Activated Carbon Decreases Invasive Plant Growth by Mediating Plant-Microbe Interactions

To restore lands invaded by dense, non-native vegetation, it may be necessary to develop targeted restoration tools than can remove the mechanism used by these non-native species as a competitive advantage. Activated carbon (AC) is one such tool, with the ability to disrupt the mechanisms of plant to plant communication (allelopathy) and positive plant to microbe communication commonly used by non-native species. Previous studies have shown the success of high concentrations, 1000g/m2, of AC in native plant community restoration on a small scale. Here, our goals are twofold: first, to test AC effectiveness in restoring desirable plant communities on a larger scale, and secondly, to identify the primary mechanism, allelopathy versus microbial interactions, through which AC impacts native and non-native species. AC treatments in Methow Valley, Washington tested the effectiveness of AC restoration at a large-scale and tested five concentrations and two type of AC to determine lowest effective concentration. Following three growing seasons, the large-scale application at a 1000 g/m2 application rate decreased undesirable specie cover and positively impacted the relative abundance of desirable to undesirable species. However, the effectiveness of AC concentrations below 1000 g/m2 cannot yet be determined and may require a longer time scale and additional monitoring. A greenhouse experiment was performed to separate AC effects on allelopathy from that of microbial interactions, which used native and non-native species common to the study site, grown in pair in sterilized (i.e. all microbes removed) and live (i.e. containing microbial communities) AC-treated soils. Both native and non-native species experienced a decreased biomass in AC-treated live soils, with no effect in AC-treated sterile soils. Overall, AC live soils produced a positive effect on relative abundance; the ratio of native to non-native biomass was highest in AC-treated live soils. From these results, it is concluded that the primary pathway through which AC works is changes in the plant-microbial interactions of both native and non-native species