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Grazing and resource availability control soil nematode body size and abundance–mass relationship in semi‐arid grassland
Author(s) -
Andriuzzi Walter S.,
Wall Diana H.
Publication year - 2018
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/1365-2656.12858
Subject(s) - soil texture , grassland , herbivore , ecology , biomass (ecology) , grazing , ecosystem , abundance (ecology) , biology , soil biology , abiotic component , agronomy , arid , soil water , environmental science
Body size is a central functional trait in ecological communities. Despite recognition of the importance of above ground–below ground interactions, effects of above‐ground herbivores on size and abundance–size relationships in soil fauna are almost uncharted. Depending on climate and soil properties, herbivores may increase basal resources of soil food webs, or reduce pore space, mechanisms expected to have contrasting effects on soil animal body size. We investigated how body size and shape of soil nematodes responded to mammalian grazers in three semi‐arid grassland sites, along a gradient of soil texture and organic matter ( OM ) in a long‐term herbivore removal study. We analysed nematode mass, length, diameter, body size distribution and biomass distribution. We formulated two mechanistic hypotheses to assess whether resource availability or pore space was the dominant abiotic control and modulated the effects of grazing. In ungrazed soils, average and maximum nematode size, as well as abundance and biomass of large nematodes, were greater in the high‐ OM than in the low‐ OM soil, and intermediate in the medium‐ OM soil. Grazing promoted larger sizes in the low‐ OM soil, where it had been shown to increase OM and microbial biomass, and led to more homogeneous average size and body size distribution across sites. The results support the hypothesis that nematode size was controlled by basal resource availability rather than by pore space. However, body shape might have been constrained by small pores in the fine‐texture, high‐ OM soil, where nematodes were more elongated. Grazing may facilitate larger sizes in soil nematode communities by boosting basal resources where these are limiting, with important implications for estimations of nematode biomass and contribution to carbon and nutrient cycling. These findings contribute to the insofar‐limited mechanistic understanding of how herbivores can shape functional traits of soil fauna and demonstrate that animals at one trophic level may control patterns in body size and abundance–size relationships in other trophic levels without a direct predator prey or competitive linkage between them.