. Estimating the combined effects of cheatgrass invasion and fire on U.S. ecosystem carbon storage

Abstract
Cheatgrass, (Bromus tectorum), is invading native sagebrush ecosystems in the Great Basin region of the western U.S. Cheatgrass alters the landscape and makes it more flammable, promoting larger fires. Together, cheatgrass invasion and more frequent fire have the potential to alter carbon storage in the Great Basin. However, to our knowledge, no studies have quantified changes in carbon storage in all carbon pools for native sagebrush, invaded and unburned areas (sagecheat), and invaded and burned cheatgrass areas. We performed a systematic literature review to identify all studies assessing the consequences of invasion or invasion and fire on one or more of five carbon pools (aboveground biomass (AGB), litter, belowground biomass (BGB), and organic and total soil). We identified 25 articles containing unique carbon studies, based on location, current and native vegetation, carbon pool, and soil depth (if applicable), to assess carbon storage in uninvaded/unburned, invaded/unburned, and invaded/burned sites. AGB carbon was significantly higher in sagecheat than sagebrush and was significantly higher in sagebrush than cheatgrass. BGB carbon was significantly lower in sagecheat and cheatgrass than sagebrush. Litter C was not significantly different in cheatgrass compared to sagebrush. Organic C in surface soils (0-10 cm) was significantly lower in sagebrush and sagecheat than in cheatgrass. The numerical trend of higher organic soil C in cheatgrass was not significant at 10-20 cm depth. Total C in surface soils (0-10 cm) was not significantly different in cheatgrass and sagecheat. We lack a complete picture of the combined effects of cheatgrass invasion and fire on C storage in the region. Notable gaps include 1) litter quantification in sagecheat systems and comparisons with sagebrush; and 2) total soil carbon measurements in surface soils (sagebrush) and deeper soils (sagebrush vs. sagecheat vs. cheatgrass). A better understanding of the link between cheatgrass, fire, and carbon storage advances our understanding of how human activities alter fundamental environmental processes and can inform the management and control of fire-prone invasive grasses.