Vegetation Response in a Colorado Grassland-shrub Community to Extreme Drought: 1999–2010

Abstract

We examined vegetation changes in a mixed grassland-shrub community in eastern Colorado between 1999–2010, a period that encompassed both extreme drought and moisture recovery, as well as slightly higher than long term average temperatures. Shrub cover significantly increased while grass cover significantly decreased following the drought years of 2002–2003. Grass cover had still not fully recovered 7 y after the drought, primarily due to the slow recovery of blue grama (Bouteloua gracilis). Blue grama was no longer dominant in this community, becoming secondary in importance to alkali sacaton (Sporobolus airoides). Increase in shrub cover and density were especially notable in rabbitbrush (Ericameria nauseosa) and tree cholla (Cylindropuntia imbricata). Although rabbitbrush density declined in the drought, overall cover of remaining individuals increased, even during the drought. Cholla density increased by nearly 200 plants/ha from 543 plants/ha to 726 plants/ha, all post drought.