Forskning ved Københavns Universitet - Københavns Universitet


Are herbarium mosses reliable indicators of historical nitrogen deposition?

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

Mosses collected decades ago and stored in herbaria are often used to assess historical nitrogen deposition. This method is effectively based on the assumption that tissue N concentration remains constant during storage. The present study raises serious doubt about the generality of that assumption. We measured tissue N and C concentrations as well as δ15N, δ13C, Pb and Mg in herbarium and present day samples of seven bryophyte species from six sites across Denmark. While an increase in nitrogen deposition during the last century is well-documented for the study site, we surprisingly found foliar N concentration to be higher in historical samples than in modern samples. Based on δ15N values and Pb concentration, we find nitrogen contamination of herbarium specimens during storage to be the most likely cause, possibly in combination with dilution though growth and/or decomposition during storage. We suggest ways to assess contamination and recommend caution to be taken when using herbarium specimens to assess historical pollution if exposure during storage cannot be ruled out. Analyses of moss tissue stored in a herbarium for a century raises serious concern about the reliability of this data source to past levels of nitrogen deposition.

TidsskriftEnvironmental Pollution
Udgave nummerPart 1
Sider (fra-til)1201-1207
Antal sider7
StatusUdgivet - dec. 2017

ID: 185475856