Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2004)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed 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 dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Microbial community composition in fresh water at different stations

Fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes was used to investigate the phylogenetic composition of bacterioplankton communities in several freshwater and marine samples. An average of about 50% of the cells were detected by probes for the domains Bacteria and Archaea. Cells were concentrated from water samples (1 to 100 ml) on white polycarbonate filters (diameter, 47 mm; pore size, 0.2 mm; type GTTP 4700 [Millipore, Eschborn, Germany]) by applying a vacuum of <25 kPa. They were subsequently fixed by covering the filter with 3 ml of a freshly prepared, phosphate-buffered saline (pH 7.2)-4% paraformaldehyde (Sigma, Deisenhofen, Germany) solution for 30 min at room temperature. Airdried filters are ready for hybridization and can be stored at 220°C or room temperature for several months without showing apparent changes. Probes BET42a, GAM42a, and PLA886 were used with competitor oligonucleotides as described previously amongst others in Manz et al., (1992; doi:10.1016/S0723-2020(11)80121-9). The filters were transferred to a vial containing 50 ml of prewarmed (48°C) washing solution (70 mM NaCl, 20 mM Tris-HCl [pH 7.4], 5 mM EDTA, 0.01% sodium dodecyl sulfate) and incubated freely floating without shaking at 48°C for 15 min. The filter sections were dried on Whatman 3M paper (Whatman Ltd., Maidstone, United Kingdom) and covered with 50 ml of DAPI solution (1 mg/ml in distilled water filtered through at 0.2-mm filter) for 5 min at room temperature in the dark. For each sample and probe, more than 500 cells were enumerated; for the DAPI examination, more than 1,500 cells were counted per sample. All probe-specific cell counts are presented as the percentage of cells visualized by DAPI. The mean abundances and standard deviations were calculated from the counts of 10 to 20 randomly chosen fields on each filter section. All counts were corrected by subtracting the counts obtained with the negative control NON338. Mean and standard deviation were calculated from the counts of 10 to 20 randomly chosen fields on each filter section.

NOR5/OM60 clade of the Yangtze River estuary

The phylogeny, abundance, and biogeography of the NOR5/OM60 clade was investigated. This clade includes "Congregibacter litoralis" strain KT71, the first cultured representative of marine aerobic anoxygenic phototrophic Gammaproteobacteria. Most of the NOR5/OM60 sequences were retrieved from marine coastal settings, whereas there were fewer from open-ocean surface waters, deep-sea sediment, freshwater, saline lakes and soil. The abundance of members of the NOR5/OM60 clade in various marine sites was determined by fluorescence in situ hybridization using a newly designed and optimized probe set. Relative abundances in coastal marine waters off the Yangtze estuary were up to 3% of the total 4',6-diamidino-2-phenylindole (DAPI) counts. A small cruise was undertaken from 2006-09-06 to 2006-09-08 in the Yangtze River estuary. Samples were taken from surface water, and immediately fixed with 1% paraformaldehyde (PFA) for 1 h, filtered onto polycarbonate filters (Millipore, 47 mm in diameter, 0.2 µm pore size) and stored frozen at -20 °C.

New particle formation at the coastal Antarctic site Neumayer in 2012 and 2014

We measured condensation particle (CP) concentrations and particle size distributions at the coastal Antarctic station Neumayer (70°39'S, 8°15'W) during two summer campaigns (from 20 January to 26 March 2012 and 1 February to 30 April 2014) and during polar night between 12 August and 27 September 2014 in the particle diameter (Dp) range from 2.94 nm to 60.4 nm (2012) and from 6.26 nm to 212.9 nm (2014). During both summer campaigns we identified all in all 44 new particle formation (NPF) events. From 10 NPF events, particle growth rates could be determined to be around 0.90±0.46 nm/h (mean ± std; range: 0.4 nm/h to 1.9 nm/h). With the exception of one case, particle growth was generally restricted to the nucleation mode (Dp < 25 nm) and the duration of NPF events was typically around 6.0±1.5 h (mean ± std; range: 4 h to 9 h). Thus in the main, particles did not grow up to sizes required for acting as cloud condensation nuclei. NPF during summer usually occurred in the afternoon in coherence with local photochemistry. During winter, two NPF events could be detected, though showing no ascertainable particle growth. A simple estimation indicated that apart from sulfuric acid, the derived growth rates required other low volatile precursor vapours.

Dissolved nitrogen in soil solution of the Jena Experiment (Main Experiment, year 2002)

This data set contains measurements of dissolved nitrogen (total dissolved nitrogen: TDN, dissolved organic nitrogen: DON, dissolved ammonium: NH4+, and dissolved nitrate: NO3-) in samples of soil water collected 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. In April 2002 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 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-) and ammonium (NH4+) 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+). In 5% of the samples, TDN was equal to or smaller than mineral N. In these cases, DON was assumed to be zero.