Simulated Climate Change Effects of Snowpack Manipulations on Soil Temperature and Moisture in the Sierra Nevada Mountains

Future changes in climate are predicted to significantly affect the type and amount of precipitation in the Sierra Nevada Mountains of California and Nevada. Because most of the yearly precipitation in this region falls as snow, changes in snowfall amount, snowfall timing, and duration of the snowpack may dramatically affect the timing and persistence of soil temperature and moisture, and biological processes dependent on these soil factors. The objective of our study was to quantify the effects of manipulating snowpack amounts on soil temperature and moisture over a two year period, including both the addition and removal of snow in a Pinus jeffreii (Jeffrey Pine) forest located northeast of Lake Tahoe, Nevada. Soil temperatures measured during the first winter (above average snow year) remained higher in control plots when snow was present, and in snow-addition plots, than in snow-removal plots. However, these effects did not persist in the second year when total snowfall amounted to only 20% of that occurring in the first year. Surprisingly, the effects on soil moisture persisted through the summer of year two with soil VWC in snow removal plots averaging approximately 50% drier than the snow addition plots (6.5% average VWC in snow removal and 13.2% in snow addition plots) and 13% drier on average than the control plots (7.5% average VWC in control plots).These results suggest the possibility of prolonged reductions in soil moisture, soil microbial activity, plant growth, and even increased danger of wildfires if anthropogenic climate change reduces snowfall amount and snowpack duration.