Strategic Mulching of Trees in Forested Urban Parkland for Rooting Medium Amendment

Trees planted along city streets and in urban parks are subject to many adversities that affect growth and can often result in mortality. The application of organic mulch to the rooting medium of newly planted urban trees has the potential to improve the soil chemical and physical properties necessary for tree root health. This study examined the difference in soil nutrient supply rates (μg/10cm2/28 days) between three areal treatments of wood chips (0.75 m, 1.0m and 1.5 m radii) and before mulch application versus after mulch application using Analysis of Covariance. PRSTM-Probes were inserted into the soil over six 28-day periods to measure the supply rate of bioavailable nutrients (NO3-, NH4+, P, K, S, Ca, Mg, and Cu). Meteorological data and other soil chemical and physical factors were measured and included as covariates in the statistical model. Results indicate that mulching had a significant effect (p<0.05) on P supply rates; supply rates were lower in the reference plots compared to the treatment plots post-mulching. S, Ca, Mg, and Cu supply rates decreased after mulch application; however, the decrease was observed in all plots, which is likely due to temporal variations in plant demand rather than mulching. The wood chips also had a significant impact on buffering fluctuating soil temperatures and reducing soil moisture loss compared to non-mulched plots. The knowledge obtained from this research can be used to improve urban forest management strategies by providing a more in-depth understanding of the prescriptive use of organic mulch.