Phosphorus fractions in soil of the Jena Experiment (Main Experiment, year 2007)

This data set contains measurements of phosphorus fractions (Hedley fractions) in soil collected 2007 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 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. Sequentially, 20 ml NaHCO3 (adjusted to pH 8.5), 30 ml NaOH, and 35 ml HCl were used as extraction solutions for 0.5 g soil. The last step comprised the combustion (550 °C) of the remaining soil to destroy all organic material followed by shaking with 20 ml H2SO4. Organic P concentrations of the respective fractions were calculated as the difference between total dissolved P and inorganic P. Duplicate phosphate concentrations of P fractions in soil were measured photometrically (molybdenum blue-reactive P) with a Continuous Flow Analyzer (Bran&Luebbe, Germany).本数据集包含2007年采集自大型草原生物多样性实验（耶拿实验，Jena Experiment；详见下文）主实验样地的土壤磷组分（Hedley fractions）测定数据。该主实验共设置82块20×20米的草原样地，所用植物材料来自涵盖4个功能群（禾草、豆科植物、高大草本与小型草本）的60个物种种库。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）的梯度样地。所有样地通过每年两次的除草与刈割进行维护。 土壤采样与分析流程如下：每块样地于0-15厘米土层使用内径1厘米的土钻采集5份独立土样，将同一样地的5份土样混合为1份复合土样。采用四步连续磷分级法（Hedley fractions）对土壤样品进行前处理：依次以20毫升pH调至8.5的碳酸氢钠、30毫升氢氧化钠、35毫升盐酸作为浸提液，对0.5克土壤进行分步浸提。最后一步为将残留土壤置于550℃下灼烧以完全破坏有机质，随后加入20毫升硫酸振荡提取。各组分的有机磷浓度通过总溶解磷与无机磷的浓度差值计算得到。对土壤磷组分的磷酸盐浓度进行平行测定：采用光度法（钼蓝反应法检测活性磷），使用德国Bran&Luebbe公司生产的连续流动分析仪完成检测。