Incorporation of Plant Carbon Into the Soil Animal Food Web of an Arable System

Abstract

We used stable isotopes to examine the incorporation of plant carbon into the belowground food web of an agricultural system. Plots were established and planted with maize (Zea mays) in a rye field (Secale cereale) near Göttingen (northern Germany) in May 1999. In October 1999, April 2000, and October 2000, meso- and macrofauna and maize and rye litter were collected in each plot and analyzed for 13C and 15N content. 15N signatures suggested that the soil animal species analyzed span three trophic levels with the trophic position of species varying little in time. The species investigated formed a continuum from primary to secondary decomposers to predators. On average, predator species differed from primary and secondary decomposers by 3.9 sigma15N suggesting that they fed on a mixed diet of both decomposer groups. The combined analysis of 13C and 15N signatures allowed us to identify links between prey and consumer species. In October 1999, shortly after maize residues had been incorporated into the plots, maize-born carbon was present in each of the animal species investigated, including top predators. The incorporation of maize carbon into the belowground food web increased during the following 12 months but the concentration of maize-born carbon never exceeded 50% in any of the species. Furthermore, the ranks of the incorporation of maize-born carbon of the species changed little. The results suggest that the belowground food web relies heavily on carbon originating from plant residues from before the recent two growing seasons. In most species the amount of maize-born carbon increased continuously; however, in some species it decreased during winter, suggesting that these species switched to a diet based more on C3 plants during winter, or predominantly metabolized carbon incorporated during the last growing season. The study documents that the combined analysis of 13C and 15N signatures in soil invertebrate species, after replacement of C3 by C4 plants, is a powerful tool to better understand the structure of the belowground food web and the flux of carbon through it.

Roots rather than shoot residues drive soil arthropod communities of arable fields

“…Moreover, planting of C4 plants at locations with C3 plant history (or vice versa) allows tracing the incorporation of root-derived resources into soil food webs. Based on this approach, the turnover of soil C (Arrouays et al 1995), the use of C resources by earthworms (Spain et al 1990;Martin et al 1992) and the utilisation of C resources by soil arthropods in arable fields has been investigated (Albers et al 2006;von Berg et al 2010), but to the best of our knowledge this is the first study quantifying the contribution of (C4-derived) plant residue resources of below-and aboveground origin to soil arthropod nutrition.…”

Fire affects root decomposition, soil food web structure, and carbon flow in tallgrass prairie

“…This technique has been used to study plant-C utilization by microbial communities in soils by examining 13 C incorporation into microbial phospholipid fatty acids (PLFAs; e.g., Denef et al, 2009;Rubino et al, 2010;Kohl et al, 2015;Soong et al, 2016). Also, natural abundances of 13 C and 15 N have been useful for studying structures of soil faunal communities (e.g., collembolans, earthworms, enchytraeids, arthropods, gastropods, and nematodes; Chahartaghi et al, 2005;Albers et al, 2006;Goncharov et al, 2014;Crotty et al, 2014;Kudrin et al, 2015). Furthermore, C flow though soil faunal trophic groups can be traced and quantified using 13 C in labeling experiments (Albers et al, 2006;Pollierer et al, 2007;Elfstrand et al, 2008;Ostle et al, 2007;D'Annibale et al, 2015;Gilbert et al, 2014).…”

“…Also, natural abundances of 13 C and 15 N have been useful for studying structures of soil faunal communities (e.g., collembolans, earthworms, enchytraeids, arthropods, gastropods, and nematodes; Chahartaghi et al, 2005;Albers et al, 2006;Goncharov et al, 2014;Crotty et al, 2014;Kudrin et al, 2015). Furthermore, C flow though soil faunal trophic groups can be traced and quantified using 13 C in labeling experiments (Albers et al, 2006;Pollierer et al, 2007;Elfstrand et al, 2008;Ostle et al, 2007;D'Annibale et al, 2015;Gilbert et al, 2014). However, root turnover and aboveground litter inputs are the main basis for soil faunal trophic groups in the chiefly detrital-based grassland soil food webs (Ostle et al, 2007), and these previous studies often focus only on C from recent photosynthate, ignore some of the most abundant soil fauna groups (e.g., nematodes), and do not consider how disturbances, such as fire, might affect C pathways belowground.…”

Evaluating the importance of trophobiosis in a Mediterranean ant community: a stable isotope analysis

“…To disentangle the food web relations between ants, associated arthropods, and host plants, we analyzed stable isotope ratios ( 13 C/ 12 C, 15 N/ 14 N), which has been proven as powerful tool in the analysis of terrestrial and aquatic food webs (Blüthgen et al, 2003;Schmidt et al, 2004;Albers et al, 2006;Hood-Nowotny and Knols, 2007;Tillberg et al, 2010). Typically, animals become isotopically enriched relative to their diet by 0-1 % for carbon (DeNiro and Epstein, 1978;Michener and Schell, 1994) and 3-5 % for nitrogen (DeNiro and Epstein, 1981;Minagawa and Wada, 1984;Post, 2002), which allows a categorization of trophic levels (Newton, 2010).…”