ALPINE PLANT FUNCTIONAL TRAITS CHANGE WITH INCREASED SOIL TEMPERATURES AT THE SW MONTANA GLORIA TARGET REGION

Abstract:

Alpine plants are sensitive to climate change. GLORIA, (Global Observation Research Initiative in Alpine environments) is a vast network of alpine plant and temperature monitoring sites on mountain summits. The SW Montana GLORIA Target Region (2008-2020 and onward) in the Pioneer Mountains is on Mt. Keokirk (9801 ft., 45.5938° N, -112.9510° W) and Mt. Fleecer (2873 m, 45.8264°N, 112.8019°W). We deployed Hobo Tidbit v2 Temperature Loggers with hourly readings, 5-10 cm underground, at each cardinal direction and 5 m beneath each of four summits along an elevational gradient from treeline to the alpine zone. Every five years we survey the distribution of plant species and their qualitative functional traits because they interact with climatic factors. Plant species, their functional traits, and soil temperatures varied with year, summit, and aspect on Mt.Keokirk as well as on Mt. Fleecer. Perhaps the most profound changes were on Mt. Keokirk, where summer temperatures rose between 2014-18. On the southern aspect, the average daily soil temperature increased steadily from 17.37° C on 8-3-15 to 20.58° C on 8-10-18 and was concurrent with changes in plant functional traits and species. From 2013-19, and observable in 2020, the relative percent cover of Potentilla nivea, a stoloniferous species of the rose family, increased from 5.75 +/- 2.8 (2013) to 14.00 +/- 6.68 and, noticeably, the relative percent cover of P. nivea increased by over 50% in some 1M X 1M quadrats. Since stolons are aboveground clonally reproductive horizontal stems, their increase suggests continued clonal reproduction with increased temperatures. However, stolons are just one form of clonal reproduction and the percent cover of species with rhizomes decreased from 12.37 to 4.87%, likely reflecting a decrease in Carex and grass species. When all four aspects of Mt. Keokirk were considered together, vascular plant cover decreased from 44.52 to 38.87%. Monocots decreased from 11.37 to 3.7%, and dicots increased from 29.98 to 33.12%. Overall morphology shifted, with a decrease in mat forming plants from 13.25 to 6.00% and cushion plants from 8.12 to 5.00%. The relative percent cover of VAM plants increased from 33.00 to 40.48, suggesting that plants forming mycorrhizal symbioses are influenced by temperature on Mt. Keokirk.