ALBERT

Description: This collection contains measurements of standing below ground biomass, belowground biomass productivity and morphological root parameters measured on the Main Experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the Main Experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Since 2010, plots were weeded three times per year. The following series of datasets are contained in this collection: 1. Standing below ground biomass: Coarse and fine root biomass was measured in 2003, 2004, 2006 and 2008 in 0 - 30 cm depth. In 2011 and 2014, total root biomass was sampled down to 40 cm depth. Some years report the data divided into sublayers. Every year, several soil cores were taken per plot and pooled before the whole bulk material or a subsample was washed for roots. Roots were dried at 60 - 70 °C and weighed. Standing root biomass was calculated as g m-2. 2. Below ground biomass productivity in 0 - 30 cm depth: Coarse and fine root biomass production from June to September 2003, September 2003 to July 2004 and July 2007 to June 2008 was measured by the ingrowth core method. In 2008, the data is reported divided into sublayers. Each time, five soil cores were taken per plot and replaced by root free soil from the field site. The initially root-free ingrowth cores were removed after a while and pooled plot-wise. To extract the newly formed roots, a subsample of the bulk material was washed for roots. Roots were dried at 70 °C and weighed. Root biomass productivity was calculated as g m-2. In addition, C- (only in 2003 and 2004) and N-concentration of the fine roots was determined. 3. Morphological root parameters of newly formed roots in 0 - 30 cm depth: Root length density and mean root diameter of newly formed roots from June to September 2003 and September 2003 to July 2004 were measured by the ingrowth core method. Each time, five soil cores were taken per plot and replaced by root free soil from the field site. The initially root-free ingrowth cores were removed after a while and pooled plot-wise. To extract the newly formed roots, a subsample of the bulk material was washed and scanned. Root length and mean diameter were determined by using WinRhizo (Regent Instruments, Quebec, Canada). 4. Morphological root parameters of standing roots in 0 - 30 cm depth: In 2004, mean diameter of standing roots was measured by sampling three soil cores per plot. To extract the standing roots, a subsample of the bulk material was washed and scanned. Mean diameter was determined by using WinRhizo (Regent Instruments, Quebec, Canada).

Description: This data set contains four time series of particulate and dissolved soil nitrogen measurements from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. 1. Total nitrogen from solid phase: Stratified soil sampling was performed every two years since before sowing in April 2002 and was repeated in April 2004, 2006 and 2008 to a depth of 30 cm segmented to a depth resolution of 5 cm giving six depth subsamples per core. In 2002 five samples per plot were taken and analyzed independently. Averaged values per depth layer are reported. In later years, three samples per plot were taken, pooled in the field, and measured as a combined sample. Sampling locations were less than 30 cm apart from sampling locations in other years. All soil samples were passed through a sieve with a mesh size of 2 mm in 2002. In later years samples were further sieved to 1 mm. No additional mineral particles were removed by this procedure. Total nitrogen concentration was analyzed on ball-milled subsamples (time 4 min, frequency 30 s-1) by an elemental analyzer at 1150°C (Elementaranalysator vario Max CN; Elementar Analysensysteme GmbH, Hanau, Germany). 2. Total nitrogen from solid phase (high intensity sampling): In block 2 of the Jena Experiment, soil samples were taken to a depth of 1m (segmented to a depth resolution of 5 cm giving 20 depth subsamples per core) with three replicates per block ever 5 years starting before sowing in April 2002. Samples were processed as for the more frequent sampling but were always analyzed independently and never pooled. 3. Mineral nitrogen from KCl extractions: Five soil cores (diameter 0.01 m) were taken at a depth of 0 to 0.15 m (and between 2002 and 2004 also at a depth of 0.15 to 0.3 m) of the mineral soil from each of the experimental plots at various times over the years. In addition also plots of the management experiment, that altered mowing frequency and fertilized subplots (see further details below) were sampled in some later years. Samples of the soil cores per plot (subplots in case of the management experiment) were pooled during each sampling campaign. NO3‐N and NH4‐N concentrations were determined by extraction of soil samples with 1 M KCl solution and were measured in the soil extract with a Continuous Flow Analyzer (CFA, 2003–2005: Skalar, Breda, Netherlands; 2006–2007: AutoAnalyzer, Seal, Burgess Hill, United Kingdom). 4. Dissolved nitrogen in soil solution: Glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1–1.6 µm (UMS GmbH, Munich, Germany) were installed in April 2002 in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for nitrate (NO3-), ammonium (NH4+) and total dissolved nitrogen concentrations with a continuous flow analyzer (CFA, Skalar, Breda, The Netherlands). Nitrate was analyzed photometrically after reduction to NO2- and reaction with sulfanilamide and naphthylethylenediamine-dihydrochloride to an azo-dye. Our NO3- concentrations contained an unknown contribution of NO2- that is expected to be small. Simultaneously to the NO3- analysis, NH4+ was determined photometrically as 5-aminosalicylate after a modified Berthelot reaction. The detection limits of NO3- and NH4+ were 0.02 and 0.03 mg N L-1, respectively. Total dissolved N in soil solution was analyzed by oxidation with K2S2O8 followed by reduction to NO2- as described above for NO3-. Dissolved organic N (DON) concentrations in soil solution were calculated as the difference between TDN and the sum of mineral N (NO3- + NH4+).

Description: This collection contains measurements of physical and chemical soil properties on the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained in general by bi-annual weeding and mowing. Since 2010, plot size was reduced to 5 x 6 m and plots were weeded three times per year. The following series of datasets are contained in this collection: 1. Physical soil properties - Soil texture: Proportion of sand, silt and clay in the fine soil was measured in April 2002 before plot establishment at 27 locations distributed throughout the experimental site. Undisturbed soil cores were taken to 100 cm depth and separated in depth increments with a resolution of 10 to 20 cm. Grain size fractions according to DIN 19683-2 were then determined by a combined sieve and hydrometer analysis. Values for each plot were interpolated by ordinary kriging. - Bulk density: Bulk density was sampled down to 100 cm depth in 2002 and 30 cm depth in 2004, 2006 and 2008. Several undisturbed soil cores were taken per plot and separated in depth increments before the bulk material was sieved, dried and weighed. - Soil hydraulic properties: Field capacity and permanent wilting point at 10, 20 and 30 cm depth were derived from soil texture data of 2002 and bulk density 2006 by using pedotransfer functions. Applied was equation four and five of Zacharias and Wessolek (2007) to derive parameters of the water retention curve. Water contents at field capacity and permanent wilting point were obtained using the van Genuchte Eq (e.g. eq 1 in Zacharias and Wessolek), and calculating water contents at - 330 cm matric potential (field capacity, 1/3 of atmospheric pressure) and at -15000 cm. -Soil porosity: the fraction of total volume occupied by pores or voids measured at matric potential 0, already published on https://doi.pangaea.de/10.1594/PANGAEA.865254. 2. Chemical soil properties - Lime content: Percentage of CaCO3 in the soil was measured in April 2002 before plot establishment at 27 locations distributed throughout the experimental site. Undisturbed soil cores were taken to 100 cm depth and separated in depth increments with a resolution of 10 to 20 cm. The bulk material was sieved and CaCO3 content of the fine soil was determined as volumetric determination according to DIN 19684-5. - Soil organic matter: Percentage of soil organic matter was measured in April 2002 before plot establishment at 27 locations distributed throughout the experimental site. Undisturbed soil cores were taken to 100 cm depth and separated in depth increments with a resolution of 10 to 20 cm. The bulk material was sieved and organic content of the fine soil was determined using a loss-on-ignition method. - Soil pH value: soil pH value was determined 2002 and 2010 in water and 2002 also in calcium chloride. Five soil samples were taken per plot and bulk material was diluted in water and calcium chloride. PH values were then measured with an electrode.

Description: This data set contains two time series of measurements of dissolved phosphorus (organic, inorganic and total with a biweekly resolution) and dissolved inorganic phosphorus with a seasonal resolution. In addition, data on phosphorus from soil samples measured in 2007 and fractionated by different acid-extrations (Hedley fractions) are provided. All data measured at the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. 1. Dissolved phosphorus in soil solution: Suction plates installed on the field site in 10, 20, 30 and 60 cm depth were used to sample soil pore water. Cumulatively extracted soil solution was collected every two weeks from October 2002 to May 2006. The biweekly samples from 2002, 2003 and 2004 were analyzed for dissolved organic phosphorus (DOP), dissolved inorganic phosphorus (PO4P) and dissolved total phosphorus (TDP) by Continuous Flow Analyzer (CFA SAN ++, SKALAR [Breda, The Netherlands]). 2. Seasonal values of dissolved inorganic phosphorus in soil solution were calculated as volume-weighted mean values of the biweekly measurements (spring = March to May, summer = June to August, fall = September to November, winter = December to February). 3. Phosphorus fractions in soil: Five independent soil samples per plot were taken in a depth of 0-15 cm using a soil corer with an inner diameter of 1 cm. The five samples per plot were combined to one composite sample per plot. A four-step sequential P fractionation (Hedley fractions) was applied and concentrations of P fractions in soil were measured photometrically (molybdenum blue-reactive P) with a Continuous Flow Analyzer (Bran&Luebbe, Germany).

Description: This data set contains three time series of measurements of soil carbon (particular and dissolved) from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. 1. Particulate soil carbon: Stratified soil sampling was performed every two years since before sowing in April 2002 and was repeated in April 2004, 2006 and 2008 to a depth of 30 cm segmented to a depth resolution of 5 cm giving six depth subsamples per core. Total carbon concentration was analyzed on ball-milled subsamples by an elemental analyzer at 1150°C. Inorganic carbon concentration was measured by elemental analysis at 1150°C after removal of organic carbon for 16 h at 450°C in a muffle furnace. Organic carbon concentration was calculated as the difference between both measurements of total and inorganic carbon. 2. Particulate soil carbon (high intensity sampling): In one block of the Jena Experiment soil samples were taken to a depth of 1 m (segmented to a depth resolution of 5 cm giving 20 depth subsamples per core) with three replicates per block ever 5 years starting before sowing in April 2002. Samples were processed as for the more frequent sampling. 3. Dissolved organic carbon: Suction plates installed on the field site in 10, 20, 30 and 60 cm depth were used to sample soil pore water. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer. Annual mean values of DOC are provided.

Description: This collection contains measurements of environmental conditions measured on the plots of the different sub-experiments at the field site of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. The following series of datasets are contained in this collection: 1.Soil temperature measurements on plots of the Main Experiment; 2. Quantification of the duration that individual plots of the Main Experiment were submerged during a flooding event occurring in June 2013

Description: This collection contains measurements on physical soil properties of the plots of the different sub-experiments at the field site of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing

Description: This collection contains measurements of vegetation and soil surface cover measured on the plots of the different sub-experiments at the field site of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. The following series of datasets are contained in this collection: 1. Measurements of vegetation cover, i.e. the proportion of soil surface area that is covered by different categories of plants per estimated plot area. Data was collected on the plant community level (sown plant community, weed plant community, dead plant material, and bare ground) and on the level of individual plant species in case of the species that have been sown into the plots to create the gradient of plant diversity.

Description: This collection contains measurements of element concentrations in plants on the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. The following series of datasets are contained in this collection: 1. Carbon and nitrogen concentration in plants: C and N concentration in aboveground plant biomass was measured twice a year (once in 2002 and 2009) from 2002 to 2012. Plants were clipped at 3 cm above ground level in three or four rectangles of 20 x 50 cm size per plot. Target species were pooled per plot and harvest, dried at 70 °C for at least 48 h and cut up with an analysis mill (Kinematica, Littau, Schweiz). The cut material was milled in a ball-mill and carbon and nitrogen concentration was determined with an elemental analyzer. In 2010, phosphorous and potassium concentration was measured additionally. For this purpose, a subsample of the dried and cut material was milled and digested with HNO3 at 200 °C and at about 600-700 MPa using the microwave-assisted high pressure digestion unit (Ethos, Mikrowellen-Laborsysteme (MLS), Leutkirch, Germany). Phosphorus concentrations were determined in a Continuous Flow Analyzer, AA3-system (Bran and Lübbe, Hamburg-Norderstedt, Germany). For K measurement, atom absorption spectroscopy (AAS, Zeenit 700P, Analytik Jena, Jena, Germany) was used. 2. Carbon and nitrogen concentration in plants of the drought experiment: C and N concentration in aboveground plant biomass was measured once a year in 2008 and 2009 on the subplots of the drought experiment. Plants were harvested in rectangles of 20 x 50 cm size. Target species were dried at 70 °C for 48 h, grounded to powder and analyzed with an elemental analyzer. 3. Element analysis of phosphorous (P), calcium (Ca), potassium (K), sodium (Na) and magnesium (Mg) in plants: P, Ca, K, Na and Mg concentrations in aboveground plant biomass were measured twice a year (once in 2004) from 2003 to 2007. Plants were clipped at 3 cm above ground level in three or four rectangles of 20 x 50 cm size per plot. Target species were pooled per plot and harvest, dried at 70 °C for at least 48 h, shredded and milled. Each sample was digested with HNO3 at 200 °C and at about 600-700 MPa using the microwave-assisted high pressure digestion unit (Mars 5 Express, CEM, Lintfort, Germany). Phosphorus concentrations were determined in a Continuous Flow Analyzer, AA3-system (Bran and Lübbe, Hamburg-Norderstedt, Germany). For Ca, K, Na and Mg measurement, atom absorption spectroscopy (AAS, AS240FS Fast Sequential AAS, Varian, Palo Alto, USA) was used.

Description: This data set comprises time series of aboveground community plant biomass (Sown plant community, Weed plant community, Dead plant material, and Unidentified plant material; all measured in biomass as dry weight) and species-specific biomass from the sown species of several experiments at the field site of a large grassland biodiversity experiment (the Jena Experiment; see further details below). Aboveground community biomass was normally harvested twice a year just prior to mowing (during peak standing biomass twice a year, generally in May and August; in 2002 only once in September) on all experimental plots in the Jena Experiment. This was done by clipping the vegetation at 3 cm above ground in up to four rectangles of 0.2 x 0.5 m per large plot. The location of these rectangles was assigned by random selection of new coordinates every year within the core area of the plots. The positions of the rectangles within plots were identical for all plots. The harvested biomass was sorted into categories: individual species for the sown plant species, weed plant species (species not sown at the particular plot), detached dead plant material (i.e., dead plant material in the data file), and remaining plant material that could not be assigned to any category (i.e., unidentified plant material in the data file). All biomass was dried to constant weight (70°C, 〉= 48 h) and weighed. Sown plant community biomass was calculated as the sum of the biomass of the individual sown species. The data for individual samples and the mean over samples for the biomass measures on the community level are given. Overall, analyses of the community biomass data have identified species richness as well as functional group composition as important drivers of a positive biodiversity-productivity relationship. The following series of datasets are contained in this collection: 1. Plant biomass form the Main Experiment: In the Main Experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). 2. Plant biomass from the Dominance Experiment: In the Dominance Experiment, 206 grassland plots of 3.5 x 3.5 m were established from a pool of 9 species that can be dominant in semi-natural grassland communities of the study region. In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 3, 4, 6, and 9 species). 3. Plant biomass from the monoculture plots: In the monoculture plots the sown plant community contains only a single species per plot and this species is a different one for each plot. Which species has been sown in which plot is stated in the plot information table for monocultures (see further details below). The monoculture plots of 3.5 x 3.5 m were established for all of the 60 plant species of the Jena Experiment species pool with two replicates per species like the other experiments in May 2002. All plots were maintained by bi-annual weeding and mowing.