Mineral nitrogen from KCl extractions of soil from the Jena Experiment (Main Experiment up to 15cm depth, year 2005)

As an estimate of plant‐available N, this data set contains measurements of inorganic nitrogen (NO3‐N and NH4‐N, the sum of which is termed mineral N or Nmin) determined by extraction with 1 M KCl solution of soil samples 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. Soil sampling and analysis: Five soil cores (diameter 0.01 m) were taken at a depth of 0 to 0.15 m of the mineral soil from each of the experimental plots in April and September 2005. Samples of the soil cores per plot 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, Skalar, Breda, Netherlands).

本数据集用于估算植物有效氮含量，包含大型草原生物多样性实验（耶拿实验(Jena Experiment)；详见下文）主实验样地的土壤样品经1 M氯化钾(KCl)溶液浸提后测得的无机氮（硝态氮NO3‐N与铵态氮NH4‐N，二者之和为矿质氮，即Nmin）含量。
该主实验以涵盖4个功能群（禾草类、豆科类、高大草本与小型草本）的60个物种种库为基础，共设置82块20×20 m的草原样地。2002年5月，研究人员从该物种种库中选取不同数量的植物物种播种至各样地，以此构建植物物种丰富度（1、2、4、8、16与60种）与功能群丰富度（1、2、3、4个功能群）的梯度序列。各样地通过每年两次除草与刈割进行维护。
土壤采样与分析：2005年4月与9月，从各实验样地的矿质土壤0~0.15 m深度处采集5个直径0.01 m的土芯。每次采样批次中，同一样地的所有土芯样品将被混合均匀。采用1 M氯化钾溶液浸提土壤样品，随后使用连续流动分析仪（Continuous Flow Analyzer, CFA，Skalar公司，荷兰布雷达）测定土壤浸提液中的硝态氮与铵态氮浓度。