Climate change impacts invasive perennial grass establishment

Photo Credit

USDA Forest Service Photo

Clonal traits are counted and measured on young plants of B. inermis and P. smithii in the greenhouse.

Perennial grasses produce new stems primarily through clonal growth, which involves the production and outgrowth of belowground buds. For a non-native species to successfully invade a native habitat it must survive multiple hurdles from dispersal to colonization to establishment to landscape spread. The establishment phase of a perennial grass invasion requires young plants to develop their clonal infrastructure including their belowground buds. Building clonal growth capacity could be enhanced or hampered by disturbances like grazing or changing precipitation patterns.

Climate change is expected to increase the timing between rainfall events during the growing season in the northern Great Plains where smooth brome (Bromus inermis) is invading native grassland dominated by western wheatgrass (Pascopyrum smithii). Grasslands are extensively used as rangelands, providing forage for livestock and wildlife. Using a temperature-controlled greenhouse, we examined how clonal traits of native P. smithii and non-native B. inermis seedlings were affected under altered precipitation frequencies and a single grazing event during their first growing season. 

We found that P. smithii maintained similar clonal growth under three simulated precipitation frequencies whereas B. inermis clonal growth declined as precipitation became more intermittent. Clonal growth of the non-native B. inermis was greater than the native P. smithii under all simulated precipitation frequencies except the most intermittent scenario. 

In addition, a single grazing event did not affect either species’ response to precipitation variability but did slightly reduce their clonal growth. In young plants, clonal traits of the invasive grass favored its superior expansion and population growth compared to the native grass except under the most severe climate change scenario. Grassland restoration using native P. smithii seeds would be successful in most years due to its resilient clonal growth in a changing climate.