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Accepted manuscript

Changing dominance of invasive Phragmites australis and native plant colonization with variation in management, wildfires, and soils in a desert wetland

Published online by Cambridge University Press:  29 October 2024

Scott R. Abella*
Affiliation:
Associate Professor, University of Nevada Las Vegas, School of Life Sciences, Las Vegas, NV, USA and Founder and Ecologist, Natural Resource Conservation LLC, Boulder City, NV, USA
Shelley L. Porter
Affiliation:
Research Assistant, University of Nevada Las Vegas, School of Life Sciences, Las Vegas, NV, USA
Kathleen A. Kline
Affiliation:
Research Assistant, University of Nevada Las Vegas, School of Life Sciences, Las Vegas, NV, USA
Lindsay P. Chiquoine
Affiliation:
Research Associate, University of Nevada Las Vegas, School of Life Sciences, Las Vegas, NV, USA
Benjamin S. Jurand
Affiliation:
Environmental Specialist, Clark County Wetlands Park, Las Vegas, NV, USA
*
Author for correspondence: Scott R. Abella, University of Nevada Las Vegas, School of Life Sciences, 4505 South Maryland Parkway, Las Vegas, NV 89154-4004. (Email: [email protected])
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Abstract

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Among the most widely distributed species globally, common reed (Phragmites australis (Cav.) Trin. ex Steud.) has generated extensive interest in invasive plant science and management because its introduced strains are highly invasive and often form monocultures that alter ecosystem properties. In desert wetlands in Las Vegas, Nevada, USA, where management goals included reducing hazardous P. australis fuels and increasing native plant diversity, we assessed variation in P. australis cover, the degree of native plant colonization, and soil seed banks after P. australis management treatments (cutting, glyphosate-imazapyr herbicide) and wildfires across gradients in soil properties. Based on change in P. australis cover during six measurement events over 24 months, 24 study sites formed three groups: 1) decreasing cover, where initially high P. australis cover (60-85%) decreased to < 5% following multiple cutting or herbicide treatments; 2) sustaining low cover, where wildfire or clearing was associated with initially low P. australis cover which remained low (< 30%) after multiple herbicide applications; and 3) sustaining high cover (45-100% initially and remaining 30-100%), including sites unmanaged or treated/burned only once. High soil salinity correlated with low post-management P. australis cover. No native plants were detected in the sustaining high P. australis cover group, despite natives occurring in the seed bank. Where management reduced P. australis cover, minimal native plant colonization did occur. Secondary invasion by other non-native plants was nearly absent. Our results suggest that if P. australis can be initially cleared, multiple herbicide applications can persistently keep cover low, especially on drier, saline soils. Slow native plant colonization suggests that a phased approach may be useful to initially reduce P. australis cover, keep it low via repeated treatments, and actively revegetate sites with native species tailored to the moisture-salinity gradient across P. australis-invaded habitats.

Type
Research Article
Copyright
© Weed Science Society of America, 2024