Landscape dynamics fostering the development and persistence of long-lived creosotebush (Larrea tridentata) clones in the Mojave Desert

Outward growth of single genetic individuals of creosotebush (Larrea tridentata) produces large, ring-shaped clones. Clones may reach ages of several thousand years and it has been predicted that old clones should occur in older, geologically stable parts of the landscape. Paradoxically, large clones are rare or absent on older, stable geomorphic surfaces (Pleistocene alluvial fan remnants). Instead, clones are most common in places where fluvial and eolian deposition has repeatedly occurred throughout the Holocene. Clones in such locations are derived from plants that originally established on surfaces of older, now buried deposits. The unweathered sandy alluvium of young surface deposits readily absorbs precipitation; plant function is enhanced in these settings. Repeated alluvial deposition also provides fine sand that is locally redistributed by the wind to form sub-canopy coppice dunes. Moisture absorbed by and retained in coppice dunes further enhances plant performance and prospects for long-term survival. On older surfaces where repeated alluvial deposition has not occurred, development of fine-textured soil horizons strongly inhibits infiltration of precipitation and the depth of moisture percolation, which negatively impacts plant performance. Long-lived clones and associated coppice dunes are extremely sensitive landscape features; this sensitivity has conservation implications in terms of land use and management.