Northwestern University & The Chicago Botanic Garden Glencoe, IL, United States
Abstract: Climate change is altering temperature and precipitation trends at a scale that will fundamentally change the environment and resources available to plants. Due to a combination of higher temperatures and reduced precipitation, drought frequency and severity is increasing in many regions across the globe, and is expected to increase substantially in the western USA. Although plants have various strategies for withstanding drought, those strategies are often mired in tradeoffs among survival, reproduction, and growth. The tradeoffs between these relationships can be especially interesting to consider for animal pollinated perennial plant species in areas with large moisture extremes, such as subalpine areas. These plant species may prioritize survival over reproduction and therefore sacrifice key components of their reproduction in drought conditions. This study investigated the relationship between drought, physiological drought stress, floral characteristics, and demographic consequences in a subalpine plant, Linum lewisii. The study was conducted at the Rocky Mountain Biological Laboratory in Gothic, Colorado in 2022 and utilized rainout shelters to create drought conditions. Our main questions were Q1) How does reduced precipitation influence physiological drought stress? Q2) How does reduced precipitation influence flower characteristics: flowering duration, flower size and flower abundance? Q3) How does reduced precipitation influence plant size, plant survival and seed set?
We monitored the physiology, floral characteristics, and demography of 120 L. lewisii individuals from May until August. The main impacts of reduced precipitation were a shortened flowering season and a reduction in leaf size. Linum lewisii had a marginally significantly shorter flowering season (p < 0.10) and significantly smaller leaves (p < .005) in the reduced precipitation plots compared to the control plots, but stomatal conductance did not differ significantly between treatments. More years of data collection are necessary to understand the mechanisms and specific effects of reduced precipitation on physiology and plant reproduction in L. lewisii. Based on the first year of our study, it is possible that the reductions to flowering season length and leaf size represent drought mitigation strategies to allow for successful reproduction and avoidance of stomatal closure.
