Flooding Regime and Restoration of the Middle Rio Grande Riparian Ecosystem

J.F. Schuetz, M.C. Molles, Jr., C.N. Dahm and C.S. CrawfordDepartment of Biology, University of New Mexico

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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/Vadose Zone

Schematic Subsystems H°/predictions For flooded vs. nonfloodedsites:

i) interstitial DO Alluvial Aquifer ii) conductivity (salinity)

leaf litterwoody debris

water table

i) leaf decompositionii) forest floor respiration

ii) root growth/biomassi) 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 FloorCollect data on soil respirationStudy cottonwood leaf decomposition

Collect arthropods using pitfall traps

Determine standing stock of litter

Estimate coarse woody debris

Alluvial AquiferMonitor groundwater levels

Conduct chemical analyses on groundwater

Soils and Vadose Zone

Measure soil moisture from the surface to 1 meter

Study root growthDetermine 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

AcknowledgementsFunding agencies: NSF Grant DEB-9903973

Cooperating agencies and institutions:Middle Rio Grande Conservancy DistrictBosque del Apache National Wildlife RefugeCity of Albuquerque Open Space DivisionNew Mexico State Land OfficeRio Grande Nature CenterGrinnell CollegeThe Nature ConservancyBelen Consolidated Schools

Personnel: Nate Bohls, Sam Gray, Karyth Becenti, Leslie Barker, Nick Johnson