**4. Discussion**

In contrast to our predictions, we found no detectable below-ground impacts of lynx-killed roe deer carcasses. Our results differ from other published studies, such as on muskox (*Ovibos moschatus*) carcasses in the arctic [19], moose in Isle Royale [18], American bison (*Bison bison*) in prairies [21] and kangaroos (*Macropus giganteus*) in Eucalyptus woodland [42], that detected an effect of carcass decomposition on soil and vegetation nutrients concentration [18–21,25], begging the question, what differs in our study system? A number of potential explanations present themselves, but all must be seen in light of the fact that only the liquids resulting from the invertebrate maggot activity and microbial decomposition leach into the soil [25].

First, the effect of roe deer carcasses on soil and vegetation is expected to vary depending on how much of its prey is consumed by the lynx and how much the remnants are consumed or dispersed by scavengers [24,26]. Since roe deer are quite small ungulates, with a mean adult body mass of 20–30 kg [43], and lynx tend to consume most of the consumable meat and organs over the course of 1 to 5 days after a kill [44,45], the amount of nutrients available for leaking into the soil is rather limited. Moreover, vertebrate scavengers tend to arrive within a few hours or days and rapidly remove the rest

of the meat/organs [30]. On our sample of kills, more than 90% of the meat was removed from almost all carcasses when we first examined the kill sites several days after the lynx had abandoned the kills.

This issue is enhanced by the fact that a good proportion of the kills (6 out of 18) happened in the winter season, when insects are inactive and decomposition rates are lower—thus giving even more time for scavengers to remove meat and disperse body parts. Combined, these issues point to a need to consider the methodology when comparing studies. Our use of real predator-killed and consumed carcasses contrasts to most other studies that simulate this effect with whole carcasses and which often exclude scavengers through fencing [42]. This difference needs to be considered when generalizing between carrion derived from different sources and between studies with different methodologies.

Second, another reason for not finding an effect could lie with the time interval between roe deer death and carcass sampling. In this study, similarly to a study conducted on much larger European bison (*Bison bonasus*) carcasses in a temperate forest [20], we collected samples two or more years after death. For European bison, we were able to detect an effect on pH and calcium that lasted up to seven years after the death of the animal. However, the turnover of nitrate in soil was very fast (up to one year) even though bison are significantly larger than roe deer (average body mass across sexes is over 500 kg [46]) and we might expect the impact on soil and vegetation to last longer. In a tallgrass prairie system, the nutrients released from American bison carcasses affected plant species composition for at least five years after bison death, thus increasing grassland heterogeneity [21]. Other studies on kangaroo carcasses (ca 30 kg) have also shown that nutrient effects can still be evident after five years [42].

Thirdly, the lack of elevation in nutrients in the plants that we sampled close to a carcass could be because sampled *V. myrtillus* belonged to the same clone and therefore to various degree exchange resources underground between ramets or store nutrients in storage organs [47–49], thus potentially diluting the spatial impact of the nutrient pulse. It is, however, unlikely that the controls (20 m) should belong to the same clone as the plants close to the carcass. A final consideration concerns our sample sizes. Although not very large, they are very much within the range of sample sizes used in similar studies that have found significant results. Therefore, although we may not be able to reject the existence of any effects of the carcasses, we feel comfortable to say that if they exist, they are much more subtle than other studies have shown for larger carcasses in different ecosystems.

Our findings underline the complexity, diversity and context dependence of ecological processes, as well as illuminating the dangers of over-generalizations from case studies to universal principles. Although there is a growing list of case studies documenting a diversity of large predator-mediated trophic cascades in terrestrial as well as aquatic ecosystems, there are also multiple reviews that underline that there are also many exceptions [6,50] and calls for caution [51]. Genuine scientific progress in this value-laden field will only be possible by building up a solid body of positive and negative results embracing the diversity of contexts (both ecological and anthropogenic) in which predation occurs in the Anthropocene [52,53].

**Author Contributions:** Conceptualization, I.J.M.T. and J.D.C.L.; methodology, C.M., C.S., I.J.M.T. and J.D.C.L.; formal analysis, C.M. and I.J.M.T.; writing—original draft preparation, C.M., C.S., I.J.M.T. and J.D.C.L.; writing—review and editing, C.M., C.S., I.J.M.T. and J.D.C.L.; funding acquisition, J.D.C.L. and I.J.M.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was conducted as part of the Scandlynx project which is mainly funded by the Norwegian Directorate for Nature Management, the Research Council of Norway (projects 134242, 165814, 183176, 212919, 251112), the county governor's office of Viken county, and the Norwegian Institute for Nature Research. IJMT was also funded by two individual grants from the Research Council of Norway's cultural agreement program with the Netherlands (2002-03 and 2003-04) and two grants from the Schure-Beijerinck-Popping fund. CM was funded by a postdoctoral grant at the Norwegian University for Science and Technology, Trondheim.

**Acknowledgments:** The authors are grateful to all the landowners who permitted our activity on their land, and to Martin Hauger and Øistein Høgseth for assistance in the field. The Ski municipality assisted by providing carcasses and the Norwegian University for Life Sciences provided drying ovens for vegetation samples.

**Conflicts of Interest:** The authors declare no conflict of interest.
