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Keywords:

  • allelopathy;
  • Bromus tectorum;
  • Centaurea diffusa;
  • disturbance;
  • exotic invasion;
  • native plant;
  • PLFA;
  • Pseudoroegneria spicata;
  • Shrub-steppe;
  • soil microbial community;
  • tillage

Due to its potential to inhibit plant–microbe interaction and allelopathy, there is a growing interest in the use of activated carbon (AC) as a soil manipulation for native plant restoration. Here I describe the long-term effects of AC on native and non-native plant growth in the field and the short-term effects of AC on soil microbial communities. I added AC (1% by mass) with or without native seed to plots in three ex-arable fields dominated by non-native plants in the Methow Valley, Washington, U.S.A. Six years after a single application, AC plus native seed addition restored native plant dominance by decreasing non-native abundance from 34 ± 4% to 14 ± 2%, and increasing native abundance from 10 ± 2% to 42 ± 8%. Relative to non-AC-treated soils, AC decreased the abundance of the bacterial (16:0), fungal (18:1 ω9c, 18:1 ω6,9,12c), and mycorrhizal (16:1 ω5c) lipids that were associated with non-native-dominated soils. This research suggests that AC effects on plant growth might be due to a complex combination of its direct effects on heterotrophic, symbiotic, and pathogenic soil organisms as well as its ability to sequester allelochemicals. This research showed that soil manipulations may be a necessary component of native plant restoration because seed addition alone did not restore native plant dominance, but AC plus seed treatment did restore native plant dominance.