Biological invasions by exotic, invasive plants are widely recognized as a threat to biodiversity and ecosystem function. Invasive plants alter ecosystem processes, specifically shifts in plant community composition and nutrient cycling. Subtle ecosystem effects of non-native species invasion are often undetected and understudied. Invasion driven changes to above- and below-ground processes and structure can create feedbacks that increase site susceptibility to further invasion. Enhancing resistance to further invasion in systems already experiencing altered community structure and nutrient cycling continues to challenge restoration ecologists. To investigate practical ecological methods designed to enhance biotic resistance of a system to invasion, I tested the effectiveness of six different soil manipulations to alter chemical, physical, and biological aspects of forest soils that influence the invasion of two invasive, exotic species, Berberis thunbergii and Microstegium vimineum. I focused on experimental manipulations of nitrogen availability, surface leaf litter, and mycorrhizal infection in greenhouse and field studies to provide a multi-pronged approach to investigations of exotic species invasion success. Nitrogen additions tested the response of two exotic and two native species to different forms and concentrations of nitrogen. Exotic species were found to be more plastic in their growth response to either nitrogen form in both excessive or limiting concentrations. Topsoil removal showed some success in limiting inorganic nitrogen availability but trends were not consistent. Woodchip additions were not successful at immobilizing nitrogen or increasing the C:N ratio of the soil. Aluminum sulfate, added to increase soil acidity, was also not consistently effective, but did lower soil pH temporarily. The nitrification inhibitor applied to field plots proved to be ineffective in forest soils. Leaf litter addition applied to field soils in which Microstegium seeds were planted did not inhibit but enhanced its growth compared to soils without litter. And finally although Microstegium roots were found to be responsive to arbuscular mycorrhizal colonization, its growth in two different forest soils was not negatively affected by removal of mycorrhizal inoculum. This research highlights the plasticity of these two exotic species to a variety of environmental conditions and reveals the challenges of forest soil restoration.After four weeks of growth, significantly more seedlings had germinated in the oak soil (t-value 8.07, palt;0.0001) than in the ... percent survival was enhanced by most of the litter types, but the effect of the each litter type depended on soil typeanbsp;...
|Title||:||The Effects of Soil Manipulations on Invasion Success of Two Exotic Species, Japanese Barberry (Berberis Thunbergii) and Japanese Stiltgrass (Microstegium Vimineum).|
|Author||:||Kristen Ann Ross|
|Publisher||:||ProQuest - 2008|