Woody species encroachment in grasslands and the associated regime shifts are a global phenomenon and of concern in the Great Plains with significant economic and ecological consequences. The goal of this research is to determine the role that soils and soil processes, particularly those facilitated by the microbial community, play during the directional shift from a grassland-forest ecosystem into dense forests and the ability of the ecosystem to recover to its previous state after prescribed burn. We investigated the impact of eastern redcedar (Juniperus virginiana) encroachment at two locations in Nebraska: the Sandhills grasslands and the Loess Canyons. Soil physicochemical properties were determined and soil microbial community was assessed using both genomics (Amplicon Sequencing & Metagenomics) and Fatty Acid Methyl Esterase (FAME) analysis to identify both taxonomy and abundance, respectively. At the Sandhills sites, open to dense canopy sites were selected for the study. At the Loess Canyons, we investigated unburned and burned grasslands and invaded eastern redcedar sites along a chronosequence from 2002 to 2019.
Results/Conclusions
At the Sandhills sites, tree invasion and increased canopy density was associated with a reduction in plant diversity and abundance. Soil organic matter and NO3- declined and we observed an increase in pH. Microbial biomass was largely bacterial in open grassland, and largely fungal in dense ERC plots. Soil pH and soil organic matter were the main soil attributes that affected soil microbial community composition (Pearson’s correlation analysis and the Monte Carlo test), with soil variables also explaining microbial biomass (partial regression analysis, 31.2%-65.0%). Our work also revealed that understory plant height/age, cover, species richness, tree species, and tree density significantly affected the microbial community composition. These findings suggest that the invasion of woody species into the Sandhills alters soil properties, which subsequently affected soil microbial community characteristics. Our results from the Loess Canyons are pending. If woody encroachment into Nebraska grasslands fundamentally alters belowground chemical and microbial properties, prioritizing prevention rather than post-invasion management may be an effective invasive management strategy.