The Shifting Relationships Between Weather and Radial Growth in Big Sagebrush (Artemisia tridentata) Over time

ABSTRACT Climate is a driving factor for plant habitat suitability and growth. Interannual weather trends have become more variable, and for long-lived, established plants, this has likely affected the variability in annual growth. Similar to other woody plants, big sagebrush ( Artemisia tridentata ) is long-lived and puts on annual growth rings. Previous studies have shown that the width of the annual rings (i.e., radial growth) is correlated with a number of weather variables. However, it is unknown if these growth-weather relationships for big sagebrush have shifted given the past changes in climate. Our study investigated the relationships between annual anomalies in radial growth and annual anomalies in four weather variables over time: minimum and maximum temperature, precipitation, and vapor pressure deficit (VPD). Using annual ring data collected from 161 big sagebrush individuals in southwestern Wyoming, we calculated annual anomalies for the weather variables and radial growth using a moving 5-year window from 1965 to 2016. We then used linear regression to evaluate the relationships between growth and weather anomalies and assessed how those relationships have changed over time. We found strong relationships between radial growth annual anomalies and precipitation and VPD anomalies over time. In addition, we found that correlations between anomalies of three of our four weather variables and radial growth anomalies significantly shifted over the last 50 years. Precipitation anomalies showed trends of increasingly positive correlations with radial growth anomalies, whereas maximum temperature and VPD anomalies showed increasingly negative correlations over time. The results of our work demonstrate that the associations between radial growth and weather have likely changed over the last 50 years. If these trends continue into the future under projected climate change, these long-lived shrubs may experience reduced growth and/or reduced habitat suitability.