Effects of Tree Root Density on Soil Total Porosity and Non-Capillary Porosity Using a Ground-Penetrating Tree Radar Unit in Shanghai, China

Bingqin Yu,Zhiwen Yang,Changkun Xie,Shize Cai,Zulan Mo,Yan Chen,Tianlei Liu,Yongpeng Lv

doi:10.3390/su10124640

Bingqin Yu, Zhiwen Yang + Show 6 more

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https://doi.org/10.3390/su10124640

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Abstract

To explore the relationship between arbor root density and corresponding physical soil properties (total porosity, non-capillary porosity, specific weight, bulk density, moisture content, and permeability), noninvasive methods such as Tree Radar Unit (TRU) were utilized to detect the root systems of 10 species of tree that are commonly used in Shanghai green spaces with more than 70% frequency of occurrence. Using TRU and soil investigation, root density and soil porous features were determined for different tree species, depth slices, and distances. The relationships among root density, soil porosity, and non-capillary porosity were identified using variance analysis and regression analysis. The results indicated that root density decreased with increasing distance from the trunk and soil depth. Soil porosity and non-capillary porosity had significantly positive and linear correlations with root density. Compared with lawns, trees such as Zelkova serrata, Koelreuteria paniculata, Cinnamomum camphora, and Metasequoia glyptostroboides had the greatest effects on soil improvement through soil porosity and non-capillary porosity. Due to the spatial distribution of root systems, trees could be divided into three types based on their influence at various soil depths.

Highlights

Sponge city construction, low-impact development, and rainwater management in green spaces in Shanghai, China, have become important issues
The values for M. grandiflora (42.8%), O. fragrans (42.7%), and L. lucidum (40.2%) were lowest in deeper soil layers. These results suggested that there were three categories of soil total porosity respectively in shallow and deep soil layers, which was fairly consistent with the three groups of tree root system distribution
The results indicated that the variance of non-capillary porosity of trees was significant, and it primarily reflects the effects of tree root systems on non-capillary porosity in the shallow soil layer of 15–30 cm

Summary

Introduction

Low-impact development, and rainwater management in green spaces in Shanghai, China, have become important issues. Green spaces include two parts: the overground part, with limbs and canopy; and the underground part, with roots and soil. Studies have suggested that limbs, canopy, and roots are related to rainwater regulation and storage capacity of green spaces [1]. Especially soil porous characteristics, have a great impact on rainfall infiltration [2]. When rainfall flows downward to deeper soil layers, the process of hydraulic redistribution is affected by roots, accounting for 74% (

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