resilience; propagule pressure; extreme drought; invasibility; seedling establishment; plant-AMF networks ; soil pathogens; soil moisture; climate change
Stuart-Haëntjens Ellen, De Boeck Hans J., Lemoine Nathan P., Mänd Pille, Kröel-Dulay György, Schmidt Inger K., Jentsch Anke, Stampfli Andreas, Anderegg William R.L., Bahn Michael, Kreyling Juergen, Wohlgemuth Thomas, Lloret Francisco, Classen Aimée T., Gough Christopher M., Smith Melinda D. (2018), Mean annual precipitation predicts primary production resistance and resilience to extreme drought, in Science of The Total Environment
, 636, 360-366.
Stampfli Andreas, Bloor Juliette M. G., Fischer Markus, Zeiter Michaela (2018), High land-use intensity exacerbates shifts in grassland vegetation composition after severe experimental drought, in Global Change Biology
, (5), 2021-2034.
Kreyling Juergen, Dengler Jürgen, Walter Julia, Velev Nikolay, Ugurlu Emin, Sopotlieva Desislava, Ransijn Johannes, Picon-Cochard Catherine, Nijs Ivan, Hernandez Pauline, Güler Behlül, von Gillhaussen Philipp, De Boeck Hans J., Bloor Juliette M.G., Berwaers Sigi, Beierkuhnlein Carl, Arfin Khan Mohammed A.S., Apostolova Iva, Altan Yasin, Zeiter Michaela, Wellstein Camilla, Sternberg Marcelo, Stampfli Andreas, Campetella Giandiego, Bartha Sandor, Bahn Michael, Jentsch Anke (2017), Species richness effects on grassland recovery from drought depend on community productivity in a multisite experiment, in Ecology Letters
, 20(11), 1405-1413.
De Boeck Hans J., Bloor Juliette M. G., Kreyling Jürgen, Ransijn Johannes C. G., Nijs Ivan, Jentsch Anke, Zeiter Michaela (2017), Patterns and drivers of diversity-stability relationships under climate extremes, in Journal of Ecology
, 106, 890-902.
Zeiter Michaela, Schärrer Sara, Zweifel Roman, Newbery David M., Stampfli Andreas (2016), Timing of extreme drought modifies reproductive output in semi-natural grassland, in Journal of Vegetation Science
, 27, 238-248.
The question of what drives community assembly is crucial for an understanding of how communities will behave under global change, including scenarios of climate change or increased propagule pressure of exotic species. In current ecological thinking, competition with resident plants is often assumed to play an important role in biotic resistance to plant invasions. Therefore, opportunities for invasion are supposed to be better when the resident plants are damaged or stressed, for example as a consequence of drought, which in turn results in changed pulses of light and unexploited nutrients. As dry spells tend to increase in length and intensity over large regions of the globe including Switzerland, due to climate change, ecologists are concerned about the possibility that plant communities and ecosystems may become more invasible and shift to new states or loose current functions.Recent field experiments simulating extreme drought events in grasslands have not often found an increase in invasibility. This implies that drought effects are not only mediated by competition but also by other biotic interactions such as those with antagonistic and mutualistic soil microbes. Indeed, ecologists have convincingly argued that soil pathogens and arbuscular mycorrhizal fungi (AMF) are important determinants of plant community composition and functioning. However, the bulk of evidence is based on simplified experimental conditions in the greenhouse and few attempts have been made to simultaneously investigate the role of these ecological mechanisms in the field where biotic interactions are much more complex and environmental fluctuation and heterogeneity may have a paramount influence. This proposal is a continuation of the project Invasibility of Swiss grasslands. Research questions are inspired by surprising results of the extreme-drought experiment of the previous project, i.e. the lack of a relationship between establishment of sown species and productivity of the resident community over a wide gradient of productivity, the predominantly negative drought-legacy effect on establishment success, and the clearly weaker establishment success of non-indigenous vs. indigenous grassland species in the field, but not in the greenhouse. We propose three complementary experiments to investigate mechanisms of drought-legacy effects (Fig. 1). The experiments are linked by the overall questions of whether, and how much, climate change (variable summer precipitation, manipulated by rainout shelters and irrigation) and land-use intensification (productivity) affect the performance of added invader species (invasibility) mediated by biotic interaction. Biotic interactions considered include those with resident plants and soil microbes, and their various roles as competitors for light, competitors for nutrients, providers of nutrients via plant-AMF networks, pathogens, and mutualists will be studied.EXPERIMENT A is a field experiment started in 2014 at twelve grasslands sites across Switzerland, covering an annual productivity gradient in the range of 180-1200 gm-2. EXPERIMENT B will be started in 2015 in two of these sites, in fertilized and unfertilized grassland. The greenhouse-EXPERIMENT C is a follow-up study of EXPERIMENT A using soil samples with stored microbial legacies of ‘precipitation history’. Based on the results of these experiments we wish to enhance our mechanistic understanding of grassland invasibility in Switzerland and make an important step forward in the prediction of global-change effects on herbaceous vegetation.Fig. 1 Three complementary experiments investigate invasibility in response to an integrated set of drivers (summer precipitation, productivity) mediated via biotic filters: EXPERIMENT A aims at quantifying the importance of resident plants, soil fungal pathogens and soil fungal mutualists. EXPERIMENT B quantifies the various roles of resident plants as suppliers of, or competitors for resources. EXPERIMENT C investigates whether the performance of invader species under different moisture conditions is affected by ‘precipitation history’ via soil microbes.