Experimentally simulating environmental change in a montane meadow system via reduced snowpack and passive warming: soil and plant responses
Global and regional climate patterns suggest that the environment in the western United States is trending towards warmer and drier conditions. The ecological effects of climate change could include shifts in distribution and phenological changes for many plants and animals. This study provides an initial examination of climatic and phenological (timing of key biological events) trends in an effort to understand how montane plants may be affected by climatic changes. To explore the consequences of increased temperatures and decreased snow cover, we conducted an experiment in a montane meadow where snow removal and passive heating were used to mimic the effects of predicted environmental changes. We manipulated soil temperature using open-sided passive warming chambers, and soil moisture by manually removing snow in the spring of 2010 and 2011. Our treatments included control, snow removal, passive warming, and snow removal + passive warming. We measured soil temperature at the surface and soil moisture at a 25cm depth to confirm that open-sided passive warming chambers and manual snow removal had the intended effects on temperature and moisture. In 2011, we recorded plant phenological response dates for emergence (green-up), budding, flowering, and senescence in three common perennial plants (Arrowleaf Balsamroot (Balsamorhiza sagitatta), Wild Buckwheat (Eriogonum umbellatum), and Western Groundsel (Senecio integerrimus)) in each of the treatments. Frost damage was recorded in Arrowleaf Balsamroot (Balsamorhiza sagitatta) in 2011.
We concluded that open-sided passive warming chambers significantly increased soil minimum nighttime temperatures at a 25 cm depth but had no impact on maximum daily temperatures. The range between the 25 cm soil maximum daily temperature and the minimum daily was significantly increased due to the increase in minimum temperatures. Soil moisture at 25 cm depth was decreased throughout the season in the snow removal treatment when compared to the control in 2011 but not 2010, when there was less snow to remove. Soil moisture was not significantly different in 2010 or 2011 when any of the other treatments were compared.
Plant responses to the treatments differed between the three species measured. Time to emergence was significantly increased in B. sagitatta in the snow removal and passive warming treatments but not when snow removal and passive warming were combined. Budding time was also advanced in B. sagitatta in the snow removal and snow removal + passive warming treatments but not the passive warming only treatments. Green-up time was advanced in E. umbellatum in the snow removal and snow removal + passive warming treatments. The treatments had no impact on the S. integerrimus.