https://doi.org/10.5061/dryad.vt4b8gv08

The Kreinitz experiment site is located near the village of Kreinitz-Zeithain, Saxony, Germany (51°23’ 08” N, 13°15’41” E; 115 m a.s.l.). The local climate is characterized by a mean annual precipitation of 578 mm and mean annual temperature of 9.4 °C (30-year average 1981-2010, Oschatz station of German Weather Service DWD, ~15 km from the site). Maximum precipitation is normally observed during the growing season (Table S1), which usually starts in late March and ends in late October / early November (Scheuner, 2004). The soil is a humic cambisol on a bedrock of sand and gravel (93 % sand, 6 % silt, 1 % clay) with a pH of 5.5 (Schwarz et al., 2015). 

Kreinitz was planted in a field that was cultivated until 1990. In summer 2005, the site was plowed and harrowed, and two experimental blocks were set up, each of them containing 49 plots of 5 m x 5 m area with distances of 2.5 m between plots and of c. 10 m between blocks. In November of 2005, two-year old tree saplings, obtained from a local nursery, were planted on each plot in five staggered rows with six individuals in each row (Fig. S1; 30 trees per plot). The distance between rows was 1.0 m, and trees within rows were separated by 0.8 m, resulting in a density of 1.2 individuals m-2 within a plot.

To construct the gradient in tree diversity, six native tree species that are abundant in Central European forests were selected, including four broadleaved and two coniferous species: Fagus sylvatica L. (European beech), Fraxinus excelsior L. (common ash), Quercus petraea (Matt.) Liebl. (sessile oak), Tilia cordata Mill. (small‐leaved linden), Picea babies (L.) H. Karst. (Norway spruce), Pinus sylvestris L. (Scots pine). The 49 plots within each block were randomly assigned to six different diversity levels and to different species combinations within each diversity level: bare soil (not further considered in this paper), species monocultures (six “combinations”), two-species mixtures (15 combinations), three-species mixtures (20 combinations), five-species mixtures (six combinations), as well as the six-species mixture (one combination), resulting in 49 treatments (48 excluding the bare soil). The 30 planting positions within each plot were randomly, but in equal proportions, assigned to the respective species. For the first two years (2006, 2007), plots were regularly weeded to facilitate establishment of saplings, and dead saplings were replaced by individuals of the same age and same seed source. Leaf litter (c. 600 g m-2) was also added to each plot to facilitate tree establishment from planting until 2009, with litter identity and amount representing the planted tree species composition.

Description of the data and file structure

biodiversity_effects.xlsx

biomass_increment_tree_survival.xlsx

all_year_data_ht_basal_diameter

Missing data are indicated in the dataset as "NA". Instances of "NA" signify that the variable was not measured during the inventory due to either its small size, or because the individual tree was deceased.

Sheets

• 2008-2013: Height and basal diameter of tree individuals from 2008 to 2013. Multiple observations for a given tree individual refer to multiple stems of that individual.
• 2016-2018: Height, basal diameter and diameter at breast height (DBH) of tree individuals in 2016 and 2018. Multiple observations for a given tree individual refer to multiple stems of that individual. In 2016, both basal diameter and DBH were measured for each stem. In 2018, DBH was measured for each stem, and basal diameter only for smaller stems.