Flooding Regime and Restoration of the Middle Rio Grande Riparian Ecosystem J.F. Schuetz, M.C. Molles, Jr., C.N. Dahm and C.S. Crawford Department of Biology, University of New Mexico Photo by A. Molles

Damming and diversion of the river Altered volume and timing of the Rio Grande’s flow Isolated riparian forest (“bosque”) Aging native cottonwood forest Few new cottonwood stands Invasion by exotics Drought conditions Why Study the Bosque?

Study Sites

iii) nativedetritivores iii) net N mineralization i) variation in water table depth ii) soil moisture Cottonwoods Forest Floor Soils/ VadoseZone SchematicSubsystems H ° /predictions For flooded vs.nonfloodedsites: i) interstitial DO Alluvial Aquifer ii) conductivity (salinity) leaf litter woody debris water table i) leaf decomposition ii) forest floor respiration ii) root growth/biomass i) C:N & C:P in new leaf tissue iv) flowering iii) litterfall, C:N in litterfall v) defoliation Subsystems Under Study and Hypotheses

Cottonwood Canopy Sample leaves from the canopy and measure C:N:P Collect litterfall Subsample cottonwood leaves from litterfall to determine C:N Measure diameter at breast height of trees within study site Record percentage of flowering trees

Forest Floor Collect data on soil respiration Study cottonwood leaf decomposition Collect arthropods using pitfall traps Determine standing stock of litter Estimate coarse woody debris

Alluvial Aquifer Monitor groundwater levels Conduct chemical analyses on groundwater Soils and Vadose Zone Measure soil moisture from the surface to 1 meter Study root growth Determine net nitrogen mineralization in soils

What will we do with the results? Limited scientific data to assess the ecological benefits of managed flooding Data: 2001 – flood 2002 – drought Provide natural resource managers and water policy- makers with information to make decisions on the use of managed floods

Acknowledgements Funding agencies: NSF Grant DEB Cooperating agencies and institutions: Middle Rio Grande Conservancy District Bosque del Apache National Wildlife Refuge City of Albuquerque Open Space Division New Mexico State Land Office Rio Grande Nature Center Grinnell College The Nature Conservancy Belen Consolidated Schools Personnel: Nate Bohls, Sam Gray, Karyth Becenti, Leslie Barker, Nick Johnson