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Driving factors behind the eutrophication signal in understorey plant communities of deciduous temperate forests
Author(s) -
Verheyen Kris,
Baeten Lander,
De Frenne Pieter,
BernhardtRömermann Markus,
Brunet Jörg,
Cornelis Johnny,
Decocq Guillaume,
Dierschke Hartmut,
Eriksson Ove,
Hédl Radim,
Heinken Thilo,
Hermy Martin,
Hommel Patrick,
Kirby Keith,
Naaf Tobias,
Peterken George,
Petřík Petr,
Pfadenhauer Jörg,
Van Calster Hans,
Walther GianReto,
Wulf Monika,
Verstraeten Gorik
Publication year - 2012
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1111/j.1365-2745.2011.01928.x
Subject(s) - understory , deciduous , plant community , ecology , temperate deciduous forest , environmental science , species richness , canopy , temperate rainforest , deposition (geology) , temperate forest , vegetation (pathology) , quadrat , temperate climate , ecosystem , biology , shrub , medicine , paleontology , pathology , sediment
Summary 1. Atmospheric nitrogen (N) deposition is expected to change forest understorey plant community composition and diversity, but results of experimental addition studies and observational studies are not yet conclusive. A shortcoming of observational studies, which are generally based on resurveys or sampling along large deposition gradients, is the occurrence of temporal or spatial confounding factors. 2. We were able to assess the contribution of N deposition versus other ecological drivers on forest understorey plant communities by combining a temporal and spatial approach. Data from 1205 (semi‐)permanent vegetation plots taken from 23 rigorously selected understorey resurvey studies along a large deposition gradient across deciduous temperate forest in Europe were compiled and related to various local and regional driving factors, including the rate of atmospheric N deposition, the change in large herbivore densities and the change in canopy cover and composition. 3. Although no directional change in species richness occurred, there was considerable floristic turnover in the understorey plant community and a shift in species composition towards more shade‐tolerant and nutrient‐demanding species. However, atmospheric N deposition was not important in explaining the observed eutrophication signal. This signal seemed mainly related to a shift towards a denser canopy cover and a changed canopy species composition with a higher share of species with more easily decomposed litter. 4. Synthesis. Our multi‐site approach clearly demonstrates that one should be cautious when drawing conclusions about the impact of atmospheric N deposition based on the interpretation of plant community shifts in single sites or regions due to other, concurrent, ecological changes. Even though the effects of chronically increased N deposition on the forest plant communities are apparently obscured by the effects of canopy changes, the accumulated N might still have a significant impact. However, more research is needed to assess whether this N time bomb will indeed explode when canopies will open up again.