DOI: 10.5061/dryad.m37pvmd8s
title: Data from: Trophic niche variation in springtails across soil depth

description: Soil invertebrates move vertically to forage and avoid environmental
 stress. However, how invertebrates change their diet with depth is poorly
 understood, limiting our understanding of the trophic plasticity of soil
 invertebrates. Trophic consistency may be due to the existence of similar
 trophic niches at the microscale across soil layers (‘micro-scale feeding
 hypothesis’), but also due to feeding at certain depth despite moving
 between layers. To examine these alternatives, we conducted a microcosm
 experiment incubating springtails (Ceratophysella denticulata) in six
 separate forest soil layers (L, F/H, 0–3, 3–6, 6–9 and 9–12 cm depth of
 the mineral soil) and analyzed changes in Collembola stable isotope ratios
 (13C/12C, 15N/14N). As expected, 13C/12C and 15N/14N ratios in litter and
 soil organic matter increased with depth, whereas 13C/12C ratios of
 Collembola did not significantly differ across layers suggesting
 consistent basal resource use supporting the micro-scale feeding
 hypothesis. By contrast, 15N/14N ratios of Collembola increased with
 depth, following the trend of organic matter from litter to 0–3 cm soil,
 but not beyond. These results suggest that carbon and nitrogen nutrition
 of springtails is decoupled, and that the use of litter to calibrate
 15N/14N values for estimating trophic positions of soil animals requires
 careful interpretation. Our results highlight the importance of soil depth
 as determinant of trophic positions of soil animals and point to principal
 differences in nitrogen resource acquisition between litter and soil in
 soil animal decomposers. Overall, the vertical structure of soils and
 microscale view of trophic interactions need closer attention to better
 understand niche differentiation and resource acquisition of soil animals.
description: Soil cores (ø 5 cm) were taken in a beech forest in Dassel on
 October 18, 2022. Soils were separated into six depths: L-layer (litter;
 depth ~ 3 cm), F/H-layer (3 cm, fragmented litter and humus material), 0–3
 cm, 3–6 cm, 6–9 cm, and 9–12 cm soil depth
 (A<sub>h</sub>-layer). The soil texture was silt loam (clay
 21%, silt 53%, and sand 26%). Samples were stored at -20°C for two weeks,
 and then freeze-dried for defaunation. Water was added to adjust moisture
 content to the level at sampling. Soil animals were inoculated by using
 1-6-day old juveniles of <em>Ceratophysella denticulata</em>.
 After incubating for four weeks in 20°C for 4 weeks, bulk stable isotopes
 of litter and soil were measured after drying at 60°C and grinding samples
 in a ball mill (Retsch, MM200). Collembolans were extracted from the
 litter/soil using heat, kept in 50% diethylene glycol, and then
 transferred into 70% ethanol for storage. As the available dry weight of
 collembolans was smaller than 100 µg, the bulk stable isotope ratios of
 <sup>13</sup>C/<sup>12</sup>C and
 <sup>15</sup>N/<sup>14</sup>N were measured using
 a modified setup adopted for small sample size (Langel and Dyckmans,
 2014). Atmospheric nitrogen and Vienna PeeDee belemnite were used as
 primary standards. Acetanilide
 (C<sub>8</sub>H<sub>9</sub>NO, Merck, Darmstadt)
 was used as an internal standard. Natural variation in stable isotope
 ratios of carbon and nitrogen was expressed as δX (‰) =
 (R<sub>sample</sub> – R<sub>standard</sub>) /
 (R<sub>standard</sub>) x 1000, with R the ratio between the
 heavy and light isotopes
 (<sup>13</sup>C/<sup>12</sup>C and
 <sup>15</sup>N/<sup>14</sup>N).
description: # Data from: Trophic niches of springtail across soil depth in a lab
 microcosm experiment
 [https://doi.org/10.5061/dryad.m37pvmd8s](https://doi.org/10.5061/dryad.m37pvmd8s) This dataset includes results of a lab experiment testing the effects of depth on trophic niche of soil collembolans using bulk stable isotope analysis. ## Description of the data and file structure The dataset "data.for.Dryad_copy.csv" includes C, N, and stable isotopic C and N ratios of soil from six layers, as well as isotopic ratios of collembolans that have incubated in each separated soil layers. * Sample: unique identifier of each microcosm * id_block: each of the five replicate block * id_depth: each of the six depths: litter, F/H, 0-3, 3-6, 6-9, 9-12 (coded in A-F) * animal_nr: number of collembolan individuals used for stable isotope analysis * Weight_animal_mg: animal dry biomass (mg) used for bulk stable isotope analysis * delta_15N.animal: delta 15N of Collembola * delta_13C.animal: delta 13C of Collembola