Effects of nitrogen on the photosynthetic response and distribution of Bromus tectorum

Abstract

Bromus tectorum is the most widely distributed invasive species in the Great Basin. The effects of B. tectorum invasion include changes in plant community composition, nutrient and water availability, and increased wildfire frequency. However, its eradication from the region is unlikely. Therefore, effective management strategies to control B. tectorum are needed. In the Great Basin, nitrogen limits plant growth, but nitrogen availability often increases after environmental disturbances (e.g. wildfires). In my dissertation, we examined the effects of increased nitrogen availability on B. tectorum. First, we evaluated the effects of nitrogen availability on productivity and photosynthetic response of greenhouse-grown B. tectorum. Second, we developed a semi-mechanistic model to estimate assimilation rate of B. tectorum in response to leaf nitrogen content, temperature, light, and vapor pressure gradient. The model was developed using information derived from greenhouse-grown plants and validated using field-grown plants. Finally, we examined how assimilation rate of B. tectorum varied across the landscape. To achieve this, we used the semi-mechanistic model to estimate assimilation rate using large scale climate data and different levels of leaf nitrogen content. This study advances our knowledge about the physiological responses of B. tectorum to changes in nitrogen availability and climate variables.