Aboveground community and species-specific plant biomass from the Jena Experiment (Main Experiment, year 2003)

This data set contains aboveground community biomass (Sown plant community, Weed plant community, Dead plant material, and Unidentified plant material; all measured in biomass as dry weight) and species-specific biomass from the sown species of 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.
Aboveground community biomass was harvested twice in 2003 just prior to mowing (during peak standing biomass in late May and in late August) on all experimental plots of the main experiment. This was done by clipping the vegetation at 3 cm above ground in four rectangles of 0.2 x 0.5 m per large plot. The location of these rectangles was assigned prior to each harvest by random selection of coordinates within the core area of the plots (i.e. the central 10 x 15 m). The positions of the rectangles within plots were identical for all plots. The harvested biomass was sorted into categories: individual species for the sown plant species, weed plant species (species not sown at the particular plot), detached dead plant material (i.e., dead plant material in the data file), and remaining plant material that could not be assigned to any category (i.e., unidentified plant material in the data file). All biomass was dried to constant weight (70°C, >= 48 h) and weighed. Sown plant community biomass was calculated as the sum of the biomass of the individual sown species. The data for individual samples and the mean over samples for the biomass measures on the community level are given. Overall, analyses of the community biomass data have identified species richness as well as functional group composition as important drivers of a positive biodiversity-productivity relationship.

本数据集涵盖地上群落生物量（含播种植物群落（Sown plant community）、杂草植物群落（Weed plant community）、枯落植物材料（Dead plant material）与未鉴定植物材料（Unidentified plant material），所有生物量指标均以干重计量），以及该大型草原生物多样性实验——耶拿实验（the Jena Experiment，详见下文细节）主实验样地中播种物种的物种特异性生物量。

主实验阶段，研究人员从包含60个物种的物种库中建立了82块20×20米的草原样地，该物种库涵盖4个功能群：禾草类、豆科类、高大草本与小型草本。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块样地，以此构建植物物种丰富度（1、2、4、8、16与60个物种）与功能群丰富度（1、2、3、4个功能群）的梯度序列。所有样地通过每年两次除草与刈割进行维护。

2003年，在两次刈割前（即5月末与8月末的地上生物量峰值期），研究人员对所有主实验样地的地上群落生物量开展采样，共完成两次采样。采样方法为：在每块大样地内的4个0.2×0.5米矩形区域中，剪取3厘米高度以上的植被。每次采样前，均通过在样地核心区域（即中央10×15米范围内）随机选取坐标确定矩形区域的位置，且所有样地内矩形区域的布设位置完全一致。

采集得到的生物量被划分为四类：播种植物物种的单种生物量、杂草植物物种（即对应样地未预先播种的物种）、分离得到的枯落植物材料（即数据文件中标记的Dead plant material），以及无法归类至任何类别的剩余植物材料（即数据文件中标记的Unidentified plant material）。所有生物量样品均经70℃烘干至恒重（烘干时长≥48小时）后称重。播种植物群落生物量通过汇总各单种播种物种的生物量求和计算得到。

数据集同时提供了单个样品的生物量数据，以及群落水平生物量指标的样地平均值。总体而言，针对该群落生物量数据的分析已证实，物种丰富度与功能群组成是驱动正的生物多样性-生产力关系（biodiversity-productivity relationship）的核心影响因子。