Consumption rates and food selectivity data from Alpine soil macro-decomposers fed on a wide range of litter types in a microcosm cafeteria experiment

Here we present data from food selectivity experiments of four abundant Alpine decomposer species (two earthworms and two millipedes). We conducted cafeteria feeding experiments in microcosms in a climate chamber offering to the specimens three representative alpine litter types of differing in litter quality (i.e. dwarf shrub, grass, and forb) as single litters and mixtures. We monitored parameters such as biomass, consumption rates (absolute and relative), and calculated from the latter food selectivity indices to investigate preferences. The tested specimens showed a high intra- and interspecific variability as they fed on all offered litter types and qualities. The epi-endogeic earthworm Lumbricus rubellus (Hoffmeister, 1843), dominant in alpine pastureland, had highest mean consumption rates (34.7 ± 24.7 mg), while Dendrobaena octaedra (Savigny, 1826), a strictly epigeic earthworm, showed considerably lower consumption rates. The tested millipedes showed similar consumption patterns, with Cylindroiulus fulviceps (Latzel, 1884) being less active than C. meinerti (Verhoeff, 1891). We found several cases where litter mixtures were preferred over single litters, including higher consumption rates of low-quality dwarf shrub litter by D. octaedra and C. meinerti when mixed with high-quality litter. Nowadays, alpine pastureland are threatened mainly by abandonment which reverted to shrubland. Our results helped us to understand that alpine soil macro-decomposer such as earthworms and millipedes are generalists feeding on a wide range of litter qualities, allowing them, in theory, to better adapt to the new evolving litter resources that become available when pastures are abandoned.