Growth of native and exotic plants during the 2000 Low Steady Summer Flows Or: Be careful what you ask for… Marianne E. Porter Michael J.C. Kearsley Dept. of Biol. Sciences Northern AZ. University Flagstaff, AZ

Possible LSSF Experiment Outcomes: * Bla Bla Bla native fish recruitment * Bla Bla Bla seasonal hydrology * Bla Bla Bla near-shore current velocity * Bla Bla Bla increased water temperature *Recruitment of clonal herbaceous species (Equisetum, Juncus, Phragmites) *Recruitment of exotic species (Tamarix, Alhagi) in near shore areas

Importance of plant colonization Vegetated shoreline: vegetation (primarily Tamarix chinensis) in or directly over the water, either rooted or inundated. May have intermittent stretches of other shoreline types. Densities of humpback chub are nearly double those found in other shoreline types (Converse et al 1998).

31,500 19,000 8,000 River Stage Pre-Low Flows Conditions

Research Questions: Do plants colonize newly available habitat? (8 kcfs – 19 kcfs) Nature of these colonists?Native / Exotics? Clonal / Seed-dispersed? Impacts of a short-duration high flow? Effects of low flows on extant vegetation at the 31 kcfs stage elevation?

Sampling Transect Design 31 kcfs 19 kcfs 8 kcfs = 0.25 m 2 Plot 5 – 18 Plots / Transects 6 – 14 Transects / Site Sampled Monthly June – Sept 2000 April 2001

Study Period Hydrograph Sampling

Nearshore Vegetation Study Sites

Data Analysis Repeated Measures AOV on Plant Densities Time, Site, Time*Site Data Transformations All Species Individual Species Tamarisk, Equisetum

Plant colonization: June

Plant colonization: August

Plants Below 19 kcfs

High elevation Equisetum

All Equisetum

Low and High Elevation Tamarisk

Winter Mortality is Low

River’s Edge Mortality

Conclusions Plants colonized areas below 19,000 cfs creating subadult fish habitat Colonists primarily Tamarisk Clonal herbaceous species were slower Fall high flows reduced plant densities Winter mortality was low for all species Recreation impacts of near-shore plants