Abstract
AbstractAimThe formation of a local vegetation mosaic may be attributed to local variation in abiotic environmental conditions. Recent research, however, indicates that self‐facilitating organisms and negative species interactions may be a driving factor. In this study, we explore whether heterogeneous geohydrological conditions or vegetation feedbacks and interactions could be responsible for a vegetation mosaic of rich and poor fen species.LocationLake Aturtaun, Roundstone Bog, Ireland.MethodsIn a floating fen, transects were set out to analyze the relation between vegetation type and rock–peat distance and porewater electrical conductivity. Furthermore, three distinct vegetation types were studied: rich fen, poor fen and patches of poor fen within rich fen vegetation. Biogeochemical measurements were conducted in a vertical profile to distinguish abiotic conditions of distinct vegetation types.ResultsGeohydrological conditions may drive the distribution of poor and rich fen species at a larger scale in the floating fen, due to the supply of minerotrophic groundwater. Interestingly, both rich and poor fen vegetation occurred in a mosaic, when electrical conductivity values at 50 cm depth were between 300 µS/cm and 450 µS/cm. Although environmental conditions were homogeneous at 50 cm, they differed markedly between rich and poor fen vegetation at 10 cm depth. Specifically, our measurements indicate that poor fen vegetation lowered porewater alkalinity, bicarbonate concentrations and pH. No effects of rich fen vegetation at 10 cm depth on biogeochemistry was measured. However, rich fen litter had a higher mineralization rate than poor fen litter, which increases the influence of minerotrophic water in rich fen habitat.ConclusionsThese results strengthen our hypothesis that species can drive formation of vegetation mosaics under environmentally homogeneous conditions in a floating fen. Positive intraspecific self‐facilitating mechanisms and negative species interactions could be responsible for a stable coexistence of species, even leading to local ecosystem engineering by the species, explaining the local vegetation mosaic at the microscale level in a floating fen.
Highlights
Positive intraspecific self-facilitating mechanisms and negative species interactions could be responsible for a stable coexistence of species, even leading to local ecosystem engineering by the species, explaining the local vegetation mosaic at the microscale level in a floating fen
Peatlands often consist of large complexes that include rich fen, poor fen and bog vegetation (Joosten & Clarke, 2002; Rydin & Jeglum, 2006), which can be related to heterogeneity in environmental conditions, such as hydrology, acid buffering capacity and nutrient supply (Lamers et al, 2015)
Differences in environmental conditions can result in local vegetation mosaics within one ecosystem, resulting in distinct dominating species depending on prevailing abiotic conditions (Kuhry, Nicholson, Gignac, Vitt, & Bayley, 1993)
Summary
These results strengthen our hypothesis that species can drive formation of vegetation mosaics under environmentally homogeneous conditions in a floating fen. Peat mosses play an important role in ombrotrophication (increasing dominance of rainwater over minerotrophic water) of floating fens (Granath, Strengbom, & Rydin, 2010), due to their ability to create strong positive self-facilitating feedbacks, which are related to hydrological and biogeochemical factors (Bootsma, Van Den Broek, Barendregt, & Beltman, 2002; van Breemen, 1995) These feedbacks include acidification (Cusell et al, 2015; Soudzilovskaia et al, 2010; van den Elzen et al, 2017), low decomposition in combination with a high nutrient uptake, a high growth efficiency of peat mosses (Fritz, Lamers, Riaz, Berg, & Elzenga, 2014), peat accumulation and retention of base-poor rainwater. To self-facilitation, we hypothesized that ecosystem engineering of both poor and rich fen species could affect the local environment and contributed to the vegetation mosaic
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