Data for the article: Trophic positions of soil microarthropods in forests increase with elevation, but energy channels remain unchanged

Mountain forests are at risk as the consequences of climate change will
likely lead to altered tree species boundaries. Characterizing food webs
along elevation gradients in primary forests may help to predict the
potential consequences of such changes, for example with regard to the
decomposition of dead organic matter. Here, for the first time, we studied
trophic variations in two species‐rich microarthropod taxa, Collembola and
Oribatida, along an elevation gradient of primary forest at Changbai
Mountain, China. Samples were taken at seven elevations of 150‐m
elevational difference between 800 and 1700 m. At each elevation,
Collembola and Oribatida were extracted from litter samples of eight
subplots. We applied three state‐of‐the‐art methods to elucidate trophic
positions and basal resource use at community level: Bulk stable isotope
analysis of nitrogen (Δ15Nbulk) and carbon (Δ13Cbulk), compound‐specific
stable isotope analysis of amino acids (CSIA‐AA), and dietary routing of
neutral lipid fatty acids (NLFAs). Trophic positions calculated using
Δ15Nbulk and CSIA‐AA (TPCSIA) in both taxa increased similarly with
elevation by about half and one third of a trophic position, respectively.
Stable isotope mixing models and linear discriminant analysis
bootstrapping using δ13C of essential amino acids indicated fungi as the
most important resource at all elevations for both taxa. Also, proportions
of marker NLFAs changed little across elevations in both taxa; overall
high proportions of linoleic acid indicated high fungal contributions, but
in Collembola the contribution of bacterial markers was generally higher
than in Oribatida. Δ13Cbulk did not respond linearly to the elevation
gradient; however, changes in elevation differed between Collembola and
Oribatida. A strong linear relationship between δ15N of phenylalanine and
δ15N of litter indicated litter as the basis of energy channels in both
taxa. Overall, food web functioning likely changes with changing forest
types along elevation gradients, with microarthropods switching from
feeding closer to the base of the food web at lower elevations to feeding
at higher trophic levels at higher elevations, potentially compromising
their role in litter decomposition and nutrient cycling.