Spatial and temporal variability in hydrologic connectivity are important controls on alpine plant ecology and biogeochemical cycling. In the Colorado Rocky Mountains, we expect that earlier snowmelt and higher growing season temperatures in a warmer world – “too much summer” –will influence local or “patch” scale water storage and nutrient cycling, as well as how patches aggregate to yield catchment-scale export of water and nutrients. We expect that some patches may continuously act as hotspots for plant productivity or nutrient cycling, whereas others may be briefly hydrologically and/or biogeochemically active. At the Niwot Ridge Long-term Ecological Research site, we have completed the first of a 6-year study addressing: (1) What is the spatial organization of landscape patches across an alpine catchment? and (2) How will patch-scale behavior and hydrologic connectivity change with “too much summer”? Within a headwater catchment, we are combining sensor-based measurements of soil temperature and water status; manual measurements of soil properties and biogeochemical cycling; and unmanned aerial system-based measurements of snow depth, plant phenology, and soil moisture (5-50 cm resolution). We will integrate these observations within a physically-based distributed hydrologic model to understand water and nutrient export at the catchment-scale and under different climate forcings.
Results/Conclusions
This talk will describe initial results from field and modeling efforts that aid in identifying patches within the landscape and beginning to assess how connectivity evolves over time. For example, measured soil properties and infiltration rates suggest spatial variability over very short length scales (1-2 m2). UAS surveys reveal dominant hydrological flow paths across hillslope and catchment scales, with distinct snowmelt-driven and spring-fed patches, particularly on the eastern side of the study catchment. Soil nitrogen (N) transformations are variable, with the highest rates of nitrate production in soils at tree line, indicating that shifts in tree line will likely feed back to affect source areas of N. Major thrusts in hydrologic simulation have been integration of sensor observations and field measurements to link patches across the watershed, as well as towards model validation. Our next steps include designing field tracer experiments to assess connectivity among patches, and applying a cluster analysis to our to our extensive, multi-scale, coordinated dataset to determine patch types across the study area, and model refinement. This research brings insight into how alpine catchments will change in the future, and provides important information for natural resource managers in the Colorado Rocky Mountains.