Passive Restoration Potential of RiparianAreas Invaded by Giant Reed (Arundodonax) in Texas

摘要

s complex environments that include terrestrial and quatic ecosystems, riparian areas are the most threat-ened habitats in North America, suffering impacts fromanthropogenic activities, such as extraction and regula-tion of water and pollution, as well as ecologically-drivenchanges due to climate change and invasion by non-nativespecies (Poff et al. 2011). The current condition of theriparian corridor along the bi-national Rio Grande/RioBravo River, which forms much of the United States-Mexico border, is considered one of the world's primeexamples of damage caused by overextraction and otherhuman activities to riparian ecosystems in arid regions(Wong et al. 2007). A shared resource, the Rio Grandehas been heavily managed to provide water to a robustagricultural economy and burgeoning urban areas onboth sides of the border, and it is acutely contaminatedby agricultural and industrial runoff. The Rio Grandebasin has also been heavily impacted by non-native inva-sive plant species, including giant reed (Arundo donax), arhizomatous woody non-native grass that has invaded atleast 40,000 ha of the narrow riparian corridor along theriver and its tributaries (Yang et al. 2011). Invasive non-native weeds often drive or accelerate riparian ecosystemdecline by outcompeting native plant species (Mason et al.2007). Giant reed has significantly reduced native biodi-versity in riparian ecosystems across arid regions of NorthAmerica, transforming riparian landscapes into thick,impenetrable monotypic stands (McGaugh et al. 2006;Yang et al. 2011). In addition, giant reed has negativelyimpacted water supply due to its great evapotranspirativecapacity (Watts and Moore 2011), and it has decreasedborder security along the Rio Grande (Yang et al. 2011).These impacts have justified and informed a long-termintegrated management plan for control of this weed. Cur-rent management of giant reed include a combination ofmechanical control and chemical herbicides (Spencer et al.2008), and more recently, classical biological control usingnatural enemies (Goolsby et al. 2009). Despite these con-trol efforts, little is known about the successional responseor potential for restoration after the removal or control ofgiant reed from riparian habitat. A succession of diverse native vegetation after a given treatment may signify ahigh potential for passive restoration (Prach et al. 2001),whereas re-invasion by the same or another non-nativespecies may suggest a need for active restoration efforts(Zavaleta et al. 2001), such as intentional plantings orplanned revegetation.