Variation in the location and timing of experimental severing demonstrates that the persistent rhizome serves multiple functions in a clonal forest understory herb

1. In clonal plants, persistent rhizomes can serve multiple purposes,
including resource storage, modulation of heterogenous resource
distributions, maintenance of bud banks and promotion of recovery from
disturbance. Clonal plants are commonly long-lived and, in temperate
zones, often exhibit organ preformation. Thus, investigations of how the
timing of disturbance to the rhizome affects plant performance must occur
over multiple growing seasons, but these types of studies are rare. 2. We
conducted a field experiment to examine how the persistent rhizome
supports the existing shoot, new ramet production, and recovery from
damage using mayapple (Podophyllum peltatum; Berberidaceae), a common
herbaceous perennial of low-light forest understories in Eastern North
America. Mayapple maintains a long-lived rhizome and exhibits a
developmentally-programmed seasonal pattern of resource transport and new
ramet initiation. We varied both the position and timing of rhizome
severing in rhizome systems with terminal sexual or vegetative shoots, and
tracked plants for two years following severing. 3. The location and
timing of severing affected both plant persistence (production of new
shoots) and performance (leaf area), with effects differing for new shoots
at the front vs. the back of the rhizome system. Across years, severing
location and past years’ shoot size influenced plant persistence and
performance, while the effect of timing of severing diminished; initial
sexual status had little effect on rhizome system response that was not
accounted for by initial leaf area. Severing generally led to the
establishment of two independent rhizome systems. Relative to
unmanipulated control systems, these two systems had more total leaf area,
but less average leaf area per system. 4. Synthesis. Our results point to
the rhizome as a resource integrator that affects plant responses to
disturbance immediately following damage and in subsequent growing
seasons. Rhizome bud age and/or subtending rhizome size, and developmental
program influence responses to disturbance. While the effects of
experimental disturbance on plant performance decreased two years after
disturbance, further long-term investigation is needed to fully understand
the demographic consequences of damage to persistent rhizomes.