Experimental Evidence of Large Changes in Terrestrial Chlorine Cycling Following Altered Tree Species Composition
2015
Montelius, Malin | Thiry, Yves | Marang, Laura | Ranger, Jacques | Cornelis, Jean-Thomas | Svensson, Teresia | Bastviken, David
Organochlorine molecules (Clₒᵣg) are surprisingly abundant in soils and frequently exceed chloride (Cl–) levels. Despite the widespread abundance of Clₒᵣg and the common ability of microorganisms to produce Clₒᵣg, we lack fundamental knowledge about how overall chlorine cycling is regulated in forested ecosystems. Here we present data from a long-term reforestation experiment where native forest was cleared and replaced with five different tree species. Our results show that the abundance and residence times of Cl– and Clₒᵣg after 30 years were highly dependent on which tree species were planted on the nearby plots. Average Cl– and Clₒᵣg content in soil humus were higher, at experimental plots with coniferous trees than in those with deciduous trees. Plots with Norway spruce had the highest net accumulation of Cl– and Clₒᵣg over the experiment period, and showed a 10 and 4 times higher Cl– and Clₒᵣg storage (kg ha–¹) in the biomass, respectively, and 7 and 9 times higher storage of Cl– and Clₒᵣg in the soil humus layer, compared to plots with oak. The results can explain why local soil chlorine levels are frequently independent of atmospheric deposition, and provide opportunities for improved modeling of chlorine distribution and cycling in terrestrial ecosystems.
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