Presentation Title

The effect of drought on the comparative fitness of transplanted Stipa pulchra in the presence of an invasive weed

Faculty Mentor

Stephen Davis

Start Date

18-11-2017 2:15 PM

End Date

18-11-2017 3:15 PM

Location

BSC-Ursa Minor 100

Session

Poster 3

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

Abstract

Studies on the relative health of Stipa pulchra, a California native perennial bunchgrass, were conducted at the transplant garden on the Drescher campus of Pepperdine University in the Spring semesters of 2016 and 2017. Stipa pulchra is a staple species in Southern California with great ecological significance as a food source for native wildlife, a consumer of methane, and a key species in pest suppression. Following the trend of other perennial native grasses, S. pulchra populations are dwindling due to competition with Avena fatua and other invasive species introduced by human activities. In the 2016 study, data was collected in the midst of historic five-year drought in California. Stomatal conductance, measured using a steady state porometer, dark adapted fluorescence, measured using a modulated fluorometer, water potential, measured with a Scholander Pressure Chamber, and height of S. pulchra and A. fatua were recorded and compared. As hypothesized, wild-type S. pulchra exhibited greater overall fitness-- in stomatal conductance, height, and water potential -- than both transplanted S. pulchra and A. fatua.

The follow-up study was conducted at the same study site in 2017 after the occurrence of abnormally high winter rainfall. It was hypothesized that all plants would exhibit higher fitness as a result of the rainfall and that A. fatua would have greater relative fitness than wild-type or transplanted S. pulchra. A. fatua exhibited a higher relative fitness than both the transplant and wild S. pulchra, as indicated by significantly higher stomatal conductance. The transplanted S. pulchra showed signs of stress in its low levels of dark adapted fluorescence and water potential. Comparison of the research also revealed an overall increase in plant growth from the previous year’s drought. The findings demonstrate the impact of competitive invasive species on the growth of a struggling native species, especially in conditions of stress.

Summary of research results to be presented

Spring 2017: Measured stomatal conductance (µmol/m2•s) of the transplant S. pulchra, wild S. pulchra, and A. fatua.

A. fatua has a higher stomatal conductance than both the transplant and the wild S. pulchra, as indicated by one-way ANOVA (p < 0.0001) followed by Fisher’s LSD (A. fatua vs transplant N. pulchra, p < 0.0001; A. fatua vs. wild N. pulchra, p = 0.0002). The letters a, b denote significant differences. Error bars represent ± 1 SE, n = 12.

Measured stomatal conductance for A. fatua (weed), transplanted S. pulchra, naturally occurring S. pulchra (wild). Wild S. pulchra demonstrated significantly higher stomatal conductance than both the transplanted N. pulchra and the invasive A. fatua, as indicated by one way ANOVA followed by Fisher’s LSD at P > 0.01 and P > 0.05, respectively. No significant difference in stomatal conductance was found when comparing the transplanted S. pulchra and the weed A. fatua. Error bars represent ±1 SE, n=6.

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Nov 18th, 2:15 PM Nov 18th, 3:15 PM

The effect of drought on the comparative fitness of transplanted Stipa pulchra in the presence of an invasive weed

BSC-Ursa Minor 100

Studies on the relative health of Stipa pulchra, a California native perennial bunchgrass, were conducted at the transplant garden on the Drescher campus of Pepperdine University in the Spring semesters of 2016 and 2017. Stipa pulchra is a staple species in Southern California with great ecological significance as a food source for native wildlife, a consumer of methane, and a key species in pest suppression. Following the trend of other perennial native grasses, S. pulchra populations are dwindling due to competition with Avena fatua and other invasive species introduced by human activities. In the 2016 study, data was collected in the midst of historic five-year drought in California. Stomatal conductance, measured using a steady state porometer, dark adapted fluorescence, measured using a modulated fluorometer, water potential, measured with a Scholander Pressure Chamber, and height of S. pulchra and A. fatua were recorded and compared. As hypothesized, wild-type S. pulchra exhibited greater overall fitness-- in stomatal conductance, height, and water potential -- than both transplanted S. pulchra and A. fatua.

The follow-up study was conducted at the same study site in 2017 after the occurrence of abnormally high winter rainfall. It was hypothesized that all plants would exhibit higher fitness as a result of the rainfall and that A. fatua would have greater relative fitness than wild-type or transplanted S. pulchra. A. fatua exhibited a higher relative fitness than both the transplant and wild S. pulchra, as indicated by significantly higher stomatal conductance. The transplanted S. pulchra showed signs of stress in its low levels of dark adapted fluorescence and water potential. Comparison of the research also revealed an overall increase in plant growth from the previous year’s drought. The findings demonstrate the impact of competitive invasive species on the growth of a struggling native species, especially in conditions of stress.