Mycorrhizal responses to nitrogen fertilization in boreal ecosystems: potential consequences for soil carbon storage

By K. Treseder, Katie M. Turner, Michelle C. Mack. 2007

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Mycorrhizal fungi can contribute to soil carbon sequestration by immobilizing carbon in living fungal tissues and by producing recalcitrant compounds that remain in the soil following fungal senescence. We hypothesized that nitrogen (N) fertilization would decrease these carbon stocks, because plants should reduce investment of carbon in mycorrhizal fungi when N availability is high. We measured the abundance of two major groups of mycorrhizal fungi, arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi, in the top 10 cm of soil in control and N‐fertilized plots within three Alaskan boreal ecosystems that represented different recovery stages following severe fire. Pools of mycorrhizal carbon included root‐associated AM and ECM structures; soil‐associated AM hyphae; and glomalin, a glycoprotein produced by AM fungi. Total mycorrhizal carbon pools decreased by approximately 50 g C m−2 in the youngest site under N fertilization, and this reduction was driven mostly by glomalin. Total mycorrhizal carbon did not change significantly in the other sites. Root‐associated AM structures were more abundant under N fertilization across all sites, and root‐associated ECM structures increased marginally significantly. We found no significant N effects on AM hyphae. Carbon sequestered within living mycorrhizal structures (0.051–0.21 g m−2) was modest compared with that of glomalin (33–203 g m−2). We conclude that our hypothesis was only supported in relation to glomalin stocks within one of the three study sites. As N effects on glomalin were inconsistent among sites, an understanding of the mechanisms underlying this variation would improve our ability to predict ecosystem feedbacks to global change.

Subfields: Insect Science, Plant Science, Soil Science

View Paper: https://www.semanticscholar.org/paper/3ad6a96cb146dd40fd0df8683176dd6f732d4780

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Citations in the corpus

Low levels of nitrogen addition stimulate decomposition by boreal forest fungi (2009, methodology): “The Basidiomycetes Pholiota carbonaria and Agrocybe praecox were isolated from sporocarps collected from an early successional black spruce forest that burned in 1999 (Treseder et al., 2007), and Polyporus varius (also a Basidiomycete) was cultured from a decaying spruce stump at the same site.”
Long‐term experimental manipulation of climate alters the ectomycorrhizal community of Betula nana in Arctic tundra (2011, result): “The relatively small change in ECM community composition observed with fertilizer treatment is consistent with other studies showing little effect of N fertilization on belowground ECM communities (Wallenda & Kottke, 1998; Peter et al., 2001; Treseder et al., 2007).”
Microbial activity and soil respiration under nitrogen addition in Alaskan boreal forest (2008, background): “At our site, other indicators of fungal biomass such as hyphal counts and mycorrhizal colonization also do not decline with N addition, and may even increase slightly (Treseder et al., 2007).”
Mycorrhizal dynamics under elevated CO2 and nitrogen fertilization in a warm temperate forest (2008, result): “Shifts in soil glomalin concentrations under N additions have been inconsistent in previous studies (Wuest et al. 2005; Treseder et al. 2007).”
Litter decay rates are determined by lignin chemistry (2012, background): “P) forest site described in Treseder et al. (2007). The forest is an upland boreal ecosystem in central Alaska, USA (63 550 N, 145 440 W).”
Consequences of More Intensive Forestry for the Sustainable Management of Forest Soils and Waters (2011, background): “easily accessed by the trees [20], the decomposition of large macromolecules to peptides, amino acids and inorganic N-forms, and the relationships between trees and their symbiotic mycorrhizal fungi are particularly important to the supply of N to primary producers [21,22].”