The Ecology of Tree Roots and the Practical Significance Thereof

Abstract

Tree root growth is opportunistic and occurs wherever the environment is favorable. A balance exists between the root system and the remainder of the plant, so that if part of the root system dies, part of the crown will also die. Both parts are connected by a well-developed conduction system. Approximately 99 percent of the roots occur within the surface meter of soil and extend outward over an area one to two or more times the height of the tree. Large woody roots form the framework and are typical in pattern for each species. The fine feeder roots occur in the leaf and litter layer, if present, and the surface mineral soil. Keen root competition occurs at the surface if a turf exists under the tree. Also, herbicides, etc. used on lawns may have detrimental effects on the trees through these fine absorbing roots. In the urban environment roots may follow cracks and crevices in pavements, pipelines, sewers and cables. At the same time the installation of these utilities may cut across established tree root systems with unfortunate consequences.

Estimation of Water Use of Landscape Trees

“…Assume for the sake of conservatism that the roots of that tree are confined beneath the crown volume and within the upper 0.5 meter of soil. This has been shown not to be the case (21), but these estimates will serve to illustrate a point. Given the above parameters, the soil volume available to the plant's roots is 157.08 cubic meters, or 157,080,000 cubic centimeters.…”

Root Systems of Trees-Facts and Fallacies

“…They provide minimal anchorage but store significant amounts of carbohydrates in specialized units called amyloplasts. Their primary function is absorption of water and mineral elements and are best referred to as absorbing roots (19). Tubular extensions of epidermal cells known as root hairs, significantly increase the absorptive surface area of the root.…”

“…Woody roots are large lateral roots which form at root-stem bases and serve as anchorage and support for the tree. They form the framework and are distinct for each species (19). They also serve important roles in water, mineral, and organic compound transport, as well as storing carbohydrates (28).…”

“…Thomas Perry in his 1982 review "The Ecology of Tree Roots and the Practical Significance Thereof" (19) wrote an excellent summary of root growth and factors influencing their development. It is the authors' desire to summarize research subsequent to his paper, and discuss what current studies have disclosed in order to facilitate a better understanding of root growth processes.…”

A Description of Urban Soils and Their Desired Characteristics

“…The first is that the urban soil is seldom a loam with 50 percent pore space, as the bulk density tends to be greater than 1.33 mg/m 3 , causing pore space to be less than 50 percent; and secondly, in the confined rooting space of the urban tree, the roots seldom extend fully to the crown projection. The suggested situation is that the roots are confined to a small space and the soil provides less available water than the model permits (15). In open areas where the roots are relatively unrestrained, the model is probably appropriate.…”