Plant Sciences Commons^™

Deep Learning Can Be Used To Classify And Segment Plant Cell Types In Xylem Tissue, Reem Al Dabagh, Benjamin Shin, Sean Wu, Fabien Scalzo, Helen Holmlund, Jessica Lee, Chris Ghim, Samuel Fitzgerald, Marinna Grijalva

Seaver College Research And Scholarly Achievement Symposium

Studies of plant anatomical traits are essential for understanding plant physiological adaptations to stressful environments. For example, shrubs in the chaparral ecosystem of southern California have adapted various xylem anatomical traits that help them survive drought and freezing. Previous studies have shown that xylem conduits with a narrow diameter allows certain chaparral shrub species to survive temperatures as low as -12 C. Other studies have shown that increased cell wall thickness of fibers surrounding xylem vessels improves resistance to water stress-induced embolism formation. Historically, these studies on xylem anatomical traits have relied on hand measurements of cells in light micrographs, …

Effects Of Invasive Species On Post-Fire Ceanothus Spinosus Seedling Establishment, Nina Duchild, Frank W. Ewers, Stephen D. Davis

Featured Research

This study compared seedling establishment of the native chaparral species Ceanothus spinosus in two different burn sites at Pepperdine University following the Woolsey Fire of November 2018. One site was a low-density fuel site, and experienced a “cool burn,” and the other site was a high-density fuel site and experienced a “hot burn.” In the low-density fuel site, fire type-conversion had occurred, resulting in a dominance of exotic species. The high-density fuel site was populated by many native fire-following species and chaparral shrubs, exemplifying pristine post-fire conditions. Initially, I hypothesized that seedling success in the cool burn site would be …

Seedling And Resprout Survival Of Three Chaparral Species Following Woolsey Wildfire, Karagan L. Smith, Stephen D. Davis

Featured Research

Fire is a common natural disaster that effects Southern California. Combined with recent chronic drought, there has been an increase in the damage and frequency of these fires in recent years. Three chaparral species are common to the Pepperdine campus: Malosma laurina, Ceanothus spinosus, and Ceanothus megacarpus. The survival of these native species is essential because they are indicators for the changes that are occurring in our local ecosystem and provide further implications of how our ecosystem responds to natural disaster. Seedling recruitment and resprouting are mechanisms these chaparral species use to reestablish postfire. Postfire data have been recorded …

Post-Fire Soil Microbiome Recovery And Respiration In A Chaparral Ecosystem, Mari R. Irving, Stephen D. Davis

Featured Research

This study characterizes post-fire recovery of microbial and fungal populations adjacent to three keystone chaparral plant species affected by varying burn intensities via systematic measurement of soil respiration. The CO₂ released from soil surrounding Ceanothus spinosus, Heteromeles arbutifolia and Malasma laurina affected by mild, severe or no heat during the Woolsey Fire of November 2018 were monitored and used as an indicator of microbial, fungal, and root activity. We hypothesized that soil which experienced less intense heat would exhibit higher rates of respiration based on preliminary data taken in March 2019. However, the opposite was observed from May through …

Photosynthetic Response Of Pentagramma Triangularis To Summer Desiccation, Brandon R. Grinovich, Stephen D. Davis

Featured Research

Ferns are thought to have been some of the first vascular plants to develop, perhaps on the order of 390 million years ago. Since then, ferns have speciated and developed innovative methods of survival especially in relation to water stress. Research conducted in 2016 by Helen Holmlund showed that eight California fern species fell into four primary classes of survival strategies, one of those being resurrection. Pentagramma triangularis is one of the resurrection-type ferns and is endemic to the western coast of the United States. As P. triangularis desiccates during the summer it enacts a physiological response by which it …

The Impact Of The Woolsey Fire On The Fungus Botryosphaeria Dothidea, Juan Arguijo

Featured Research

Southern California suffered a six-year drought in 2012 through 2018 during which the laurel sumac, Malosma laurina, experienced water stress and the fungus Botryosphaeria dothidea began to kill this plant, causing a massive dieback of this keystone chaparral species in the Santa Monica Mountains. Botryosphaeria is an opportunistic endophytic fungus that invades the xylem of woody type plants and waits till the plant starts to experience stress to proliferate. In November of 2018, the Woolsey fire burned up to 96,000 acres of vegetation. I ran tests at two sites on the Pepperdine University campus, the Baxter Ridge Site which …

Heteromeles Arbutifolia Associated Post-Fire Soil Microbiome Recovery And Respiration In A Chaparral Ecosystem, Gabrielle Boeger, Lauren Dedmon, Emma Thomsen, Alexander Soloniuk

Featured Research

The purpose of this post-Woolsey Fire project is to examine the relationship between soil respiration in areas of cool burns and hot burns relative to individuals of Heteromeles Arbutifolia. It was hypothesized that the soil subjected to a cooler burn would have greater respiration rates due to increased survival of microorganisms compared to a hotter burn. An Li-6800 CO2 Flux Chamber was used to collect measurements for several replicates. Significance was detected in the “Day 3” data, with the soil respiration higher at the cool burn site. Temperature and soil flux also varied directly. In the future experiments including increasingly …

Soil Respiration In Burned And Unburned Sites Of The Santa Monica Mountains, Sydney C. Jones, Micah S. Kim, Sierra H. Ball, Stephen D. Davis

Featured Research

Soil respiration (the flux of CO₂ released by the soil due to microbial and root respiration and organic matter decomposition) can be affected by fire (Qu et al., 2009, Richards et al., 2012, Ryu et al., 2009). After the 2018 Woolsey Fire in the Santa Monica Mountains, we hypothesized that soil respiration would be greater in unburned soil than in burned soil. This is because fire can decrease soil nutrient concentration, which could decrease soil microbial concentration and also because fire could burn and kill soil microbes and roots. To test this relationship, we recorded soil respiration on three …

Physiological Performance Of Ceanothus Spinosus In Hot Burn And Cool Burn Sites, Rishi Gattu, Christian Hill, Chris Kulpaca

Featured Research

After the Woolsey Fire, many fire adapted plants will resprout. However, increased fire frequency has negatively impacted the reproduction of many native species, while enhancing the survivorship of many invasive species. We compared the physiological performance of Ceanothus spinosus resprouters in areas that burned hotter compared to areas that burned cooler. We hypothesized that resprouters in hotter burn sites would have better physiological performance than resprouters in cooler burn sites. The resprouters in hotter burn sites would have better performance because of decreased competition from invasive species. We measured physiological performance using a Li-Cor LI-6400, specifically photosynthesis, transpiration, and stomatal …

Comparative Fitness Of Post-Fire Transplant Stipa Pulchra And Wild Stipa Pulchra In Competition With Avena Fatua, Ashley Bonin, Madison Cook, Sara Head

Featured Research

In the Spring Semesters of 2016 and 2017, research was conducted on the relative fitness of Stipa pulchra in the transplant garden on the Drescher campus at Pepperdine University. The first study in 2016 examined the fitness of Stipa pulchra and Avena fatua in the transplant and wild gardens after a five year drought in California. In the results of this experiment, the hypothesis was supported when observing that the wild S. pulchra depicted higher fitness that the transplant S. pulchra in areas of stomatal conductance, height, water potential, percent sun and dark-adapted fluorescence. The second study in 2017 investigated …

A Survey Of Post-Fire Chaparral Species’ Densities Using Point Quarter Sampling, Emma C. Stenz, Brandon R. Grinovich, Catherine H. William, Michael E. Gayed, Stephen D. Davis, Grace Palmer

Featured Research

The purpose of this observational study was twofold: to add to the existing data regarding the plant species composition of the Pepperdine hillsides and to set in place a foundation for post-fire chaparral recovery studies that will ensue over the coming years through various programs and classes. The 2018 Woolsey Fire burned nearly all of the natural environment surrounding Pepperdine University and the greater Malibu region, so it is a matter of urgency to take this opportunity to learn more about how this natural environment of the chaparral responds to a catastrophic event like fire. We focused primarily on facultative …

Carbon Dioxide Flux Rate For Cold Burn And Hot Burn Sites, Sophia Cheong, Alexander G. Grissom, Grace K. Lank

Featured Research

This experiment seeks to further expand modern understanding of post-fire ecology via systematic measurement of soil respiration within areas burned by cool, mild flames and hot, intense flames caused by the recent Woolsey Fire. We theorized that within hot burned areas, soil respiration would be less than that of the cool burned areas because the microbe population in the hot burned areas would be affected far more than those subjected to a cool burn. By measuring soil respiration with our Li-6800 CO₂ soil flux chamber at each of the according disc sites within hot and cold burned areas we …

Comparison Of Postfire Seedling Recruitment Of 2019 In Three Key Chaparral Species, Karagan Smith, Reid Furukawa, Brett Muramoto, Stephen D. Davis

Featured Research

Fire is a common natural disaster that sweeps through Southern California. Combined with periods of acute, and most recent, chronic drought, we have seen an increase in the damage and frequency of these fires in recent years. Three chaparral species are common to the Pepperdine campus: Malosma laurina, Ceanothus spinosus, and Ceanothus megacarpus. The survival of these three native species is essential because they serve as biomarkers for the changes that are occurring in our local ecosystem and provide further implications for how our ecosystem is responding to natural disaster. Seedling recruitment is a mechanism that is used by …

The Presence Of Fungal Pathogen, Botryosphaeria Dothidea, In Post-Fire Malosma Laurina Resprouts, Georgiana Gibson, Sarah Parker, Lauren Van Tress

Featured Research

Botryosphaeria dothidea is an opportunistic fungal pathogen that infects plants, causing cankers to form on branches and stems, ultimately causing cell cavitation and embolism in the plant. Botyrosphaeria dothidea was found in much of the chaparral vegetation present in the Santa Monica Mountains prior to the November 2018 fire. In this study, we focused on the presence of Botryosphaeria dothidea in the chaparral plant Malosma laurina on Pepperdine University’s campus in 2 different populations: unburned and resprouts. We looked at whether the November 2018 fires had eliminated the pathogen from post-fire Malosma laurina resprouts, using the unburned Malosma laurina population …

Post-Fire Competition Between Native Ceanothus Spinosus And Exotic Grasses, Katarina Carter, Nina Duchild

Featured Research

In our experiment, we investigated the post-fire competition between native Ceanothus spinosus and exotic grasses in low and high-density fuel sites. We hypothesized that C. spinosus seedlings in the high-density fuel site would be larger and more numerous than seedlings in the low-density fuel site, due to differences in competition from exotics. Our results showed that there was no significant difference in seedling height of C. spinosus in the high-density fuel site (5.33 ± 0.55 cm) and in the low-density fuel site (4.31 ± 0.51 cm). There was also no significant difference in the average number of seedlings in the …

A Post-Fire Comparison Of Resprouts To Unburned Malosma Laurina Shrubs In The Santa Monica Mountains Of Southern California, Anthony Joseph Adducci Ii, Sierra Jo Smith, Dylan Jesse Waddill

Featured Research

Fire is a cornerstone to Mediterranean ecosystems but increased droughts, climate change and human interference has caused a shift in fire frequency and severity. This experiment accessed the physiological performance of Malosma laurina resprouts in burned areas compared to mature Malosma laurina in unburned areas. Specifically, we hypothesized that the stomatal conductance, photosynthesis rate, and electron transport rate of the burned resprouts would all be higher than the unburned shrubs as there are more nutrients available in the soil post-fire and the resprouts have a larger root to stem ratio. Using the LI-6400 Portable Photosynthesis System, we measured the physiological …

Post Fire Seedling And Resprout Survival Of Melasma Laurina, Matthew Sturtevant, Gil So

Featured Research

For this research project we set out to see how seedling and resprout survival rate of melasma laurina would fare in the post fire environment found around pepperdine. The expected seedling survival was set to be 1% and the resprout survival was at 100%. From our field research we found that the the seedling survival was 41% and the resprout 57.3%. By using a T-test we had a p value < 0.001 for both data sets, this means that our data deviated greatly from our expected data and meant that we had to reject our hypothesis.

How Soil Salinity Affects The Stomatal Conductance Of Baccharis Salicifolia (Mulefat/Seepwillow), Andrew Kim, Caroline Wilkerson, Mahala Bayless, Peter Du

Featured Research

This is a poster presentation demonstrating the project our group has been working on. We hypothesize that the stomatal conductance of mulefat will decrease as soil salinity increases in both pre-rain and post-rain conditions because the plant tries to absorb salt water. However, the salt water cannot pass through plant tissue and draws water out of the plant. Since plant requires water for photosynthesis, water being drawn out means less water is available for the plant to do photosynthesis. We have tested our hypothesis by collecting soil samples in Legacy park, and recorded stomatal conductance by using a leaf porometer

How Soil Salinity Affects The Stomatal Conductance Of Baccharis Salicifolia (Mulefat/Seepwillow), Andrew Kim, Caroline Wilkerson, Mahala Bayless, Peter Du

Featured Research

This is a poster presentation demonstrating the project our group has been working on. We hypothesize that the stomatal conductance of mulefat will decrease as soil salinity increases in both pre-rain and post-rain conditions because the plant tries to absorb salt water. However, the salt water cannot pass through plant tissue and draws water out of the plant. Since plant requires water for photosynthesis, water being drawn out means less water is available for the plant to do photosynthesis. We have tested our hypothesis by collecting soil samples in Legacy park, and recorded stomatal conductance by using a leaf porometer

A Comparison Of Different Methods Of Dehydration On Baccharis Salicifolia, Michael Nicholas, Sinjun Hong

Featured Research

Baccharis salicifolia is a native riparian plant living in many places near to the Santa Monica Mountains. One of these locations is Legacy park, which has had many events effect it that has led to some very unfortunate changes. The park’s soil was tested earlier this year by a group of undergraduate students lead by Dr. Stephen Davis and was found to have a very high salinity level. The plants in the park appeared to be struggling to survive and had signs of dehydration and wilting. This led to us questioning the types of dehydration of the plants. Areas of …

A Comparison Of Photosynthetic Rate, Stomatal Conductance, And 
Electron Transport Rate Between Malosma Laurina And Encelia Californica, Yujin Choi, Isabella Armstrong, Catherina Haas, Micah Kim

Featured Research

In the Santa Monica Mountains, there are two main vegetation types: chaparral, which makes up __% of plants in these mountains, and coastal sagebrush, which makes up __%. Despite California’s acute environmental stress, both of these plants manage to survive, and even thrive in some cases. We were interested in seeing if in spite of these vast anatomical and physiological differences, these plants were able to survive at similar health rates, measured in photosynthetic rate, stomatal conductance, and electron transport rate (ETR). We have decided to choose 2 plants from 2 different leaf types of different vegetation types: Malosma laurina …

Comparison Of Photosynthesis, Stomatal Conductance, And Water Potential Between Native Rhus Integrifolia And Invasive Nicotiana Glauca, Tiffany J. Egbo, Emma J. Navarro, Malaun A. Phillips, Cameron I. Zohary

Featured Research

Invasive species, such as Nicotiana glauca, are a prominent part of the Santa Monica Mountains, and could be responsible for displacing native species such as Rhus integrifolia. It was observed in the field that Nicotiana glauca was doing better than Rhus integrifolia, so our group decided to indirectly test this. Because of the invasiveness of its species, it is essential to measure the health of a native species to see if the invasive species is posing as a massive threat. Water potential, stomatal conductance, fluorescence, photosynthetic rates and electron transport rates were compared among the two plants …

A Student’S Perspective On Engagement In Ecological Research During Their First Semester In College, Natalie M. Aguirre, Karagan L. Smith, Cristian M. Garcia, Cheryl Swift, Stephen D. Davis

Biology

Pepperdine University and Whittier College jointly initiated a new first-year seminar series in the fall of 2016 that engaged students in authentic research, their first semester on campus. The goals are listed below. Assessment of these goals included both qualitative focus groups and quantitative survey questionnaires administered by an outside assessment agency, WestEd.org.

Ninety-two percent of students reported that their first-year seminar improved learning in concurrent courses and ninety to ninety-three percent of students said their first-year seminar increased their interest in STEM. In addition, students self-reported a significant improvement in all aspects of their ability to plan and conduct …

Post Drought Recovery In Malosma Laurina After Severe Dieback During California’S Historic Drought Of 2012-2016, Karagan L. Smith, Guinevere X. Mesh, Natalie M. Aguirre, Gabriella N. Palmeri, Helen I. Holmlund, Stephen D. Davis

Biology

Malosma laurina is a species of chaparral shrub that dominates coastal exposures of the Santa Monica Mountains of southern California. Between 2012 and 2016, protracted drought with half normal rainfall over a five-year period (175 mm), led to severe dieback, exceeding 50% whole plant mortality at some sites. The drought dissipated in 2017 with an annual rainfall that exceeded the 140-yr normal by 108 mm. As a result of this elevated annual rainfall in 2017, we were interested in documenting the potential for full recovery of Malosma laurina as a keystone species of coastal chaparral shrub communities. We tested the …

Bioaccumulation Of Zinc In Bermuda Grass (Cynodon Dactylon), Drew Fisher, H. Marie Surratt, Louise Gebauer, Andrew Palaski

Featured Research

Phytoremediation is the plant based process to remove toxins such as heavy metals from the soil. In this experiment, we hypothesized Bermuda grass (Cyndon dactylon) will absorb a detectable level of zinc, a nontoxic metal, from the soil. We grew two separate groups of grass: the control and the experimental, which was watered with zinc acetate. Neither of the groups produced enough yield within the weeks given to the experiment, but if it went according to plan, we would have used flame atomic absorption spectroscopy to evaluate the relative concentrations of zinc. Significant uptake of zinc could reveal a possible …

A Comparison Of Electron Transport Rate, Photosynthetically Active Radiation, Light-Adapted Fluorescence, And Dark-Adapted Fluorescence Between Stipa Pulchra And Pennisetium Setaceum, Sydney Adams, Brandon Chuck, Agatha Heng, Amelia Vento, Stephen D. Davis

Featured Research

The purpose of this investigation was to provide an explanation into how the invasive species Pennisetium setaceum, Fountain Grass, is able to outcompete the native California grassland species Stipa pulchra, Purple Needle Grass. We used a light adapted and a dark adapted fluorometer to measure the photosynthetic radiation (PAR), leaf temperature, alpha (α), light adapted fluorescence (Fv’/Fm’), dark adapted fluorescence (Fv/Fm), and the electron transport rate (ETR) on young Fountain Grass and Purple Needlegrass. After collecting and analyzing the data, we concluded that the dark adapted fluorescence (Fv/Fm) was the only statistically significant measurement where the Fv/Fm of S. pulchra …

A Comparison Of Electron Transport Rate, Photosynthetically Active Radiation, Light-Adapted Fluorescence, And Dark-Adapted Fluorescence Between Stipa Pulchra And Pennisetium Setaceum, Sydney Adams, Brandon Chuck, Agatha Heng, Amelia Vento, Stephen D. Davis

Featured Research

The purpose of this investigation was to provide an explanation into how the invasive species Pennisetium setaceum, Fountain Grass, is able to outcompete the native California grassland species Stipa pulchra, Purple Needle Grass. We used a light adapted and a dark adapted fluorometer to measure the photosynthetic radiation (PAR), leaf temperature, alpha (α), light adapted fluorescence (Fv’/Fm’), dark adapted fluorescence (Fv/Fm), and the electron transport rate (ETR) on young Fountain Grass and Purple Needlegrass. After collecting and analyzing the data, we concluded that the dark adapted fluorescence (Fv/Fm) was the only statistically significant measurement where the Fv/Fm of S. pulchra …

A Comparison Of Fluorescence And Etr Between Malosma Laurina And Rhus Integrifolia, Talia Danze, Jennifer Ipe, Viridiana Hernandez-Lopez, Stephen D. Davis, Talia Cao

Featured Research

Malosma laurina and Rhus integrifolia are both native species to the Santa Monica Mountains and belong to the same family, Anacardiaceae. The two natives have lived alongside each other but in recent years M. laurina has been heavily affected by the prolonged drought. The Malosma laurina population in the Santa Monica Mountains has withstood wildfires and droughts, and has remained relatively stable and healthy up until recently. A recent Pepperdine graduate published her findings explaining the high levels of dieback in Malosma laurina and attributed it to the fungus, B. dothidea. We hypothesized that Rhus integrifolia would have higher fluorescence …

A Comparison Of Electron Transport Rate, Photosynthetically Active Radiation, Light-Adapted Fluorescence, And Dark-Adapted Fluorescence Between Stipa Pulchra And Pennisetium Setaceum, Sydney Adams, Brandon Chuck, Agatha Heng, Amelia Vento, Stephen D. Davis

Featured Research

The purpose of this investigation was to provide an explanation into how the invasive species Pennisetium setaceum, Fountain Grass, is able to outcompete the native California grassland species Stipa pulchra, Purple Needle Grass. We used a light adapted and a dark adapted fluorometer to measure the photosynthetic radiation (PAR), leaf temperature, alpha (α), light adapted fluorescence (Fv’/Fm’), dark adapted fluorescence (Fv/Fm), and the electron transport rate (ETR) on young Fountain Grass and Purple Needlegrass. After collecting and analyzing the data, we concluded that the dark adapted fluorescence (Fv/Fm) was the only statistically significant measurement where the Fv/Fm of …

A Comparison Of Electron Transport Rate, Photosynthetically Active Radiation, Light-Adapted Fluorescence, And Dark-Adapted Fluorescence Between Stipa Pulchra And Pennisetium Setaceum, Sydney Adams, Brandon Chuck, Agatha Heng, Amelia Vento, Stephen D. Davis

Featured Research

The purpose of this investigation was to provide an explanation into how the invasive species Pennisetium setaceum, Fountain Grass, is able to outcompete the native California grassland species Stipa pulchra, Purple Needle Grass. We used a light adapted and a dark adapted fluorometer to measure the photosynthetic radiation (PAR), leaf temperature, alpha (α), light adapted fluorescence (Fv’/Fm’), dark adapted fluorescence (Fv/Fm), and the electron transport rate (ETR) on young Fountain Grass and Purple Needlegrass. After collecting and analyzing the data, we concluded that the dark adapted fluorescence (Fv/Fm) was the only statistically significant measurement where the Fv/Fm of S. pulchra …