Influence of millipedes on litter decomposition, N mineralization, and microbial communities in a coastal forest in British Columbia, Canada

Laboratory experiments were conducted with the millipede Harpaphe haydenian a haydeniana Wood (Polydesmida: Xystodesmidae) to determine (i) its litter feeding preferences, (ii) rates of leaf litter consumption, (iii) feeding e ffects on available nitrogen, and (iv) functional microbial diversity. The millipede exhibited a preference for Douglas-fir (Pseudotsuga menziesii (Mi rb.) France) and, to a lesser extent, Sitka spruce (Picea sitchensis (Bong. ) Carriere) litter compared with western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don) litter when giv en a choice. When only one litter type was provided, millipedes consumed co nsiderably more western redcedar than Douglas-fir, Sitka spruce, or western hemlock. Among the six broadleaf species tested, paper birch (Betula papyr ifera Marsh.), bigleaf maple (Acer macrophyllum Pursh), vine maple (Acer ci rcinatum Pursh), and red alder (Alnus rubra Bong.) were consumed at much hi gher rates than swordfern (Polystichum munitum (Kaulf.) Presl.) or salal (G aultheria shallon Pursh). Daily rates of conifer litter consumption ranged between 10 and 20% of the millipede's fresh biomass and may translate to 36 % of the annual litter fall. Our results suggest that trans formation of co nifer litter into millipede frass can increase rates of litter decompositio n and N mineralization, as well as influence microbial activity and diversi ty in coastal forests.