The conifer-carbon connection in sagebrush steppe
How could more trees be “bad” for carbon? Conifers are expanding into the shrub-dominated sagebrush steppe across much of the Western U.S.A., which increases carbon storage both aboveground and belowground (in soils and roots) – but the long-term impacts of conifer expansion are complex. Short-term increases in carbon storage from increased tree cover can be lost to wildfire. Conifer expansion increases woody fuel loads, making large, severe wildfires more likely. High plant mortality after severe fire, even in relatively fire-resilient perennial grasses, increases the risk of annual grass conversion and subsequent losses of up to 50% of ecosystem carbon, including soil carbon. Preventing conifer expansion through early intervention can protect the large belowground carbon stores of healthy sagebrush steppe.