DOI: 10.5061/dryad.2fqz612qg
title: Pastures and climate extremes: Impacts of cool season warming and drought on the productivity of key pasture species in a field experiment

description: Shifts in the timing, intensity and/or frequency of climate extremes, such
 as severe drought and heatwaves, can generate sustained shifts in
 ecosystem function with important ecological and economic impacts for
 rangelands and managed pastures. The Pastures and Climate Extremes
 experiment (PACE) in Southeast Australia was designed to investigate the
 impacts of a severe winter/spring drought (60% rainfall reduction) and,
 for a subset of species, a factorial combination of drought and elevated
 temperature (ambient +3 °C) on pasture productivity. The experiment
 included nine common pasture and Australian rangeland species from three
 plant functional groups (C3 grasses, C4 grasses and legumes) planted in
 monoculture. Winter/spring drought resulted in productivity declines of
 45% on average and up to 74% for the most affected species (Digitaria
 eriantha) during the 6-month treatment period, with eight of the nine
 species exhibiting significant yield reductions. Despite considerable
 variation in species’ sensitivity to drought, C4 grasses were more
 strongly affected by this treatment than C3 grasses or legumes. Warming
 also had negative effects on cool-season productivity, associated at least
 partially with exceedance of optimum growth temperatures in spring and
 indirect effects on soil water content. The combination of winter/spring
 drought and year-round warming resulted in the greatest yield reductions.
 We identified responses that were either additive such that there was only
 as significant warming effect under drought (Festuca), or
 less-than-additive, where there was no drought effect under warming
 (Medicago), compared to ambient plots. Results from this study highlight
 the sensitivity of diverse pasture species to increases in winter and
 spring drought severity similar to those predicted for this region, and
 that anticipated benefits of cool-season warming are unlikely to be
 realised. Overall, the substantial negative impacts on productivity
 suggest that future, warmer, drier climates will result in shortfalls in
 cool-season forage availability, with profound implications for the
 livestock industry and natural grazer communities.
description: Data included here include aboveground biomass summed across
 multiple harvests between June 1st 2019 and Nov 30th 2019 associated with
 nine pasture and rangeland species included at the Pastures and Climate
 Extremes field facility at the Hawkesbury Experiment Forest run by the
 Hawkesbury Institute for the Environment of Western Sydney University.
 Detailed methods on species establishment and experimental design can be
 found the associated publication, however briefly all aboveground biomass
 was clipped to 5cm using a sickle mower and hand-hand shears between 2-3
 times during the winter and spring seasons. The weed fraction has been
 removed from this total, and all biomass was dried to constant mass prior
 to weighing. File name: AGBiomassDryad
 Column descriptions: SubPlotID (This provides a unique identifer
 for each individual subplot within the larger experiment- combining
 shelter, plot and subplot location information), SubPlotType (This is a
 three letter code linking the species grown in a subplot based on common
 names), SubPlotType2 (this is a three letter code linking the genus name
 for each species in a subplot), FxnlTyle (This is a functional group
 classification including 'C4 grass', 'C3 grass', and
 'Legume', Water (drought treatment levels; drought- 60%
 reduction in precipitation and control- modelled precipitation based on
 the long-term average in Richmond, NSW), Temperature (warming treatment
 levels; elevated- +3 degrees C continuously relative to control plots, and
 Ambient- as measured in field for canopy and soil surface temperature),
 Group (factorial combination of Water and Temperature treatments to
 comprise four groups; aT-C, aT-D, eT-C, eT-D), Shelter (Factor describing
 the location of the sward among shelters; 1-6), Plot (placement within a
 shelter; numeric 1-8), Biomass (Aboveground biomass summer for a subplotID
 between June 1st and Nov 30th 2019; units are kg ha-1).
 Supporting environmental data are also provided here, including
 soil volumetric water content (%; SoilMoisture_dailymean) and temperature
 (degrees C; SoilTemperature_dailymean) measurements from sensors installed
 in individual species swards. Canopy and soil surface temperatures were
 recorded at the treatment level and are included here (degrees C;
 CanopyTemperature_dailymean). Records for the air temperature 
 (AirTemp_dailymean) as well as relative humidity (RH_dailymean) and levels
 of photosynthetically active radiation (PAR; PAR_dailymean) inside and
 outside shelters are also included. File name:
 SoilMoisture_dailymean Column descriptions: Date (Date
 of measurement YEAR-MO-DA), SubPlotID (This provides a unique identifer
 for each individual subplot within the larger experiment- combining
 shelter, plot and subplot location information, SubPlotType2 (this is a
 three letter code linking the genus name for each species in a
 subplot), Group (factorial combination of Water and Temperature treatments
 to comprise four groups; aT-C, aT-D, eT-C, eT-D), Water (drought treatment
 levels; drought- 60% reduction in precipitation and control- modelled
 precipitation based on the long-term average in Richmond, NSW),
 Temperature (warming treatment levels; elevated- +3 degrees C continuously
 relative to control plots, and Ambient- as measured in field for canopy
 and soil surface temperature), Location (refers to the placement of the
 sensor in the soil column where 'upper' measures 0-15cm and
 'lower' measures 15-30cm depth), Shelter (Factor describing the
 location of the sward among shelters; 1-6), Plot (placement within a
 shelter; numeric 1-8), Subplot (refers to directional placement within a
 plot; letters A-D), SM_Mean_per (daily mean volumetric soil water content,
 units expressed as %), SM_Mean_se (daily standard error of volumetric soil
 water content, units expressed as %). File name:
 SoilTemperature_dailymean Column descriptions: Date
 (Date of measurement YEAR-MO-DA), SubPlotID (This provides a unique
 identifer for each individual subplot within the larger experiment-
 combining shelter, plot and subplot location information, SubPlotType2
 (this is a three letter code linking the genus name for each species in a
 subplot), Group (factorial combination of Water and Temperature treatments
 to comprise four groups; aT-C, aT-D, eT-C, eT-D), Water (drought treatment
 levels; drought- 60% reduction in precipitation and control- modelled
 precipitation based on the long-term average in Richmond, NSW),
 Temperature (warming treatment levels; elevated- +3 degrees C continuously
 relative to control plots, and Ambient- as measured in field for canopy
 and soil surface temperature), Location (refers to the placement of the
 sensor in the soil column where 'upper' measures 0-15cm and
 'lower' measures 15-30cm depth), Shelter (Factor describing the
 location of the sward among shelters; 1-6), Plot (placement within a
 shelter; numeric 1-8), Subplot (refers to directional placement within a
 plot; letters A-D), ST_mean (daily mean soil temperature, units are
 degrees C), ST_se (daily standard error of soil temperature, units
 expressed as degrees C). File name:
 CanopyTemperature_dailymean Column descriptions: Date
 (Date of measurement YEAR-MO-DA), PlotID (Factor describing the Shelter
 and Plot location of the measurement), Shelter (Factor describing the
 location of the sward among shelters; 1-6), Water (drought treatment
 levels; drought- 60% reduction in precipitation and control- modelled
 precipitation based on the long-term average in Richmond, NSW),
 Temperature (warming treatment levels; elevated- +3 degrees C continuously
 relative to control plots, and Ambient- as measured in field for canopy
 and soil surface temperature), IR_Mean (daily mean canopy and soil surface
 temperature, units are degrees C), IR_se (daily standard error of canopy
 and soil surface temperature, units expressed as degrees C).
 File name: AirTemp_dailymean Column
 descriptions: Date (Date of measurement YEAR-MO-DA), Shelter (Factor
 describing the location of the sward among shelters; 1-6), Location
 (Factor describing whether the sensor is located 'inside' or
 'outside' the rainout shelters covering the PACE field facility,
 AirTemp_Daily (daily mean air temperature, units are degrees C), AirTempse
 (daily standard error of air temperature, units expressed as degrees
 C). File name: RH_dailymean Column
 descriptions: Date (Date of measurement YEAR-MO-DA), Shelter (Factor
 describing the location of the sward among shelters; 1-6), Location
 (Factor describing whether the sensor is located 'inside' or
 'outside' the rainout shelters covering the PACE field facility,
 Humidity_Daily (daily mean relative humidity, units are %), Humidityse
 (daily standard error of relative humidity, units are %).
 File name: PAR_dailymean Column descriptions:
 Date (Date of measurement YEAR-MO-DA), Shelter (Factor describing the
 location of the sward among shelters; 1-6), Location (Factor describing
 whether the sensor is located 'inside' or 'outside'
 the rainout shelters covering the PACE field facility, PAR_Daily (daily
 mean PAR, units are micromoles m-2), PARse (daily standard error of PAR,
 units expressed as micromoles m-2)