Date of Award
Master of Science
Over the last 30 years, Crab Orchard National Wildlife Refuge in Southern Illinois has made a strong and well-documented effort to convert agricultural lands to forest to further their mission of wildlife and habitat conservation. Our research seeks to assess the influence that this land use conversion has on ecological function and to establish ecological indicators of successful restoration. We examined five potential soil-based indicators of ecological function across a chronosequence of afforested sites at the refuge and compared them to nearby row crop agricultural sites and mature forest sites with similar soils and landscape positions. Collected soil samples were analyzed for total carbon, total nitrogen, labile carbon, aggregate stability, and bulk density. Soil texture analysis was also conducted to validate comparisons among sites. The data were analyzed using a multivariate analysis of variance comparing land uses as well as linear regression analyses looking at the influence of age since restoration on an index value created by subtracting the soil indicator value of the nearby agricultural site from that of the forested site. The index value was used as the dependent variable in order to control for variation among sites and isolate the influence of age. Aggregate stability and labile carbon were positively correlated with age since restoration and bulk density was negatively correlated with age since restoration. These three soil parameters were promising indicators of restored ecological function in afforested sites. Target values for these indicators were proposed. Our results help to determine the timeframe in which these ecological functions return following restoration and can be used to assess the success of current and future afforestation projects.
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