The role of litter in the success of the invasive plant, reed canary (Phalaris arundinacea)

Reed canary is an invasive plant in tallgrass prairie lowlands throughout much of the central North American grasslands.  Invasive plants are often characterized by high growth rates, quick response to increased resources and rapid decomposition of litter. Reed canary, in contrast, often has thick mats of litter that build up and may act to preempt growth of other species.  We used the litterbag technique to compare litter decomposition rates between reed canary and big bluestem (Andropogon gerardii) a native tallgrass.  Over two years reed canary leaf litter had lower rates of decomposition than big bluestem.  We set up a series of field manipulations of litter to test the idea that reed canary litter suppresses the emergence and growth of co-existing native grasses.  The study site was Allwine Prairie, a restored, tallgrass prairie in eastern Nebraska.  Results indicate that reed canary litter differentially affected the tillering and growth rates of its own tillers and those of the native grasses.  Litter dynamics, either the speeding up or slowing down of decomposition, may be an important means by which invasive plants colonize and maintain dominance in native ecosystems.