Increase and Spatial Variation in Soil Infiltration Rates Associated with Fibrous and Tap Tree Roots

Dashuai Zhang,Jijian Lian,Liang Chen,Qizhong Guo,Zhaogeng Wang

doi:10.3390/w11081700

Dashuai Zhang, Jijian Lian + Show 3 more

Open Access

https://doi.org/10.3390/w11081700

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Abstract

Trees play important roles in urban stormwater management; through the loosening of soils by root growth, they increase infiltration and reduce runoff, helping to mitigate flooding and recharge groundwater. Malus baccata with fibrous roots and Sophora japonica with tap roots were studied experimentally to assess their enhancement of soil infiltration. A blank test without a tree was conducted for comparison. Steady-state soil infiltration rates at the bottom of test tanks were measured as 0.28 m/d, 0.33 m/d, and 0.61 m/d for the blank test, M. baccata, and S. japonica, respectively. This represents a 19% increase in the infiltration rate by planting M. baccata and a 118% increase by planting S. japonica. A larger increase in the infiltration rate by S. japonica is consistent with the effects of deeper and more vertical roots that help loosen deeper soils. Spatial variations in soil infiltration rates were also measured. Infiltration rates for M. baccata (1.06 m/d and 0.62 m/d) were larger than those for S. japonica (0.91 m/d and 0.51 m/d) at the same depths (0.35 m and 0.70 m); this is consistent with the expected effects of the shallower and more lateral roots of M. baccata. This study furthers our understanding of the roles of trees in watersheds and urban environments.

Highlights

With urbanization, the area of impervious surfaces is increased, which can lead to increased flooding and groundwater shortages [1,2,3,4]
The same trend was obtained in other tanks where M. baccata and S. japonica were planted. These results suggest that trees with a tap root system affect deep soil permeability due to their deeper and more vertical roots, which help to loosen deeper soils and transport more water to the base of the tank [45,46], and that trees with fibrous root systems which have shallower and more horizontal roots have little influence on the permeability of deep soils [47,48,49]
It is noteworthy that the value of soil infiltration rates in vertical (0.35 m, Figure 6) and horizontal directions (0.35 m, Figure 7) represent different soil layers

Summary

Introduction

The area of impervious surfaces is increased, which can lead to increased flooding and groundwater shortages [1,2,3,4]. Plant roots increase infiltration and reduce runoff, which help mitigate flooding and recharge groundwater [7]. Trees and grasses can increase the number of pores in soils and promote soil permeability by root growth [12]. The growth of roots can improve soil porosity and decrease soil density [13,14,15]; likewise, pores can accelerate the growth of roots by increasing the volume of air in the soil [16,17,18]. Mishra and Sharma [19] observed that the bulk density of surface soils decreased from 1.66 t/m3 to 1.37 t/m3 in three years with the growth of Prosopis juliflora, and the porosity of the soil increased from

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Conclusion