Table of Contents Justin Morgenroth and Graeme D. Buchan Soil Moisture and Aeration Beneath Pervious and Impervious Pavements .................................. 135 Abstract. Pervious paving has been increasingly installed in urban areas as a stormwater management strategy. Pervious pavements exhibit similar strength to impervious analogues, but are highly permeable to air and water. These functional characteristics have led to speculation that pervious paving, used instead of impervious paving, could benefit urban trees. Given that permeability to air and water will have a direct effect on the soil environment, this paper describes research that explores the effect of pervious pavement on underlying soil physical conditions. Results indicate that while soil moisture and aeration dynamics differ greatly beneath paved and unpaved surfaces, differences are usually insignificant between pervious and impervious paving. If urban trees do benefit from overlying pervious paving relative to impervious paving, it is probably not a consequence of soil moisture or aeration. The results challenge existing theories and contribute to the understanding of how pervious pavements affect the moisture and aeration dynamics of underlying soils. Key Words: Concrete; Permeable; Porous; Road; Sidewalk; Water. Tomás Martínez-Trinidad, W. Todd Watson, Michael A. Arnold, Leonardo Lombardini, and David N. Appel Carbohydrate Injections as a Potential Option to Improve Growth and Vitality of Live Oaks ...... 142 Abstract. This study evaluates the effects of carbohydrate injections on the growth and vitality of live oak (Quercus virginiana P. Miller). Glucose, sucrose, or a 50:50 mixture of both carbohydrates at increasing concentrations [0, 40, 80, and 120 g/L (0, 5.3, 10.6, and 16.0 oz/gal)] were injected into live oaks. Trunk and root growth, net photosynthesis, root and twig carbohydrate concen- tration, and chlorophyll fluorescence were monitored. Isotope composition of twig and root samples was measured as an indicator of injected carbohydrate distribution. There were significant differences (P < 0.05) in trunk growth among types of carbohy- drates, but no significant differences for carbohydrate concentrations. The mixtures of sucrose and glucose had the largest effect on growth compared to either sugar alone, suggesting that glucose and sucrose alone were used in processes other than trunk growth. 50:50 mixtures caused a greater effect on overall mean growth indices than either sugar alone. Glucose content in twigs and starch in roots were significantly different (P < 0.05) among overall means for concentrations with increased levels found in trees treated with the greatest concentrations. Chlorophyll fluorescence Fv/Fm revealed highly significant differences (P < 0.001) among overall concentrations. Carbon isotope values did not reveal a definite trend that corroborated the exogenous carbohydrate distribu- tion. Results from this experiment suggest that carbohydrate trunk injections can have an impact on growth and vitality of live oak. Key Words. Glucose; Quercus virginiana; Sucrose; Sugars; Tree Vitality. Michael Booth and Dan Johnson Pressurized-Canister Trunk Injection of Acephate, and Changes in Abundance of Red Elm Bark Weevil (Magdalis armicollis) on American Elm (Ulmus americana) ...................................... 148 Abstract. Portable pressurized injection vials (Ecoject System) were used in an experiment to assess injection of acephate into elm trees (Ulmus americana) as a means of reducing within-tree abundance of red elm bark weevil (REBW), Magdalis armi- collis. A total of 25 elm trees were treated, each paired with an untreated tree. A total of 400 pressurized canisters were used in the study. REBW population density, as indicated by sticky-paper trap catches, on treated and untreated trees did not differ sig- nificantly at the time of trunk injection. Two weeks after injection, the average REBW trap catch on the 25 untreated trees had increased, whereas the average trap catch on the 25 treated trees had decreased. The resulting average trap catch from the treated trees was significantly lower than that of the control trees. Although subsequent declines in REBW populations precluded a longer record of the effects of tree injection, the significant reductions apparent in the first two weeks following injection indicated the method was effective in reducing REBW abundance. The impact on REBW populations was detectable even though treated and untreated trees were contiguous, indicating that selective treatment of individual trees could be part of an effective operational treatment for REBW management. No phytotoxic effects were detected by spectrophotometric assessment of leaf chlorophyll. Key Words. Acephate; American elm; Canadian Prairies; Chlorophyll; Ecoject; Magdalis armicollis; Population Reduction; Red Elm Bark Weevil; Spectrophotometric; Sticky Trap Sampling; Trunk Injections; Ulmus americana. ©2009 | International Society of Arboriculture | ISSN:1935-5297
May 2009
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