Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2016
Publication Date: 4/4/2017
Citation: Sanderson, M.A., Johnson, H.A., Liebig, M.A., Hendrickson, J.R., Duke, S.E. 2017. Kentucky bluegrass invasion alters soil carbon and vegetation structure on northern mixed-grass prairie of the United States. Invasive Plant Science and Management. 10(1):9-16. doi: 10.1017/inp.2016.2.
Interpretive Summary: Significant vegetation change has occurred on native rangelands of the northern Great Plains of the USA. We used analysis of carbon and nitrogen isotopes in soil samples from 1959, 1991, and 2014 to determine potential effects of vegetation change on soil properties. Invasion of native prairie at Mandan by Kentucky bluegrass has resulted in a buildup of standing dead vegetation and litter, which is less resistant to decomposition than native vegetation and therefore may be less readily retained in soil. Carbon isotope analysis indicated a significant input of carbon from invasive species from 1991 to 2014. There appears to have been an effect of invasion on N cycling, which may have been more influenced by grazing animals than vegetation. There also appears to have been a gain in C in both pastures during the last 24 years, indicating that nonnative grass invasion has altered carbon balance and cycling. Invasion of native prairie by nonnative grasses can alter soil carbon composition and potentially affect nutrient cycling.
Technical Abstract: Long-term data from a grazing experiment near Mandan, ND USA (46°46’12’N, -100°55’59’W) indicate invasion of native prairie by Kentucky bluegrass (Poa pratensis L.), an exotic grass. We hypothesized that bluegrass invasion altered soil 13C and 15N levels tracking the increased abundance of invasive cool-season grass aboveground. In 2014, soil samples were collected to depths of 0 to 7.6 and 7.6 to 15.2 cm in pastures grazed similarly since 1916. Samples were analyzed for total C and N and 13C and 15N isotopes and compared against archived samples from 1991. Vegetation change from native to exotic grasses changed the isotopic composition of soil C. The soil d13C at both 0 to 7.6 and 7.6 to15.2 cm depths became more negative between 1991 and 2014. Soil d13C became less negative and d15N increased with increasing stocking rate at both soil depths. Soil C and N levels at 7.6 cm increased by 35% (1.2 g C kg-1) and 27% (0.09 g N kg-1) from 1991 to 2014; however, levels at the 7.6 to 15.2 depth did not change. Vegetation changes on native prairie during the last 25 years caused changes in soil C and N that may have long-term effects on nutrient cycling.