While the extent of grasslands in Southern Ontario has been greatly reduced, urban and suburban areas provide numerous potential sites for their restoration. Grassland restoration in cities can provide ecological and cultural benefits, but soil conditions may be less than optimal for native species recovery. This thesis explores the use of soil amendments in order to address nutrient deficiency on old-field meadow restoration sites. Five treatments were tested, namely the addition of (1) nitrogenous fertilizer, (2) native legume species, (3) biochar, (4) a combination of the previous three, and (5) an unaltered control. Each treatment was replicated four times on two different test plots in Waterloo Region, Ontario, Canada (Huron Natural Area and Springbank Farm), for a total of 40 subplots. The experimental plots were tilled in the fall of 2011, a randomly selected treatment was applied to each subplot, and then all were seeded with a mix of five native meadow species (2 grass, 2 forb, 1 sedge). Soil samples were taken from each subplot both before treatment application and also at the end of the growing season in 2012, and tested for nutrient levels (N, P, K), pH and organic matter. Species richness, as well as soil temperature and moisture, were regularly monitored over the growing season. In the fall of 2012, above-ground vegetation was harvested to assess accrued biomass. In order to detect differences in means, results were tested using one-way and repeated-measures ANOVAs, where appropriate. Pearson???s product-moment correlations were also employed to test for linear dependence between variables. There were no significant differences between treatments in terms of soil nutrients or pH at either site. At Huron Natural Area, post-treatment biochar-treated subplots had slightly higher levels of organic matter than controls (p=0.095). Values for species richness, above-ground biomass, soil temperature and soil moisture did not vary significantly between treatments. Species richness at Huron Natural Area was positively correlated with 2011 N (r=0.42; p=0.07) and organic matter (r=0.52; p=0.02) levels, while at Springbank Farm it was negatively correlated with 2012 N levels (r=-0.67; p<0.001). Above-ground biomass at Huron Natural Area was positively correlated with 2011 and 2012 P levels (both r=0.52; p=0.02), while at Springbank Farm it was positively correlated with 2011 N, P, K and organic matter, and 2012 N, P and K (all r>0.44; p<0.05). At Huron Natural Area, above-ground biomass was negatively correlated with soil temperature (r=-0.64; p<0.0001) and positively correlated with soil moisture (r=0.38; p=0.1). This study uncovered a strong, but variable, relationship between N concentration and species richness in old-field meadows. Furthermore, productivity was tightly correlated with different soil nutrient concentrations at each study site. The results demonstrate the need for restoration approaches to address local soil conditions on order to be effective. To date, there have been very few studies on meadow restoration, particularly in North America. More, and longer-term, multivariate studies are needed in order to test the effectiveness of different techniques.

<p>This study seeks to investigate the dynamics of dead plant carbon over fifty years of old-field forest development at the Calhoun Long Term Soil-Ecosystem Experiment (LTSE) in South Carolina, USA. Emphasis is on the transition phase of the forest, which is less well studied than the establishment and early thinning phase or the steady state phase. At the Calhoun LTSE, the biogeochemical and ecosystem changes associated with old field forest development have been documented through repeated tree measurements and deep soil sampling, and archiving of those soils, which now allow us to examine changes that have occurred over the course of forest development to date.</p><p> In this dissertation, I first quantify the accumulation of woody detritus on the surface of the soil as well as in the soil profile over fifty years, and estimate the mean residence times of that detrital carbon storage. Knowing that large accumulations of C-rich organic matter have piled onto the soil surface, the latter chapters of my dissertation investigate how that forest-derived organic carbon has been incorporated into mineral soils. I do this first by examining concentrations of dissolved organic carbon and other constituents in soil solutions throughout the ecosystem profile and then by quantifying changes in solid state soil carbon quantity and quality, both in bulk soils and in soil fractions that are thought to have different C sources, stabilities, and residence times. To conclude this dissertation, I present the 50-year C budget of the Calhoun LTSE, including live and dead plant carbon pools, to quantify the increasing importance of detrital C to the ecosystem over time.</p><p>This exceptional long term soil ecosystem study shows that 50 years of pine forest development on a former cotton field have not increased mineral soil carbon storage. Tree biomass accumulated rapidly from the time seedlings were planted through the establishment phase, followed by accumulations of leaf litter and woody detritus. Large quantities of dissolved organic carbon leached from the O-horizons into mineral soils. The response of mineral soil C stocks to this flood of C inputs varied by depth. The most surficial soil (0-7.5cm), saw a large, but lagged, increase in soil organic carbon (SOC) concentration over time, an accumulation almost entirely due to an increase of light fraction, particulate organic matter. Yet in the deepest soils sampled, soil carbon content declined over time, and in fact the loss of SOC in deep soils was sufficient to negate all of the C gains in shallower soils. This deep soil organic matter was apparently lost from a poorly understood, exchangeable pool of SOM. This loss of deep SOC, and lack of change in total SOC, flies in the face of the general understanding of field to forest conversions resulting in net increases in soil carbon. These long term observations provide evidence that the loss of soil carbon was due to priming of SOM decomposition by enhanced transpiration, C inputs, and N demand by the growing trees. These results suggest that large accumulations of carbon aboveground do not guarantee similar changes below.</p> / Dissertation

Thesis (MScConsEcol (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / In the Mediterranean climate regions of the world, agricultural practices have caused considerable landscape transformation and lead to introduction of alien species that now dominate secondary succession on abandoned agricultural fields. Various restoration attempts have been made to reduce alien plant species cover, and to enhance the re-establishment and cover of native plant species. However, results and successes were mostly short-term due to re-growth and persistence of the weedy alien species, which has been suggested to be caused by land use history, especially the nutrient enrichment of soil, and particularly phosphorus and nitrogen. This study investigated different soil properties (pH, electrical conductivity (EC), soil moisture, as well as available phosphorus (P) and total nitrogen (N)) on 10 and 20 year old abandoned fields, as a function of depth in three habitats (ridge (old cultivated area), ditch (old drainage line) and slope (intermediate zone between ridge and ditch)) on the old fields. The relationship between these soil properties and the vegetation occurring on the two old fields was established. At the same time, restoration treatments (autumn burn, combination of autumn burn and herbicide, herbicide application alone, as well as spring burn) were conducted to reduce the cover and abundance of non-native plant species and Cynodon dactylon, and to enhance cover of native species. Results from the study show that levels of all investigated soil properties were higher on the younger field. The highest difference was observed in EC and pH. Seasonal differences in both soil properties could also be observed. A principal component analysis indicated that the dynamic of all soil properties shaped the vegetation type on old fields, with the main soil properties being dependent on land-use history and time since abandonment. This study suggests that EC and pH could be part of parameters that drive the persistence of undesirable species persistence on old fields and inhibit native plant species instead.