Abstract

New remote sensing and in situ measurement capabilities afford improved understanding of distributed ecohydrological processes in mountainous regions. In this regard, distributed ecohydrologic instrument clusters allow us to observe micro-scale variability in snow-vegetation interactions while remotely sensed data allow us to observe integrated ecosystem-scale response to snow-water availability. Instrument clusters deployed in the Central and Southern Rockies and the Sierra Nevada reveal the dominant role of vegetation in controlling the timing and magnitude of snow accumulation and snowmelt. In this regard, vegetation structure largely controlled the distribution of snow accumulation with 29% greater accumulation in open versus under-canopy locations. Snow ablation rates were diminished by 39% in under-canopy locations. Similarly, differences in climate altered snow-season duration, snowmelt infiltration and evapotranspiration. Commencement of the growing season was coincident with melt-water input to the soil and lagged behind springtime increases in air temperature by several days. Similarly, the timing of peak soil moisture was highly dependent upon snow ablation, occurring within one week of snow disappearance on average. Analysis of remotely sensed vegetation greenness data at the regional scale reveals a coherent signal with regard to these plot-scale measurements. A strong elevational dependence in the relationships between snow disappearance timing and peak vegetation greenness are evident whereby vegetation greenness is highly sensitive to inter-annual variability in snow disappearance timing at low - mid elevations whereas higher elevation forest greenness was relatively insensitive. These elevational variations suggest a switch from water limitations at the lower elevation to energy limitations at the highest elevations. Given potential future changes in the hydroclimatology of mountainous regions, the results of these multi-scale measurements may identify tipping points regarding ecosystem responses to water availability across elevational gradients.

Citation

Molotch, N.P., Musselman, K.N., Trujillo, E., Brooks, P.D., McConnell, J. R., Williams, M.W. (2010): Ecohydrological response to snowmelt dynamics from plot to regional scales. AGU Fall Meeting Abstract C14B-02..