Towards a better understanding of pyrodiversity—biodiversity relationships (PyroDiv)

• Applicants: Professor Dr. Norbert Hölzel; Dr. Johannes Kamp
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 541357927

With accelerating climate and land-use change, ecosystem disturbance is increasing globally, leading to ecosystem reorganization. Fire is a global change symptom and driver. Fire regimes are intensifying rapidly, with large implications for ecosystems and human health. An integral part of fire regimes is pyrodiversity – the spatio-temporal variation in fire size, recurrence rate and intensity. Pyrodiversity is important for ecosystem structure, as it can drive fire regimes itself via feedback processes. Pyrodiversity also drives biodiversity and associated ecosystem functions. The genesis, maintenance, drivers and ecological implications of pyrodiversity are poorly understood. Pyrodiversity seems increasingly driven by land-use change, especially the accumulation of plant biomass as fuel after land abandonment. The exact drivers in these processes, e.g. the level of grazing intensity in grassland ecosystems, have rarely been studied. Ecological theory predicts that biodiversity increases with pyrodiversity, but this has rarely been tested, and the exact shape of the relationship is unknown, as is the generality of the concept. In project PyroDiv, we set out to study the patterns and mechanism of pyrodiversity-biodiversity relationships in temperate grasslands. We predict i) that land abandonment and decreasing grazing patterns diminish pyrodiversity at the landscape scale, ii) that pyrodiversity is largely driven by pyric herbivory, i.e. interactions between fire fuel availability, ungulate movements and grazing pressure, and iii) that a higher pyrodiversity leads to higher biodiversity. We will harness a gigantic natural experiment, the abandonment of millions of hectares pasture following the collapse of the Soviet Union, and an associated increase in fire frequency on the Eurasian steppes in Kazakhstan, an emerging global fire hot spot. To test these predictions, we will first map annual change in pyrodiversity 1985 to 2023 with high-resolution satellite remote sensing. We will then, for the first time outside North America, quantify the extent of pyric herbivory, and its impact on pyrodiversity, through an analysis of the movements of GPS-tagged Saiga antelopes and domestic horses. We will establish drivers of pyric herbivory by measuring fodder quality and plant nutrient content. We will finally define the shape of pyrodiversity-biodiversity relationships at landscape-scale, applying a fieldwork-based multi-taxa analysis. We will test the effect of pyrodiversity on functional and taxonomic diversity of birds, small mammals, Orthoptera, beetles and plants. Our results will provide new insight into the drivers of pyrodiversity at large scales, the interplay of land use, pyric herbivory and pyrodiversity in grassland systems, and general rules of community assembly at varying levels of pyrodiversity. These insights will be useful to advance ecological theory, and to inform conservation and restoration of temperate grassland ecosystems.

• DFG Programme: Research Grants