| Abandoned agricultural lands in the Intermountain West are plagued by dense, persistent non-native vegetation. Targeted restoration tools are required to remove the competitive advantage of these non-natives while also removing the soil legacies they leave behind. Activated carbon (AC) is one such tool, with the ability to disrupt the mechanisms of allelopathy, positive plant-soil feedbacks, and altered nutrient cycling commonly used by non-native species. Previous studies have shown the success of high concentrations 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 changes, through which AC impacts native and non-native species. A large scale AC treatment in Methow Valley, Washington tested the effectiveness of AC restoration at a large scale and tested five concentrations and two types of AC to determine lowest effective application. Following treatment, sites were monitored for vegetation cover for three years. The large-scale application produced similar results to the previous study at a 1000 g/m2 application rate, with a 28% increase in the ratio of desirable:undesirable species cover and a decrease to 25% undesirable species cover. However, the effectiveness of AC concentrations below 1000 g/m2 cannot yet be determined and may require a longer time scale and additional monitoring to assess restoration success. A greenhouse experiment was performed, which used native and non-native species common to the study site, grown in pairs in sterilized and live AC-treated soils to separate AC effects on allelopathy from that of microbial interactions. Both native and non-native species experienced a 25% decreased biomass in AC-treated live soils, with a minimal decrease in A- treated sterile soils for native species and no effect in AC-treated sterile soils for non-native species. 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. |
