TWIG UGent (Belgium)

The acronym TWIG stands for Tree Wheels In Geerbos. This 'climate forest' was planted by Ghent University (UGent) as a symbol for its sustainability ambitions and to sequester a little bit of their CO2 emission. The experiment was established near Geerbos in Melle in 2017. Circular plots were planted with one up to three tree species and from high to low tree density.

aerial view location plantation
The TWIG plantation near the old forest parcel 'Geerbos'

The experiment consists of circular plots that follow the Nelder Wheel design. Trees are planted along concentric circles with increasing radii. Hence, the planting density is higher in the center of the plots than at the plot border. The central area of the wheels is planted as well, but those trees are not part of the Nelder design. The plots are planted with one up to three tree species from a species pool of four species: two associated with ectomycorrhiza (Fagus sylvatica, Quercus robur), two with arbuscular mycorrhiza (Acer pseudoplatanus, Prunus avium). All four monocultures, the six 2-species mixtures, and the four 3-species mixtures are planted. The monocultures and 3-species mixtures are replicated once. Mixing is on a tree by tree level within plots. The plots are grouped into blocks that represent 'close to forest edge' vs. 'non forest edge' and 'deep clay' vs. 'more shallow clay'.

design TWIG experiment
The tree wheels of the TWIG plantation

Site characteristics

location Melle
former land use arable field, maize
altitude 16 m
soil type Retisol (WRB)
Ldc - moist, sandy silt with degraded texture B horizon (Belgian Soil Classification System)
area 2.4 ha
no of plots 22
plot size radius = 15.7 m
no of trees planted 4598
planting date Feb 2017
diversity variables species richness
functional diversity
diversity gradient 1, 2, 3 sp.
AM, EM fungi
size species pool 4
species pool AM species: Acer pseudoplatanus, Prunus avium
EM species: Fagus sylvatica, Quercus robur
contact person Kris Verheyen

The main research focus is investigating how tree density affects the diversity effects on tree growth and carbon sequestration.

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

  • 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 -

photo February 2017
The experiment was planted on 17 February 2017 with the help of lots of volunteers, BOS+, and Ghent University.