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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #118768
Title: ROOT SYSTEMS OF SOME CHIHUAHUAN DESERT PLANTS

Author
item Gibbens, Robert
item Lenz, James

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2000
Publication Date: 10/1/2001
Citation: GIBBENS, R.P., LENZ, J.M. ROOT SYSTEMS OF SOME CHIHUAHUAN DESERT PLANTS. JOURNAL OF ARID ENVIRONMENTS. 2001. V. 49(2). P. 221-263.

Interpretive Summary: To aid in interpreting the ecological role of plant species this study was undertaken to determine root system architecture of common plants in each of the life forms of plants, shrubs, grasses, and forbs, making up plant communities on the Jornada Experimental Range in the northern Chihuahuan Desert. Root systems of 11 shrub or shrub-like species, 11 grass species, 19 perenial forb species and 4 annual forb species were excavated at 18 sites with soil textures ranging from fine-silty to sandy. Besides having extensive, widespreading roots in upper soil horizons all of the shrubs, with one exception, had deeply penetrating roots reaching to 5 m depth or more. Grass root systems were concentrated in upper soil horizons and did not penetrate below 1.6 m depth. Perennial forb root systems usually penetrated deeper than grass root systems but not as deeply as shrubs. Root systems of all life forms were highly intermingled in upper soil horizons indicating competition for soil water and nutrients is intense. It is believed that the plasticity and architecture of the shrub root systems, enabling them to compete with the grasses for soil water in the upper soil horizons and also access soil water at depths beyond the reach of grass roots, has been a major reason for the increase of shrubs during the historical period in this arid environment. This information on root system architecture will be invaluable in designing studies to acquire further knowledge of underground biomass dynamics and competitive interaction of plant species.

Technical Abstract: Root systems of 11 shrub or shrub-like species, 11 grass species, 19 perennial forb species and 4 annual forb species were excavated on the Jornada Experimental Range in the northern Chihuahuan Desert in southern New Mexico, USA. Maximum radial horizontal spread of shrub root systems usually occurred above calcic and petrocalcic horizons at depths above 1 m. .With one exception, all shrub species roots were traced through calcic and petrocalcic horizons to depths down to 5 m. Upward growing roots reaching very shallow depths (< 10 cm) were common for most shrub species. Thus, the shrubs can readily access soil water and nutrients from both surface and deep soil horizons. Grass root systems on sandy soils extended radially up to 1.4 m, perhaps an adaptation to capture more soil water from the frequent small rainfall events. Grass roots did not extend through calcic or petrocalcic horizons and none penetrated deeper than 1.6 m. Perennial forb root systems varied in depth of branching but often penetrated into o through calcic and petrocalcic horizons and, like shrubs, have an advantage over grasses during droughts. Root systems of the annual forbs, excavated at the end of a season of above average precipitation, reached depths of 0.5 to 1.2 m. At each of the 18 excavation sites the roots of all the plant life forms were highly intermingled in the upper soil horizons, indicating that competition for water and soil nutrients is intense. It is believed that the plasticity and architecture of the shrub root systems, enabling them to compete with the grasses for soil water in the upper soil horizons and also access soil water at depths beyond the reach of grass roots, has been a major reason for the increase of shrubs during the historical period in this arid environment.