Ecosystem processes are intrinsically coupled to the hydrological cycle. Spatial and temporal patterns in plant communities are governed by the interaction between climate and characteristics such as soil, terrain position and moisture status. Understanding plant responses to climate variability, disturbances and stress requires recognition of the hydrologic controls imposed by landscape position. For example, topography is known to influence soil moisture redistribution, local microclimate and radiation exposure which can further lead to differences in vegetation patterns. In semi-arid and arid regions, the signature of topography on ecosystem structure is even more evident as water is a limiting plant resource. Our group studies the interaction between hydrologic and ecologic processes in arid and semi-arid landscapes through a combination of modeling, remote sensing and field data collection.  
     
   
 
  Our study site is a small drainage basin in the Sevilleta National Wildlife Refuge. The drainage is cut into a coarse, flat-lying alluvial fan deposit of the Sierra Ladrones Formation, consisting primarily of schist and quartzite clasts with a sandy matrix. The drainage basin has an area of 0.034 km2 which is dissected by an east-flowing ephemeral channel that divides the north and south facing hillslopes. The north-facing slope is composed primarily of one seed juniper (Juniper monosperma) with an individual spacing of a few meters interspersed with a black gramma (Bouteloua eriopoda). The south-facing hillslope is primarily creosotebush (Larrea tridentata) with a mixture of grasses and other species. The catchment head slope region is differentiated significantly from the two facing hillslopes both in terms of its plant community and their relative size. In addition, an active ecotone boundary is present along the head slope, as evidenced by the die-off of a number of juniper trees.  
     
 
  Knowledge gathered through field data collection is utilized for parameterizing of models to study ecohydrological dynamics. We have conducted work using a hillslope energy balance model and a one-dimensional vadose model applied to the two different hillslopes. Distributed simulations of the spatial and temporal response of plants to soil moisture availability are also being conducted through the use of the TIN-based Real-time Integrated Basin Simulator (tRIBS) and its modifications for semiarid domains. Our approach combines current knowledge about processes that drive vegetation dynamics in the short term into a mechanistic model to facilitate investigation of the long term interactions between topography, hydrology, vegetation and climate.Scientific inquires will be addressed through the spatially-explicit hydrological model that will integrate vegetation as an adaptive and evolving component.  
     
 
               
       
First-order drainage basin in Sevilleta National Wildlife Refuge with opposing hillslopes and ecotonal boundary
  
Distribution of soil properties and root density for opposing hillslopes in first-order drainage basin for use in hydrological modeling