title: Mosses influence phosphorus cycling in rich fens by driving redox conditions in shallow soils.
abstract: Mosses play an integral role in the hydrologic regimes of ecosystems where they cover the soil surface, and thus affect biogeochemical cycling of elements influenced by soil oxidation-reduction (redox) reactions, including the plant growth-limiting nutrients, nitrogen and phosphorus (P). In rich fens where P often limits plant growth, we hypothesized that feedbacks between mosses and redox conditions would determine P availability to shallow-rooted forb species that constitute much of these wetlands' unusually high plant species diversity. In a moss removal experiment in three fens, forb tissue P and microbial P were greater while anion exchange membrane (AEM) resin P was lower where mosses occurred than where they were removed, suggesting both higher availability and greater demand for P in moss-covered soils. Coupled physicochemical and biological mechanisms drove moss effects on P cycling, ultimately through effects on soil oxygenation or reduction: higher redox potential underlying mosses corresponded to greater microbial activity, phosphatase enzyme activity, and colonization by arbuscular mycorrhizal fungi (AMF), all of which can promote greater P availability to plants. These more oxidized soils stimulated: (1) greater microbial activity and root vigor; (2) correspondingly greater P demand via microbial uptake, forb uptake, and iron (Fe)-P reactions; and (3) greater P supply through soil and root phosphatase activity and AMF colonization. This work demonstrates that mosses improve vascular plant P acquisition by alleviating stresses caused by reducing conditions that would otherwise prevail in shallow underlying soils, thus providing a mechanism by which mosses facilitate plant species diversity in rich fens.
authors: Cary Institute of Ecosystem Studies, Millbrook, NY 12545, USA. crowleyk@caryinstitute.org
authors: Katherine F
authors: KF
authors: Crowley
authors: Barbara L
authors: BL
authors: Bedford
mesh_terms: D044002:Bryophyta / Q000502:physiology*; D017753:Ecosystem; D007501:Iron / Q000737:chemistry; D019684:Magnoliopsida / Q000378:metabolism*; D009518:New York; D010084:Oxidation-Reduction; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism*; D018517:Plant Roots / Q000201:enzymology; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D012987:Soil; D010758:Phosphorus; D007501:Iron; D010744:Phosphoric Monoester Hydrolases