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ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #376512
Research Project: Restoration and Conservation of Great Basin Ecosystems

Location: Range and Meadow Forage Management Research

Title: Spatial variation in soil microbial processes as a result of woody encroachment depends on shrub size in tallgrass prairie

Author
item CONNELL, ROBERT - Kansas State University
item O'Connor, Rory
item NIPPERT, JESSE - Kansas State University
item BLAIR, JOHN - Kansas State University

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2020
Publication Date: 1/12/2021
Citation: Connell, R.K., O'Connor, R.C., Nippert, J.B., Blair, J.M. 2021. Spatial variation in soil microbial processes as a result of woody encroachment depends on shrub size in tallgrass prairie. Plant and Soil. 460:359-373. https://doi.org/10.1007/s11104-020-04813-9.
DOI: https://doi.org/10.1007/s11104-020-04813-9

Interpretive Summary: As woody plants encroach into grassland ecosystems, we expect that altered plant-soil interactions will lead to changes in the microbial processes that affect carbon storage and nutrient cycling. In the tallgrass prairie, one resprouting native shrub that is replacing prairie grasses is rough-leaf dogwood. We investigated the effects that rough-leaf dogwood has on the soil chemistry, microbial nutrient demand, and carbon mineralization at different locations under different sized rough-leaf dogwood shrubs. Total soil carbon and nitrogen increased with shrub size in every location but the edge where it was near grasses. Microbial demand for nitrogen also increased as shrubs increased in size. Across all shrub sizes and sampling locations, potential soil carbon mineralization rates were higher when microbes broke down proportionally more shrub-derived (C3) organic matter than grass-derived (C4) organic matter. This research suggests that soil microbial processes are influenced by both the amount of time and location beneath woody plants and in particular rough-leaf dogwood.

Technical Abstract: Aims As woody plants encroach into grassland ecosystems,we expect altered plant-soil interactions to changethe microbial processes that affect soil carbon storageand nutrient cycling. Specifically, this research aimed to address how (1) soil chemistry, (2) microbial nutrientdemand, and (3) the rate and source of potential soil C mineralization vary spatially under clonal woody shrubs of varying size within a mesic grassland. Methods We collected soil samples from the center, the midpoint between the center and edge, the edge, and the shrub-grass ecotone of multiple Cornus drummondii shrubs across a shrub-size gradient in infrequently burned tallgrass prairie. Results Total soil carbon and nitrogen increased with shrub size at every sampling location but the edge. Microbial demand for nitrogen also increased as shrubs increased in size. Across all shrub sizes and sampling locations, potential soil carbon mineralization rates were higher when microbes broke down proportionally more shrub-derived (C3) organic matter than grass-derived (C4) organic matter. Conclusions Our results suggest that the spatiotemporal context of woody encroachment is critical for understanding its impact on belowground microbial processes. In this ecosystem, a longer period of occupancy by woody plants increases potentially mineralizable soil carbon.