Endozoochory varies with ecological scale and context

• Published in: Ecography
• Main Authors: Anne Bråthen, Kari, T. González, Victoria, Iversen, Marianne, Killengreen, Siw, T. Ravolainen, Virve, A. Ims, Rolf, G. Yoccoz, Nigel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Norway; Finnmark; Northern Norway
• Online Access: http://dx.doi.org/10.1111/j.0906-7590.2001.04976.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.0906-7590.2001.04976.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.0906-7590.2001.04976.x

Several studies on endozoochory have established large herbivores as important for seed dispersal, yet no studies have evaluated how endozoochory is dependent on ecological scale and context. Here we address effects of reindeer density on endozoochory in a hierarchical, multi‐scale study, encompassing several ecological contexts. We found reindeer density effects on endozoochory to vary with spatial scale. Higher reindeer densities at the level of landscape areas, as indexed through faeces abundance, were related to both less species and lower abundance of emerging plants from faeces. In contrast, there was no effect of higher reindeer densities at the level of herding districts (i.e. large scale assemblages of landscapes). Lack of consistency between scales reflects ecological hierarchy, indicating that reindeer density effects on endozoochory best matches at the scale of landscapes. Pasture seed plant composition was only partly an important ecological factor. That is, ericoid species, the dominating plants in the pastures, were also the most abundant seed plants found to emerge from the faeces. However, most herbaceous seed plant species in the pastures were not emerging from the faeces and the few that emerged were positively related to the site fertility and altitude of the pasture. Studies addressing endozoochory of ruminants are typically concerned with seed plants, whereas in this study we also found indications of that diaspores of ferns are viable after passing the digestive tract of large herbivores. Vascular spore plants were even more abundant in the faeces than were vascular seed plants. Results from this study demonstrate that reindeer may counteract a potentially negative impact on seed limitation from their grazing by returning viable seeds in their faeces. However, in Finnmark, northern Norway, this effect is only marginal, relates only to a very few species and individuals and shows ecological scale and context dependence.