TY  - JOUR
A1  - Verheyen, Kris
A1  - Baeten, Lander
A1  - De Frenne, Pieter
A1  - Bernhardt-Römermann, Markus
A1  - Brunet, Jorg
A1  - Cornelis, Johnny
A1  - Decocq, Guillaume
A1  - Dierschke, Hartmut
A1  - Eriksson, Ove
A1  - Hedl, Radim
A1  - Heinken, Thilo
A1  - Hermy, Martin
A1  - Hommel, Patrick
A1  - Kirby, Keith J.
A1  - Naaf, Tobias
A1  - Peterken, George
A1  - Petrik, Petr
A1  - Pfadenhauer, Joerg
A1  - Van Calster, Hans
A1  - Walther, Gian-Reto
A1  - Wulf, Monika
A1  - Verstraeten, Gorik
T1  - Driving factors behind the eutrophication signal in understorey plant communities of deciduous temperate forests
JF  - The journal of ecology
N2  - 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.
KW  - atmospheric deposition
KW  - determinants of plant community diversity and structure
KW  - Ellenberg indicator values
KW  - forest herbs
KW  - forest management
KW  - large herbivores
KW  - north-western Europe
KW  - resurveys
KW  - (semi-)permanent plots
Y1  - 2012
U6  - https://doi.org/10.1111/j.1365-2745.2011.01928.x
SN  - 0022-0477
VL  - 100
IS  - 2
SP  - 352
EP  - 365
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -