New lab NSF postdoctoral research fellow Roxanne Cruz-de Hoyos (center) is leading up summer efforts to measure quaking aspen drought tolerance. To do this she has to collect leaf hydraulic vulnerability curves, which involve a substantial amount of work in the lab – and the field. Here is how her process works.

The work begins on Google Earth, selecting target sites on the landscape for scouting and rigging – the leaves Roxy wants to study need to come out of the canopy before dawn, to ensure they are not under water stress, which means visiting sites the day before to prepare them for removal with ropes.

The next morning, the crews get up at around 4AM and pack field gear – here volunteer Jocelyn is on the right, along with Roxy, Gabriel, and Nicole on the left.

Then it is a GPS-guided headlamp hike out to the sites, with the forest all still quiet and dark.

Once the tree is found, the focal branch is pulled out of the canopy with the pre-rigged ropes…

…and the branch is stored in a large plastic bag to keep it under low water stress.

After a few more collections, the sun has come up, and the branch samples are carried out of the forest back to the lab.

Back in the lab, leaves from the branches are set up on a scanner for repeat-imaging over several days, to watch as gas bubbles form in the leaves as they slowly dehydrate.

Also repeatedly, the water potential in the leaves is measured with a pressure chamber (here led by Gavin, though Nicole has been leading much of this work). Together these datasets let Roxy measure how the leaf’s ability to conduct water declines under increasingly severe drought conditions. It is many hours of work per sample, but the data may be critical for determining which parts of the forest are going to be more sensitive than others to climate change.

Roxy just wrapped up her field season this week, and I can’t wait to see what her data say!