Acer rubrum L. and Liriodendron tulipifera L. are prolific throughout their ranges in the Southeastern U.S. and also have increasingly important roles in forestry and wood products in this region. The relatively low density and intermediate strength of the wood makes them versatile for use in many different wood products. Exploring the genetic structure of these species could provide a foundation for further genetic and breeding exploration with these economically important trees. This study utilizes amplified fragment length polymorphism to determine the level of genetic diversity of these species in contrasting physiographic provinces. AFLP was performed using five primer combinations on samples collected from six unmanaged populations of each species in the Mountains and Coastal Plain of the Southeastern U.S. Wood density was determined using an X-ray densitometer. A. rubrum lacked strong genetic structure while L. tulipifera showed differentiation between physiographic provinces. Genetic diversity of A. rubrum was lower within the Mountain populations (He: 0.327) than the Coastal Plain populations (He: 0.365). The average wood density for A. rubrum is lower in the Mountains (539.00 kg/m^3) than in the Coastal Plain (575.43 kg/m^3). Genetic diversity of L. tulipifera was higher overall (He: 0.289) than within the Mountain populations (He: 0.281) or the Coastal Plain populations (He: 0.271). The average wood density for L. tulipifera is greater in the Mountains (445.45 kg/m^3) than in the Coastal Plain (441.67 kg/m^3). / Master of Science

Use of soil amendments at planting is one of the time-honored traditions in horticulture, although their effectiveness has been questioned by many. Recently, humate and humate-based products, generally known as biostimulants, have been marketed to increase transplant success. In this study, three experiments were conducted to examine the effects of soil amendments and biostimulants on post-transplant growth of landscape trees. The first experiment, conducted in a greenhouse, determined the effects of several biostimulant treatments (granular humate, water-soluble humate, liquid humate, liquid humate+ = humic acid, hormones, and vitamins) and fertilizer levels (low, medium, high) on the growth of container-grown Corylus colurna L. (Turkish hazelnut) seedlings. Biostimulants did not increase top growth compared to control treatments, but root growth was increased by granular humate at a medium fertilizer rate. The second experiment examined the effects of biostimulants (granular humate, water-soluble humate, liquid humate+) on the post-transplant root growth and sap-flow of landscape-sized balled and burlapped Acer rubrum L. (red maple) grown in root observation compartments (rhizotrons). Biostimulants did not increase root growth over control treatments, but sap-flow was increased. The third experiment, conducted in the field (Groseclose silt loam soil) investigated the effects of soil amendments (peat, and compost) and biostimulants (granular humate, and liquid humate+) on the post-transplant growth of Crataegus phaenopyrum (Blume) Hara (Washington hawthorn) and red maple transplanted bare-root, and grown under combinations of irrigated vs non-irrigated and fertilized-at-planting vs non-fertilized-at-planting regimes. Hawthorn controls generally had less top growth than the other soil treatments as a whole. No soil treatment was higher than control for top growth of red maple. However, root growth of red maple was highest in the peat-treated trees. Stem diameter and dry mass for the control and compost treatments were higher than the biostimulant treatments in irrigated plots, but no differences were observed in non-irrigated plots. Granular humate-treated trees resulted in higher stem diameter and dry mass than the liquid humate+-treated trees in non-irrigated plots. There were no effects of fertilizer, or irrigation on growth after two growing seasons for either species. / Master of Science

Reference ecosystems are a valuable tool for restoration and management efforts in degraded ecosystems. Longleaf pine (Pinus palustris), a pyrophytic southeastern U.S. ecosystem, have declined precipitously in extent since European settlement. Pine mortality and growth patterns were examined in a 15-year re-measurement study in two old-growth stands. Both stands experienced postire mortality and short-lived decreases in basal area. Distance to nearest neighbor had a significant effect on mortality of small (<10 cm DBH) pine. To better approximate reference conditions, saplings of five co-occurring hardwood species were destructively measured for bark accumulation and taper using bark and wood thickness. Significant species differences were detected in bark:wood ratio (P<0.001), with no difference in wood diameter. Blackjack oak (Quercus marilandica) had a bark:wood ratio 3x the closest species and steeper slopes of bark accumulation, suggesting that it is a fireapted species. These results will inform reference conditions for critical regional pine restoration efforts.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Urban runoff continues to impair water quality and there is an increasing need for stormwater management within the limited confines of urban spaces. We propose a system of structural soil and trees that can be incorporated beneath pavement. Structural soil has a high load-bearing capacity yet is engineered to support tree root growth. Stormwater is directed into a structural soil reservoir below the pavement where tree roots can also thrive. Two container experiments evaluated tree function in this system. We examined whether tree roots can grow into compacted subsoils and if root penetration increases soil infiltration rate. Quercus velutina, Acer rubrum, and a no-tree variant were planted in 26.5 L (7 gal) containers and the rootballs surrounded by compacted clay loam. Roots grew into all layers of the compacted soil. Infiltration rate increased by 63% (+/-2%) compared to no-tree containers. A second experiment evaluated water uptake and tree development in fluctuating water tables. Quercus bicolor and Fraxinus pennsylvanica were planted in 94.6 L (25 gal) containers with structural soils (either Stalite or CU® Structural Soil). Trees were subjected to fluctuating water tables simulating infiltration rates of 2, 1, and 0.1 cm/hr for two growing seasons. Trees thrived in all infiltration regimes but roots were shallower in slowly drained treatments. Trees grew best and transpired the highest water volume with moderate infiltration. Even if trees uptake only small volumes of water, increased canopy size compared to conventional plantings (because of greater penetrable soil volume) allows greater rainfall interception thus decreasing runoff. / Master of Science

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