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 (BD_modified) 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, BD_mofieid, 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 BD_modified, 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.

中文翻译：

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建议评估城市路边树木系统土壤质量的关键变量

目的

城市路边土壤是路边树木的重要生长介质。但是，典型的评估变量在描述路旁土壤的特性方面受到限制。我们使用建议的变量和建议的最佳变量来评估路边土壤的特性，这些变量代表路边树木的健康状况。

材料和方法

收集了73种路旁土壤进行测量，同时准备了6种城市森林土壤作为对照。样本用于评估建议变量和新变量。前者包括堆积密度，抗穿透性（PR），pH，有机物（OM），双乙酸荧光素（FDA）活性和呼吸作用。为了改善建议的变量，我们使用PR修改了堆密度，并研究了颗粒有机物（POM）的元素比率和稳定的同位素特征。使用两个标准来选择城市路边土壤的变量：（1）该变量应识别路边和城市森林土壤的鲜明特征；（2）该变量应与城市树木健康变量具有高度相关性：叶绿素含量和树木活力。

结果和讨论

使用传统方法测量的堆积密度低估了土壤压实度，因为获得完整的岩心具有挑战性。修改后的体积密度（BD_修改后建议从土壤PR中获得）以更好地表示土壤压实度。路边土壤受到除冰材料，建筑碎屑和大气碱性颗粒的影响，从而增加了土壤的pH值。树木起源受到限制的路旁土壤中，OM含量出乎意料的更高，这可能是由于土壤OM源（例如车辆排放物，动物排泄物和下水道洪水）造成的。这些OM源可能会改变C / H比（POM-C / H）和POM的稳定同位素特征，从而导致OM质量发生变化。土壤呼吸作用更好地反映了路旁土壤微生物活性的变化，而不是FDA活性。新建议的土壤变量BD _mofieid，pH，POM-C / H和RES与叶绿素含量和树木活力显着相关（P <0.05）。

结论

使用多元回归分析，新建议的一组土壤变量，包括BD_修正值，pH值，POM-C / H和土壤呼吸，显示出对城市路边树木生长的高预测力。未来的研究应将这些变量应用于其他城市或更广阔的地区，并确认其对路边树木健康的预测能力。