Biederman, Lori Ann (2007-05). Directing ecological restoration: impact of organic amendments on above- and belowground ecosystem characteristics. Doctoral Dissertation.
Thesis
Increasing interest among restoration ecologists exists in developing strategies that stimulate biotic interactions and promote self-regulation in restored systems. These approaches should target above- and belowground organisms because they interact to regulate ecosystem pattern and process. In the following dissertation, I compare the ability of organic amendments to alter above- and belowground biological community structure and function to promote prairie establishment on Castle Drive Landfill in Garland, Dallas County, Texas. Treatments included altering the location of organic amendments in the soil profile, either applied to surface or incorporated, and varying the amount applied. Plant community composition, grass population dynamics, soil nutrient conditions, and soil biological parameters were monitored for three growing seasons. Aboveground, the surface treatments were superior for the establishment of desired and undesired plant species. Plant density patterns can be attributed to the amelioration of physical conditions and the accidental burial of seed during incorporation. Grass population dynamics suggest that surface-amended plots supported establishment, but high-volume incorporated treatments were better for enhancing survival through seasonal and long-term drought. Belowground biological responses were affected by the plant community, and not by the amendment treatments. Soil microbial biomass and carbon mineralization potential were larger in those treatments with greater plant density. The structure of the nematode community suggests that decomposition in the surface-amended plots was directed through bacterial channels while decomposition in the incorporated plots was through fungal channels. It is likely that the higher rates of plant productivity in surface treatments stimulated root exudation, thereby favoring bacteria and the nematodes that feed on them. Treatment differences in decomposition pathway were attenuated after 17 months. The soil quality indicators, Cmic/Corg, qCO2, nematode family richness and nematode density, were not affected by the restoration treatments or plant density, but did increase over time. The results of this study suggest that restoration managers should direct their energies into establishing and promoting a high-quality plant community. This can be manipulated with amendments, but care is needed not to exceed thresholds within location treatments.
