Publication Date:
2012-08-05
Description:
Atmospheric deposition is a global concern contributing to soil acidification and biodiversity changes in forest ecosystems. Although acidifying deposition has decreased in the last decades in Europe, few evidence of ecosystem recovery from acidification has been reported until now. The objective of this study was to reconstruct spatio-temporal changes in soil pH across the entire French forest territory over the last 100-year period through herb species assemblages. Data were collected from floristic databases resulting in a total of 120,216 plots covering French forests and spanning from 1910 to 2010. To define acidity figures, pH values were inferred from herb assemblages for each plot of the prediction dataset based on a WA-PLS model ( R 2 = 0.80, SD = 0.59 for the validation dataset). Spatio-temporal trends of mean pH changes were obtained by comparing plots with respect to the period (mean year of the period =1933, 1966, 1984, 1997, 2007) and substrate (acidic and non-acidic forest areas). Bioindicated pH highlighted a decrease of soil pH in both acidic and non-acidic forest areas. The sharpest and most significant pH decrease occurred before 1984 in acidic areas, reaching 0.34 pH units. Subsequently, no significant changes were observed, with a tendency toward stabilization. By contrast, the pH decrease reached 0.19 pH units in non-acidic areas, only reaching significance between 1984 and 1997. Thereafter we observed a slight and significant pH increase. Spatially, pH trends revealed a regionalized character of acidification regarding the substrate, which could not be related to the extent of deposition modeled by the European Monitoring and Evaluation Programme. Both temporal and spatial trends highlight the lagged responses of non-acidic areas compared to acidic areas. Hence, floristic reconstructed pH trends demonstrate a gradual cessation and recovery from acidification of French forests after a period of intense atmospheric pollution. © 2012 Blackwell Publishing Ltd
Print ISSN:
1354-1013
Electronic ISSN:
1365-2486
Topics:
Biology
,
Energy, Environment Protection, Nuclear Power Engineering
,
Geography
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