The effect of soil texture and vegetation on carbon accrual in restored grasslands
Abstract
Settlement of the Midwest, with the subsequent conversion of tallgrass prairie to agricultural fields, has led to a drastic reduction of soil carbon (C). As agricultural fields are returned to grasslands, it is important to understand the factors influencing rates of C and nitrogen (N) accrual in order to better predict C storage rate and capacity. In this study, we first evaluated the effect of soil texture, plant productivity, species richness and C4 grass-legume complementarity on soil C and N. In addition, we used a chronosequence approach to estimate the rate of soil C and N accrual. Soil samples were collected at depths up to 90 cm from remnant prairies, high-diversity prairie restorations, medium and low-diversity plantings enrolled in the Conservation Reserve Program (CRP), and crop fields in Newton County, IN and Lee County, IL. Vegetation surveys and biomass collections were conducted in the prairie and conservation areas to estimate plant species richness, functional group abundance, and productivity. We found that soil silt + clay content was the most important predictor for soil C and N content, in Newton and Lee Counties. Difference among field treatments fell along lines of soil texture, as fields with high silt + clay content were the first to be converted to agriculture due to their greater productivity compared to the sandy prairie remnants. As predicted, soil C and N increased with plant productivity. However, we found soil C and N decreased with species richness. There was no effect of legumes on soil C and N content in C4 grass dominated grasslands. In our chronosequence study, soil C and N increased with time since restoration, however the pattern was not significant over the initial chronosequence when remnant prairies were excluded. After omitting remnant prairies, the relationship between C and time since restoration was strengthened when variance due to silt + clay content was accounted for in the Newton County MD and LD restorations and Lee County low silt + clay restoration chronosequence, through residual analysis. Standardized multiple linear regression (MLR) showed soil C and N increased with silt + clay content both counties, and decreased with species richness, particularly in Lee County. Standardized MLR showed C and N to increase with field age in Newton County, but decrease with field age in Lee County. This may be due to leaching of C and N because the oldest restorations were located in areas with greater slope and well-drained soils. Labile soil C decreased slightly with time since restoration in both Newton and Lee Counties.
Degree
M.S.
Advisors
Dukes, Purdue University.
Subject Area
Ecology|Soil sciences|Range management
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