Leaf scorch is a common symptom of declining trees in urban landscapes, especially Northern red oaks, Quercus rubra. Established trees with a known history of abiotic leaf scorch were systematically evaluated for depth of root flare, girdling root severity, soil compaction (resistance), soil nutrient profile, pH, and soil oxygen profile. Photosynthesis efficiency, leaf pressure potential, leaf conductance, leaf transpiration, and plant tissue nutrition were measured to examine differences in physiological function between scorched and non-scorched oaks on the same site and among sites. Leaf scorch was significantly positively correlated to planting depth. Planting depth was positively correlated to girdling roots and smaller DBH. However, leaf scorch was not significantly correlated with the presence of girdling roots. Soil treatment with micro-fine sulfur, and Mauget injections increased iron but not manganese in leaf nutrient levels. Scorched trees had smaller DBH, greater planting depth than non-scorched trees. Tree height and DBH was positively correlated with less compacted soils. Scorched leaves had a significantly higher temperature compared to non-scorched. Scorched trees had lower levels of manganese, and higher levels of zinc. Phosphorus, though deficient, showed a positive correlation to leaf scorch. Photosynthetic efficiency and leaf conductance data from 2009 and 2010 were highly similar. Scholander pressure chamber data from 2008 and 2009 were highly similar. A better understanding of the functional capabilities of girdling roots in oaks is needed to better interpret some results.
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