CONICET | Buscador de Institutos y Recursos Humanos

Evidence suggests that tree plantations change soil methane (CH 4 ) fluxes (magnitude and/or direction of thefluxes) compared to herbaceous land (i.e. afforestation effect) due to the effect of trees increasing methanotrophbacteria abundance and enhancing soil gas diffusivity. However, the magnitude of this afforestation effect ishighly variable across studies. Here, we evaluated whether the variation in the afforestation effect depends onforestry management strategies, described by stand age and density, as well as taxonomic identity of the treespecies, and the interaction with climatic conditions. To this end, we conducted a meta-analysis using 47 pairedsamples of afforested and contiguous herbaceous land from 14 studies located in different biomes worldwide. Wefound that afforestation predominantly increases the capacity of soil net CH 4 uptake (i.e. more negative fluxes)compared to herbaceous land, but the magnitude of this effect was highly heterogeneous across paired samples.This heterogeneity was explained by environmental conditions, but significant effects of forest stand age anddensity were also found proving the importance of forest management on this ecological service. Soil net CH 4uptake following afforestation increases with increasing stand age. Although the stand stocking effect could betested with a limited number of studies (24 out of the 47 paired samples), the results suggest that net CH 4 uptakedecreases with tree stocking (stand density) in the range of values up to 1500 individuals per ha. No change inCH 4 fluxes was observed above this high stand density. Contrary to our expectations, no effect of taxonomicidentity of the trees considering the most planted genera (Pinus and Eucalyptus) was observed in the average soilCH 4 fluxes. Furthermore, a significant correlation between the afforestation effect on soil water content and CH 4flux suggests that the most plausible cause of the increased soil net CH 4 uptake is driven by the forest impact onsoil desiccation, which in turn increases in sites with higher water limitation (i.e. higher potential evapotranspiration and high temporal rainfalls variations within the ranges of the available studies). Finally, our studyprovides evidence that by modifying rotation time and stand stocking, afforested land may increase its environmental service as a sink of atmospheric CH 4 .

enviar mensaje