The BIOTREE experiment in Thuringia (Bechstedt, Kaltenborn, Mehrstedt) has been established in 2003/2004 and consists of three subexperiments: BIOTREE-SPECIES, focusing on species richness effects BIOTREE-FD, focusing on functional diversity effects, and BIOTREE-SIMPLEX, focusing on the effects of evenness on ecosystem functioning. Replicate forest communities were created based on the pool of local tree species and one exotic species. The main goals of the experiments are (1) quantifying the effects of tree diversity on key ecosystem processes, e.g., tree growth, long-term C sequestration, nutrient cycling, and structural characteristics, and (2) understanding the mechanisms of BDEF relationships and how forest management can influence them or ensure both economic and ecological sustainability.
|Aerial view of the BIOTREE-FD experiment in Bechstedt (June 2012)|
A diversity gradient was established by manipulating the number of species per plot. Each plot was subdivided in three subplots to accommodate a management treatment: (1) no management, (2) thinning according to close-to-nature forestry, and (3) thinning in plots in which 4 additional species adjusted to the site were planted. Trees were planted in monospecific cells of 8 m x 8 m. These cells were randomly distributed within a subplot, and this distribution was repeated in the two other subplots of the plot. Within a cell, the trees were planted on rows that were 2 m apart. The within-row distance between trees depends on the planted species. The subexperiment consists of two sites: Mehrsted (calcareous soil, 1-6 species per plot) and Kaltenborn (acidic soil, 1-4 species per plot).
|The plots of BIOTREE-SPECIES at the Mehrsted and Kaltenborn sites
and the within-plot design of a 4-species plot at the two sites
The BIOTREE-FD experiment has a gradient of tree functional diversity, at a constant number of tree species. All 25 plots contain 4 tree species, taken out of a total species pool of 16 species. The functional diversity of the plots - based on leaf type, light requirement, mean annual increment and litter C/N ratio - varies between very low and very high. Within each hexagonal plot, trees were planted in 44 monospecific round cells of 20 trees (planting distance 1 m x 2 m), i.e., 11 cells per tree species per plot.
|The plots and within-plot design of BIOTREE-FD in Bechstedt|
In the BIOTREE-SIMPLEX experiment, a gradient of tree species evenness has been established, by using different abundances of four species. There are 36 plots in total, with three different evenness levels and two different densities, replicated twice. The evenness levels are (1) dominant (70:10:10:10), (2) co-dominant (30:30:30:10), and (3) even (25:25:25:25), with all possible abundance combinations of the four species. Planting distances in the low density treatment are 2 x 1.5m (80 individuals per plot), and 1 x 1.5m in the high density treatment (150 individuals per plot).
|The plots and within-plot design of BIOTREE-SIMPLEX in Kaltenborn.
An example of a high-density, co-dominant mixture is shown.
|former land use||grassland, then pasture||cropland till 1975, then grassland||pasture||pasture|
|altitude||293 m||325 m||400 m||325 m|
|soil type||Stagnic vertisols dominated by clay and silt on a limestone bedrock||Orthoeutric arenosols with loamy sand on a sandstone bedrock||Stagnic vertisols on a limestone bedrock||Orthoeutric arenosols with loamy sand on a sandstone bedrock|
|area||40 ha||23 ha||11 ha||1.5 ha|
|no of plots||40||16||25||36|
|plot size||72 m x 144 m||48 m x 124 m||43.5 m x 56 m||16 m x 16 m|
|no of trees planted||137 612||31 096||22 000||4140|
|planting date||spring 2003||spring 2004||spring 2003||spring 2004|
|diversity variables||species richness||species richness||functional diversity||species evenness|
|diversity gradient||1, 2, 4, 6 sp.||1, 2, 3, 4 sp.||very low - very high||low, mid, high|
|size species pool||10||8||16||4|
|species pool||Main tree species: Acer pseudoplatanus, Fagus sylvatica, Larix decidua, Pseudotsuga menziessii, Quercus petraea, Tilia cordata
Additional tree species: Acer platanoides, Carpinus betulus, Fraxinus excelsior, Prunus avium
|Main tree species: Fagus sylvatica, Picea abies, Pseudotsuga menziessii, Quercus petraea
Additional tree species: Abies alba, Acer pseudoplatanus, Fraxinus excelsior, Sorbus aucuparia
|Acer campestre, A. platanoides, A. pseudoplatanus, Betula pendula, Carpinus betulus, Fagus sylvatica, Fraxinus excelsior, Larix decidua, Pinus sylvestris, Populus tremula, Prunus avium, Quercus pertraea, Sorbus aucuparia, S. torminalis, Tilia cordata, Ulmus glabra||Fagus sylvatica, Picea abies, Pseudotsuga menziessii, Quercus petraea|
|contact persons||Michael Scherer-Lorenzen, Charles Nock|
Studies will focus on the relationship between tree species richness, functional diversity or tree species evenness and soil properties, tree growth and mortality, herb layer diversity and composition, herbivory damage, and carbon sequestration. Regular inventories for height and diameter growth, crown sizes and mortality have been done every three years. Additional data sampling was done within the EU-projects BACCARA and FunDivEUROPE.
Send an e-mail to the contact persons, visit the experiment's own website, or explore the publications:
|Mixed plots at the BIOTREE-FD experiment in Bechstedt (May 2014)|