How do urban environments affect root development?

Urban settings impose severe alterations to tree roots due to the multiple physical and chemical forces at work. Compacted soil tends to inhibit natural down growth patterns. Pavement impedes the downward extension of roots, thereby forcing them out through unnatural settlements. Chemical contamination of the soil has a poisonous effect on delicate root structures. A relatively small soil volume prevents mature development from being completely inhibited.

Compacted soils form an oxygen-starved environment in which root systems suffocate. Heavy equipment and foot traffic compress soil particles tightly together. Consequently, for the exchange of gases, roots require air pockets to be eliminated. Roots die back from the tips inward due to a lack of oxygen being available for respiration. Tree tops show crown thinning within a few months.

Chemical contamination gives injury without noise. Each winter, road salts dissolve in groundwater. The root cells are dehydrated by them through osmosis. Herbicides applied to adjacent lawns seep into the soil's moisture. They injure the root hairs, which are concerned with the absorption of food. Recovery requires several growing seasons.

Limited volumes of available soil cause unnatural growth patterns. Tree roots usually require more soil than the spread of the crown. Urban trees are confined to small tree pits. This produces girdling roots, restricting the trunk. The life span is reduced from decades to but a few years in extreme cases.

Paved barriers create thermal stress on trees. Concrete absorbs heat, causing soil temperatures to increase by 10°C. This can help cook shallow roots during the summer months and prevent winter dormancy cycles. Additionally, trees expend extra energy to repair heat-damaged tissues.

Read the full article: 7 Essential Facts About Tree Root Systems