The potential for endozoochorous dispersal of temperate fen plant species by free-roaming horses

Questions: Can free-roaming Konik horses digest and subsequently disperse seeds of plant species growing in a temperate fen environment? Which species have the potential to be dispersed internally (endozoochory), and do they share common plant and seed traits? How could potential dispersal via endozoochory impact upon grazing management and the natural recolonization of wetland vegetation at a landscape scale? Location: Wicken Fen NNR, Cambridge, UK. Methods: Twelve dung samples were collected for one calendar year (Jun 2009–May 2010) from a free-roaming herd of Konik horses grazing vegetation at Wicken Fen NNR. Germinable seed content of the dung was determined by means of a seedling emergence study. Species presence and estimated cover/abundance were recorded for the grazed (background) vegetation in spring and summer 2009. Results: Almost one-third of all species present in the background vegetation were also identified in the dung samples. There was an equal split between graminoids and forbs, but substantially more graminoid germinable seeds. Species were dispersed year-round, with the number of species peaking in Sep and again in Dec. Of the 13 traits measured, there were significant differences between dung and background vegetation for six traits. Mean values for seed release heights (minimum and maximum) and dispersule weight were significantly lower in species found in the dung, whilst dung species had significantly greater numbers of seeds per shoot, inferred Ellenberg nitrogen values and seed bank persistence. Conclusion: Year-round free-roaming grazing has the potential to make a considerable contribution to the long-range dispersal of species growing in temperate fen habitats, and is likely to complement alternative dispersal strategies. However, germination and establishment of species post-dispersal fate will be governed by a wide range of environmental conditions.