DOI: 10.71615/bexis.32027
title: Seedling trait data of 180 grassland species used in: Different from the start: Key dimensions of seedling traits of Central European temperate grassland species

description: During the last two decades, the research on plant functional traits has advanced rapidly. However, so far, research has focused on traits of adult plants, while research on seedling traits is scarce. Seedling traits, however, could play an important role during plant establishment from seeds and they are essential to understand the full plant life cycle. We studied seedling traits related to the timing of germination and seedling development (number of days until germination, time until two leaves developed), above- and belowground morphological seedling traits (seedling height, specific leaf area (SLA), root tissue density, specific root length), relative growth rate as well as seedling above- and belowground biomass in the stage, when seedlings had developed the first two true leaves. For this, we examined ca 229 temperate grassland species in a microcosm experiment under ambient light and temperature conditions in an open greenhouse (at the UFZ Field Station Bad Lauchstädt, Saxony-Anhalt, Germany) between November 2020 and July 2022. <br>The microcosm experiment was part of the project SeedDiv within the framework of the DFG-funded joint project Biodiversity Exploratories (https://www.biodiversity-exploratories.de).
description: Study design: Species were selected from the species inventories of the grassland experimental plots of the Biodiversity Exploratories (EPs) (Hinderling & Keller 2023) including all species, that occurred between 2008 and 2019 on more than three plots irrespective of their cover abundances or on fewer plots with a cover-abundance >1% resulting in 233 species. When possible, seeds were bought commercially from local suppliers preferentially from provenances in or close to the Exploratory regions. Seeds of some species, where it was not possible to buy seeds, we collected ourselves in the summer of 2020. (For seed sources see data set ID 31927). Seeds were stored at room temperature (at approx. 22°C) until they were prepared for the experiment.&lt;br&gt;The microcosm experiment was carried out in a greenhouse with open windows and a glass roof that closes during rain at the field station of the Helmholtz Centre for Environmental Research, UFZ, in Bad Lauchstädt (51.3923°,11.8759°, 117 m a.s.l.). The experiment was sown between the 16th and 24th of November 2020. Sowing in late autumn guaranteed cold stratification and/or short days, which are necessary for several species to induce germination. All species were sown in trays (QuickPot Standard QP® 96T; HerkuPlast, Kubern GmbH) with 96 cells of 3.8 x 3.8 cm size and 7.8 cm depth, which were arranged in six rows each with 12 cells on each tray. The experiment consisted of two blocks, and in both blocks, each species was sown in six consecutive cells with 2-3 seeds per cell. When several seeds per cell germinated, later-germinating seedlings where removed as soon they emerged. The position of each species was randomly assigned in both blocks. Seedlings of some species were heavily affected by frost in late February 2021. Therefore, we re-sow these species on 2nd March 2021. Moreover, a couple of species failed to germinate in the first year or we received the seed material too late. These species were sown again with new seed material in 2021. Species were sown on 9th November 2021. For re-sowing, we used the same substratum (see below) and followed the same procedure during sowing. &lt;br&gt;In addition, all species were separately sown with 50 seeds in pots of 11 x 11 cm size (12 cm depth) with five replicates per species resulting in ca. 1165 microcosms. The pots were arranged in five blocks each with one replicate per species. A some species, with only a few seeds available, could only be sown in the trays and not in pots.&lt;br&gt;Pots and trays were filled with commercial potting substrate (Fruhstorfer Erde®, Type P70, Industrie-Erdenwerke Archut GmbH, Lauterbach, Germany) mixed with 25 vol% mineral sand. The mixture contained 66.35 mg kg⁻¹ plant-available phosphorus, and 283.80 mg kg⁻¹ plant-available potassium (both determined with the CAL method). Soil carbon concentration was 65.2 mg g-1, and total soil nitrogen concentration was 1.3 mg g-1. The pH (measured in a CaCl2 solution) was 7.0. Seeds were gently pressed on the soil surface and covered with a thin layer of mineral sand to avoid loss through wind. Pots and trays were watered regularly as needed. | Sampling design: Seedlings (mainly from trays) were harvested once the first two true leaves or leaf pairs (in case of species with opposite leaves) were fully expanded. First, the seedling's stretched height was measured, and then the seedling was carefully taken out with a long-handled spoon including all soil from the tray cell. Roots were rinsed with tap water and stored in tap water until root scanning. The aboveground part was stored in moist paper towels to reach water saturation until further sample processing. All samples were processed within the next 24 hours after sampling. | Sample preparation: Roots were scanned with a flatbed scanner at 900 dpi (Epson Color Scanner Expression 10000 XL, 2007 Epson America Inc.) in a transparent plastic tray filled with water. Then, the roots were dried at 70°C for 48 h and weighed to get root biomass. The first two true leaves (or leaf pairs in the case of species with opposite leaves) were scanned with a flatbed scanner at 300 dpi (Epson Perfection V550 Photo, 2007 Epson America Inc.) as grey-level images. The scanned leaves and the remaining aboveground parts (stem, cotyledons) of the seedlings were also dried at 70°C for 48 h and weighed to obtain seedling aboveground biomass and root-to-shoot ratio. | Sample analysis: Root scans were analyzed with the WinRhizo Software (v. 2007; Regent Instruments Inc., Quebec, Canada) using an automatic mode with Lagarde thresholding to derive the average root diameter (RootDiam; mm), specific root length (SRL; root length per root dry weight; m g-1) and root tissue density (RTD; root dry weight per volume; mg cm-3).&lt;br&gt;Leaf area was obtained by analyzing the images with the software Image J (Schneider et al. 2012). The leaf area divided by the dry mass of the scanned leaves resulted in specific leaf area (mm2 mgdw-1; SLA). Further, the leaf area per leaf was calculated, to better compare leaf area between species with leaf pairs and individual leaves. Relative growth rate was estimated by calculating the natural logarithm of the biomass (at harvest at the stage of the first two true leaves) divided by the number of days from germination until harvest. | Equipment: WinRhizo Software (v. 2007; Regent Instruments Inc., Quebec, Canada), Epson Color Scanner Expression 10000 XL (2007, Epson America Inc.), Epson Perfection V550 Photo (2007, Epson America Inc.) | Data preparation: The data set does contain the values of all measurements used in the publication after checking the raw data for plausibility and according to the selection specified in the manuscript. | Literature references: Schneider, Caroline A.; Rasband, Wayne S.; Eliceiri, Kevin W. (2012): NIH Image to ImageJ: 25 years of image analysis. In: Nature methods 9 (7), S. 671–675. DOI: 10.1038/nmeth.2089. | Data references: Hinderling, J., & Keller, S. (2023) Vegetation records for grassland EPs, 2008 – 2022. Version 7. Biodiversity Exploratories Information System. Dataset. https://www.bexis.uni-jena.de/ddm/data/Showdata/31389