Assistant Professor, School of Forestry, Northern Arizona University School of Forestry, Northern Arizona University, United States
Background/Question/Methods Prolonged reduction in precipitation in the deserts of the southwestern US is likely to affect dryland biodiversity and increase anthropogenic impacts on ecosystems. Stress-tolerant species, such as dryland bryophytes, remain sensitive to climate change, especially altered rainfall. Bryophytes are known for their intraspecific variation, but substantial evidence for trait changes induced by global change is lacking. Here, we focused on Syntrichia caninervis, a moss found prominently in the drylands of the Northern Hemisphere. S. caninervis makes an important contribution to carbon and nutrient cycling, soil aggregation, and hydrology in the Southwest; and any effect of climate change on the extent and traits of their populations could have further impacts on ecosystem-level processes. We investigated the effects of long-term induced drought on percentage cover and five morphological traits measured in dry stems of the dryland moss species S. caninervis. We used an 8-year community multisite rainfall reduction experiment on the Colorado Plateau to test morphological and cover changes in response to drought and the influence of elevation.
Results/Conclusions We compared the percentage cover of overall moss species and Syntrichia caninervis between control and drought plots using a blocked ANOVA with site as a random effect. Total moss cover was 31.6% lower in drought plots (F(1,24) = 6.617, p = 0.017), and although S. caninervis was the dominant species, we did not find a significant difference between mean cover in the control (10 .9%, SE= 12.6) and drought plots (7.5%, SE= 6.8). Changes in some morphological traits were related to long-term imposed drought and elevation. We found that drought decreased awn length (t = -1.969, p = 0.061) and increased rhizoid length (t = 2.215, p = 0.037), but these traits were not influenced by elevation. Changes in belowground stem tissue increased in response to drought at hotter, drier, lower elevation sites but decreased at higher elevation sites in our gradient (R2 = 0.244, F(1,22) = 7.105, p = 0.014). The prolonged drought studied has been shown to impact dryland moss cover, and further induce changes in S. caninervis traits that could play a key role in the adaptation of non-vascular plants under environmental change and modify contributions to ecosystem function throughout its range.