Table of Contents P. Eric Wiseman, Susan D. Day, and J. Roger Harris Organic Amendment Effects on Soil Carbon and Microbial Biomass in the Root Zone of Three Landscape Tree Species .................................................................................................. 262 Abstract. There is increasing interest in amending degraded soils with organic matter to improve soil quality, especially in urban areas where rehabilitation of damaged soils may enhance tree growth and provision of ecosystem services. To assess the potential of such organic amendments for producing a sustained alteration in soil biological characteristics, researchers studied the effects of three organic amend- ments incorporated into the root zone of three tree species on root development, soil carbon dynamics, and soil microbial biomass over one year beginning 20 months aſter amendment application. Soil amendment with leaf-based, and to a lesser extent, biosolids-based com- posts increased root length within the amended root zone of red maple (Acer rubrum), but not of pin oak (Quercus palustris) or chestnut oak (Q. montana). There was a concomitant increase in microbial biomass carbon for red maple. Across all species, sphagnum peat moss amendment reduced microbial biomass carbon by 47% compared to unamended root zones and suppressed maximum seasonal soil res- piration relative to composts. In contrast, leaf-based compost increased microbial biomass carbon by 12% (P = 0.0989) compared to unamended root zones. Carbon/nitrogen ratios remained stable throughout most of the year except in the root zones of chestnut oak and pin oak amended with peat, where it declined 44%–85%. Total soil carbon was stable in all treatments, although unamended soils aver- aged about 40% lower than amended soils. Across all species and treatments, cumulative fine root length explained 19% of the variation in microbial biomass carbon. The study authors conclude that soil microbial activity can be increased by compost amendment of the root zone and that this increase is mediated to some degree by tree roots. In addition, stable C/N ratios suggest this alteration in the root zone may be sustainable. Further research may clarify whether compost amendment combined with tree planting can accelerate soil restoration. Key Words. Acer rubrum; Quercus montana; Quercus palustris; Soil Food Web; Soil Rehabilitation; Soil Respiration; Tree Roots; Urban Soil. Daniel C. Burcham, Eng-Choon Leong, Yok-King Fong, and Puay-Yok Tan An Evaluation of Internal Defects and Their Effect on Trunk Surface Temperature in Casuarina equisetifolia L. (Casuarinaceae) ............................................................................... 277 Abstract. Tree risk assessment is important when communities choose to cultivate trees near people and property, and many tools may be used to enhance these assessments. The effectiveness of determining internal tree stem condition by measuring trunk surface temperatures with infrared cameras was assessed in this study. The trunk surface temperature of 48 Casuarina equisetifolia was evaluated; the trees were felled and dissected to quantify internal stem defects; and a mixed-methods approach was employed to determine the presence of defects. In total, 27% of trees were decayed, 62% discolored, 6% cavitated by termite infestations, and 2% undamaged. Qualitative visual evaluation of the infrared images revealed the close association of external stem features, opposed to internal defects, with surface temperature distributions. External features, such as cankers, detached bark, and mechanical damage, were associated with temperature anomalies. The trees’ internal condition accounted for a small percentage of the variability in evaluated temperature measurements (r2 was found between the extent of internal defects and surface temperature distributions. These results are practically important for the arbo- ricultural professional community because they show the technique does not provide accurate results about the internal condition of trees. Key Words. Casuarina equisetifolia; Diagnostic Device; Infrared Camera; Internal Defect; Singapore; Temperature; Thermal. E. Thomas Smiley, Brian Kane, Wesley R. Autio, and Liza Holmes Sapwood Cuts and Their Impact on Tree Stability ........................................................................ 287 Abstract. Sapwood may be lost due to wood decay fungi or mechanical damage. Assessing the impact of sapwood loss on the likelihood of tree failure has not been empirically tested. The purpose of this research was to determine the effect of the loss of sapwood on the flexural stiffness of tree trunks for different species and trunk sizes. Three tree species (Acer rubrum, Liquidambar styraciflua, and Quercus acutissima) were tested at two sites using pull testing techniques. A portion of the stem was mechanically removed and the trees were again pull tested. As the percent reduction in cross-sectional area increased, the percent reduction in stress to deflect trunks decreased linearly, regardless of species. Stress from sapwood loss was compared to an equivalent calculated loss in heartwood with the same cross-sectional area. The cal- culated loss of heartwood to cause an equivalent magnitude of stress was almost twice as large as cut area of sapwood. Trees were also tested by pulling in opposite directions with respect to sapwood loss. The percentage reduction in stress was greater for trees tested in compression. Key Words. Acer rubrum; Decay; Likelihood of Impact; Liquidambar styraciflua; Notch Cuts; Quercus acutissima; Sapwood Loss; Strength Loss; Tree Risk Assessment. = 0.001–0.096). Overall, no clear relationship ©2012 | International Society of Arboriculture | ISSN:1935-5297
November 2012
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