Influence of terrain aspect on water partitioning, vegetation structure and vegetation greening in high-elevation catchments in northern New Mexico

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We investigated vegetation structure, water partitioning dynamics and vegetation greening from 2000 through 2012 in three catchments draining north and east aspects of Redondo Peak in northern New Mexico. Vegetation structure was quantified from 1-m lidar data, while vegetation greening was quantified using remotely sensed normalized difference vegetation index (NDVI). Hydrological partitioning at the catchment scale was estimated with a metric of catchment-scale water fluxes and vegetation water use [Horton index (HI)]. The predominantly north-facing catchment, when compared with the other two eastern catchments, receives less solar radiation, exhibits less forest cover and smaller biomass and has more surface run-off (˜15% of P) as a consequence of a smaller vaporization (85% of P) and smaller vegetation water consumption (HI = 0·85). Moreover, the north-facing catchment showed smaller peak NDVI values (5·98) and shorter growing season length (121 days) as a consequence of energy limitation. In contrast, the two eastern catchments receive larger solar radiation and have more biomass and forest cover (>76%), smaller surface run-off (<10% P) and higher vaporization (>90% P) and vegetation water consumption (HI = 0·95). The eastern catchments had larger vegetation greening (6·28–6·58) and a longer growing season (148–160 days). Snowpack conditions, such as maximum snow water equivalent and duration of the snow on the ground, explain over 95% of water partitioning (HI) that in turn influenced annual vegetation greening (R2 = 0·48–0·67; p < 0·05). This catchment-scale study in perennial streams indicates that terrain aspect at a similar altitude (2700–3435 m) strongly controls energy, water distribution and vegetation productivity in high-elevation ecosystems. Copyright © 2015 John Wiley & Sons, Ltd.

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