Proceedings of the Third International Conference on Invasive ...

<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 4: Spartina Control and Managementmaintain elevated sediments and altered biogeochemicalprocesses (Fig. 2A, left side). Active water movement and<strong>the</strong> scouring action <strong>of</strong> shifting cobbles and gravel shouldhamper this process. Ultimately, we predict that analternative state will not be maintained due to <strong>the</strong> transitionalprocess <strong>of</strong> water movement increasing sediment erosionaround plant roots and decreasing subsequent vascular plantand infaunal recruitment. As a result, negative feedbackprocesses in <strong>the</strong> maintenance component <strong>of</strong> <strong>the</strong> alternativestate will shift cobble beach community structure to arestored state (Fig. 2A, right side). Algal recruitment willincrease as sediment erosion occurs and cobbles re-emerge,pushing <strong>the</strong> community into a positive feedback loop thatincludes loss <strong>of</strong> sediment, decreased native vascular plantrecruitment, and continued increases in algal and infaunalrecruitment (Fig. 2A, right side).We hypo<strong>the</strong>size that mudflat habitats, because <strong>the</strong>yexperience lower wave action, will have increased vascularplant recruitment, and allow for <strong>the</strong> maintenance <strong>of</strong>cordgrass sediment accretion and biogeochemical processes(Fig. 2A, left side). We expect that a positive feedback loopgenerated by slower water movement and <strong>the</strong> presence <strong>of</strong>vascular plants will maintain sediment characteristicscreated by cordgrass, decrease algal and infaunalrecruitment, and continue to increase native vascular plantrecruitment (Fig. 2A, left side).Finally, we suggest that high and low salinity marshespreviously invaded by cordgrass will experience recruitment<strong>of</strong> higher intertidal vascular plant assemblages, ra<strong>the</strong>r than<strong>the</strong> original assemblage, due to <strong>the</strong> increased tidal elevationproduced by cordgrass-accreted sediments. We expect that<strong>the</strong>se plants will be good at maintaining sediment depth andbiogeochemical processes originally created by cordgrass.Their presence will be maintained via a positive feedbackloop that increases <strong>the</strong>ir own continued recruitment whiledecreasing that <strong>of</strong> <strong>the</strong> lower intertidal plant communitypresent before <strong>the</strong> invasion (Fig. 2B, left side). However, ifwater movement is sufficient to erode sediments or if plantrecruitment is low or delayed, marsh communities may shiftinto a restored state (Fig. 2B, right side).Testing <strong>the</strong>se hypo<strong>the</strong>ses will require both large andsmall-scale experiments in areas where cordgrass has beenremoved. Ultimately, this research will provide natural areamanagers with better ways <strong>of</strong> predicting and evaluating <strong>the</strong>consequences <strong>of</strong> post-removal impact across differenthabitat types. It may be that active removal <strong>of</strong> nativevascular plant assemblages will be necessary in habitats suchas mudflats where restoration could be continually hinderedby <strong>the</strong> recruitment and positive feedbacks produced by <strong>the</strong>seplants. Although invasive species removal and restoration isa critical component to <strong>the</strong> management <strong>of</strong> many naturalareas, most research is site or species-specific. The proposedresearch will help establish <strong>the</strong> importance <strong>of</strong> a general<strong>the</strong>ory on <strong>the</strong> contextual dependence <strong>of</strong> invasive speciesremoval that can be applied to communities with varyingspecies assemblages, physical conditions, and degrees <strong>of</strong>invasion.ACKNOWLEDGEMENTSWe thank <strong>the</strong> many hands that assisted with <strong>the</strong> researchincluding C. Catton, C. Gozart, E. Hellquist, A. Hysert, T.Reeder, T. 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