A Story of Drought: A Mixed Methods Approach to Analyzing Impacts on Tree Growth in the Colorado Front Range

Keywords: drought, dendrochronology, remote sensing, resilience, NDVI
Session Type: Virtual Paper Abstract
Day: Monday
Session Start / End Time: 2/28/2022 05:20 PM (Eastern Time (US & Canada)) - 2/28/2022 06:40 PM (Eastern Time (US & Canada))
Room: Virtual 6

Abstract

As the climate changes, Colorado’s forests are experiencing increased drought stress, associated with changes in precipitation, temperature, and the timing of snowmelt. In this analysis, we integrated dendrochronological methods and remote sensing tools to assess forest-climate interactions in a transitional ecosystem between the drier foothills scrubland life zone and more mesic montane conifer forests of the Colorado Front Range. After collecting and processing tree core samples for three dominant species (pinyon pine (Pinus edulis), ponderosa pine (Pinus ponderosa), and Douglas fir (Pseudotsuga menziesii)), we analyzed climate-growth relationships for each species. We then identified years of synchronous growth declines due to drought (1963, 2002, 2011, and 2013). Focusing on growth patterns before, during, and after the onset of drought, we evaluated components of resilience for each species and persisting legacy effects. To better understand drought impacts on forest canopy processes, we then utilized intra-annual NDVI time series as a proxy for productivity. Finally, we interpret the remote sensing and tree-ring datasets together to build a more holistic interpretation of forest-climate dynamics. Our preliminary results indicate that within the Colorado Springs study site, ponderosa pines are least drought-resistant, while pinyon pines are most resistant to severe drought. This is consistent with findings elsewhere in the arid and semi-arid Western U.S. Furthermore, our data suggested a relationship between growing season NDVI and BAI (basal area index), illustrating the interconnectedness of canopy productivity and radial tree growth.