Mineral nitrogen from KCl extractions of soil from the Jena Experiment (Main Experiment up to 30cm depth, year 2003)

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 and 0.15 to 0.3 m of the mineral soil from each of the experimental plots in March, June, and October 2003. 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可利用氮，其中包含了对大型草原生物多样性实验（耶拿实验（Jena Experiment）；详见下文）的主实验样地土壤样品采用1 M氯化钾溶液萃取所得的无机氮（硝态氮NO₃-N与铵态氮NH₄-N，二者之和被称为矿质氮或Nmin）检测数据。在该主实验中，研究人员从涵盖4个功能群（禾草类、豆科类、高大草本与小型草本）的60个物种库中，构建了82块20×20米的草原样地。2002年5月，研究人员从该物种库中选取不同数量的植物物种播种至各样地，以构建植物物种丰富度（1、2、4、8、16及60种）与功能群丰富度（1、2、3、4个功能群）的梯度。所有样地均通过每年两次的除草与刈割进行管护。
土壤采样与分析：2003年3月、6月及10月，从各实验样地的矿质土壤0~0.15米与0.15~0.3米深度处采集5个土芯（直径0.01米）。每次采样期间，将同一样地的土芯样品混合均匀。采用1 M氯化钾溶液萃取土壤样品以测定硝态氮（NO₃-N）与铵态氮（NH₄-N）浓度，并使用连续流动分析仪（Continuous Flow Analyzer, CFA；Skalar公司，荷兰布雷达）对土壤萃取液进行检测。