Suggested key variables for assessment of soil quality in urban roadside tree systems

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SUITMA+20

Suggested key variables for assessment of soil quality in urban roadside tree systems You Jin Kim 1

&

Gayoung Yoo 1,2

Received: 7 February 2020 / Accepted: 1 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract Purpose Urban roadside soils are important growth media for roadside trees. However, typical assessment variables are limited in describing the characteristics of roadside soils. We assessed the characteristics of roadside soils using the pre- and new suggested variables and recommended optimal soil variables that are representative of roadside tree health. Materials and methods Seventy-three roadside soils were collected for measurement, while six urban forest soils were prepared as a control. Samples were used to evaluate both pre-suggested and new variables. The former included bulk density, penetration resistance (PR), pH, organic matter (OM), fluorescein diacetate (FDA) activity, and respiration. To improve the pre-suggested variables, we modified the bulk density using PR and investigated the elemental ratios and stable isotopic signatures of particulate organic matter (POM). Two criteria were used to select the variables for urban roadside soils: (1) the variable should identify distinct characteristics of roadside and urban forest soils and (2) the variable should have a high correlation with urban tree health variables: leaf chlorophyll content and tree vigor. Results and discussion The bulk density measured using the conventional method underestimated soil compaction because obtaining intact cores was challenging. The modified bulk density (BDmodified) obtained from the soil PR is suggested to better represent soil compaction. The roadside soils were affected by de-icing materials, construction debris, and atmospheric alkali particles, which increased the soil pH. The unexpectedly higher OM contents in the roadside soils, where tree origins are limited, possibly due to soil OM sources such as vehicular emissions, animal excreta, and sewer flooding. These OM sources may alter the C/H ratio (POM-C/H) and the stable isotopic signature of POM, leading to OM quality changes. Soil respiration better reflected the changes in the microbial activity of the roadside soils, rather than FDA activity. The newly suggested soil variables, BDmofieid, pH, POM-C/H, and RES, were significantly correlated with leaf chlorophyll content and tree vigor (P < 0.05). Conclusions Using a multiple regression analysis, the newly suggested set of soil variables, including the BDmodified, soil pH, POM-C/H, and soil respiration, showed high predictive power for the growth of urban roadside trees. Future studies should apply these variables to other cities or broader areas and confirm their predictive ability regarding the health of roadside trees. Keywords Urban roadside soil . Soil quality variable . Roadside tree health . Soil organic matter quality

1 Introduction Responsible editor: Stefan Norra * Gayoung Yoo [email protected] 1

Department of Applied Environmental Science, Kyung He