Silica gel packets as a novel dehumidification strategy for enhancing plant drought experiments

Background/Question/Methods

As global temperatures rise, the frequency and severity of extreme weather events such as drought will also increase. To predict how these changes may affect ecosystems, drought experiments aim to model future drought conditions. While controlled watering regimes and rainout shelters have proven effective means for simulating soil drought, recent work has demonstrated that rainout shelters may be insufficient at simulating atmospheric drought. At our Cal State LA mesocosm experiment, we imposed a novel aboveground drought treatment by suspending two 100-gram silica packets 12 centimeters above the soil surface of each of six pots (15 gallons each). For our belowground drought treatments, half of those pots were drought-watered (n=3), and the rest were ambient-watered (n=3). We measured relative humidity and temperature every 10 minutes for five months in all six treated mesocosms and an additional three control reference mesocosms (ambient air and ambient soil, n=3).

Results/Conclusions

We found that packets effectively simulated atmospheric drought when combined with soil drought manipulations. Packets are best at reducing ambient air humidity (by ≥5%) when relative humidity is high (≥45%). Importantly, higher humidity is common under rainout shelters. Finally, packets worked consistently well when replaced at least every 2-3 days. Our quantitative assessment of the efficacy of silica packets as practical, low-cost, and reliable dehumidification agents has the potential to improve our understandings of realistic ecological drought effects that are predicted in the next 50-100 years.