Is Creosote Distribution Random?

Introduction

Larrea tridentata (creosote) ranges from the deserts of southern California to Texas and deep into Mexico. It is among the most wide-ranging shrubs in North America. It occurs from near sea level to above 4,500 ft.

Details

If plants were randomly distributed, you would expect some to occur in clumps and others to be very far apart. The pattern of creosote distribution is not random; clumps are unusual, and plants are often evenly distributed over an area. Statistically, the pattern is non-random. The shrubs are not spaced on a grid, but they do not grow just anywhere.

Why is the spacing non-random? A common explanation is competition among individual plants for water and nutrients. Desert soils are often short on both. Two plants growing at some distance from each other may prevent seedling establishment between them by using up the available moisture and nutrients.

Thus, plants that grow too close together compete for resources, and one (or both) will eventually wither. Competition keeps the plants at arm’s length. The exact distance between plants is not fixed, but it is non-random. Clumping is the exception, not the rule; spacing is the rule.

Other mechanisms could also contribute to the spacing of the shrubs. Roots may communicate by releasing chemicals into the soil—signals that say, “I’m here already; don’t bother sending your roots this way.” In some cases, the “message” could be inhibitory compounds that cause each plant to keep its distance from neighbors.

Additional Reading: Annual Plants Associated with Creosote

Additional Reading: Communication Between Desert Shrubs

Single creosote shrub

Aerial view showing non-random distribution of shrubs

Creosote shrubs showing the spacing between plants

Creosote shrubs showing the spacing between plants

Creosote shrubs