois at Chicago to determine the carbon and nitrogen stable isotope ratios (13C12C and 15N14N, respectively), carbon and nitrogen concentrations (% dry mass), carbon-to-nitrogen ratios and relative water content

Tree quality parameters

Data on Poulsenia armata seed quality at the level of tree at Los Tuxtlas forest, Mexico, from 2012. Data includes habit type, plot, tree tag, as well as, total nitrogen per tree and total nitrogen per tree