Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.

Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Soil Carbon and Nitrogen Dynamics in Abandoned Agricultural Lands

Yi Yang, University of Nebraska - Lincoln

Abstract

Abandoned agricultural lands (old fields) have the potential to sequester C and mitigate atmospheric CO2. Currently, factors controlling the soil C and N dynamics after agricultural cessation are poorly understood, especially the long-term effect of burrowing animal soil disturbance, although they are ubiquitous in abandoned agricultural lands. Also, most C sequestration research only focuses on the top 30 cm, and we lack a clear understanding of C dynamics below 30 cm. In this dissertation, I first developed a process model to simulate the effect of pocket gopher disturbance on soil C accumulation in the old field ecosystems (Chapter 2). I found pocket gopher disturbance reduced soil C accumulation rates, and vegetation recolonization on gopher mounds was the critical factor that determines the impact that gophers have on the soil C pool. Next, I examined the changes in C and N pools in both surface and subsurface soil at 21 old fields. I found the C accumulation in the surface soil was offset by the losses in the subsurface soil. By quantifing the inputs and outputs at different depths in these old fields, I found that roots are the primary input of C to subsurface soil. However, 85% of roots are located in the top 20 cm of soil. Thus, subsurface soil receives little organic matter inputs from roots, which leads to losses of C. Finally, in Chapter 4, I analyzed part of a soil C survey to the depth of 100 cm across the conterminous United States. I compared the soil organic C (SOC) stocks between the croplands and Conservation Reserve Program (CRP) lands at 0-5, 5-30, and 30-100 cm. I found CRP lands, on average, did not accumulate a significant amount of SOC after agricultural cessation, which is likely due to a reduction of SOC stock in the subsurface, despite SOC accumulated in the surface. My dissertation research highlights the essential roles of burrowing animals and subsurface soil C dynamics in C sequestration efforts after agricultural abandonment. My results suggest active land management strategies should be applied to achieve CO2 mitigation goals in abandoned agricultural lands.

Subject Area

Ecology|Environmental science|Soil sciences

Recommended Citation

Yang, Yi, "Soil Carbon and Nitrogen Dynamics in Abandoned Agricultural Lands" (2019). ETD collection for University of Nebraska - Lincoln. AAI27739474.
https://digitalcommons.unl.edu/dissertations/AAI27739474

Share

COinS