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:

  • 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, 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 (2016) Experimental assessment of tree diversity - ecosystem functioning relationships in young forest plantations. PhD thesis, Ghent University
  • 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

photo Gedinne photo Hechtel-Eksel photo Zedelgem
Gedinne in 2015, Hechtel-Eksel and Zedelgem in 2016 (photos: Thomas Van de Peer)