The PIs will study how the essential plant nutrient nitrogen (N) is transferred from soil microorganisms to plants during snow melt in the Colorado alpine. The PIs preliminary studies show that there is a decline in the population of soil microorganisms during snow melt and that this decline coincides with an increase in N in the soil. Surprisingly this pulse of N is almost entirely retained within the system and does not pollute downstream water sources. The PIs will study the mechanics of how plants and fungi associated with plant roots compete with soil microorganisms for the N released during snow melt. The PIs will also investigate what causes the decline of soil microorganisms during snow melt. These studies will help us to understand how N is retained in alpine systems. This information is important since N inputs (from car exhaust and power plant emissions) are increasing and N acts as a pollutant if it is flushed from alpine areas into downstream drinking water supplies.