Soil organic matter from the Jena Experiment (Main Experiment, year 2002)

This data set contains measurements of soil organic content, i. e. percentage of organic matter. Data presented here is 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 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.
Soil organic content was determined from undisturbed soil cores at 27 locations distributed throughout the experimental site in spring 2002 before plot establishment. Two of the locations are now reference plots and thus not included in this data set. Soil cores were taken to 100 cm depth and separated in depth increments with a resolution of ten cm from ground level to 40 cm depth and 20 cm from 40 cm to 100 cm depth. The bulk material was passed through a sieve with 2 mm mesh size and only fine soil was used for the investigation of soil organic content. Percentage of organic matter for every sample was then determined at the laboratory for geoecology of Jena University using a loss-on-ignition method (DIN 19684-3).

本数据集包含土壤有机含量（即土壤有机质百分比）的测定数据。此处所呈现的数据源自大型草地生物多样性实验（耶拿实验，详见下文）的主实验样地。主实验中，研究人员从隶属于4个功能群（禾草、豆科植物、高大草本与小型草本）的60个物种库中，建立了82块20×20米的草地样地。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于样地，以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。样地日常维护采用每年两次除草与刈割的方式。自2010年起，样地面积缩减至5×6米，且每年除草三次。
2002年春季，在样地建立前，研究人员在实验场地内分布的27个点位采集原状土柱，用以测定土壤有机含量。其中2个点位现已作为参照样地，未纳入本数据集。土柱采集深度达100厘米，分层方式为：0至40厘米土层以10厘米为间隔细分，40至100厘米土层以20厘米为间隔细分。采集的块状土样过2毫米孔径筛，仅取细土部分用于土壤有机含量分析。随后，耶拿大学地理生态学实验室采用灼烧减重法（DIN 19684-3）测定了所有样品的有机质百分比。