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Aquatic grazers reduce the establishment and growth of riparian plants along an environmental gradient
Author(s) -
Veen G. F. Ciska,
Sarneel Judith M.,
Ravensbergen Lone,
Huig Naomi,
Paassen José,
Rip Winnie,
Bakker Elisabeth S.
Publication year - 2013
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.12168
Subject(s) - grazing , riparian zone , abiotic component , macrophyte , eutrophication , ecology , biomass (ecology) , biology , aquatic plant , range (aeronautics) , environmental science , nutrient , agronomy , habitat , materials science , composite material
Summary The establishment of riparian plants is determined by abiotic conditions and grazing, although it is usually presumed that the former are most important. We tested the impact of aquatic grazers on the survival and growth of establishing riparian plants and whether the impact of grazing interacts with abiotic conditions. We conducted an experiment across 10 D utch wetlands, covering a large range of water depth and nutrient availability. We introduced 1‐year‐old plants of an emergent (common reed, P hragmites australis ) and a floating (water soldier, S tratiotes aloides ) species in individual enclosures ( n = 5 per site) that excluded predominantly waterbirds, which were the most abundant grazers, and on adjacent unprotected plots. Survival and growth were measured during one growing season. Grazing reduced growth (as biomass) of P hragmites and S tratiotes by a mean of 25 and 60%, respectively. Grazing decreased survival of S tratiotes , but not of P hragmites . Shallow water, water‐level fluctuations, eutrophic conditions and enough light favoured both growth and survival of P hragmites . Growth of S tratiotes was unaffected by these factors, but they reduced its survival. For both species, grazing effects on biomass were consistent across environmental conditions, but for P hragmites, grazing effects on survival were influenced by abiotic conditions. We conclude that aquatic grazers significantly reduce the establishment and growth of macrophytes in the riparian zone over a wide range of environmental conditions.