Inter‐annual changes in detritus‐based food chains can enhance plant growth response to elevated atmospheric CO₂

Abstract

Elevated atmospheric CO2 generally enhances plant growth, but the magnitude of the effects depend, in part, on nutrient availability and plant photosynthetic pathway. Due to their pivotal role in nutrient cycling, changes in abundance of detritivores could influence the effects of elevated atmospheric CO2 on essential ecosystem processes, such as decomposition and primary production. We conducted a field survey and a microcosm experiment to test the influence of changes in detritus-based food chains on litter mass loss and plant growth response to elevated atmospheric CO2 using two wetland plants: a C3 sedge (Scirpus olneyi) and a C4 grass (Spartina patens). Our field study revealed that organism's sensitivity to climate increased with trophic level resulting in strong inter-annual variation in detritus-based food chain length. Our microcosm experiment demonstrated that increased detritivore abundance could not only enhance decomposition rates, but also enhance plant growth of S. olneyi in elevated atmospheric CO2 conditions. In contrast, we found no evidence that changes in the detritus-based food chains influenced the growth of S. patens. Considered together, these results emphasize the importance of approaches that unite traditionally subdivided food web compartments and plant physiological processes to understand inter-annual variation in plant production response to elevated atmospheric CO2.

Biodiversity mediates the effects of stressors but not nutrients on litter decomposition

“…Invertebrate decomposers are particularly sensitive to the impacts of metals and pesticides 38–40,48 . This is consistent with the general expectation that larger organisms are more sensitive to environmental change due to longer generation time, higher energetic demands and lower population densities 21,64,65 . These different sensitivities between groups of decomposers could imply that the biodiversity-mediated effects of stressors on decomposition are more strongly linked to shifts in invertebrates than microbes such as reported in a previous review 48 .…”

“…The selective effects of environmental change emerge because different organisms differ in their response to environmental change. For example, larger organisms and predators are often more negatively affected than smaller organisms at lower trophic levels 8,20,21 . In addition, several variables that are not directly related to biodiversity control ecosystem functions (e.g.…”

Thinning‐induced canopy opening exerted a specific effect on soil nematode community

“…The high sensitivity of predators and omnivores in comparison with microbivorous nematodes is in line with the proposal that higher trophic levels are more vulnerable to environmental change than lower trophic levels (Cesarz et al, 2017;Hines, Eisenhauer, & Drake, 2015;Voigt, Perner, & Hefin Jones, 2007). One likely reason is that soil biota in the higher trophic level needs longer time to accommodate changes in habitat factors than that in lower trophic level due to the life strategy (Ferris et al, 2001;Valladares, Cagnolo, & Salvo, 2012); another possible explanation may be the distinct linkages among guilds in the soil food webs, because different trophic levels participate in differential interactions, including competition, predation, and mutualistic symbiosis.…”

Soil‐mediated effects of global change on plant communities depend on plant growth form

“…), and it can also influence the composition and activity of soil fauna (Hines et al. , Mueller et al. , McKluney ).…”

“…The influences of elevated CO 2 on nutrient availability for plant uptake may be partially offset by climate warming, which can enhance N-mineralization (Bai et al 2013). However, warming also induces soil dessication, which can determine whether soil microbial activity results in N-mineralization or N-immobilization , and it can also influence the composition and activity of soil fauna (Hines et al 2015, Mueller et al 2016a, McKluney 2017. Notably, soil antagonists and mutualists, which often depend upon abundance of their host plant species (Maron et al 2011, Bever et al 2015, show mixed responses to climate (Garrett et al 2006, Elad and Pertot 2014, Classen et al 2015.…”