Arable vegetation of calcareous soils (Caucalidion) Plant community of the year 2022: Pflanzengesellschaft des Jahres 2022

Research output: Journal contributionsJournal articlesResearchpeer-review


  • Erwin Bergmeier
  • Stefan Meyer
  • Fionn Pape
  • Hartmut Dierschke
  • Werner Härdtle
  • Thilo Heinken
  • Norbert Hoelzel
  • Dominique Remy
  • Angelika Schwabe
  • Sabine Tischew
  • Simone Schneider

Arable vegetation of calcareous soils, the plant community alliance known as Caucalidion, has been newly elected “Plant community of the Year 2022”. In this review article, we provide an overview of the Caucalidion in Germany, its species composition, life cycle and biodiversity, distribution, habitat and phytosociological variation, its history, reasons of decline, and conservation management both at present and in view of future options. The Caucalidion is a well-defined alliance characterized by more than 50 plant species in Germany alone, alas a majority of them is now scarce and listed in the national Red Data Book. Caucalidion vegetation has been associated with grain farming since as early as the Bronze Age, although its species composition has altered over time due to changes in crop species, tillage and farming technology. Generally, the number and proportion of segetal plants in grain fields has increased. However, the past decades have seen an unprecedented intensification and increase in production of arable farming, yet to the cost of soil health, diversity and abundance of wildlife. Most characteristic species of the Caucalidion are archaeophytes, some of which accompanying arable farming since millennia, others since mediaeval times. However, the plant species pool typical of calcareous fields in Germany (comprising more than 150 species sufficiently frequent to occur in at least 10 % of the – historical – relevés in at least one region or community association) consists of at least 55 % native plant species. The Caucalidion has a European (warm-)temperate, suboceanic to subcontinental distribution area, from the British Isles to southern Sweden, and from Central Spain to the surroundings of the Black Sea. It is mainly distributed in South-Central European and sub-Mediterranean regions. In Germany, it occurs at all altitudinal belts that support agriculture, and covers all productivity classes of arable soil including the top high-yield sites. Three plant community types (associations) of the Caucalidion occur in Germany: The Fluellen community (Kickxietum spuriae) reaches the country in the west and is found on thick calcareous loams and clays under suboceanic conditions. The community named after Night-flowering Catchfly (Euphorbio exiguae-Melandrietum noctiflori) occurs on deep loess and chernozem as well as calcaric cambisols mostly in the north of the Caucalidion distribution area. Finally, the more southerly distributed Bur-parsley community (Caucalido platycarpi-Conringietum orientalis) depends on often thin calcareous clay loams under warmer and drier conditions. Caucalidion vegetation is currently associated almost entirely with autumn-sown cereal varieties, but until in the recent past spring-sown cereals have also been common on calcareous fields. The rhythm of arable plant growth determines the food resources on cultivated lands. In the Caucalidion, as in other plant communities of arable fields, annual plants dominate, comprising a mixture of life cycles including autumn-germinating and springgerminating plants as well as others that may germinate anytime when conditions are favourable. Historical relevés of the 1950s to 1970s reveal mean total cover values of arable plants of 35 to over 40 %, approximating the crop cover values. Published references to arable weeds by botanists of the 18th and 19th century highlight the local abundance of Caucalidion plants including species known as being extremely rare today. The variety of arable plants throughout the year with their leaves, buds, flowers, pollen, nectar and seeds satisfies the dietary needs of all kinds of arable wildlife, provided that cereal stubbles are left after harvest as stubble-fields support late flowering and fruiting plants essential for seed-eating birds and other fauna. Pollinators are represented in arable fields by both generalists and specialists such as wild bees feeding exclusively on Sinapis arvensis or Convolvulus arvensis, respectively, both common and locally abundant in Caucalidion fields. The 19th and early 20th century losses of the arable flora were due to more and more efficient seed cleaning, changes in crop rotation with loss of fallow, and increasing mechanization. This process accelerated towards the end of the 20th century by revolutionary changes in arable farming methods, including massive increases in the application of agrochemicals such as herbicides and artificial nitrogen fertiliser, and the loss of crop stubbles in the autumn and winter. In the past decades, species-rich Caucalidion vegetation together with its farmland wildlife has drastically declined to mostly tiny areas extant only in scattered field margins. Conservation management of field margin strips, set up for the first time in the late 1970s in the Eifel Mountains by the initiative of Wolfgang Schumacher, is now safeguarded by various biodiversity action plans in the federal states providing financial compensation to contractual farmers for production losses. Despite the success of programmes devoted to the conservation management of field margin strips rich in Caucalidion species their future development may be bleak due to discontinuation of the programmes and compensatory payments, competing – and eventually more profitable – agri-environment schemes, the ongoing abandonment of unproductive fields, and increasingly the use of even such fields for energy crop cultivation. Recent evidence highlights the importance of habitat continuity for rare Caucalidion plant species. Changes in the European Union’s Common Agricultural Policy are urgently needed to improve the future situation of agro-ecosystems. Current negotiations and subsequent national implementation should prioritize environmental services of farmland management against unbalanced conventional agriculture directed only to yield maximisation and increasingly to the profits of outside farmland investors. Economic incentives should be directed towards a substantial increase in the proportion of organic farming and to implement a network of sites of nature conservation importance, arable plant sanctuaries in farmed fields at the landscape level, across agricultural regions. They represent focus areas for the local arable wildlife species pool and may serve as reservoirs for rare species selected for re-introduction in surrounding landscapes where they are gone. The authors of this review article consider the election of the Caucalidion as “Plant community of the Year 2022” as supportive for stakeholders active in improving conditions for soil and biodiversity protection through sustainable farming and arable plant conservation management at local, national and international levels, and especially acknowledge the years-long successful conservation efforts of numerous contract farmers participating in agri-environment programmes supporting our arable flora and wildlife.

Translated title of the contributionAckerwildkraut-Vegetation der Kalkäcker (Caucalidion): Pflanzengesellschaft des Jahres 2022
Original languageEnglish
Pages (from-to)299-350
Number of pages52
Publication statusPublished - 2021

Bibliographical note

Publisher Copyright:
© 2021

    Research areas

  • Biology - arable farmland, arable flora, biodiversity loss, common agricultural policy, community ecology, conservation management, cornfield floewers, farmland history, plant community, syntaxonomy, weed