Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Natural Resource Management

First Advisor

A. Joshua Leffler


grassland, net ecosystem exchange (NEE), nitrogen mineralization, plant community, rainfall, soil microbial community composition


Climate change is leading to larger and less frequent rainfall in the Northern Great Plains (NGP). We ask if this change in rainfall would influence carbon (C) and nitrogen (N) cycling in the NGP. First, we collected soils from C3 and C4 grass dominated plant communities from western South Dakota and conducted an incubation experiment to explore the effects of soil water content (SWC) and temperature on soil respiration (Rs) and N mineralization rate (ΔIN). Second, we conducted a three-year rainfallmanipulation (RaMP) experiment with two distinct rainfall regimes (frequent/small and infrequent/large events with constant total monthly precipitation) and two grasses plant communities (C3 and C4 plant communities) with five replications in western South Dakota. The measurements and analysis were grouped into aboveground [net ecosystem exchange (NEE) and aboveground biomass] and belowground components (ΔIN, active- C, and soil microbial community composition). In the incubation experiment we hypothesized that the response of Rs and ΔIN to SWC and temperature would be different between C3 and C4 plant communities. In the RaMP experiments we hypothesized that larger and less frequent rainfall events would (1) increase C uptake and aboveground biomass in the C4 but not in the C3 plant community; and (2) reduce ΔIN and alter microbial community composition in both plant communities and increase active-C in the C4 but not in the C3 plant community. We observed: (1) the greatest Rs and ΔIN occurred at 30% SWC and 25˚C in the C4 plant community. (2) Larger and less frequent rainfall events decreased C uptake in the C3 plant community but did not change biomass in both plant communities. (3) Larger and less frequent rainfall events reduced ΔIN in both communities but did not change active-C and soil microbial community composition. We conclude: (1) soils from the C4 plant community showed greater Rs and ΔIN than from the C3 plant community in the optimal SWC and temperature that might result from more belowground C allocation in the C4 plant community. (2) Though larger and less frequent rainfall events reduced C uptake in the C3 plant community and reduced ΔIN in both plant communities, both aboveground and belowground ecosystems showed resistance to the altered rainfall regime, particularly in the C4 plant community of greater biodiversity.

Library of Congress Subject Headings

Plant communities.
Plant-water relationships.
Rain and rainfall.
Climatic changes.


South Dakota State University



Rights Statement

In Copyright