Historical nitrogen content of bryophyte tissue as an indicator of increased nitrogen deposition in the Cape Metropolitan Area, South Africa

Authors

Daniel Wilson
William Stock, Edith Cowan University
Terry Hedderson

Document Type

Journal Article

Faculty

Faculty of Computing, Health and Science

School

School of Natural Sciences / Centre for Ecosystem Management

RAS ID

7670

Comments

Wilson, D., Stock, W. D., & Hedderson, T. (2009). Historical nitrogen content of bryophyte tissue as an indicator of increased nitrogen deposition in the Cape Metropolitan Area, South Africa. Environmental Pollution, 157(3), 938-945. doi: 10.1016/j.envpol.2008.10.021. Available here

Abstract

Information on changes in precipitation chemistry in the rapidly expanding Cape Metropolitan Area (CMA) of South Africa is scarce. To obtain a long-term record of N deposition we investigated changes in moss foliar N, C:N ratios and nitrogen isotope values that might reflect precipitation chemistry. Tissue from 9 species was obtained from herbarium specimens collected between 1875 and 2000 while field samples were collected in 2001/2002. There is a strong trend of increasing foliar N content in all mosses collected over the past century (1.32–1.69 %N). Differences exist between ectohydric mosses which have higher foliar N than the mixohydric group. C:N ratios declined while foliar delta-15N values showed no distinct pattern. From relationships between moss tissue N and N deposition rates we estimated an increase of 6–13 kg N ha−1 a−1 since 1950. Enhanced N deposition rates of this magnitude could lead to biodiversity losses in native ecosystems. This study of bryophyte tissue nutrient contents shows a historical increase in N deposition rates to the low nutrient adapted plant biodiversity hotspot in the Western Cape, South Africa.

DOI

10.1016/j.envpol.2008.10.021