Annual grass invasions and wildfire deplete ecosystem carbon storage by >50% to resistant base levels

Ecological disturbance can affect carbon storage and stability and is a
key consideration for managing lands to preserve or increase ecosystem
carbon to ameliorate the greenhouse gas problem. Dryland soils are massive
carbon reservoirs that are increasingly impacted by species invasions and
altered fire regimes, including the exotic-grass-fire cycle in the
extensive sagebrush steppe of North America. Direct measurement of total
carbon in 1184 samples from landscapes of this region that differed in
invasion and wildfire history revealed that their impacts depleted soil
carbon by 42-49%, primarily in deep horizons, which could amount to
24.8-29.0 Tg carbon lost across the >500,000 ha affected annually.
Disturbance effects on soil carbon stocks were not synergistic, suggesting
that soil carbon was lowered to a base-level ‘floor’, beneath which
further loss was unlikely. Restoration and maintenance of resilient
dryland shrublands/rangelands could stabilize soil carbon at magnitudes
that are relevant to the global carbon cycle.