DOI: 10.25829/bexis.31370-13
title: Biomass, species richness and environmental data from all three regions of the Biodiversity Exploratories, 2020-2021, used in: "Biomass removal promotes plant diversity after short-term extensification of managed grasslands"

description: Here we test an hypothesis involving proposed effects of fertilization and biomass removal (by mowing/grazing) on plant biodiversity (here species richness and Shannon diversity). Specifically, we aim to distinguish between direct and indirect effects of fertilization on plant biodiversity, and how biomass removal due to mowing/grazing mediates these pathways. We thus aim to understand how different drivers of land-use extensification may, or may not, promote plant biodiversity. To address these questions, we used data from a full factorial experiment, replicated within managed grasslands in three regions in Germany. We compare the effects of land-use drivers crossing fertilization with a combined treatment of biomass removal (mowing/grazing treatment): (a) fertilized biomass removal (in LUX: EP-C), (b) unfertilized biomass removal (in LUX: UP-C), (c) unfertilized reduced biomass removal (in LUX: RP-C) and (d) fertilized reduced biomass removal (in LUX: RP-F). In particular, we tested the following hypotheses: (1) Fertilization will cause plant species richness and Shannon diversity to decline, both directly and indirectly, by altering light competition due to increased biomass production and thereby increased standing biomass. (2) Biomass removal partly compensates for the negative effects of fertilization on species richness and Shannon diversity, by decreasing levels of standing biomass and thereby reducing light competition or changing the competitive dominance of plant species.br /In order to do so, we performed vegetation records and estimated standing biomass using a rising plate-meter in all grassland EPs and in the new experiments (LUX: EP-C, RP-C, RP-F, UP-C), in the spring and summer season (April to May and July to August respectively) in 2020 and 2021. In each plot (7 x 7 m) we were assigned to a 1 x 1 m subplot, in which we estimated the species specific cover of each plant species (in percent). Furthermore, we measured standing biomass using a rising plate meter with 4 replicates per subplot. The data collection was part of the project BEF-Loops within the framework of the DFG-funded joint project Biodiversity Exploratories (https://www.biodiversity-exploratories.de).br /Important note!br /This data set is a processed version for the paper "Biomass removal promotes plant diversity after short-term extensification of managed grasslands (Andraczek et al.)". This data derived from other raw data sets (ID 31203, ID 31204 and data from LUI Tool based on ID 25086).
description: In all three regions, we investigated how different land-use drivers (fertilization and mowing/ grazing) influence plant biodiversity via direct or indirect pathways. To do so, we selected 16 grassland sites (6 in the Schwäbische Alb and Hainich-Dün, and 4 in Schorfheide-Chorin), representing grasslands managed at relatively high intensities, and set-up a full factorial experimental design in autumn 2019 consisting of biomass removal and fertilization treatments.br /Thus, the Biodiversity Exploratories established four 7×7 m plots per grassland plot, containing one of four combinations: fertilized biomass removal (in LUX: EP-C), unfertilized biomass removal (in LUX: UP-C), unfertilized reduced biomass removal (in LUX: RP-C), fertilized reduced biomass removal (in LUX: RP-F).br /In the fertilized biomass removal treatment the frequency of fertilization (kg N m- 2), grazing (number of livestock units per grazing duration) and mowing (number of cuts) differed along a land-use gradient (medium to high land-use).br /In the unfertilized biomass removal treatment, fertilization was stopped completely, while mowing and grazing continued at the same intensity and frequency as in fertilized biomass removal plots.br /In the unfertilized reduced biomass removal treatment, land-use intensity was reduced to mowing only once a year in August or September, while stopping grazing and fertilization completely.br /As in the reduced land-use treatment, land-use intensity was reduced in the fertilized reduced biomass removal treatment, while fertilization was manually applied (as organic or inorganic fertilizer). The amount (kg N m-2) and frequency of fertilizer application was comparable to the amounts of fertilizer applied in the respective fertilized biomass removal plot.br /In each of these plots, the Biodiversity exploratories established a 1×1 m subplot, where plant biomass and species composition was monitored. For each treatment (i.e. fertilized biomass removal, unfertilized biomass removal, unfertilized reduced biomass removal, and fertilized reduced biomass removal), there was one plot/subplot in 16 different fields, yielding to 64 studied subplots in total.|Sampling design: From 2020 to 2021, and in both spring and summer, we measured standing biomass (using a rising plate meter) and performed vegetation relevés. All measurements were performed in a 1 m × 1 m area of all 7 m × 7 m plots in all 16 grasslands, including the subplots of the full factorial design: fertilized biomass removal (in LUX: EP-C), unfertilized biomass removal (in LUX: UP-C), unfertilized reduced biomass removal (in LUX: RP-C), fertilized reduced biomass removal (in LUX: RP-F).br /To quantify light competition for plants below the canopy, we measured light availability of photosynthetically active radiation (using PAR Sensor, Skye Instruments, in µmol sec-1 m-2) both at ground level and at 1.5 m height. To test an alternative indirect relationship of fertilization or biomass removal via soil moisture, we additionally measured soil moisture (ML3 ThetaProbe Soil Moisture Sensor, in %) with three replicates per subplot.|Equipment: Rising plate meter (Jenquip Manual Plate Meter, measurements were calibrated using data collected from the Botany Core team in spring 2021, ID 31180)br /ML3 ThetaProbe Soil Moisture Sensor br /PAR Sensor, Skye Instruments|Data processing: For each subplot, we quantified species richness and Shannon Diversity (Magurran et al. 2004). See raw data ID 31203.br /Standing biomass was quantified using biomass estimates which were converted into standing biomass using a calibration formula. This calibration formula was based on calibration data collected in spring 2021 from 2 x 150 subplots (1×1 m each) in additional grassland sites in all three regions (2 x 50 subplots per regions) including all fertilized biomass removal plots, containing biomass estimates measured via a rising plate-meter (average per subplot) and actual standing biomass measurements from the same subplot (see ID 31180). The calibration formula was then derived by performing a linear model with actual standing biomass (in g m-2) as response variable and rising-plate meter measurements (in 0.5 cm increments) as predictor variable. Prior to calculating the calibration model, we excluded data from five subplots due to measurement errors. Following the calibration model, biomass estimates explained 83.22 % of the variance in actual standing biomass (t = 37.94, p &gt; 0.01, RSD = 38.85 g m-2). Using the intercept and slope of the calibration model, we converted the biomass estimates into actual standing biomass following the equation: dry biomass (g m-2) = -38.66 + 8.68 × Plate meter measurement.br /In addition to standing biomass, we also quantified biomass production in all subplots which was defined as all biomass produced in a given time (Spring until Summer) including biomass removed by mowing or grazing. Only biomass removed by higher trophic levels other than livestock (e.g. herbivorous arthropods) could not be included in our biomass production estimate. We quantified biomass production following Riehl et al. 2001:Biomass production_Summer = (Standing biomass_Summer * (Livestock units_Summer * Grazing duration_Summer * 14700) + Yield mowing_Summer) - (Standing biomass_Spring * (Livestock units_Spring * Grazing duration_Spring * 14700) + Yield mowing_Spring) with livestock units in unit m-2, grazing duration in number of grazing days, ‘14700’ referring to the mean fodder consumption of an average livestock unit in g per day, and yield mowing in g m-2. In particular, yield mowing is defined for spring, as the sum between all mowing events between the start of the growing season (1st of April) and the end of the first field survey (15th of May), and in summer, as the sum for all mowing events between the end of the first field survey and the end of the second field survey (14th of August). These periods were also applied to calculate the grazing duration and livestock units per subplot. We only calculated biomass production in summer as in this season we expect a mismatch between standing biomass and biomass production due to land-use (e.g. removal of biomass due to mowing or grazing), while in spring biomass measurements were in most plots done before mowing and grazing events took place, and hence standing biomass was almost equivalent to biomass production of the early spring season.br /To quantify light competition in each subplot we calculated the inverse ratio between the average light availability of photosynthetically active radiation above canopy height and ground level (light availability hereafter) per subplot, with light availability close to 0 indicating low light availability and close to 1 indicating higher light availability.br /Additionally, we obtain a mean background fertilization intensity value over the time before our experiment was set up (2017-2019), background fertilization intensity was averaged across time.|Literature references: Cayuela L, Macarro I, Stein A, Oksanen J. Taxonstand: Taxonomic Standardization of Plant Species Names. R package version 2.2. 2019.Magurran AE. Measuring Biological Diversity. Oxford: Blackwell Publishing; 2004.br /Riehl G. Ermittlung von Erträgen auf dem Grünland. Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie,. 2001. Lenth RV. Estimated Marginal Means, aka Least-Squares Means: R package version 1.7.0. 2021.br /Zuur AF, Ieno EN, Elphick CS. A protocol for data exploration to avoid common statistical problems. Methods in Ecology and Evolution. 2010;1:3–14. doi:10.1111/j.2041-210X.2009.00001.x.br /Fox J, Weisberg S. An {R} Companion to Applied Regression, Third Edition. Thousand Oaks CA: Sage. 2019.br /Oksanen J, Blanchet FG, Friendly M, Kindt R, Legendre P, McGlinn D, et al. vegan: Community Ecology Package. R package version 2.5-7. 2020.br /Arbizu PM. pairwiseAdonis: Pairwise Multilevel Comparison using Adonis. R package version 0.4. 2017.br /Lefcheck JS. piecewiseSEM : Piecewise structural equation modelling in r for ecology, evolution, and systematics. Methods Ecol Evol. 2016;7:573–9. doi:10.1111/2041-210X.12512.|Data references: BExIS Datasets included in this data set: ID 31180 - Calibration data for calibrating biomass estimations (measured via rising plate-meter)