Several studies have reported a positive relationship between species richness and ecosystem functioning. However, if much of a particular ecosystem function is performed by one species (i.e. a functionally dominant species) and this species is also a competitive dominant that excludes other taxa from a habitat, then it is possible to obtain a negative relationship between richness and ecosystem functioning. Results of a leaf pack breakdown experiment in a small stream suggested that the caddisfly Pycnopsyche gentilis, a common detritivorous insect in North American headwater streams, was both a functional and competitive dominant. In a second experiment we compared the effect of Pycnopsyche on leaf breakdown to that of other detritivore taxa by enclosing them with leaf packs in a section of headwater stream in which they were uncommon (Pycnopsyche transplant experiment). Final leaf pack mass was significantly lower in the Pycnopsyche enclosure treatment; leaves exposed to a greater diversity of detritivores displayed little reduction in leaf mass. These results demonstrated that Pycnopsyche was a functionally dominant detritivore. In a third experiment (Pycnopsyche density experiment) we found that Pycnopsyche was also a competitively dominant species. Leaf packs and large Pycnopsyche were placed in enclosures that were permeable to the majority of other detritivores but not Pycnopsyche. Leaf mass lost increased with increasing Pycnopsyche density. Leaf packs exposed to Pycnopsyche, however, contained fewer detritivore taxa which suggested that Pycnopsyche was also a competitive dominant. There was a negative relationship between three measures of diversity and leaf litter breakdown in the Pycnopsyche density experiment. Experiments conducted in natural communities that incorporate important species interactions may produce diversity‐ecosystem function relationships other than the positive ones that are commonly reported.

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Information on the hibernation ecology of Bog Turtles (Glyptemys muhlenbergii) throughout their range is limited. Few studies have identified suitable hibernacula or documented behavior during hibernation including site fidelity, communal hibernation, and entrance and emergence times. Our study presents long-term documentation of hibernation in a relatively understudied portion of the species' range. From fall 2005 to spring 2014, we observed the hibernation of 13 marked turtles in an isolated population located in the southern Appalachian Mountains of North Carolina. During the course of our study, nine turtles were radio-tracked for 1-5 y. Turtles spent about six months in hibernation, usually entering the hibernaculum in late September into October and emerging in mid-April. Using radiotelemetry, we identified 11 hibernacula of three types: root masses of trees/shrubs, root masses of cinnamon ferns (Osmundastrum cinnamomeum), and sedge (Carex stricta) clumps. Site fidelity and communal use were common in our study. Ten turtles located in multiple winters repeated their use of a hibernaculum in at least two of those winters. Twelve turtles hibernated communally in at least one year. No mortality was observed at the hibernacula. Our study demonstrates the importance of root masses with soft deep substrate for survival in long, harsh winter conditions. Bog Turtles spend about half of every year, and therefore half of their lives, in hibernation, making the identification and protection of suitable habitat for hibernation imperative for successful management to ensure the long-term viability of the species.