Do litter-feeding macroarthropods disrupt cascading effects of land use on microbial decomposer activity?

Abstract

Plant traits are known to control litter decomposition rates through afterlife effects on litter quality.Land-use practices that modify plant traits, e.g. livestock grazing and soil fertilization, also have cascading effects on litter decomposition. However, almost all studies of these afterlife effects ignored the role of soil detritivores in the decomposition processes. We explored how the feeding activities of a macroarthropod modify microbial activity in leaf litter. Dead leaves from two grassland species, Bromopsis erecta and Potentilla verna, were collected in fertilized or unfertilized grazed plots and fertilized or unfertilized ungrazed plots. We determined how intraspecific variation in litter quality in response to sheep grazing and soil fertilization (i) influences the consumption and assimilation of leaf litter by the millipede Glomeris marginata, and (ii) affects the activity of microbial decomposers, assessed by substrate-induced respiration (SIR), in leaf litter before consumption and in faecal pellets and litter remains processed by Glomeris under all treatments. In the absence of millipedes, microbial activity was significantly higher in leaf litter from fertilized plots. Glomeris consumed larger amounts of leaf litter from fertilized grazed plots, owing to increased consumption of the otherwise poorly palatable Bromopsis, and produced larger amounts of faecal pellets when fed on this food. However, irrespective of the food consumed, SIR in faecal pellets was found to be similar in all treatments. Moreover, SIR in litter remains unconsumed at the end of the experiment was reduced to low and similar levels in all treatments. Overall, homogenization of microbial activity by Glomeris suppressed differences in SIR between leaf litter from fertilized and unfertilized plots, in both Bromopsis and Potentilla. Our results suggest that studies that assess afterlife effects of plant traits on decomposition using methods that exclude soil macrofauna may prove inadequate in ecosystems with abundant populations of detritivores.

Leaf litter morphological traits, invertebrate body mass and phylogenetic affiliation explain the feeding and feces properties of saprophagous macroarthropods

“…The negative relationship between body mass and mass-specific consumption and excretion rate is in line with the metabolic theory [25,27] and with several studies done on the same or closely related species, namely G. marginata, C. caerulocinctus, and Ommatoiulus rutilans (C.L. Koch, 1847) feeding on grass litter [30,56] and G. marginata, G. hexasticha, C. caerulocinctus, and Porcellio scaber feeding on Alnus glutinosa litter [28]. Interestingly, diet diversity was positively related to organism body mass.…”

Multidimensional stoichiometric mismatch explains differences in detritivore biomass across three forest types

“…Earthworms perform complex feeding strategies (Curry & Schmidt, 2007) and selective ingestion process, which likely enable them to maintain consistent body C:N ratio (Abail & Whalen, 2018). Millipedes were found to preferentially feed on N‐rich litter and dead leaves with high microbial activity (Coq et al, 2020; Frainer et al, 2016; Loranger‐Merciris et al, 2008). The high TSR values of N and P indicate that detritivores may alleviate their N and/or P deficit by compensatory feeding on micro‐organisms with generally lower C:P and C:N ratios than leaf litter (Danger & Chauvet, 2013; Makino et al, 2003).…”

Soil macrofauna in Brazil: a bibliometric review and state of the art

“…Several factors can affect the abundance and distribution of soil zoology, including the management and occupation of the area by anthropic activities, mainly by reducing organic matter and causing disturbances in the environment (Huerta & Van Der Wal 2012). However, other factors must be considered, such as vegetation, food availability, climate, topography, area history, temperature and soil type (Machado et al 2015, Borges et al 2019, Coq et al 2020, Wang et al 2020. In recent years, several studies have studied the edaphic macrofauna as a bioindicator of soil quality, since they are more sensitive to environmental changes (Paudel et al 2012, Rousseau et al 2013, Pereira et al 2017, Araujo et al 2018, Morais Sobrinho et al 2019, Schubert et al 2019, Velasquez & Lavelle 2019, Valani et al 2020.…”