Sagebrush vegetation response to experimental drought

These data are from the research project Drought and Sagebrush: Management Implications, conducted by Kerry Byrne and Kristen Kaczynski from 2016 - 2020. The dataset contains research results related to species composition, forb density, and above and belowground net primary production in response to four years of experimental drought using rainout shelters and control plots. We used rainfall shelters to create a 1-in-100-year drought at each site to understand how chronic (4 year) drought will impact common, but understudied sagebrush steppe plant communities. We conducted our study at two sites approximately 60 m apart within a grazing exclosure established in 1993 in Klamath County, Oregon, USA (42.301111, -121.018056). The two study sites have unique edaphic features that lead to differences in the ecological structure and function of the plant communities. One site (AA site) is dominated by Artemisia arbuscula (low sagebrush) while the other site (AC site) is dominated by A. cana (silver sagebrush). We found that above- and belowground net primary production at both sites were remarkably resistant to drought. Litter increased over time in drought plots at the more productive AC site, and we hypothesize that hydraulic lift and litter interacted to increase shallow soil water content under drought at that site. The AA site, with harsher edaphic features and a soil duripan, experienced fewer changes in plant community composition than the more productive AC site, potentially due to the presence of specialized plant species at the harsher site. Non-native plant cover increased (primarily from Ventenata dubia, an invasive annual grass) and native forb cover and density decreased over time. This suggests that management may be needed to conserve native forb diversity and limit species invasion, especially as climate and fire regimes change. Methods At each site (AA - Artemisia arbuscula and AC- Artemisia cana) in early to mid July of each year (2016 - 2020), we non-destructively estimated aboveground net primary production within drought (n=5) and control (n=5) plots, estimated the absolute cover of each species within the plots, and counted the seedling density of common forb species and the two focal Artemisia species. In Oct of each year, we excavated one or two root ingrowth cores and filled them each with sieved root-free soil from the sites. Each following Oct, we removed the ingrowth cores and dried and weighed the roots to estimate belowground net primary production in each plot (data for 2017 - 2020). We monitored soil water content at shallow depths in each treatment (0 – 10 cm at AA site, n =3; 5 – 15 cm at AC site, n = 2) every 4 h to evaluate the effectiveness of the drought treatment. We monitored deeper (20 - 30 cm) soil water in one plot for each treatment at the AC site, but not the AA site.