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Doctoral thesis, 2023

Fire and herbivory – key drivers of temperate open ecosystems : Effects of consumer control on woody and herbaceous plant communities in temperate wood-pasture

Amsten, Karin


The decline of open and semi-open habitats is an important reason behind the ongoing worldwide loss of biodiversity. Understanding the drivers of habitat openness is an important key for preventing the continued loss of these ancient ecosystems. In other continents, fire and herbivory are well-studied and identified as important processes in preventing open habitats from turning into closed forests. The aim of this thesis is to apply the established concept of consumer control in a new context: the northern areas of temperate Europe. In a large field experiment in a Swedish wood-pasture, we first studied how two consumers, prescribed grass fire and grazing by cattle, alone or in combination, affected the survival and growth of planted tree saplings (I). The tree species demonstrated different strategies to resist fire or herbivory. Either they survived by re-sprouting or they quickly grew out of reach of the consumers. In addition, we studied the effect of the two consumers on the establishment and reproduction of sowed open habitat forbs (II). Herbivory improved the conditions for the establishment of forbs, but fire promoted the production of inflorescences. A release of grazing pressure increased the number of remaining flowers at the end of the growing season, confirming the importance of variation in herbivory intensity over time for the persistence of forbs. In a third study, we studied the interaction between fire and cattle grazing (III). We followed the foraging behaviour of cattle with camera traps and found that when a larger proportion of an area was burned, the cattle preferred to graze in the newly burned areas. This led to a reduction in fuel, altering the future fire pattern. In a final study, we evaluated the long-term effects of fire and herbivory by comparing the biomass of woody and herbaceous vegetation (IV). Without fire and herbivory, trees out-shaded grasses and forbs, leading to conversion from an open grassy ecosystem to a tree-dominated forest. In conclusion, herbivores and potentially also fire can be important drivers of openness, also in temperate Northern Europe, but further research is needed to understand the effect of different fire and grazing regimes.


consumer control; fire; grassland; grazing; herbivory; open ecosystem; savanna; vegetation structure; wood-pasture

Published in

Acta Universitatis Agriculturae Sueciae
2023, number: 2023:74
ISBN: 978-91-8046-200-6, eISBN: 978-91-8046-201-3
Publisher: Swedish University of Agricultural Sciences

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