Experiment
The Satakunta forest diversity experiments were established in 1999-2000 to study the effects of tree species richness, functional diversity (broadleaved vs. coniferous), and intraspecific genetic diversity on different aspects of ecosystem functioning in boreal forests.

Canopy of a birch-alder plot in the Satakunta tree species diversity experiment (2015)

Design

tree species diversity experiment
The experiment was established in spring 1999 on three clear-cut areas (about 1.5-2 ha each) in the Satakunta area, south-western Finland: area 1, area 2, and area 3.
Each area contains 38 plots randomly allocated to 19 treatments (monocultures and various mixtures of 5 tree species). There are 2 replicates of each treatment per area (6 replicates altogether). Species mixtures are composed in such a way that they represent a gradient from completely coniferous forest (pine, spruce and larch) through mixed conifer/deciduous stands to deciduous ones (birch and alder). Plots are 20 m x 20 m and contain 13 rows with 13 seedlings in each row (i.e., 169 seedlings per plot) planted at 1.5 m intervals. In mixed stands, different tree species are present in equal proportions (50 : 50, 33 : 33 : 33 or 20 : 20 : 20 : 20 : 20), but species positions within a plot are random to mimic natural stands. The tree material used in this experiment originated from a local tree nursery, is genetically diverse and of local southern Finnish provenances.
One replicate of each treatment within an area was thinned in 2013, providing the opportunity to compare tree species diversity effects at two different densities.

The random allocation of the mixtures at one of the sites (area 2). The pictograms indicate whether the mixture contains coniferous or broadleaved species.	The planting design of a 2-species plot

birch clone diversity experiment
The experiment has been established near Lankoski, SW Finland, in 2000.
It consists of a single 2 ha area containing 48 plots of 20 m x 20 m planted with eight different genotypes of silver birch. The eight silver birch genotypes used in the experiment are of southern Finnish origin (61-63 ºN) and have been obtained by micropropagation of vegetative buds of mature trees. The eight clones selected for the experiment are known to differ in their growth and leaf characteristics as well as in resistance to herbivores and pathogens. Plots are randomly assigned to the following genotypic diversity treatments: single-genotype plots, two-genotype mixtures (5 different combinations), four-genotype mixtures (5 different combinations), and an eight-genotype mixture. Each particular genotype combination is replicated 2-6 times within the experimental area, allowing separation of effects of genotype diversity and genotype composition. In mixed stands, different birch clones are planted in equal proportions and their positions within plots are randomized. We originally planted 100 trees per plot (10 rows, 10 trees in each at 2 m intervals).
The experiment was thinned in 2013 to reduce tree density by half while keeping proportions of different clones equal.

The plots in the birch clone diversity experiment. The clone identities are abbreviated by capital letters.

Site characteristics

subexperiment	tree species	birch clones
location	Pomarkku (area 1, 2) Onnenkoski (area 3)	Lankoski
former land use	coniferous forest (mainly spruce) clear-cut in 1998 stumps and minor branches left on site	coniferous forest (mainly spruce) clear-cut in 1999 stumps and minor branches left on site
altitude	20-60 m	30 m
soil type	podzols	podzols
area	c. 4.5 ha	c. 2 ha
no of plots	114 (3 x 38)	48
plot size	20 m x 20 m	20 m x 20 m
no of trees planted	19 266	4800
planting date	1999	2000
thinning date	2013 (1 replicate of each treatment)	2013 (all plots)
diversity variables	species richness functional diversity	genetic diversity
diversity gradient	1, 2, 3, 5 sp. broadleaved, coniferous	1, 2, 4, 8 clones
size species pool	5	1 (8 clones)
species pool	Alnus glutinosa Betula pendula Larix sibirica Picea abies Pinus sylvestris	Betula pendula
contact person	Julia Koricheva

Research
The research in the Satakunta forest diversity experiments focuses on unravelling the relationships between tree species and genetic diversity on various above- and belowground processes including tree growth and survival, light absorption and light use efficiency, insect and mammalian herbivory, litter decomposition, and soil microbial processes. Our current research explores to what extent tree species richness and genotypic diversity effects on ecosystem processes are mediated by changes in tree growth and plant secondary metabolites. Taken together, the Satakunta tree species diversity and birch clone diversity experiments provide a unique opportunity to compare effects of trees species and intraspecific genetic diversity on boreal forest ecosystem functioning and services.

Extra information

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

theses

• Muiruri EW (2016) The mechanisms of forest diversity effects on insect herbivores. PhD thesis, Royal Holloway University of London
• Nguyen D (2015) Effects of tree species diversity on foliar fungal distribution. PhD thesis, Swedish University of Agricultural Sciences Uppsala
• Grossiord C (2014) Impact of tree species diversity on water and carbon relations in European forests. PhD thesis, University of Lorraine
• Hantsch L (2013) Tree diversity effects on species richness and infestation of foliar fungal pathogens in European tree diversity experiments. PhD thesis, Martin-Luther University Halle
• Morath S (2013) Effects of tree species diversity on insect herbviory. PhD thesis, Royal Holloway University of London

papers

• 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 - https://doi.org/10.1111/geb.13461
• 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 - https://doi.org/10.1111/conl.12829
• 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 - https://doi.org/10.1002/ece3.5627
• 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
• Koricheva J, Hayes D (2018) The relative importance of plant intraspecific diversity in structuring arthropod communities: A meta-analysis. Functional Ecology 32: 1704-1717 - doi: 10.1111/1365-2435.13062
• Muiruri EW, Barantal S, Iason GR, Salminen J-P, Perez-Fernandez E (2018) Forest diversity effects on insect herbivores: do leaf traits matter? New Phytologist 221(4): 2250-2260 - https://doi.org/10.1111/nph.15558
• Otsing E, Barantal S, Anslan S, Koricheva J, Tedersoo L (2018) Litter species richness and composition effects on fungal richness and community structure in decomposing foliar and root litter. Soil Biology and Biochemistry 125: 328-339 - https://doi.org/10.1016/j.soilbio.2018.08.006
• Guerrero-Ramírez NR, Craven D, Reich PB, Ewel JJ, Isbell F, Koricheva J, Parrotta JA, Auge H, Erickson HE, Forrester DI, Hector A, Joshi J, Montagnini F, Palmborg C, Piotto D, Potvin C, Roscher C, van Ruijven J, Tilman D, Wilsey B, Eisenhauer N (2017). Diversity-dependent temporal divergence of ecosystem functioning in experimental ecosystems. Nature Ecology & Evolution 1(11): 1639-1642 - doi: 10.1038/s41559-017-0325-1
• Muiruri EW, Koricheva J (2017) Going undercover: increasing canopy cover around a host tree drives associational resistance to an insect pest. Oikos 126: 339-349 - doi: 10.1111/oik.03307
• Nguyen D, Boberg J, Cleary M, Bruelheide H, Hönig L, Koricheva J, Stenlid J (2017) Foliar fungi of Betula pendula: impact of tree species mixtures and assessment methods. Scientific Reports 7: 41801 - doi: 10.1038/srep41801
• Muiruri EW, Rainio K, Koricheva J (2016) Do birds see the forest for the trees? Scale-dependent effects of tree diversity on avian predation of artificial larvae. Oecologia 180: 619-630 - doi: 10.1007/s00442-015-3391-6
• Tedersoo L, Bahram M, Cajthaml T, Põlme S, Hiiesalu I, Anslan S, Harend H, Buegger F, Pritsch K, Koricheva J, Abarenkov K (2016) Tree diversity and species identity effects on soil fungi, protists and animals are context dependent. The ISME Journal 10: 346-362 - doi: 10.1038/ismej.2015.116
• 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
• Barton KE, Valkama E, Vehviläinen H, Ruohomäki K, Knight TM, Koricheva J (2015) Additive and non-additive effects of birch genotypic diversity on arthropod herbivory in a long-term field experiment. Oikos 124: 697-706 - doi: 10.1111/oik.01663
• Domisch T, Finér L, Dawud SM, Vesterdal L, Raulund-Rasmussen K (2015) Does species richness affect fine root biomass and production in young forest plantations? Oecologia 177: 581-594 - doi: 10.1007/s00442-014-3107-3
• Haase J, Castagneyrol B, Cornelissen JHC, Ghazoul J, Kattge J, Koricheva J, Scherer-Lorenzen M, Morath S, Jactel H (2015) Contrasting effects of tree diversity on young tree growth and resistance to insect herbivores across three biodiversity experiments. Oikos 124: 1674-1685 - doi: 10.1111/oik.02090
• Muiruri EW, Milligan HT, Morath S, Koricheva J (2015) Moose browsing alters tree diversity effects on birch growth and insect herbivory. Functional Ecology 29: 724-735 - doi: 10.1111/1365-2435.12407
• Paine CET, Amissah L, Auge H, Baraloto C, Baruffol M, Bourland N, Bruelheide H, Daïnou K, de Gouvenain RC, Doucet J-L, Doust S, Fine PVA, Fortunel C, Haase J, Holl KD, Jactel H, Li X, Kitajima K, Koricheva J, Martínez-Garza C, Messier C, Paquette A, Philipson C, Piotto D, Poorter L, Posada JM, Potvin C, Rainio K, Russo SE, Ruiz-Jaen M, Scherer-Lorenzen M, Webb CO, Wright SJ, Zahawi RA, Hector A (2015) Globally, functional traits are weak predictors of juvenile tree growth, and we do not know why. Journal of Ecology 103: 978-989 - doi: 10.1111/1365-2745.12401
• Ampoorter E, Baeten L, Koricheva J, Vanhellemont M, Verheyen K (2014) Do diverse overstoreys induce diverse understoreys? Lessons learnt from an experimental-observational platform in Finland. Forest Ecology and Management 318: 206-215 - doi: 10.1016/j.foreco.2014.01.030
• Pollastrini M, Holland V, Brüggemann W, Koricheva J, Jussila I, Scherer-Lorenzen M, Berger S, Bussotti F (2014) Interactions and competition processes among tree species in young experimental mixed forests, assessed with chlorophyll fluorescence and leaf morphology. Plant Biology 16: 323-331 - doi: 10.1111/plb.12068
• Grossiord C, Granier A, Gessler A, Pollastrini M, Bonal D (2013) The influence of tree species mixture on ecosystem-level carbon accumulation and water use in a mixed boreal plantation. Forest Ecology and Management 298: 82-92 - doi: 10.1016/j.foreco.2013.03.001
• Milligan HT, Koricheva J (2013) Effects of tree species richness and composition on moose winter browsing damage and foraging selectivity: an experimental study. Journal of Animal Ecology 82: 739-748 - doi: 10.1111/1365-2656.12049
• Vehviläinen H, Koricheva J, Ruohomäki K (2008) Effects of stand tree species composition and diversity on abundance of predatory arthropods. Oikos 117: 935-943 - doi: 10.1111/j.0030-1299.2008.15972.x
• Kaitaniemi P, Riihimäki J, Koricheva J, Vehviläinen H (2007) Experimental evidence for associational resistance against the European pine sawfly in mixed tree stands. Silva Fennica 41: 259-268
• Vehviläinen H, Koricheva J, Ruohomäki K (2007) Tree species diversity influences herbivore abundance and damage: meta-analysis of long-term forest experiments. Oecologia 152: 287-298 - doi: 10.1007/s00442-007-0673-7
• Riihimäki J, Vehviläinen H, Kaitaniemi P, Koricheva J (2006) Host tree architecture mediates the effects of predators on herbivore survival. Ecological Entomology 31: 227-235 - doi: 10.1111/j.1365-2311.2006.00784.x
• Vehviläinen H, Koricheva J (2006) Moose and vole browsing patterns in experimentally manipulated pure and mixed forest stands. Ecography 29: 497-506 - doi: 10.1111/j.0906-7590.2006.04457.x
• Riihimäki J, Kaitaniemi P, Koricheva J, Vehviläinen H (2005) Testing the enemies hypothesis in forest stands: the important role of tree species composition. Oecologia 142: 90-97 - doi: 10.1007/s00442-004-1696-y

A birch-pine-spruce mixture in the tree species diversity experiment and a plot in the birch clone diversity experiment (2015)