Water manipulation
The long-term mean total rainfall for West Perenjori Nature Reserve in
the growing season from June to October (inclusive) is 174.1 mm (± 6.2
mm standard error, Bureau of Meteorology 2021, 105-year means). As there
had been an average amount of precipitation preceding the growing season
in 2020, we aimed to alter rainfall by 50% such that typical dry and
wet years were represented.
To reduce water availability, we built rainout shelters based on the
design by Gherardi and Sala (2013, see Figure S1 for design details). We
erected the rainout shelters in mid-August after tallying emergence and
thinning interaction neighbourhoods. This allowed an average amount of
rainfall to cue emergence across all plots, after which the experimental
water manipulation was imposed until seed collection.
To increase water availability, we transferred the water collected from
the rainout shelters onto the water addition plots within three days of
each rainfall event. We added the water slowly using a watering can to
prevent run-off and recorded the amount added. Throughout the growing
season, there was 109.8 mm of rainfall across approximately six rainfall
events (Bureau of Meteorology 2021). In total, watered plots each
received an extra 29.9-38.8 L of water (27-35% increase) compared to
ambient plots.