FORBIO (Belgium)

FORBIO is an innovative, large-scale forest biodiversity experiment established in Belgium between 2009 and 2012. The acronym stands for assessment of the effects of tree species diversity on FORest BIOdiversity and ecosystem functioning. At three sites with contrasting site conditions, plots were planted with one up to four tree species. Various aspects of ecosystem functioning will be compared between plots that differ in tree species richness but have developed under the same abiotic conditions. The sites are located in Gedinne (Gribelle, Gouverneurs), Hechtel-Eksel and Zedelgem.

Planting at the Zedelgem site, March 2010

The basic experimental design is the same for each study site and follows a classical synthetic community approach. Monocultures and mixtures of two up to four tree species were planted on an environmentally homogeneous site. All species combinations occur, and there is one (blocked) replication. Each study site has 40 plots, i.e., 5 plots for each of the four diversity levels (1, 2, 3, and 4 species) and two replications. Yet, the overall number of plots in the FORBIO experiment is 127 instead of 120. At the Hechtel-Eksel site, one extra plot is left for spontaneous succession. At the Zedelgem and Gedinne sites, different provenances of oak (Zedelgem) and beech (Gedinne) were used as an extra treatment; two additional monocultures with the extra provenances were added in Zedelgem and four in Gedinne.

FORBIO sites and plots

Trees were planted on a 1.5 m x 1.5 m grid. In mixed plots, individual species were randomly assigned to homogenous groups of 3 x 3 trees. Five site-adapted but functionally dissimilar species were planted per site. Each species occurs in a similar frequency, i.e., in 20 of the 40 plots, and the two-species combinations occur in similar frequencies as well (10/40). An extensive soil survey prior to the planting enabled attributing treatments and replications to the experimental plots in such a way that there is no covariation between any of the soil variables and the presence/absence of a tree species or the diversity treatments, a major strength of the FORBIO experiment. The overall species pool consists of broadleaved as well as coniferous tree species that are particularly relevant for forestry in Belgium. The species differ in, e.g., root characteristics, temporal growth dynamics, and shade tolerance.

Site characteristics

site Gedinne Hechtel-Eksel Zedelgem
local name Gribelle and Gouverneurs Pijnven Vloethemveld
former land use forest: broadleaved until 1920, spruce plantations until 2005 heathland converted to pine plantation in 1908 agriculture: crops and grass
altitude 367-376 m (Gribelle)
421-426 m (Gouverneurs)
55-56 m 11-16 m
soil type moderately dry stony loam soils (Gbb; both sites) dry sandy soil with gravel substrate (tZbg/Podzol) relatively dry sandy soil (Zbh) to moderately wet loamy sand soil (SdP)
area 2 x 4.5 ha 8 ha 9.5 ha
no of plots 44 41 42
plot size 42 m x 42 m and 37.5 m x 42 m 36 m x 36 m 42 m x 42 m
no of trees planted 33 304 23 040 32 810
planting date April-May 2010 December 2012 December 2009, March 2010
diversity variables species richness
genetic diversity
species richness species richness
genetic diversity
diversity gradient 1, 2, 3, 4 sp.
1, 3 provenances (Fagus)
1, 2, 3, 4 sp. 1, 2, 3, 4 sp.
1, 3 provenances (Quercus)
size species pool 5 5 5
species pool Acer pseudoplatanus
Fagus sylvatica
Larix x eurolepis
Pseudotsuga menziesii
Quercus petraea
Betula pendula
Larix kaempferi
Pinus sylvestris
Pseudotsuga menziesii
Quercus petraea
Betula pendula
Fagus sylvatica
Pinus sylvestris
Quercus robur
Tilia cordata
contact person Quentin Ponette Bart Muys Kris Verheyen

Monitoring of ecosystem functioning started shortly after planting. Multiple processes are being measured, ranging from tree growth and tree quality development over element cycling to associated biodiversity dynamics. As the trees grow older, we plan to add more processes, e.g., water cycling, to the monitoring scheme so that the picture of ecosystem functioning in the different treatments will be as complete as possible. We try to assure that measurements are performed in all the plots, in order to include the full range of treatments, sites and processes in the analyses.

Extra information
Send an e-mail to the contact persons, visit the experiment's own website, or explore the publications:

  • Dhiedt E (2022) Legacy effects of tree species diversity on soil properties and seedling performance. PhD thesis, Ghent University
  • Rahman MM (2018) Effects of tree species diversity and drought on ecosystem functioning in a young forest. PhD thesis, Université de Liège
  • Van de Peer T (2018) Effects of tree species diversity on early-stage forest dynamics. PhD thesis, KU Leuven
  • Dillen M (2017) Local neighbourhood tree species composition effects in young forest stands: impact of stress, species identity and multitrophic interactions. PhD thesis, University of Groningen and Ghent University
  • Setiawan NN (2016) Experimental assessment of tree diversity - ecosystem functioning relationships in young forest plantations. PhD thesis, Ghent University
  • Dhiedt E, Baeten L, De Smedt P, Jaroszewicz B, Verheyen K (2022) Tree neighbourhood-scale variation in topsoil chemistry depends on species identity effects related to litter quality. European Journal of Forest Research 141(6): 1163–1176 -
  • Cesarz S, Craven D, Auge H, Bruelheide H, Castagneyrol B, Gutknecht J, Hector A, Jactel H, Koricheva J, Messier C, Muys B, Brien MJO, Paquette A, Ponette Q, Potvin C, Reich PB, Scherer-Lorenzen M, Smith AR, Verheyen K, Eisenhauer N (2022) Tree diversity effects on soil microbial biomass and respiration are context dependent across forest diversity experiments. Global Ecology and Biogeography 31:872-885 -
  • Zhang S, Landuyt D, Verheyen K, De Frenne P (2022) Tree species mixing can amplify microclimate offsets in young forest plantations. Journal of Applied Ecology 59:6 1428-1439 -
  • Dhiedt E, Baeten L, De Smedt P, Verheyen K (2021) Little effect of tree species richness on within- and between-plot variability in soil chemical properties in a young plantation forest. European Journal of Soil Science 1–8 -
  • Dhiedt E, Verheyen K, De Smedt P, Ponette Q, Baeten L (2021) Early tree diversity and composition effects on topsoil chemistry in young forest plantations depend on site context. Ecosystems -
  • Kwon T, Shibata H, Kepfer-Rojas S, Schmidt IK, Larsen KS, Beier C, Berg B, Verheyen K, Lamarque J-F, Hagedorn F, Eisenhauer N, Djukic I, TeaCompositionNetwork (2021) Effects of climate and atmospheric nitrogen deposition on early to mid-term stage litter decomposition across biomes. Frontiers in Forests and Global Change 4: 678480 -
  • Messier C, Bauhus J, Sousa-Silva R, Auge H, Baeten L, Barsoum N, Bruelheide H, Caldwell B, Cavender-Bares J, Dhiedt E, Eisenhauer N, Ganade G, Gravel D, Guillemot J, Hall JS, Hector A, Hérault B, Jactel H, Koricheva J, Kreft H, Mereu S, Muys B, Nock CA, Paquette A, Parker JD, Perring MP, Ponette Q, Potvin C, Reich PB, Scherer-Lorenzen M, Schnabel F, Verheyen K, Weih M, Wollni M, Zemp DC (2021) For the sake of resilience and multifunctionality, let's diversify planted forests! Conservation Letters e12829 -
  • Poeydebat C, Jactel H, Moreira X, Koricheva J, Barsoum N, Bauhus J, Eisenhauer N, Ferlian O, Francisco M, Gottschall F, Gravel D, Mason B, Muiruri E, Muys B, Nock C, Paquette A, Ponette Q, Scherer-Lorenzen M, Stokes V, Staab M, Verheyen K, Castagneyrol B (2020) Climate affects neighbour-induced changes in leaf chemical defences and tree diversity-herbivory relationships. Functional Ecology - doi:10.1111/1365-2435.13700
  • Kambach S, Allan E, Bilodeau-Gauthier S, Coomes D A, Haase J, Jucker T, Kunstler G, Muller S, Nock C, Paquette A, van der Plas F, Ratcliffe S, Roger F, Ruiz-Benito P, Scherer-Lorenzen M, Auge H, Bouriaud O, Castagneyrol B, Dahlgren J, Gamfeldt L, Jactel H, Kandler G, Koricheva J, Lehtonen A, Muys B, Ponette Q, Setiawan N, Van de Peer T, Verheyen K, Zavala M A, Bruelheid H (2019) How do trees respond to species mixing in experimental compared to observational studies? Ecology and Evolution 9: 11254-11265 -
  • Djukic I, Kepfer-Rojas S, Kappel Schmidt I, Steenberg Larsen K, Beier C, Berg B, Verheyen K, TeaComposition (2018) Early stage litter decomposition across biomes. Science of the Total Environment
  • Grossman JJ, Vanhellemont M, Barsoum N, Bauhus J, Bruelheide H, Castagneyrol B, Cavender-Bares J, Eisenhauer N, Ferlian O, Gravel D, Hector A, Jactel H, Kreft H, Mereu S, Messier C, Muys B, Nock C, Paquette A, Parker J, Perring MP, Ponette Q, Reich PB, Schuldt A, Staab M, Weih M, Zemp DC, Scherer-Lorenzen M, Verheyen K (2018) Synthesis and future research directions linking tree diversity to growth, survival, and damage in a global network of tree diversity experiments. Environmental and Experimental Botany - doi: 10.1016/j.envexpbot.2017.12.015
  • Hicks LC, Rahman MM, Carnol M, Verheyen K, Rousk J (2018) The legacy of mixed planting and precipitation reduction treatments on soil microbial activity, biomass and community composition in a young tree plantation. Soil Biology and Biogeochemistry 124: 227-235 - doi: 10.1016/j.soilbio.2018.05.027
  • Rahman MM, Castagneyrol B, Verheyen K, Jactel H, Carnol M (2018) Can tree species richness attenuate the effect of drought on organic matter decomposition and stabilization in young plantation forests? Acta Oecologica 93: 30-40 - doi: 10.1016/j.actao.2018.10.008
  • Rahman MM, Hicks LC, Verheyen K, Rousk J, Carnol M (2018) Effects of drought legacy and tree species admixing on bacterial growth and respiration in a young forest soil upon drying and rewetting. Soil Biology and Biochemistry 127: 148-156 - doi: 10.1016/j.soilbio.2018.09.026
  • Van de Peer T, Verheyen K, Ponette Q, Setiawan NN, Muys B (2018) Overyielding in young tree plantations is driven by local complementarity and selection effects related to shade tolerance. Journal of Ecology 106: 1096-1105 - doi: 10.1111/1365-2745.12839
  • Dillen M, Smit C, Buyse M, Höfte M, De Clercq P, Verheyen K (2017) Stronger diversity effects with increased environmental stress: A study of multitrophic interactions between oak, powdery mildew and ladybirds. PLoS ONE 12(4): e0176104 - doi: 10.1371/journal.pone.0176104
  • Dillen M, Smit C, Verheyen K (2017) How does neighbourhood tree species composition affect growth characteristics of oak saplings? Forest Ecology and Management 401: 177-186 - doi: 10.1016/j.foreco.2017.07.016
  • Setiawan NN, Vanhellemont M, Baeten L, Van de Peer T, Ampoorter E, Ponette Q, Verheyen K (2017) Local neighbourhood effects on sapling growth in a young experimental forest. Forest Ecology and Management 384: 424-443 - doi: 10.1016/j.foreco.2016.10.012
  • Van de Peer T, Verheyen K, Kint V, Van Cleemput E, Muys B (2017) Plasticity of tree architecture through interspecific and intraspecific competition in a young experimental plantation. Forest Ecology and Management 385: 1-9 - doi: 10.1016/j.foreco.2016.11.015
  • Dillen M, Vanhellemont M, Verdonckt P, Maes WH, Steppe K, Verheyen K (2016) Productivity, stand dynamics and the selection effect in a mixed willow clone short rotation coppice plantation. Biomass and Bioenergy 87: 46-54 - doi: 10.1016/j.biombioe.2016.02.013
  • Dillen M, Verheyen K, Smit C (2016) Identity rather than richness drives local neighbourhood species composition effects on oak sapling growth in a young forest. Forest Ecology and Management 380: 274-284 - doi: 10.1016/j.foreco.2016.09.004
  • Setiawan NN, Vanhellemont M, Baeten L, Gobin R, De Smedt P, Proesmans W, Ampoorter E, Verheyen K (2016) Does neighbourhood tree diversity affect the crown arthropod community in saplings? Biodiversity and Conservation 25: 169-185 - doi: 10.1007/s10531-015-1044-z
  • Setiawan NN, Vanhellemont M, De Schrijver A, Schelfhout S, Baeten L, Verheyen K (2016) Mixing effects on litter decomposition rates in a young tree diversity experiment. Acta Oecologica 70: 79-86 - doi:10.1016/j.actao.2015.12.003
  • Van de Peer T, Verheyen K, Baeten L, Ponette Q, Muys B (2016) Biodiversity as insurance for sapling survival in experimental tree plantations. Journal of Applied Ecology 53: 1777-1786, doi: 10.1111/1365-2664.12721
  • Verheyen K, Vanhellemont M, Auge H, Baeten L, Baraloto C, Barsoum N, Bilodeau-Gauthier S, Bruelheide H, Castagneyrol B, Godbold D, Haase J, Hector A, Jactel H, Koricheva J, Loreau M, Mereu S, Messier C, Muys B, Nolet P, Paquette A, Parker J, Perring M, Ponette Q, Potvin C, Reich P, Smith A, Weih M, Scherer-Lorenzen M (2016) Contributions of a global network of tree diversity experiments to sustainable forest plantations. Ambio 45: 29-41 - doi: 10.1007/s13280-015-0685-1
  • Setiawan NN, Vanhellemont M, Baeten L, Dillen M, Verheyen K (2014) The effects of local neighbourhood diversity on pest and disease damage of trees in a young experimental forest. Forest Ecology and Management 334: 1-9 - doi: 10.1016/j.foreco.2014.08.032
  • Verheyen K, Ceunen K, Ampoorter E, Baeten L, Bosman B, Branquart E, Carnol M, De Wandeler H, Grégoire J-C, Lhoir P, Muys B, Setiawan NN, Vanhellemont M, Ponette Q (2013) Assessment of the functional role of tree diversity: the multi-site FORBIO experiment. Plant Ecology and Evolution 146: 26-35 - doi: 10.5091/plecevo.2013.803
  • Ampoorter E, Delvaux C, De Troch R, Dewan S, Jacobs K, Rahman MM, Sousa-Silva R, Bertrand C, Carnol M, De Frenne P, Hamdi R, Muys B, Ponette Q, Vander Mijnsbrugge K, Verheyen K (2019) FORBIO Climate: Adaptation potential of biodiverse forests in the face of climate change. Final Report. Brussels: Belgian Science Policy - 44 p. (BRAIN-be - Belgian Research Action through Interdisciplinary Networks)

  • photo Gedinne photo Hechtel-Eksel photo Zedelgem
    Gedinne in 2015, Hechtel-Eksel in 2018, and Zedelgem in 2017