Quantifying macrophyte colonisation strategies—A field experiment in a shallow lake (Lake Balaton, Hungary)

• Re-establishment of macrophytes was observed in plots with all vegetation removed.
• Species-specific set of different colonisation means was proved.
• Most colonisation occurred by lateral growth, adjacent areas had strong influence.
• Importance of remaining plants for recovering of lake vegetation is emphasized.

Life-history traits like dominance of certain reproductive modes (e.g. vegetative, specialized, unspecialized or sexual propagules) and overwintering strategies (evergreen or re-sprouting) determine the success and timing of the ability of aquatic plants to colonize new areas. In the present experiment the distribution of these reproductive modes was examined in-situ, where new gaps were experimentally formed and establishment of new vegetation observed on a monthly bases in ten plots. During a period of 126 days, altogether 73% of all established plants (n = 1822) colonized by rhizomatic growth and 11% by rooting of vegetative fragments. Myriophyllum spicatum was observed to use mostly fragment rooting (81%), while Potamogeton perfoliatus followed a more mixed strategy combining re-rooting fragments and rhizomatic growth (31% and 41%, respectively). Stuckenia pectinata also preferred colonisation by rhizomes (84%). No colonisation by specialized vegetative units (tubers or turions) was observed during the study period The importance of surrounding vegetation was shown by comparing colonisation on inner and marginal sections of the plots (30% vs.70%). Three different patterns of timing of peak colonisation intensities were observed, related to species’ life-history traits. While several experimental works have been done on the regeneration and colonisation abilities of different species under laboratory conditions, information on the in-situ application of the different strategies is scarce. Insights on the modes by which plants succeed in colonising gaps helps us understand how (re)establishment of aquatic vegetation might function in lake ecosystems recovering after eutrophication.