Life Sciences Commons^™

The Rate Of Fungal Pathogen Growth (Botryosphaeria Dothidea) 
In Stems Of The Chaparral Shrub Rhus Integrifolia, Jayla D. Simmons, Edward J. Ayala, Kamara J. Satcher, Stephen D. Davis, Karagan L. Smith, Talia A. Cao

Featured Research

The fungus Botryosphaeria dothidea will grow between one to five millimeters after a week on the chaparral species Rhus integrifolia. To test this, we inoculated six individual shrub located behind the greenhouse on Campus Walk Road . On each shrub we selected two branches, receiving adequate and equal sunlight and inoculated one branch with the fungus B. dothidea and the other with a plain gel in order to compare the growth with a control group. The data we collected at the end of the one week period was similar to our initial hypothesis. The shortest growth was on the …

Post-Drought Recovery In The Chaparral Shrub Ceanothus Spinosus, Katie C. Lindley, Kylie N. Smith, Nina R. Duchild, Stephen D. Davis, Karagan L. Smith, Talia A. Cao

Featured Research

This study investigated the abilities of Ceanothus spinosus, or greenbark ceanothus, to recover after a historic drought. This plant is one of the hardiest in the Santa Monica Mountains, providing soil stabilization and nutrients to other organisms in the ecosystem. In a previous investigation done during the drought, it was found that C. spinosus subjects growing in their natural habitat experienced significant dieback, with predawn water potentials falling as low as -7 MPa and native embolisms at an average of 47.17% (Ross et al., 2016). Other parameters tested were stomatal conductance, photosynthetic rate, and chlorophyll fluorescence. Compared to the …

Comparison Of Photosynthesis Among Three Chaparral Species In The Family Anacardiaceae, Catelyn T. Price, Sarah A. Holmes, Brandon T. Harris, Stephen D. Davis, Karagan L. Smith, Talia A. Cao

Featured Research

Recent argumentative data showed a lack of niche differentiation amongst three Banksia species in Australia conducted by Lamont and Bergl, and the Anacardiaceae family in the native chaparral of the Santa Monica Mountains are supposed to be significantly similar¹. Because of this we wanted to test if there would be a significant difference between the stomatal conductance, photosynthesis, and water potential in samples of the Rhus ovata, Rhus integrifolia, and Malosma laurina (Rhus laurina) species. We tested this idea by collecting the stomatal conductance and photosynthetic rates of each plant species in the same general location with …

Testing For The Presence Of Botryosphaeria Dothidea In Ceanothus Spinosus, Brandon R. Grinovich, Chelsea N. Puncochar, Katarina L. Carter, Stephen D. Davis, Rodney L. Honeycutt, Talia A. Cao, Karagan L. Smith

Featured Research

Botryosphaeria dothidea is an opportunistic fungus found in some of the cavitated branches of the vegetation in the Santa Monica Mountains. In this study, we focused on finding the presence of Botryosphaeria dothidea in Ceanothus spinosus located on Pepperdine University’s campus. We wanted to test this hypothesis because we observed a large amount of dieback in the Ceanothus spinosus population and wanted to identify a possible contributor. Because of the large number of cavitated branches the Ceanothus spinosus contained, we hypothesized they contained fungus. To test this, we took twenty samples of twenty different Ceanothus spinosus, isolated the fungus …

A Comparison Of Water Potential, Photosynthetic Rate, Electron Transport Rate, And Stomatal Conductance Between Native Malosma Laurina And Exotic Schinus Molle, Karagan L. Smith, Agatha C. Heng, Viridiana Hernandez-Lopez, Stephen D. Davis

Biology

Schinus molle is a relatively new invasive chaparral shrub in the Santa Monica Mountains and has only recently been observed to displace native shrubs like Malosma laurina. To investigate the probable cause of S. molle’s competitive displacement of M. laurina, we compared their water status, photosynthetic rates, electron transport rates, and stomatal conductance to water vapor diffusion during the fall months of 2016. We hypothesized that S. molle would physiologically outperform M. laurina indicated by higher photosynthetic rates, electron transport rates, stomatal conductance rates, and less negative water potential. We found that there was no significant difference between dry …

The Effect Of Drought On The Comparative Fitness Of Purple Needle Grass (Stipa Pulchra) In The Presence Of An Invasive Weed, Grace M. Palmer, Taylor M. Purdy, Stephen D. Davis

Biology

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. Following the trend of other perennial native grasses, Stipa pulchra is dwindling due to competition with Avena fatua and other invasive species introduced by human activities. In 2016, in the midst of historic five-year drought in California, stomatal conductance, dark adapted fluorescence, water potential, and height of S. pulchra and A. fatua were recorded and compared. As hypothesized, the wild S. pulchra exhibited greater overall fitness-- …

Ecological And Organic Life Safety Concerns Of Hfo-1234yf, Alberni V. Ruiz

STAR Program Research Presentations

While at NOAA my research was directed by the inquiry of whether or not HFO-1234yf, a new compound being introduced into coolant system and replacing greenhouse gases HFC, is harmful to organic life. Using the computer program Matlab I was able to develop figures that represented the concentration of HFO-1234yf (HFO) in 12 different tower locations throughout the country. Comparing and contrasting concentrations of this HFO compound at each site led me to the question the possible harmful side effects this compound could bring to organic life due to the fact that concentration levels are increasing, with one factor being …

Resistance To Xylem Cavitation In Evergreen Ferns Correlates With Seasonal Dehydration Levels, Not Mechanical Strength, Helen I. Holmlund, Kaitlyn E. Sauer, Breahna M. Gillespie, Jarmila Pittermann, Stephen D. Davis

Biology

Ferns in the Santa Monica Mountains of southern California display a range of responses to severe drought. In this study, we further characterized the traits that may contribute to fern survival in a mediterranean-type climate. Due to anatomical differences between ferns and angiosperms, we predicted that ferns would exhibit no correlation between stipe mechanical strength and vulnerability to water stress-induced cavitation of stipe xylem. However, we predicted that ferns would show a correlation between seasonal water stress (minimum water potential) and cavitation resistance. Our results support these hypotheses; however, we must increase our sample size of evergreen fern species in …

Potential Recovery From Drought-Induced Dieback In A Keystone Chaparral Species, Malosma Laurina, Guinevere X. Mesh, Natalie M. Aguirre, Stephen D. Davis

Featured Research

After five years of protracted drought and water-related dieback and mortality, the coastal chaparral ecosystems of the Santa Monica Mountains have finally received increased precipitation. As a co-dominant plant species in this region, Malosma laurina (common name Laurel Sumac), provides an important indication of environmental change. This study examines the effect of the increased precipitation of the 2016-2017 rainy season on potential recovery from drought-induced dieback in M. laurina. This study shows a significant increase in tissue hydration levels and photosynthetic production of dieback plants during post-drought recovery (2017) and between irrigated control sites and dieback sites.

Comparative Fitness Of Transplanted Nassella Pulchra: A Study Of Native And Invasive Grasses, Grace Palmer, Yash Pandey, Isabelle Panos

Featured Research

Previous study of the fitness of California, perennial N. pulchra was conducted at the transplant garden on the Drescher campus of Pepperdine University in the spring of 2016. A follow up study was conducted to understand how the recent increase in rainfall has affected the comparative health of N. pulchra in the transplant garden and in the wild, as well as the health of the invasive, annual grass A. fatua. The height, water potential, photoprotection, and stomatal conductance were measured in transplant N. pulchra, wild N. pulchra, and the competing A. fatua. It was hypothesized that A. fatua …

A Comparative Study Of Adults Vs. Resprouts’ Stomatal Conductance And Xylem Water Potential In Malosma Laurina, Lauren Dam, Brinna Lee, Sarah Dahlberg, Stephen Davis

Featured Research

The purpose of this study is to compare the stomatal conductance and xylem water potential between adults and resprouts of Malosma laurina growing at the Drescher Campus at Pepperdine University. Our data suggest that stomatal conductance and xylem water potential of adult and resprout M. laurina are not significantly different (p = 0.09312, p = 0.7064 respectively), implying that M. laurina at that study site has had sufficient time to recover from the drought due to the increased levels of rainfall.

Solar Tracking Fitness In Native Lupulinus Succulentus Vs. Non-Native Malva Sylvestris, Kathryn Maidlow, Logan Scott

Featured Research

For this experiment, we hypothesized, that while both native and non-native species use solar tracking, the native species Lupulinus succulentus (bluebonnet) will solar track to increase light levels with low leaf temperatures; however, the non-native species Malva sylvestris (cheeseweed) will solar track to increase light levels with an elevated leaf temperature over the native species. Solar tracking was also hypothesized as a significant benefit to each plant species, thus we assumed that if a leaf was prevented from solar tracking that we would see a difference between the solar trackers and non-solar trackers of each species. We decided to use …

Reflectance, Transmittance, And Absorbance Values In Salvia Apiana
 Result In Better Performance Than Salvia Mellifera In Drought- Like Conditions, Haley Bekins, Caroline Boone, Kristen Hardin

Featured Research

Salvia apiana, due to the physically lighter color and thickness of the leaves, will have higher reflectance values, lower transmittance values, and lower absorbance values than Salvia mellifera. These measurements exemplify characteristics of a better adapted species for droughts, and then the absorption values can be used to calculate more information on the species like ERT. We measured transmittance and reflectance of six leaves from randomly selected plants of both species through the use of an integrating sphere. After obtaining the R and T value of each plant, we calculated the leaf absorbance,α. This was done by using the …

Dark-Adapted Fluorescence And Stomatal Conductance After Dcmu (3-(3,4-Dichlorophenyl)-1, 1-Dimethylurea)) Exposure On Malva Parviflora Plants, Piueti Maka, Mia Bryant, Isabelle Sarwono

Featured Research

The purpose of this experiment was to determine the disturbance effect of indirect exposure to DCMU (3-[3,4-dichlorophenyl]-1,1-dimethylurea), a popular herbicide, on dark adapted fluorescence and stomatal conductance in Malva parviflora plants. We utilized a test site exposed to sunlight and free from other external interference. Two main apparatuses were used to collect data; stomatal conductance was measured by a leaf porometer, and dark-adapted fluorescence (Fv/Fm) was measured using a Pulse Modulated Fluorometer. Our data yielded significant comparison results for dark-adapted fluorescence (P0.05). Additionally, observations six days after disturbance showed a drastic presence of hollyhock rust (Puccinia malvacearum) and …

A Comparison Of Photoprotection In C3 Plants Between A Native And An Invasive Species, T. Cao, M. Field, K. Godon

Featured Research

Now more so than ever with the increasing demands placed upon plant species as a direct result of climate change, competition between native and invasive species determines which species are able to survive and reproduce. Biologically the two species, native and invasive, carry out the same functions yet it is in how they carry out said functions that they differ. Prior to the commencement of the study the belief was held that the invasive species (here Avena) would contain increased photoprotection than the native species (here Elymus) for it to possess a competitive advantage. Testing of the stated hypothesis including …

Photoprotection Adaptiveness In Native (Lupinus 
Succulentus) And Invasive (Malva Parviflora) Heliotropic Plants, Joseph Davidson, Cameron Juarez, Collin Scott

Featured Research

Addressed here is the question of whether invasive heliotropic plants can adapt better than native heliotropic plants, to conditions in which their solar tracking capabilities are hindered. In order to test this, a heliotropic species native to Southern California (Lupinus succulentus) was compared to a weedy heliotropic species invasive to Southern California (Malva parviflora). We hypothesized that the photoprotection mechanisms of M. parviflora would adapt better to being restrained as it is an invasive species and it was more abundant in the area. Values of Fv’/Fm’ and qN were measured in order to compare the efficacy …

Comparison Of Physiological Measurements And Water Potential Of Malosma Laurina During And After The Drought In Southern California, Nicolette Jessen, Kirstin Van Fleet, Rachel White

Featured Research

After 5 years of drought, southern California has recently experienced increases in precipitation. Malosma laurina is a chaparral shrub that displays vulnerability to fungal infection during severe drought conditions, particularly in its adult branches, resulting in severe dieback throughout the Santa Monica Mountains. M. laurina is known to produce resprout leaves during times of environmental stress that are less affected by the fungus based on its ability to maintain water status and thus are more capable of displaying resilience in more favorable environmental conditions. We hypothesize that the increase in rain will not be enough to alter the vitality of …

Effect Of Drought On Resin Production In Woody Stems Of Rhus Ovata, Sydney T. Adams, Melody Young, Moriah Hall

Seaver College Research And Scholarly Achievement Symposium

Resin production in stems of woody plants is generated from resin canal secretions and is thought to play a significant role in protection from fungal infection and spread. This may be one of several factors associated with fungal infection and fungal induced dieback in plants during severe water stress or drought. We set out to determine if reduction in resin production in a chaparral shrub, Sugar Bush (Rhus ovata), was associated with severe drought in southern California. We hypothesized that dehydrated R. ovata would produce less resin than hydrated plants. Our null hypothesis was that there is no …

Comparison Of Leaf Water Potential, Stomatal Conductance, And Chlorophyll Fluorescence Between An Invasive Weed, Schinus Molle, And A Native Chaparral Shrub, Ceanothus Spinosus, In The Santa Monica Mountains, Adam L. Fahey, Harry Zhou, Katie Callahan

Seaver College Research And Scholarly Achievement Symposium

The Peruvian peppertree, Schinus molle, is an invasive species in California that has escaped cultivation to competitively exclude native species in the landscape. One example of such competition is between a dominant member of the chaparral shrub community, greenbark ceanothus (Ceanothus spinosus), and S. molle. The mechanism of competitive displacement of chaparral by S. molle is not understood nor has it been previously studied. We hypothesized that during severe drought, such as occurred during the sumer/fall of 2016, S. molle would have a more favorable water balance then its native competitor C. spinosus, eventually leading to higher survival and species …

Hydraulic Mechanisms Of Fungal-Induced Dieback In A Keystone Chaparral Species During Unprecedented Drought In California, Natalie M. Aguirre, Marissa E. Ochoa, Helen I. Holmlund, Frank E. Ewers, Stephen D. Davis

Seaver College Research And Scholarly Achievement Symposium

Between 2012-2016, southern California experienced unprecedented drought that caused dieback in Malosma laurina, a keystone species of chaparral shrub communities. Dieback was especially severe in coastal exposures of the Santa Monica Mountains, leading to whole plant mortality exceeding 50% at some sites. We hypothesized that the endophytic fungus causing the dieback, Botryosphaeria dothidea, was successful in invading the xylem tissue of M. laurina because of protracted water stress, carbon starvation, or a combination of the two. We tested these possibilities in a controlled pot experiment by comparing three treatments, each inoculated with the fungus: (1) irrigated controls (2) …

A Comparison Of Water Potential, Photosynthetic Rate, Electron Transport Rate, And Stomatal Conductance Between Native Malosma Laurina And Exotic Schinus Molle, Karagan L. Smith, Agatha C. Heng, Viridiana Hernandez-Lopez

Seaver College Research And Scholarly Achievement Symposium

A Comparison of Water Potential, Photosynthetic Rate, Electron Transport Rate, and Stomatal Conductance between Native Malosma laurina and Exotic Schinus molle

Karagan L. Smith, Agatha C. Heng, and Viridiana Hernandez-Lopez

First-year Students as Scholars Program

Mentors: Natalie M. Aguirre, Kaitlyn E. Sauer, and Stephen D. Davis

Schinus molle is a relatively new invasive species in chaparral shrub communities of the Santa Monica Mountains, and has only recently been observed to displace native species of shrubs, such as Malosma laurina. To investigate the probably cause of S. molle’s invasiveness and mechanisms of competitive displacement of M. laurina, we compared …

Small Scale Heterogeneity In Vegetation Structure In A Patch-Burn-Grazing Landscape, Eric G. Behrens

UNO Student Research and Creative Activity Fair

Disturbances are drivers of spatial change in the plant communities of the tallgrass prairie ecosystem. Fire and large herbivore grazing are prevalent disturbances that maintain the vegetation structure and create spatial heterogeneity in vegetation at various scales. The fire-grazing disturbance interaction occurs when areas that have been recently burned are followed by intense grazing due to the high quality of forage regrowth. This interaction has been managed in tallgrass prairies in a homogenous method using uniform burning and grazing and a heterogeneous method using patch-burn-grazing (PBG). Vegetation heterogeneity at a large scale has been studied in PBG and uniformly managed …