Mercury Accumulation is Related to the Leaf Economics Spectrum

Abstract Mercury (Hg) is a highly toxic metal with a complex biogeochemistry and the principles governing Hg uptake in different types of vegetation represent a knowledge gap. By combining published information from three sources with new data we investigated the rate of Hg accumulation in a wide range of leaf types from broadleaved and needle-leaved trees of evergreen or deciduous habit, in relation to leaf nitrogen concentration, and to specific leaf area (SLA) and leaf mass per area (LMA) using data from temperate trees in Europe and China. Leaf nitrogen, SLA and LMA are key traits along the resource conservation strategy continuum known as the leaf economics spectrum (LES), which has been shaped by evolutionary history of trees in different environments. We show, based on data from different geographical areas, that the rate of Hg accumulation by leaves and needles was significantly and linearly related to leaf nitrogen concentration, but more strongly so to SLA. The relationship of Hg accumulation with LMA was equally strong but non-linear. We conclude that leaf Hg accumulation rate of leaves and needles is connected to the LES. These results support the assessment and modelling of Hg accumulation in vegetation, including consequences of land use and climate change induced shifts in vegetation composition on Hg uptake by forest ecosystems. Importantly, the data from different geographical regions provided very similar results and conformed to general relationships with SLA and LMA. Further studies are needed to investigate if the results can be extrapolated also to other biogeographic regions.