Increasing dominance of upright brome grass in central Germany – evaluation of management strategies for promoting biodiversity in calcareous dry grasslands (BROMUS)

Calcareous dry grasslands are considered the most species-rich habitats in Germany and are under special protection under the European Fauna-Flora-Habitat Directive 92/43/EEC and on the basis of the Federal Nature Conservation Act (BNatschG). They are currently endangered by the massive spread of upright brome (Bromus erectus) due to climate and/or management factors, which is leading to a loss of characteristic, less competitive species in this extremely valuable habitat. However, as this spread has only just begun in central Germany, countermeasures are still possible through adjustments in management. The aim of the project is to investigate different management strategies that can successfully curb the spread of upright brome grass at an early stage of expansion. To this end, we will record and analyze the vegetation at different locations in central Germany within six model regions. Selected areas will be subject to at least five years of continuous management using the management options commonly used in landscape conservation: sheep grazing, goat grazing, grazing with large grazing animals (cattle and/or horses), mowing, and fallow (without management).

Project priorities

Management of upright brome (Bromus erectus)

Project region

Unteres Saaletal, Saale-Unstrut-Region, Biosphärenreservat Karstlandschaft Südharz, Naturpark Kyffhäuser, Gotha/Ilm-Kreis, Nationalpark Hainich

Further project details

• Background

  Upright brome (Bromus erectus W. Hudson 1762) is a perennial grass species that reaches heights of 30 to 90 cm. The species grows in loose to dense clumps and forms a rhizome with roots up to 60 cm deep (intensive root system). The flowering period is from May to October.

  Upright brome grass originally colonized dry, base-rich sites in southern and southwestern Europe (Sutkowska et al. 2013). In Central Europe, erect brome grass only appeared in modern times (Poschlod & WallisDeVries 2002), where it spread further, particularly through hay sowing. Since then, the species has been migrating northeastward from southwestern Germany. In central Germany, it was probably first sown and thus introduced in the mid- to late 19th century (Heinrich 2010). Currently, a strong spread of upright brome grass can be observed in the limestone dry grasslands of central Germany (Meier et al. 2021), leading to a loss of characteristic but less competitive species in this extremely valuable habitat.

  For a long time, the problem of upright brome grass immigration was only perceived sporadically, as the species is described as a characteristic grass species of semi-arid grasslands (Schubert 2001). In addition to Thuringia (Heinrich 2010), Lower Saxony, and North Rhine-Westphalia, the species has also been classified as a neophyte in Saxony-Anhalt since 2016 (Frank 2016).

  In a relatively short time, upright brome can become dominant if management is unsuitable or use is abandoned (Bornkamm 2006). The relatively large clumps and heavy litter formation significantly alter the original structure of the dry grasslands, in particular homogenizing them. The increased litter formation also promotes nitrogen availability in the soil due to increased moisture. The predominantly less competitive dry grassland species are displaced. As a result, the populations become impoverished in terms of both flora and fauna (Poniatowski et al. 2018).

  Bornkamm, R. (2006) Fifty years vegetation development of a xerothermic calcareous grassland in Central Europe after heavy disturbance. Flora-Morphology, Distribution, Functional Ecology of Plants, 201(4), 249-267.

  Frank, D. (2016) Gefäßpflanzen (Tracheophyta: Lycopodiophytina, Pteridophytina, Spermatophytina) Bestandsentwicklung. – In: Frank, D. & Schnitter, P. (Eds.): Pflanzen und Tiere in Sachsen-Anhalt: Ein Kompendium der Biodiversität. Natur+Text, Rangsdorf: 192–318.

  Heinrich, W. (2010) Zum Indigenat der Aufrechten Trespe (Bromus erectus) in Thüringen. Haussknechtia, 12, 101-126.
  Meier, T., Hensen, I. & Partzsch, M. (2021) Floristic changes of xerothermic grasslands in Central Germany: A resurvey study based on quasi-permanent plots. Tuexenia, 41, 203-226.

  Poniatowski, D., Hertenstein, F., Raude, N., Gottbehüt, K., Nickel, H. & Fartmann, T. (2018) The invasion of Bromus erectus alters species diversity of vascular plants and leafhoppers in calcareous grasslands. Insect Conservation and Diversity, 11(6), 578-586.

  Poschlod, P. & WallisDeVries, M.F. (2002) The historical and socioeconomic perspective of calcareous grasslands—lessons from the distant and recent past. Biological Conservation, 104, 361–376.

  Schubert, R. (2001) Prodomus der Pflanzengesellschaften Sachsen-Anhalts. – Mitteilungen zur floristischen Kartierung Sachsen-Anhalt: 688 pp.

  Sutkowska, A., Pasierbinski, A., Warzecha, T., Mandal, A. & Mitka, J. (2013) Refugial pattern of Bromus erectus in Central Europe based on ISSR fingerprinting. Acta Biologica Cracoviensia Series Botanica, 55, 107–119.

• Model area and site selection

  The search for suitable test areas was conducted in six model regions in central Germany (Unteres Saaletal, Saale-Unstrut-Region, Biosphärenreservat Karstlandschaft Südharz, Naturpark Kyffhäuser, Gotha/Ilm-Kreis, Nationalpark Hainich).

  Criteria for selecting sample areas within the model areas:

  • At least 5–10 years of continuous management
  • Minimum area > 0.5 ha
  • Southern exposure if possible
  • As old vegetation data available as possible
  • Either already colonized by upright Trespe or at least potentially colonizable (species occurring in the surrounding area)

  Management variants:

  • Temporary grazing with large grazing animals (cattle, equines, mixed grazing)
  • Year-round grazing with large grazing animals (cattle, equines, mixed grazing)
  • Grazing with sheep (paddock and herding)
  • Grazing with goats
  • Mowing (extensive, single cut)
  • Unmanaged fallow land

  Six suitable sample areas were randomly selected for each of the six management variants. A total of 36 sample areas were recorded. The occurrence of upright brome grass is recorded at two levels of investigation. At the large-scale level, the distribution and degree of colonization on the respective total area is examined at grid level. At the small-scale level, changes in the calcareous dry grassland vegetation are to be documented through vegetation surveys. In addition to species composition, representative vitality parameters of upright brome grass were recorded within each vegetation survey in order to determine the fitness of the respective population.

  

  

  

  

  

  

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• Demonstration area “Rödel”

  The best and most extensively studied sample area is the year-round horse grazing on the Rödel in the “Tote Täler” nature reserve and FFH area. Analysis of vegetation data as part of this project revealed that the calcareous semi-dry grasslands, which were heavily dominated by upright brome (Bromus erectus) before grazing began in 2009, were in very good condition. The dominant stands were broken up and the diversity of characteristic plant species in particular increased significantly. This process was made possible in particular by the structures that arise on areas grazed all year round through permanent but extensive and patch-like grazing. Compared to short-term, intensive grazing, year-round grazing develops a three-dimensional vegetation structure due to the high selection possibilities for grazing animals.

  Horses in particular play an important role in this process. Compared to other grazing animals such as cattle, sheep, or goats, equines can compensate for poor-quality feed by eating more frequently and almost continuously. Grass species that are almost indigestible for many herbivores due to silicate deposits in their cells and lignified fibers can be digested by equids thanks to their fiber-oriented digestive system and their high-crowned teeth, which protect against abrasion (coevolution of grasses and grazing animals since the Tertiary period). As grazers, equids selectively feed on grasses, thereby directly reducing Bromus erectus and indirectly promoting herbaceous plants. Bromus erectus was selectively eaten in all growth phases and in all seasons. Winter grazing plays an important role here, as Bromus erectus, as a sub-Mediterranean species, benefits significantly from the more recent milder winters and earlier springs.

  

  

  

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  area characteristic

  Location: 51° 13′ N; 11° 46′ E
  Elevation: approx. 250 m above sea level
  Climate: temperate to slightly continental
  Average annual temperature: 8.3°C
  Average annual precipitation: 565 mm
  Soil and geology: loess-luvisol on Middle Muschelkalk
  Nitrogen N (total): 0.31%
  Phosphorus: 0.26 mg/100 g soil
  Potassium: 19.05 mg/100 g soil
  Deposition of atmospheric nitrogen: 13 kg ha-1 a-1

  Management

  Pasture type: Year-round permanent pasture
  Start of grazing: 2009
  Pasture size: approx. 90 ha
  Livestock density: approx. 16 horses of the Konik polski breed (approx. 0.2 LU/ha/a)
  Agricultural subsidies: including voluntary nature conservation services (FNL)
  Pasture infrastructure: double-wire fence permeable to wildlife, drinking trough, minimal winter feeding (straw)

  Vegetation

  FFH-LRT 6210(*) Near-natural calcareous dry grasslands and their scrub encroachment stages (Festuco-Brometalia)
  Start of grazing in 2009: advanced stages of grass encroachment with tall oatgrass (Arrhenatherum elatius), false brome (Brachypodium pinnatum) and, in particular, Bromus erectus

  Grazing effects

  Dynamic mosaic-like use of space by grazing animals
  Reduction in litter layer coverage from 50% (± 18.7) in 2009 to 14.38% (± 9.04) in 2024
  Increase in open ground coverage from 1.09% (± 1.65) in 2009 to 7% (± 5.63) in 2024
  Increase in the number of species typical of the habitat
  Average number of species recorded in vegetation surveys increased from 31.38 (± 10.24) in 2009 to 42.63 (± 9.68) in
  2024
  Four orchid species newly recorded
  Significant increase in the population of the bee orchid (Ophrys apifera): increase in sterile individuals to 1/3 of the pasture area from 1,239 in 2013 to 4,652 in 2024

  More info can be found here.

• Knowledge transfer and public relations

  The long-term goal of the project is to publish the project results with tips on how to deal with upright brome in a specialist journal and to establish demonstration areas for carrying out activities to raise awareness among land users.