Article 10 of 12 from Trees: Dispelling Myths & Misinformation, prepared by the arborists of the Southwest Division of Bartlett Tree Experts as a community education initiative.
Earlier, we mentioned some of the differences between forest and urban trees. The nature of soils is certainly one of them. Not surprisingly, soils develop more naturally in the forest environment, achieving better structure and richness. In our communities, the construction activities that develop and maintain urban areas disrupt this process and compromise the physical, chemical, and biological properties that create healthy soils.
An ideal soil contains adequate amounts of mineral and organic material and pore space for air and water. When you consider the engineered soils that make up driveways, parking areas, foundations, and roads, you get some idea of the poor soils in which trees are often trying to exist.
One of the biggest problems with urban soils is compaction. This can occur from construction, foot traffic, vehicular traffic, and similar activities. Some residents in more rural settings who have horses, cattle, or alpacas will find their soil highly compacted around the trees that provide these animals with shade.
Treatments exist to improve the nutrient content and aeration of urban soils. These start with soil testing and may include prescription fertilization or a comprehensive root invigoration process that helps loosen the soil, adds organic matter, and adjusts the soil chemistry to best favor the tree.
This brief coverage of soil importance helps us better understand the critical nature of the next topic: protecting trees at construction sites.