Synthesis of long-term ecological monitoring data from multiple sites along the Middle Rio Grande from 1997-2008

Background/Question/Methods The Bosque Ecosystem Monitoring Program (BEMP) is long-term ecological research using K-12 teachers and their students, university interns, and staff to monitor key indicators of structural and functional change in the Middle Rio Grande riparian forest, or “bosque”. Each year BEMP involves over 500 students in year-round data collection and lab processing, and ~1200 students in 1-3 field/lab sessions, helping to increase their understanding and appreciation of science and the ecosystem.
Abiotic data collected and analyzed include groundwater, river and ditch water level and quality; precipitation; and temperature. Biotic data include plant primary productivity and cover; number, size and sex of cottonwoods; woody debris; and surface-active arthropod activity. These data provide insight into the biological quality and hydrologic connectivity of 25 BEMP sites spanning 280 km of the Rio Grande.
Anthropomorphic drivers, such as fire and mechanical clearing, are more prevalent in the bosque than the historic driver, flooding. Flooding is acknowledged as a necessary component in native cottonwood establishment, but it is also an important driver for native understory vegetation. The variety of BEMP sites allows us to track impacts of clearing (exotic tree and fuel load removal), fire, and flood on vegetation reestablishment, groundwater response and the capacity of different areas to respond to disturbance and maintain a diverse, native-dominated community. In addition to managed, post-fire recovery, and wetland sites, there are six sites bracketing Albuquerque’s new Drinking Water Project diversion dam that monitor impacts of diverting river water. University of New Mexico interns, site representatives, and contracted experts provide quality control on BEMP data.

Results/Conclusions BEMP data suggest that flooding is still the key driver of native vegetation establishment, especially after fire or restoration clearing efforts. Sites that flood after a burn or clearing have reduced fuel loads and greater native vegetation cover and diversity than sites that do not flood. At most BEMP sites, there is no evidence of water table recovery following removal of exotic vegetation, with two possible exceptions where a steady decade-long decline in groundwater stabilized after clearing.  Response to river flow is still the dominant influence on groundwater level at most sites. Areas dominated by native grasses or forbs quickly reestablish after burning. Areas that were bare pre-burn are typically reestablished by exotics (e.g. tumbleweed and kochia). Following fire, saltcedar have the quickest and highest percent of resprout growth, followed by Russian olive, then cottonwood.