CANCELLED - Soil properties and their effect on within site patchiness of the rare plant Arctomecon californica in the Mojave Desert

Background/Question/Methods

It is well known that soil composition and plant species distribution are closely linked, but the relationship between them is not easily understood. Gypsum soils in the Mojave Desert, U.S.A. support unique species including the rare plant Arctomecon californica. Several studies have attempted to explain the presence or absence of A. californica on gypsum soils, but the literature suggests that A. californica is not a gypsophile and that a more complicated relationship exists to explain this species’ distribution across the landscape. Our study helps to explain soil and environmental factors that dictate within site patchiness of A. californica. Six sites supporting A. californica were selected and a 40 meter wide belt transect was laid across each population. Transects were divided into sections based on visual density estimations and classified as High, Low, and No density. We examined soil properties from horizon’s A and B, abundance of A. californica, and community characteristics within each density class.

Results/Conclusions

Our results indicate that soil composition differs across density classes in horizon A (p= 0.02). The ‘No’ density class was correlated with greater available P, and the ‘High’ density class was correlated with greater soil EC, SO4, Fe, Ca, Co, and Ni. There were no significant differences in soil composition among density classes in horizon B. Plant communities differed across A. californica density classes (p=0.001). The largest differences among density classes were between the ‘High’ and ‘No’ classes, where the ‘No’ class had more generalist species such as Larrea tridentata, Krameria grayii, and Ephedra torreyana. Ni, Zn, Ca, and EC were the strongest soil chemistry predictors of A. californica abundance, whereas soil texture, pH, and bulk density were not significant. This research further demonstrates the importance of soil properties in determining the distribution of A. californica and clearly shows that even at small scales, soil properties differ enough to influence plant species distributions within site.