Disturbances as a Structuring Factor of Plant Palatability in Aquatic Communities

Elger, Arnaud; Bornette, Gudrun; Barrat‐Segretain, Marie‐Hélène; Amoros, Claude

doi:10.1890/02-0752

Cited by 45 publications

(43 citation statements)

References 50 publications

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“…, 2001). We have also observed that the most palatable macrophyte species are frequent in disturbed environments (Elger, Barrat‐Segretain & Amoros, 2002; Elger et al. , 2004; Elger & Lemoine, 2005).…”

Section: Discussionmentioning

confidence: 56%

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Invertebrate grazing during the regenerative phase affects the ultimate structure of macrophyte communities

2009

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1. Although the biomass of freshwater macrophytes consumed by invertebrate herbivores (excluding crayfish) is usually low, there is growing evidence that invertebrates do exert a structuring effect on macrophyte communities. To explain this, we postulated that the effect of invertebrates may be concentrated on macrophytes during their regenerative phase.2. We tested this hypothesis by means of a mesocosm-based experiment, in which we investigated the effects of different densities of pond snails [Lymnaea stagnalis (L.)] on macrophytes regenerating from the natural sediment propagule bank.3. After 2 months, a diverse macrophyte community had established in the absence of snails, mainly from sexual propagules. Under moderate snail grazing (4 individuals m-2), the ultimate biomass of macrophytes was similar, but its species composition differed dramatically. Only a few unpalatable taxa, such as Ceratophyllum demersum and Nymphaeaceae, persisted. Moreover, the relative success of macrophytes regenerating from vegetative rather than sexual propagules improved. Under higher snail grazing (20 m-2), all macrophytes disappeared before the end of the experiment.4. These results confirm that snails at natural densities can have a strong effect on the ultimate structure of macrophyte communities by selectively consuming some species at a juvenile stage. Therefore, the regenerative phase can be seen as a window of opportunity for invertebrate grazers, which can have a qualitative effect on communities that is disproportionate to the biomass consumed

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Section: Discussionmentioning

confidence: 56%

“…This was particularly obvious for Sagittaria sagittifolia , which occurred in all the control mesocosms, but failed to establish in any of the grazer‐stocked mesocosms. In a previous palatability trial, this species was the most consumed among 40 macrophyte species tested (Elger et al. , 2004).…”

Section: Discussionmentioning

confidence: 88%

Invertebrate grazing during the regenerative phase affects the ultimate structure of macrophyte communities

2009

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“…In calcareous groundwater-supplied ecosystems, the composition of plant communities has been shown to depend mainly on the phosphate and ammonium concentrations in the water (Carbiener et al 1990;Elger et al 2004). The selection of the 4 streams was consequently based on both (1) the occurrence of vegetation groups considered as representative of increasing nutrient levels, and (2) the phosphate and ammonium concentrations in the water.…”

Section: Nutrient Stressmentioning

confidence: 99%

Abiotic stresses increase plant regeneration ability

2007

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In disturbed habitats, vegetative regeneration is partly ruled by plant reserves and intrinsic growth rates. Under nutrient-limiting conditions, perennial plants tend to exhibit an increased allocation to storage organs. Under mechanically stressful conditions, plants also tend to increase allocation to below-ground biomass and storage organs. We tested whether those stresses acting differently on plants (nutrient level versus mechanical forces) led to similar effect on storage organs and regeneration ability. We measured, for an aquatic plant species, (1) the size and allocation to storage organs (stems) and (2) the regeneration ability of the storage organs. Plant stems were collected in 4 habitats ranked along a nutrient stress gradient, and having encountered null versus significant mechanical stress (flowing water). All stems were placed in similar neutral conditions and left for a period of 6 weeks before measuring their survival and growth. Dry mass allocation to the storage organ (stem) was higher in stressful habitats. Moreover, stress encountered by plants before the experiment significantly affected regeneration: stems of previously stressed plants (i.e. plants that had grown in nutrient-poor or mechanically stressful habitats) survived better than unstressed ones. Stems of plants having encountered mechanical stress before the experiment had increased growth in nutrient-rich habitats but reduced growth in the poorest habitats. These results demonstrate that regeneration could rely on the level of stress previously encountered by plants. Stress could lead to greater regeneration ability following mechanical failure. The possible mechanisms involved in these results are discussed.

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“…drought or waterlogging; Ernst, 1990;Capon, 2003) and biotic interactions (i.e. interspecific competition for light or nutrients; Menges and Waller, 1983;Willby et al, 2001 or herbivory;Elger et al, 2004), and on the other hand on population dynamics, and patterns of seed dispersal and vegetative regeneration (Marston et al, 1995;Hughes, 1997;Abernethy and Willby, 1999). Salo et al (1986) for example considered the fluvial dynamics of river systems to be fundamental in creating and maintaining high plant diversity.…”

Section: Introductionmentioning

confidence: 99%

Channel dynamics and geomorphic variability as controls on gravel bar vegetation; River Tummel, Scotland

Gilvear

Willby

2006

River Research & Apps

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This paper presents the results of an investigation into environmental controls on vegetation dynamics on gravel bars. Such environments are a hotspot of threatened plant biodiversity and the dynamics of their vegetation reflect a range of processes that should be indicative of the integrity of the wider floodplain ecosystem. The study was undertaken on a 2 ha mid-channel gravel bar complex that evolved over two decades, in response to several high magnitude flood events (including two with a return period in excess of 25 years), on a 'wandering' reach of the River Tummel, Scotland. Over 180 plant species, including a number of national or regional scarcities, had colonized. The fluvial chronology of the site was documented via sequential sets of aerial photography that revealed a number of discrete surfaces created by individual floods. Environmental heterogeneity, both within and between fluvial units, was investigated by field sampling of vegetation and abiotic variables at 66 locations. The fluvial surfaces were assigned to five habitat classes that ranged in age from two to approximately 20 years, from fine gravel to cobbles, and maintained an elevation range of up to 2.5 metres above low flow river levels. Multivariate analysis highlighted the relative importance of elevation, grain size, moisture content and infiltration and trapping of fines in controlling plant species composition. After standardizing sampling effort the habitat mosaic was found to support on average 1.36 times more species than an equivalent sample of any one habitat. In terms of biodiversity and river management, our results emphasize the importance of sustaining fluvial processes that preserve the habitat mosaic in order to conserve the characteristic biota of gravel bar complexes and river channel islands.

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Disturbances as a Structuring Factor of Plant Palatability in Aquatic Communities

Cited by 45 publications

References 50 publications

Invertebrate grazing during the regenerative phase affects the ultimate structure of macrophyte communities

Invertebrate grazing during the regenerative phase affects the ultimate structure of macrophyte communities

Abiotic stresses increase plant regeneration ability

Channel dynamics and geomorphic variability as controls on gravel bar vegetation; River Tummel, Scotland

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