Are herbarium mosses reliable indicators of historical nitrogen deposition?

作者:Nielsen Tora Finderup*; Larsen Jesper Ruf; Michelsen Anders; Bruun Hans Henrik
来源:Environmental Pollution, 2017, 231: 1201-1207.
DOI:10.1016/j.envpol.2017.04.020

摘要

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 delta N-15, delta C-13, 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 delta N-15 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.

  • 出版日期2017-12