Impact of nitrogen deposition on forest and lake food webs in nitrogen‐limited environments

Abstract

Increased reactive nitrogen (Nr ) deposition has raised the amount of N available to organisms and has greatly altered the transfer of energy through food webs, with major consequences for trophic dynamics. The aim of this review was to: (i) clarify the direct and indirect effects of Nr deposition on forest and lake food webs in N-limited biomes, (ii) compare and contrast how aquatic and terrestrial systems respond to increased Nr deposition, and (iii) identify how the nutrient pathways within and between ecosystems change in response to Nr deposition. We present that Nr deposition releases primary producers from N limitation in both forest and lake ecosystems and raises plants' N content which in turn benefits herbivores with high N requirements. Such trophic effects are coupled with a general decrease in biodiversity caused by different N-use efficiencies; slow-growing species with low rates of N turnover are replaced by fast-growing species with high rates of N turnover. In contrast, Nr deposition diminishes below-ground production in forests, due to a range of mechanisms that reduce microbial biomass, and decreases lake benthic productivity by switching herbivore growth from N to phosphorus (P) limitation, and by intensifying P limitation of benthic fish. The flow of nutrients between ecosystems is expected to change with increasing Nr deposition. Due to higher litter production and more intense precipitation, more terrestrial matter will enter lakes. This will benefit bacteria and will in turn boost the microbial food web. Additionally, Nr deposition promotes emergent insects, which subsidize the terrestrial food web as prey for insectivores or by dying and decomposing on land. So far, most studies have examined Nr -deposition effects on the food web base, whereas our review highlights that changes at the base of food webs substantially impact higher trophic levels and therefore food web structure and functioning.

Representing sub-grid scale variations in nitrogen deposition associated with land use in a global Earth System Model: implications for present and future nitrogen deposition fluxes over North America

“…In the US, oxidized N deposition is 35 projected to decrease as a result of effective controls on NO emissions, but deposition of reduced N (NH x ≡ NH 3 +NH + 4 ), primarily from agricultural emissions of NH 3 , is projected to remain elevated or even increase (Dentener et al, 2006;Ellis et al, 2013;Paulot et al, 2013;Lamarque et al, 2013;Li et al, 2016). This raises concerns of irreversible damages to sensitive biomes (Pardo et al, 2011;Meunier et al, 2016;Grizzetti, 2011;Dise, 2011), such as high-elevation lakes (Wolfe et al, 2003; 40 Baron et al, 2012;Lepori and Keck, 2012), and organisms (e.g., lichen (Johansson et al, 2012)). …”

Genotypic variability in Populus tremula L. affects how anthropogenic nitrogen enrichment influences litter decomposition

“…Scandinavia) increasingly apply fertilizers to forests (Lindkvist et al 2011). These two types of anthropogenic N inputs can have numerous consequences in N-limited boreal forests, such as increase net primary productivity and aboveground carbon (C) stocks (De Vries et al 2006;Gundale et al 2014), alter species composition and community structure (Bobbink et al 1998 and references therein; Nordin et al 1998;Strengbom et al 2003;Nordin et al 2006), and reduce diversity (Nordin et al 2005;Bobbink et al 2010;Meunier et al 2016). While impacts of N enrichment on aboveground properties are well studied, relatively little is known about how soil processes respond to N enrichment (but see e.g.…”

Stimulation of long-term ammonium nitrogen deposition on methanogenesis by Methanocellaceae in a coastal wetland

“…Growing evidence shows that increased nitrogen deposition seriously affect the health and security of ecosystems (Ban et al, 2016;Meunier et al, 2016). For the YRD region, a sensitive coastal wetland ecosystem, the effects of ammonium and nitrate nitrogen deposition on methane emission were explored in this study.…”