Spatial Distribution Characteristics of Thick Roots and Their Relationship with Site Environment of Main Street Trees in Shanghai

PurposeTo study the relationship between the distribution of urban street tree roots and site environment, providing a basis for the allocation of plant community in urban road green space.

MethodsA total of 21 road green spaces in central areas of Shanghai were selected, tree radar (Tree Radar Unit) was used to detect the distribution and type of thick root (diameter ≥2 cm) of seven main street trees: Cinnamomum camphora, Platanus acerifolia, Zelkova serrata, Ginkgo biloba, Magnolia grandiflora, Ligustrum lucidum and Koelreuteria bipinnata.

ResultsThe root types of the seven street trees were divided into four types: root of K. bipinnata was vertical and horizontal type, root of C. camphora and P. acerifolia were parallel and horizontal type, root of M. grandiflora, L. lucidum and Z. serrata were right angle type, and root of G. biloba was vertical type. In the vertical direction, the proportion of root density of C. camphora, P. acerifolia, G. biloba, L. lucidum and K. bipinnata decreased with the increase of soil depth, while the proportion of root density of Z. serrata and M. grandiflora increased first and then decreased with the increase of soil depth; in the horizontal direction, the proportion of root density of all street trees decreased with the increase of the distance from the trunk, and the street tree’s roots were concentrated at one meter away from the trunk. For arbor-arbor community composition, trees under the tree configuration and hard floor cover, root density in horizontal direction decreased with the increase of the distance away from the trunk, in vertical direction, the root density decreased with the increase of soil depth. For arbor-shrubs-herbs community composition, the root density in horizontal direction decreased with the increase of distance away from the trunk, but in the vertical direction, the root density first increased and then decreased with the increase of scanning soil depth.

ConclusionThe root distribution and root type of street trees are greatly influenced by the site environment of urban roads.