The effect of a dominant shrub on annuals plants in a desert system changes along a gradient of continentality.

The purpose of this experiment is to determine how desert shrubs influence annual plant productivity (abundance, biomass & species richness) along a regional gradient of climate. We hypothesized that the magnitude and frequency of positive interactions between shrubs and annuals will be greatest at intermediate levels of stress along a regional gradient of continentality. This experiment will begin fall 2015 and will consist of multiple sites located in California along increasing distance from the pacific ocean. These sites were chosen as they represent increasing abiotic stress (i.e. hotter and dryer the further inland). We expect positive interactions to be most frequent at intermediate levels of environmental severity but decline at the extremes. 


Examining the factors limiting shrub establishment of Ephedra californica in the presence of high competition from invasive grasses (Bromus rubens).



The purpose of this experiment is to determine the factors that are limiting Ephedra californica recruitment up at the Panoche Hills plateau in the San Joaquin Valley, California. We hypothesize that Ephedra californica is a stress-tolerant shrub species that is out competed for water and light by a highly competitive exotic grass species, particularly when disturbances such as herbivory reduce its biomass. To test this, we are running greenhouse experiments concurrently but not orthogonally testing the different factors that could be inhibiting Ephedra recruitment. This includes competition for shade, competition for soil moisture or herbivory. 

Positive interactions increase global biodiversity by expanding the realized niche of desert annuals species

The purpose of this experiment is to model the effects of positive interactions in maintaining or increasing global biodiversity. This is a common assumption of facilitation studies but it has not yet been modeled. We hypothesize that shrubs in arid ecosystems expand the realized niche of an annual plant species beyond that of the fundamental niche because of the ameliorated micro-climate located within the canopy. To test this, we will first examine to what extent a shrub modifies the climate within the canopy, then use that difference to conduct species distribution models with and without the presence of positive interactions. We expect that positive interactions may be responsible for at least 50% increase in available habitat for plant species because of the wider range of abiotic conditions

amsinckia distribution


- MSc transfered to PhD. with C.J. Lortie, York University- In Progress

Decoupling plant-plant mechanisms of facilitation of interactions in arid landscapes for the purposes of restoration.

B.Sc. (Spec. H) - Biology –York University 2012