Clonal plants occupy a major component of ecosystems throughout the world in terms of relative cover, ecosystem function and landscape dynamics. Previous estimates, mostly in Eurasian temperate and arctic biomes, have identified between 28 and 80 percent of plants have clonal adaptations. Typically, clonal plants are most abundant in habitats and ecosystems of extremes, such as those with cold, wet or dry conditions. Relatively little research has been carried out on clonal plant components of arid North America and those that have, generally focused on relatively few species. Of arid land clonal plants, Larrea tridentata has been the most commonly examined. It was the goal of this study to identify perennial clonal plants within the Northern Sonoran Desert and determine their relative abundance, cover, clonal adaptations and position within the landscape. The examined plants were limited to within the confines of the Northern Sonoran Desert region below 1,000 M elevation and were non-aquatic, non-parasitic perennial plants. Clonal plants, adaptations and relative cover were identified through field examination, herbarium specimens and the literature. Sufficient information was found on 202 perennial plant species to determine reproductive strategies and adaptations.
Results/Conclusions
Approximately 55% of the examined perennial plants were found to contain clonal adaptations. Of these, all but the possibility of Cylindropuntia bigelovii retained the ability to reproduce sexually. Axial splitting and rhizomes were found to be the most common forms of clonal adaptations with creeping stems, root crown budding and other adaptations being less common. Clonal plant abundance and adaptations to clonal reproduction were found to vary significantly between plant life forms. Grass and shrub life forms contained the greatest abundance of clonal plants, while trees and herbs contained the least. Relative cover of clonal plants was also found to vary significantly between geomorphic surfaces. Undeveloped soils, where drought conditions were most severe and near monocultures of Larrea tridentata were found, contained the highest clonal plant relative cover percentage. Several plant species were also found to vary in ability to reproduce sexually and asexually between geomorphic surfaces. For example, rhizomatous reproduction increased on some unstable geomorphic surfaces for certain plant species. Based on these observations, it was expected clonal production of plant ramets likely increases chances of survival of the resulting smaller individual plants through drought and disturbance. Clonal production of ramets, therefore, increases chances of successful sexual reproduction.