DOI: 10.5061/dryad.1c59zw40v
title: Data from: Increasing photosynthetic benefit with decreasing irrigation frequency in an Australian temperate grassland exposed to elevated carbon dioxide

description: Elevated atmospheric CO2 (e[CO2]) often enhances plant photosynthesis and
 improves water status. However, the effects of e[CO2] vary significantly
 and are believed to be influenced by water availability. With the future
 warmer climate expected to increase the frequency and severity of extreme
 rainfall, the response of plants to e[CO2] under changing precipitation
 patterns remains uncertain. We examined the effects of e[CO2] and
 different irrigation regimes on perennial ryegrass in a free-air CO2
 enrichment (FACE) experiment. Immediately after irrigation, the mean net
 photosynthetic rate was 21.2% higher under e[CO2] compared with ambient
 conditions. This benefit increased over time, reaching a 31.3% higher rate
 as days since watering increased, indicating a substantial increase in
 photosynthetic benefit with longer intervals between watering. Mean
 stomatal conductance was 21% lower in ryegrass under e[CO2] immediately
 after irrigation compared with ambient plots. However, the reduction in
 stomatal conductance under e[CO2] decreased as the interval between
 irrigation events increased, showing no difference 7–10 d after an
 irrigation event. These results imply that plants benefit most from carbon
 fertilization, assimilating relatively more carbon and losing less water,
 during periods with less frequent rainfall. These findings have
 significant implications for understanding leaf-level responses to climate
 change.
description: In a Free-Air Carbon Enrichment site (FACE) in Tasmania, we
 investigated pasture grass (perennial ryegrass) responses to elevated
 CO<sub>2</sub> and irrigation frequency. We assessed the
 impacts of treatments on gas exchange, water relations, leaf area index
 and soil water content on perennial ryegrass over one year.
description: # **Increasing photosynthetic benefit with decreasing irrigation frequency
 in an Australian temperate pasture exposed to elevated carbon dioxide**
 The first sheet contains the gas exchange data i.e. net carbon
 assimilation and stomatal conductance and the second worksheet is the
 water potential data. The third worksheet is soil water content and the
 fourth worksheet is leaf area index data. Treatments * CO2 treatments were
 ambient at 400 ppm and elevated at 550 ppm. Watering treatments were
 watered every 3, 5, and 10 days with the overall amount being the same
 over 30 days. 12 individual study plots (rings) were used 6 at elevated
 CO2 and 6 at ambient CO2. The study species was Lolium perenne.
 Measurements * Gas exchange, water potential, soil water content and leaf
 area index was measured. **Description of the data and file structure**
 The following column names occur in all sheets:                 Date -
 date on which the variable was measured.                 Ring - plot
 measured                  CO2 - CO2 concentration, ambient or elevated.  
                Water - irrigation treatment, 3, 5, or 10 days. **Gas
 exchange** * Anet is net photosynthetic rate (µmol m-2 s–1) * gs is
 stomatal conductance (mol m-2 s-1) * VpdL is vapour pressure deficit (kPa)
 of the leaf. * DSW refers to days since water i.e. since the last
 irrigation event. **Water potential** * PSI (per square inch) is a measure
 of water potential and is converted to Mpa (megapascals) which is the
 conventional way of reporting water potential. * Time.of.day is when
 measurements were taken either pre-dawn or midday. **Soil water content**
 * SWC.MIN is daily minimum, SWC.MAX is daily maximum and SWC.MEAN is daily
 mean volumetric soil water content (cm-3/cm-3). * Cycle refers to the
 watering cycle which changes each time a watering event occurs. **Leaf
 area index (LAI)** * Leaf area index was measured at the three leaf stage
 mol (m-2/m-2). **Sharing/access information** Data * Data not stored
 elsewhere and not derived from other sources.