DOI: 10.71615/bexis.32256
title: Rhizosphere soil extracellular enzyme kinetics from 12 common grassland species (Hainich 2023)

description: The project PEGasuS targets at disentangling the mechanisms of grassland plant-soil interaction along the gradient of land-use intensity (LUI). Based on ecological theories, a coupling between plant, microbial and soil stoichiometries, as well as ecoenzymes is hypothesized. A hotspot of these couplings is the rhizosphere. &lt;br&gt;This dataset contains rhizosphere soil extracellular enzyme kinetic analyses for maximum reaction velocity (Vmax) and the Michaelis constant (Km) of carbon-, nitrogen-, sulfur- and phosphorus-cycling enzymes. We sampled 15 experimental plots (EPs) in the Hainich (Germany), 10 EPs with corresponding reduced land use plots (RPs) from the REX I experiment and 5 EPs with a historic low LUI index. The soil samples were collected in May 2023. We gathered data on phosphomonoestrase, phosphodiesterase, arylsulfatase, beta-1,4-xylosidase, beta-glucosidase, beta-1,4-cellobiosidase, n-acetyl-beta-glucosaminidase and chitobiosidase.&lt;br&gt;The data collection/analysis was part of the project PEGasuS within the framework of the DFG-funded joint project Biodiversity Exploratories (https://www.biodiversity-exploratories.de).
description: Study design: We sampled the rhizosphere soil of 12 common grassland plant species (4 forbs, 4 grasses, 4 legumes). For the project we sampled 10 plots of the REX I (31457) experiment (EPs and RPs) and 5 additional low-LUI EPs (average LUI &lt; 1.1) in the Hainich region. REX I was implemented to test the effects of extensification. To implement, RPs are only mown once per year. | Sampling design: In May 2023, sampling was performed along the plot borders of the EPs to minimize effects of other experiments performed on the plots. For each target species present on a plot, three individuals were randomly selected to sample rhizosphere soil. Per plant infividual 8 - 10 rhizosphere soil samples were taken in a depth up to 10 cm using a soil corer with 0.8 cm diameter. The accumulated soil from all three indivuals per species was mixed together. After sampling the soil was kept in coolers and later stored in freezers at -20 °C. | Sample preparation: Prior to analyses, rhizosphere soil samples were sieved (5 mm) and remaining roots were removed with tweezers. | Sample analysis: Soil samples equivalent to 0.5 g dry soil were suspended in sterile deionized water (50 mL) and were homogenized using an ultrasonic horn. Enzyme assays for hydrolases involved in the C-cycle (BG, CBH, XYL), N-cycle (NAG, DCH), P-cycle (AP, BAP) and S-cycle (SU) were conducted by adding substrates bound to 4-Methylumbelliferone (MUF) at eight different substrate contents with a MES buffer (pH 6.5). When the enzymes catalyze the substrate, the fluorescent MUF releases during incubation at 30°C. The fluorescence was measured using a Tecan Infinite F200® PRO microplate reader. Measurements of three replicates per sample were used to calculate maximum reaction velocity (Vₘₐₓ) and the Michaelis constant (Kₘ). Due to the light-sensitivity of the substrates all enzyme analyses were performed in the dark. | Equipment: Soil corer &lt;br&gt;Ultrasonic horn&lt;br&gt;Tecan Infinite F200® PRO microplate reader | Data preparation: Measurements were performed in triplicates, so the calculation of Vmax and Km is based on averages.