Seed bank dynamics: the role of fungal pathogens and climate change

1. One of the climate change scenarios predicted for the UK is warmer winters and additional summer rainfall, which may favour growth and survival of fungal pathogens. We tested several hypotheses on the fate of persistent seeds in the soil and the role of fungal pathogens under this predicted climate change. 2, We buried seed bags containing fungicide-treated and non-fungicide-treated seeds of four species with persistent seed banks (Convolvulus arvensis L., Lotus corniculatus L., Medicago lupulina L. and Rubus fruticosus L.) under control and simulated climate change (winter warming plus supplemented summer rain) conditions, and monitored seed survival over 1 to 2 years. 3. Fungicide treatment resulted in a significant increase in the percentage of intact seeds recovered for only two of the four species, M. lupulina and R. fruticosus. Seeds of M. lupulina that were treated with fungicide remained viable in the soil for longer than non-treated seeds. Thus, the effect of fungal pathogens on seed persistence in the soil appears to be species specific. 4. There was no significant effect of the simulated climate (winter warming plus supplemented summer rain) on seed persistence in the soil, for any of the four species. Neither was a significant climate x fungicide treatment interaction found for any of the four species. Thus, it does not appear that the conditions provided in the simulated climate plots favoured the growth and survival of fungal pathogens affecting the soil seed banks of the four species studied here. 5. The use of fungicides in manipulative experiments and the importance of field experiments that simulate predicted climate change are discussed.