Kentucky Bluegrass Invasion Alters Soil Carbon and Vegetation Structure on Northern Mixed-Grass Prairie of the United States

Abstract

Invasive nonnative grasses pose a significant threat to rangelands of the Northern Great Plains. Long-term data from a grazing experiment near Mandan, ND (46°46′11.43″N, 100°54′55.16″W) revealed the invasion of native prairie by Kentucky bluegrass, an exotic grass. We hypothesized that bluegrass invasion altered soil13C and15N levels, tracking the increased abundance of invasive cool-season grass aboveground. In 2014, soil samples were collected to depths of 0 to 7.6 cm and 7.6 to 15.2 cm in pastures grazed similarly since 1916. Samples were analyzed for total carbon (C) and nitrogen (N) and13C and15N isotopes and compared against archived samples from 1991. Vegetation change from native to exotic grasses changed the isotopic composition of soil C. The soil δ13C at the 0- to 7.6-cm depth became more negative between 1991 and 2014. Soil δ13C became less negative with increasing stocking rate at both soil depths. Soil δ15N values at the 0- to 7.6-cm depth decreased between 1991 and 2014. Soil δ15N increased with increasing stocking rate at the 0- to 7.6-cm depth in 2014. Soil C and N concentrations at 0 to 7.6 cm increased by 35% (12 g C kg−1) and 27% (0.9 g N kg−1), respectively, from 1991 to 2014; however, concentrations at the 7.6- to 15.2-cm depth did not change. The shift from native C4to invasive C3grass did not reduce soil C storage in the long-term prairie pastures. The more deleterious effect of invasion, however, may have been the buildup of dead biomass, which alters vegetation structure and may reduce native species’ diversity and abundance.

Long-Term Efficacy of Glyphosate for Smooth Brome Control in Native Prairie

“…The recovery of key native species combined with the general decline of many invasive species in the first 10 yr demonstrates that smooth brome removal initially put this community onto a successional trajectory to recovery. The declines in native species richness 16 and 17 yr posttreatment are symptomatic of the Kentucky bluegrass invasions that have been occurring on rangelands across the Northern Great Plains (Bahm et al 2011a; DeKeyser et al 2015; Sanderson et al 2017; White et al 2013). While large-scale climactic shifts are likely a major driver of Kentucky bluegrass invasion, local environmental changes driven by smooth brome may have also increased the susceptibility of these patches to Kentucky bluegrass invasion (Carrigy et al 2016).…”

Can Agricultural Management Induced Changes in Soil Organic Carbon Be Detected Using Mid-Infrared Spectroscopy?

“…The USDA-ARS Northern Great Plains Research Laboratory (NGPRL) in Mandan (Mandan), ND, provided soils from a long-term native prairie grazing intensity experiment [29,30]. Soil cores were analyzed from 20 randomly selected locations within a 12.1 ha (heavy stocking) and a 40.5 ha (light stocking) paddock.…”

Kentucky Bluegrass Invasion in the Northern Great Plains and Prospective Management Approaches to Mitigate Its Spread

“…Plant–soil feedbacks can partially explain how exotic plant species invade and subsequently alter ecosystem functioning [ 49 , 50 , 51 , 52 ]. Plant–soil feedbacks arise because plant species differentially alter soil communities by cultivating a microbiota specific to each species.…”

“…For instance, changes in the litter–soil-nutrient dynamics provide a competitive advantage to this species and ensure its dominance by dislocating the other native species in the community [ 49 , 50 ]. In general, invasive C3 grasses contain greater nitrogen concentrations and lower recalcitrant carbon than some native C4 grasses, which can cause increasing decomposition rates and faster nutrient cycling [ 51 , 52 ]. Greater plant and litter production by invasive C3 grasses might also enhance the soil microbial activity and soil nitrogen mineralization processes [ 51 , 53 ].…”

“…In general, invasive C3 grasses contain greater nitrogen concentrations and lower recalcitrant carbon than some native C4 grasses, which can cause increasing decomposition rates and faster nutrient cycling [ 51 , 52 ]. Greater plant and litter production by invasive C3 grasses might also enhance the soil microbial activity and soil nitrogen mineralization processes [ 51 , 53 ]. A shift to a Kentucky bluegrass-dominated prairie from the mixed-grassland can also have multidimensional effects on many organisms residing at different trophic levels, from underground dwellers to the organisms that reside on the soil surface [ 6 ].…”