DOI: 10.5061/dryad.6hdr7srb2
title: Data from: Disc Mower vs. Bar Mower: Evaluation of the direct effects of two common mowing techniques on the grassland arthropod fauna

description: In Central Europe, species-rich grasslands are threatened by intensive
 agriculture with frequent mowing, contributing to the reduction of
 arthropods such as insects and spiders. However, comprehensive and
 standardized studies on the direct effects of the two most agriculturally
 relevant mowing techniques, i.e., double-blade bar mower versus disc
 mower, are lacking. In a two-year experiment, we have investigated the
 direct effect of mowing on eight abundant arthropod groups in grassland,
 covering two seasonal mowing events in both years, using a randomized
 block design. We compared (a) an unmown control, (b) a double-blade bar
 mower, and (c) a disc mower. For most of the taxonomic groups studied, a
 significantly lower number of individuals was found in the experimental
 plots immediately after mowing, regardless of the mowing technique,
 compared to an unmown control. This was not the case for Orthoptera and
 Coleoptera, which did not show a significant reduction in the number of
 individuals for both mowing techniques (Orthoptera) or only for the
 double-blade bar mower (Coleoptera). Between both mowing techniques, no
 significant differences were found for all taxonomic groups investigated.
 Synthesis and applications. Our findings suggest that mowing in general
 has a negative impact on abundant arthropod groups in grassland,
 regardless of the method used. Tractor-driven double-blade bar mowers do
 not seem to be a truly insect-friendly alternative to a conventional disc
 mower. Other factors such as cutting height and mowing regimes should be
 seriously considered to protect spiders and insects from the negative
 effects of mowing. In addition, we highly recommend the maintenance of
 unmown refugial areas. Insects and spiders that are spared by mowing can
 take refuge in these unmown areas to avoid subsequent harvesting and
 thermally unfavourable conditions that arise on mown areas. Further,
 unmown refugia are basic habitat structures for a subsequent
 recolonisation of mown areas once the flora has recovered.
description: # Disc Mower vs. Bar Mower: Evaluation of the direct effects of two common
 mowing techniques on the grassland arthropod fauna
 [https://doi.org/10.5061/dryad.6hdr7srb2](https://doi.org/10.5061/dryad.6hdr7srb2) ## Description of the data and file structure To study the effect of two conventional mowing techniques on arthropod fauna, we compared (a) an unmown control area with (b) an area mown with a double-blade bar mower (BM 11 02, working width 1.70 m, Busatis-Werke GmbH & Co. KG, Remscheid, Germany) and an area mown with (c) a disc mower (Disco 320, without conditioner, working width 3 m, Power Take-Off (PTO) speed 850 - 1000 rpm, Claas Saulgau GmbH, Bad Saulgau, Germany). To determine direct effects of mowing, three isolation squares (1 x 1 x 0.8 m, “biocenometer” according to Mühlenberg, 1989) were randomly placed on the test strip directly after mowing. After 5 min to calm the captured insects, the isolation squares were completely vacuumed with an insect vacuum (ecoVAC Insect vacuum, ecoTech Umwelt-Messsysteme GmbH, Bonn, Germany) for a total of 5 min. The mown grass was then removed from the isolation squares by hand and weighed with a crane scale. Unmown controls were equally sampled as the treated study sites. In the latter case, we used shrub shears (HSA 26, STIHL AG, Waiblingen, Germany) to cut the grass within the isolation squares of the unmown control for weighing. In total, we sampled 35 plots (105 samples) treated with the disc mower, 20 (60 samples) treated with the double-blade bar mower, and 40 control plots (120 samples). The following taxonomic groups were sorted from all 285 samples using a stereomicroscope: Araneae, Orthoptera, Cicadina, Heteroptera, Hymenoptera, Coleoptera, Diptera, and holometabolous larvae. All non-target taxa were excluded from the data analysis. We considered only individuals that have not been damaged by the mower and remained viable, therefore, excluding injured or destroyed individuals, i.e. individuals missing legs or other body parts. ### Files and variables #### File: von-Berg\_et\_al\_2024\_data.xlsx **Description:** Numbers of individuals of the eight assessed arthropod groups (Araneae, Orthoptera, Cicadina, Heteroptera, Coleoptera, Diptera and holometabolous larvae) recorded for the different treatments: unmown control, bar mower, and disc mower for the three comparisons 'control vs. bar mower', 'control vs. disc mower' and 'bar mower vs. discs mower'. Sampling was carried out using 1-m² isolation squares and an insect vacuum on the following sampling dates: 07/04, 07/06, 09/22, 09/23/2022 and 06/15, 06/19, 09/19, 09/21/2023 on the two study sites A and B. Each study site is divided into five blocks (study site A: block B1-B5, study site B: block B6-B10). Each block contains up to 5 sampled subsections (plot P1-P6). Per subsection and treatment three samples were taken at the same time. The time of sampling (daytime), the working speed of the tractor (speed in km/h), the cutting height (in cm), as well as the weight of the grass in each isolation square (grass weight in kg, shown only for the 'bar mower vs. disc mower' comparison) was recorded. Speed and cutting height are not applicable (N.A.) for the controls, as they have not been mown.