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Why do reed beds decline and fail to re‐establish? A case study of Dutch peat lakes
Author(s) -
Vermaat Jan E.,
Bos Bas,
Van Der Burg Peter
Publication year - 2016
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/fwb.12801
Subject(s) - exclosure , context (archaeology) , ecology , herbivore , phragmites , peat , grazing , environmental science , geography , biology , wetland , archaeology
Summary The decline in emergent reed beds in eutrophic shallow lakes in Europe has been linked to multiple factors, such as adverse water and sediment quality, shoreline development and fixed water level preventing recolonisation, recreational disturbances and herbivory by geese and muskrat. This study analyses the relative importance of these factors in a historical context and tests experimentally what currently may prevent the re‐establishment of emergent reed beds. We examined the historical extent of emergent reed stands (1925–2013) in relation to long‐term time series of lakeside housing development (1920–2013), abundance of greylag geese ( Anser anser ) and muskrat ( Ondatra zibethicus ) as well as water quality (1977–2013) for the shallow lowland peat lake district of Reeuwijk in The Netherlands. In addition, we carried out a comparative survey to generalise our results and an exclosure experiment to test whether current muskrat grazing pressure may hamper restoration efforts. A steady, linear decline in the extent of emergent reed beds over time corresponded significantly with a similar increase in lakeside house density. We found no correlation with herbivore stocks or water quality parameters. In the exclosures, rapid expansion of common reed ( Phragmites australis ), branched bur‐reed ( Sparganium erectum ) and submerged pondweeds ( Potamogeton spp.) occurred, suggesting muskrat herbivory as a factor‐limiting emergent reed re‐establishment in the foreshore. A combined understanding of the different roles of slow, long‐term pressures (such as housing development) and present constraints (the continuous grazing pressure by muskrat despite a culling program) is crucial to the successful restoration of reed beds in shallow lakes.