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Sammanfattning

Trophic cascades in which predators regulate densities of organisms at lower trophic levels are important drivers of population dynamics, but effects of trophic cascades on ecosystem-level fluxes and processes, and the conditions under which top-down control is important, remain unresolved. We manipulated the structure of a food web in boreal feather mosses and found that moss-inhabiting microfauna exerted top-down control of N-2-fixation by moss-associated cyanobacteria. However, the presence of higher trophic levels alleviated this top-down control, likely through feeding on bacterivorous microfauna. These effects of food-web structure on cyanobacterial N-2-fixation were dependent on global change factors and strongly suppressed under N fertilisation. Our findings illustrate how food web interactions and trophic cascades can regulate N cycling in boreal ecosystems, where carbon uptake is generally strongly N-limited, and shifting trophic control of N cycling under global change is therefore likely to impact ecosystem functioning.

Nyckelord

Boreal forest; bottom-up control; feather moss; food webs; nitrogen cycling; nitrogen deposition; Pleurozium schreberi; precipitation; top-down control; trophic interactions

Publicerad i

Ecology Letters
2016, volym: 19, nummer: 8, sidor: 967-976
Utgivare: WILEY-BLACKWELL

SLU författare

Globala målen (SDG)

SDG15 Ekosystem och biologisk mångfald

UKÄ forskningsämne

Skogsvetenskap
Jordbruksvetenskap

Publikationens identifierare

  • DOI: https://doi.org/10.1111/ele.12635

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/77113