PARENT SESSION
Oral Session #2: Riparian Ecology.
Presiding: M. Dixon
Monday, August 5. 8:00 AM to 11:30 AM. Greenlee Meeting Room, TCC.
Impacts of Soil Salinization in Lower Colorado River Impoundment Riparian Wetlands.
TALLENT-HALSELL, NITA*,1,2, CROSS, CHAD1,2, WALKER, LAWRENCE2, 1 US ENVIRONMENTAL PROTECTION AGENCY, LAS VEGAS, NEVADA2 UNIVERSITY OF NEVADA LAS VEGAS, LAS VEGAS, NEVADA
ABSTRACT- Riparian wetlands were studied at Lake Mohave, a lower Colorado River reservoir bordering Nevada and Arizona, USA to determine whether increased soil salinization, dramatic water-level fluctuations, and interspecific competition adversely affected artificial revegetation. Vegetation measurements and soil samples were collected at thirty-four 2500 m2 plots established along the 100-km shoreline. Salix gooddingii are found in monospecific stands of mature trees within the semi permanently flooded shore. The timing and duration of flooding inhibited seed germination even though viable seeds were being produced. Upon release, seeds either fell into standing water or were captured within dense Tamarix ramosissima thickets that dominate the shoreline. Soil salinity under these Tamarix thickets can reach toxic levels that inhibit native seed germination. The average soil electrical conductivity level were 4.76 + 0.10 dSm-1, with significantly different values (p=0.0001) among sites that ranged from 49.48 to 0.34 dSm-1. Values greater than 2.4 dSm-1 can prohibit Salix seedling establishment yet are suitable for Tamarix establishment. Riparian soil salinization is the consequence of anthropogenic manipulation of the Colorado River and its tributaries. Dams and impoundments create the conditions that render riparian ecosystems suitable for Tamarix establishment and unsuitable for Salix.
KEY WORDS: riparian, Salix, Tamarix, water management