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Communication at the NABS Annual meeting, Keystone, 2000
(109) FLOODING REGIME AND RIPARIAN ECOSYSTEM INTEGRITY ALONG THE RIO GRANDE.
M.C. Molles, Jr., W.S. Barnes, and C.N. Dahm. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
The southwestern United States historically supported extensive riparian cottonwood-willow forests, or bosques. These native forests have been reduced by 85% to 98% across the region and the few remnant stands are threatened. Much of this decline is attributed to flood control. For a given site within the floodplain, time since inundation by a previous flood can be represented as an interflood interval (IFI), generally in months or years in this region. The effect of flood control has been to increase the time between floods, i.e. produce longer IFIs. We hypothesize that key structural, functional, and feedback mechanisms, factors critical to riparian ecosystem integrity, require a short IFI. Cottonwoods from stands along the Rio Grande exposed to short IFIs have higher growth rates and maintain a higher canopy cover. Trees experiencing shorter IFIs also produce leaves with lower C:N and C:P ratios, lower mass to weight ratios, and lower rates of insect attack. These differences should contribute to higher primary production, higher rates of decomposition, and more rapid nutrient cycling in riparian forests with short IFIs. We propose that eliminating historic flooding in this region reduces the ecological integrity of native cottonwood riparian forest ecosystems.
Presented at 10:15 AM on Tuesday, May 30, 2000 in River - Floodplain Interactions
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