Plant Sciences Commons^™

Extensive Dieback In Malosma Laurina In Coastal Exposures Of The Santa Monica Mountains Associated With Unprecedented Drought In California, Gina S. Gilderman, Kaitlyn E. Sauer, Gabriella N. Palmeri

Featured Research

Throughout coastal exposures of the Santa Monica Mountains (SMM) there is a recent emergence of widespread dieback in Laurel Sumac (Malosma laurina). M. laurina is a keystone species of chaparral that dominates the SMM. A significant trait of M. laurina is an extensive root system exceeding 12 m in depth. We hypothesized that M. laurina was weakened by unprecedented drought in California (2013-2015) and predisposed to fungal pathogens. An initial study conducted in the summer of 2015 revealed all stem samples taken from dieback adult M. laurina plants were infected with Botryosphaeria dothidea, while zero stem samples taken …

Botryosphaeria Dothidea Impacts Relative Water Abundance In Malosma Laurina, Andrew Lozano, Michael Gribble, Jared Delapaz

Featured Research

Over the past decade, the California drought has been affecting native chaparral in the Santa Monica Mountains. Some parasitic fungi species such as Botryosphaeria dothidea have taken advantage of the drought by invading open wounds, or cankers, in a plant. When extreme environmental stress such as drought occurs, the immune system of the plant is compromised; the fungus can then multiply within the plant, blocking the vascular tissue. In this study, we aim to determine if there is a relationship between the presence of B. dothidea and an increase in the flammability of the native chaparral species Malosma laurina. …

Nodes Alter Stem Mechanical Strength In Heteromeles Arbutifolia, Gabriella E. Chan, Caleigh A. Howard, Callie E. Shelley

Featured Research

Our thesis was that the presence of nodes in stems of Heteromeles arbutifolia plants would increase the mechanical strength of the xylem and the bark, allowing the stems to be better protected against harsh weather conditions during the severe California drought. We conducted research on two sample groups, one with nodes and one without nodes. An Instron machine tested the mechanical strength by bending the stems until the xylem broke. Values for MOR (modulus of rupture) and MOE (modulus of elasticity) were measured to determine the overall strength of both groups. We found that the xylem of the stems was …

Root Hydraulic Conductance In Laurel Sumac Experiencing Severe Dieback In The Santa Monica Mountains, Natalie M. Aguirre, Avery N. Davis, Sarah B. Nelson

Featured Research

Malosma laurina (laurel sumac) is a dominant species in coastal chaparral ecosystems, extending its roots down to an average of 40 feet in rocky, sandy soils. The deep root systems of M. laurina provide structural support for the steep Santa Monica Mountains. The roots also allow M. laurina to draw from the deep water table, increasing its drought tolerance. M. laurina dieback is prevalent in coastal exposures of the Santa Monica Mountains presumably due to historic drought predisposing plant tissues to infection by the fungal pathogen Botryosphaeria dothidea. In ecosystems that experience annual dry periods, a high hydraulic conductance …

Recent Dieback In A Keystone Chaparral Species Is Caused By A Fungal Pathogen, Botryosphaeria Dothidea, Frida Morales, Mariah Taylor

Featured Research

Due to the recent drought in Southern California, the abundance of a keystone species within the Santa Monica Mountains (SMM) has been dwindling. This species, Malosma laurina, has an average root depth of 40 feet, so it has little difficulty tapping into the watershed. Recently, this species has undergone extensive dieback, which is potentially attributed to the unprecedented drought and the introduction of the fungus B. dothidea. While this fungi appears to be innocuous to M. laurina when the plant is healthy, it is more susceptible to invasion under water stress due to the dry heated conditions of …

Extensive Dieback In Malosma Laurina In Coastal Exposures Of The Santa Monica Mountains Associated With Unprecedented Drought In California, Gina S. Gilderman, Kaitlyn E. Sauer, Gabriella N. Palmeri

Featured Research

Throughout coastal exposures of the Santa Monica Mountains (SMM) there is a recent emergence of widespread dieback in Laurel Sumac (Malosma laurina). M. laurina is a keystone species of chaparral that dominates the SMM. A significant trait of M. laurina is an extensive root system exceeding 12 m in depth. We hypothesized that M. laurina was weakened by unprecedented drought in California (2013-2015) and predisposed to fungal pathogens. An initial study conducted in the summer of 2015 revealed all stem samples taken from dieback adult M. laurina plants were infected with Botryosphaeria dothidea, while zero stem samples taken …

Recent Dieback In A Keystone Chaparral Species Is Caused By A Fungal Pathogen, Botryosphaeria Dothidea, Adriana Borges, Frida Morales, Emily Pierce, Mariah Taylor

Biology

Due to the recent drought in Southern California, the abundance of a keystone species, Malosma laurina, within the Santa Monica Mountains (SMM) has been dwindling. This species has a rooting depth that exceeds 13 m, so it typically has little difficulty tapping into the water table. Recently, this species has undergone extensive dieback, which might be attributed to the unprecedented drought in California and predisposition fungal pathogen Botryosphaeria. dothidea. While this fungi appears to be innocuous to M. laurina when the plant is healthy, it is more susceptible to invasion under water stress due to the dry and …

Extensive Dieback In Malosma Laurina In Coastal Exposures Of The Santa Monica Mountains Associated With Unprecedented Drought In California, Gina S. Gilderman, Kaitlyn E. Sauer, Gabriella Palmeri

Biology

Throughout coastal exposures of the Santa Monica Mountains (SMM) there is a recent emergence of widespread dieback in Laurel Sumac (Malosma laurina). M. laurina is a keystone species of chaparral that dominates the SMM. A significant trait of M. laurina is an extensive root system exceeding 12 m in depth. We hypothesized that M. laurina was weakened by unprecedented drought in California (2013-2015) and predisposed to fungal pathogens. An initial study conducted in the summer of 2015 revealed all stem samples taken from dieback adult M. laurina plants were infected with Botryosphaeria dothidea, while zero stem samples taken …

Premature Seed Germination And High Seedling Mortality In A Chaparral Shrub (Adenostoma Fasciculatum) Caused By Severe Drought In Calfiornia, Lexe Evans, Teal Speece, Stephen D. Davis

Biology

The Santa Monica Mountains (SMM) represents one of five Mediterranean-type environments in the world. With sustained summer droughts, this ecosystem is prone to frequent wildfires, a phenomenon that has affected the SMM with regularity once every 32 years. Adenostoma fasciculatum (chamise), is a chaparral shrub well adapted to wildfire cycles because typically its seeds are triggered to germinate by high fire temperatures, smoke, and charate. In the winter of 2015, we were surprised to discover seedlings of A. fasiculatum emerging at an unburned chaparral site without the occurrence of fire. We hypothesized that drought induced canopy dieback at some microsites, …

Novel Seed Germination In Response To California’S Historic Drought May Deplete Soil Seed Banks, Amanda M. Burns, Victoria M. Lekson, Helen I. Holmlund, Stephen D. Davis

Biology

We observed novel seed germination, without a fire cue, in an obligate seeding species of chaparral (Ceanothus megacarpus) during historic drought in California (2014). We hypothesized that premature germination was promoted by drought-induced canopy dieback among adults that allowed high radiation loads to reach normally shaded soils, cracking seed coats, facilitating water uptake. We hypothesized that because premature seed germination was late in the season (April, when December is typical) roots would not have time to penetrate deep moisture resources before the onset of summer drought, leading to excessive mortality and eventual depletion of soil seed banks. We …

Comparative Foliar Water Uptake And Leaf Hydrophobicity In Island Versus Mainland Ferns, Victoria M. Lekson, Helen I. Holmlund, Nicole A. Nakamatsu, Amanda M. Burns, Stephen D. Davis

Biology

In 2014, Southern California experienced the worst drought in the last 1,200 years. In this study, the mechanisms of drought tolerance for eight species of ferns in the Santa Monica Mountains were assessed with a focus on foliar water uptake and hydrophobicity of frond (leaf) surfaces. We measured gravimetric foliar water uptake and angle of contact for a drop of water on a frond. Seasonal shifts were tracked as a method of following drought response patterns.

Fog is becoming more important due to limited ground water. Fog is far more common on Santa Cruz Island off the coast of California …

Possible Fungal Infection Leading To Malosma Laurina Dieback, Gabriella N. Palmeri, Braden S. Olsen, Kaitlyn E. Sauer, Stephen D. Davis

Featured Research

There is a significant and apparent dieback of Malosma laurina in the Santa Monica Mountains, some which is found near Pepperdine University. Other areas near Pepperdine show a flourishing growth of M. laurina and our objective was to determine why this difference in M. laurina health exists. We initially hypothesized that in addition to water stress, the unhealthy M. laurina was effected by a pathogen. Under further inspection, the unhealthy plants contained hyphae in some of their xylem vessels, while the healthy ones did not. We sought to determine whether the existence of hyphae in the unhealthy plant’s xylem affected …

Difference In Chaparral Species Population On The North And South Aspect On Pepperdine University Campus, Alexandra N. Lozano, Drew N. Rasmussen, Ashlyn L. Rawls

Featured Research

In this experiment, we analyzed the difference in population frequencies of chaparral plants along the north and south aspect of a slope on Pepperdine University campus in the Santa Monica Mountains in Malibu, CA. We began the experiment by hypothesizing the south aspect would receive the most sunlight, and thus would hold the most amount of plants. By using the Point Quarter Sampling Method, we were able to determine if our hypothesis was correct. After analyzing our data, we found no significant difference between the north and south aspect in terms on frequency. During our experiment we also measured the …

Morphological Changes In Malosma Laurina Due To Prolonged Drought In The Santa Monica Mountains, Grace S. M. Bae, Majie C. Foster, Maryelizabeth S. Stein, Mariah K. Taylor

Featured Research

Observations of Malosma laurina seedlings in Sycamore Canyon, Malibu, CA, exhibit abnormally small and wrinkled leaves. We propose that the prolonged drought in California’s Santa Monica Mountains has lead to physical malformations indicative of water strain in the leaves of M. laurina plants. In this experiment, we tested water relations of six M. laurina plants found on Pepperdine University’s Malibu campus showing similar leaf patterns to those found in Sycamore Canyon. Six M. laurina plants devoid of the abnormal leaf growth patterns functioned as our control group. Stomatal conductance, water potential, and leaf mass to area data was gathered using …

Correlation Between Hydration And Reflectance Of Yellow Petals On Encelia Californica, Jayci M. Givens, Kaylee A. Nussbaum, Caitlin R. Kawata

Featured Research

It is known that the NDVI can be used as a measure of hydration in plants because of the variation in pigments due to xanthophyll cycling (Schmitz et al., 2013). Flower petals can also exhibit variations in petal reflectance invisible to the naked eye (Fam & Espinoza, 2013). It was hypothesized that overall hydration levels of a plant would correlate to a difference in the pigments produced for petal color, and thus differences in hydration levels would correlate to differences in petal reflectance. To test this hypothesis, three flowers and two stems were collected from ten different E. californica plants, …

Fitness Parameters In Malosma Laurina Seedlings Growing Near And Away From Invasive Brassica Nigra, Natalie M. Aguirre, Agustin Vargas, Phoebe Shin

Featured Research

In this study we aim to assess the photosynthetic rate of native Malosma laurina (M. laurina) seedling, in comparison to M. laurina seedlings growing amongst several hundred B. nigra invasive plants. We predicted that there will be a difference in the stomatal conductance of each population. We measured photosynthetically active radiation (PAR), seedling height, and stomatal conductance of two isolated populations of M. laurina seedlings. One population grows near B. nigra, an invasive specie, and the other only grows amongst native plants. We found that M. laurina seedlings growing near weeds …

Effects Of Drought On Malosma Laurina Leaves, Suk Ho (Josh) Chang, Jingyi Chen, Sarah B. Nelson

Featured Research

Drought induced deformations in the chaparral plant Malosma laurina were observed following the lack of water availability during the years of 2013 and 2014. We hypothesized that the middle leaves grown during the drought would have the lowest productivity, the top post-drought leaves would have the highest productivity, and the bottom pre-drought leaves would have an intermediate level of productivity. We used a sample size of n = 6, representing 6 unique M. laurina plants. To obtain our data, we used the LI-6400 gas exchange system. In our comparisons of photosynthetic rate, stomatal conductance, and photosynthetic quenching of the top, …

Effects Of High Light Exposure On Photosynthetic Rate And Fluorescence Of Eucrypta Chrysanthemifolia, Alec Flores, Gina Gilderman, Hannah Dario

Featured Research

In this experiment, we examined how a partial shade plant, Eucrypta chrysanthemifolia, found in the Santa Monica Mountains, responded to predictive models of higher light intensities created bydrought. We hypothesized that, with higher levels of light, Eucrypta chrysanthemifolia would respond with a decreased photosynthetic rate, light-adapted, and dark-adapted fluorescence. This was performed by comparing control plants grown in an artificial shade environment to plants exposed to a series of high light intensity treatments. These partial shade plants were found on Piuma Trail in the Santa Monica Mountains. Our data supported our null hypothesis, indicating the photosynthetic rates and light-adapted …

Seedling Resprouts Of Adenostoma Fasciculatum Between Wildfire Cycles Are Promoted By Environmental Conditions That Mimic Fire-Like Environments, Lexe Evans, Teal Speece, Stephen D. Davis

Featured Research

The Santa Monica Mountains represent one of the largest Mediterranean-type environments in the world. With sustained summer droughts, this ecosystem has become prone to frequent wildfires, a phenomenon that has affected the area with regularity (approximately 21 years apart). Naturally, this cycle of wildfires has had a great effect upon the mortality and survival of the diverse chaparral varieties that inhabit the Santa Monica Mountain region. This includes the Adenostoma fasciculatum (chamise), which is the most commonly-found form of chaparral shrub in California. (Redfeldt & Davis, 1996) This species of chaparral is particularly well-adapted to survival in a climate that …

The Effects Of Salinity On The Photosynthetic Rate Of Limonium Californicum, Adriana J. Borges, Elizabeth S. Chau, Justine M. Mckitrick

Featured Research

Halophytic plants, unlike most plants, are able to survive in stressful saline environments. Halophytes possess adaptations to osmoregulate, which gives them a competitive edge in saline environments such as coastal salt marshes. Our group analyzed the responses to salinity of the halophytic plant, Limonium californicum, which is present in California’s coastal salt marshes. We hypothesized that the photosynthetic rate of the Limonium californicum plants would decrease with increasing saline water treatments. In order to test this hypothesis, we watered L. californicum plants with solutions of varying salinity over the course of four days. We measured the photosynthetic rates using …

Correlation Between Hydration And Reflectance Of Yellow Petals On Encelia Californica, Jayci M. Givens, Kaylee A. Nussbaum, Caitin R. Kawata

Featured Research

It is known that the NDVI can be used as a measure of hydration in plants because of the variation in pigments due to xanthophyll cycling (Schmitz et al., 2013). Flower petals can also exhibit variations in petal reflectance invisible to the naked eye (Fam & Espinoza, 2013). It was hypothesized that overall hydration levels of a plant would correlate to a difference in the pigments produced for petal color, and thus differences in hydration levels would correlate to differences in petal reflectance. To test this hypothesis, three flowers and two stems were collected from ten different E. californica plants, …

Differential Survival Of Chaparral Shrub Species In Response To Severe Drought, Hannah Dario, Stephen D. Davis

Biology

In this experiment, we examined how the plants in the Santa Monica Mountains are responding to the driest period in recorded history for California. Our hypothesis was that plant species with the deepest roots would have highest survivorship. We thought this because deep-rooted shrubs will have greater access to soil moisture. This hypothesis was tested by collecting data on plant survival, in a mixed chaparral stand, containing eleven species, growing in the Green Valley Preserve off of Stunt road, in the Santa Monica Mountains. The chaparral stand was 21 years old, having last burned in 1993 (Old Topanga Canyon Fire). …

Leaf Mechanical Strength Corresponds To Tissue Water Relations In Twelve Species Of California Ferns, Breahna M. Gillespie, Stephen D. Davis, Jarmila Pittermann

Biology

The dominant vegetation types in southern California’s coastal foothills are chaparral and costal sage scrub. Chaparral shrubs have mechanically strong evergreen leaves whereas coastal sage scrubs bear mechanical weak, facultative deciduous leaves. What about the ferns that live in the understory of these vegetation types, especially considering their adaptations to a summer dry, Mediterranean-type climate? We tested the hypothesis that some fern leaves are stronger than others and mechanically strong leaves are associated with greater dehydration tolerance. Twelve fern species were examined. Tissue water relations were assessed via pressure volume curves using Scholander-Hammel pressure chambers. We estimated osmotic potential at …

Relationship Between Dehydration Tolerance Of California Ferns And The Mechanical Strength Of Their Stipes, Helen I. Holmlund, Stephen D. Davis

Biology

In recent years, experts in plant physiology have begun to explore the functional traits of ferns, especially in regards to their tissue-water relations. However, to our knowledge, no scientist had yet examined the relationship between fern biomechanics and physiology. We examined the mechanical properties of fern stipes (stems) and attempted to relate those properties to ecological and physiological traits. Based on our knowledge of fern anatomy, we hypothesized that stipe mechanical strength would not correlate with water-stress resistance as it does in seed-bearing plants.

We assessed mechanical strength using Modulus of Elasticity (MOE) and tissue-water relations using pressure-volume curves. Water-stress …

Leaf Mechanical Strength Predicts Physiological Traits Among Three Life History Types In California Chaparral, Taylor S. Stucky, Nicole M. Rodriguez Purcell, Stephen D. Davis

Featured Research

The Santa Monica Mountains of southern California are located in a Mediterranean-type climate region which experiences reoccurring wildfires due to summer drought and Santa Ana winds. Chaparral vegetation, which consists mostly of evergreen, sclerophyllous shrubs, dominates the landscape. Species of chaparral shrubs have evolved three different life history types in response to fire – those that sprout after fire but do not germinate seeds (obligate sprouters = OS), those that do not sprout after fire but reestablish by seed germination (non-sprouters = NS), and those that both sprout and germinate seeds after fire (facultative sprouters = FS). There are two …

Immunomodulatory Activity Of Sambucus Mexicana And Trichostema Lanatum On Lps Stimulated Raw 264.7 Macrophage Cells, Victoria Hester, P. Matthew Joyner

Featured Research

Chumash medicinal plants Sambucus mexicana (Mexican elderberry) and Trichostema lanatum (woolly blue curls) were tested for immunomodulatory activity. Anti-inflammatory effects were determined by treating LPS induced RAW 264.7 macrophage cells with plant extracts and measuring the levels of cytokines: tumor necrosis factor alpha (TNF-alpha) and interleukin 10 (IL-10). We hypothesized that both plants would exert immunomodulatory activity by reducing the pro-inflammatory production of TNF-alpha or by promoting M2 polarization with a concurrent increase in IL-10 production. At concentration 0.01 mg/mL woolly blue curls and Mexican elderberry demonstrated anti-inflammatory activity by reducing the concentration of TNF-alpha in vitro, while levels of …

An Ethnobotanical Approach To Finding Antimicrobial Compounds In Wooly Blue Curls (Trichostema Lanatum) Using A Kirby-Bauer Disc Diffusion Assay, Matthew C. Fleming, P. Matthew Joyner

Featured Research

Plants can be an important source of creativity and production of new drugs. In this study, extracts of wooly blue curls (Trichostema lanatum) were made using DMSO and tested for antimicrobial activity on a panel of bacteria commonly found in separate ecological niches. Wooly blue curls (WBC) was chosen due to its being recorded as a strong disinfectant by the Chumash people. It was found that WBC does exhibit antimicrobial activity against gram positive bacteria and not against gram negative bacteria. However, gram negative bacteria with reduced drug efflux function became susceptible to the WBC extract.

Plasticity In Cavitation Resistance And Mechanical Strength Of Stem Xylem In Heteromeles Arbutifolia, Adults Versus Post-Fire Resprouts, Iolana N. Kaneakua, B. A. Bergman, F. W. Ewers, S. D. Davis

Biology

Background/Questions/Methods

Many species of chaparral shrubs of California undergo vigorous resprout success after wildfire. We hypothesized that the water transport properties of resprouts, as well as their biomechanical strength would differ from adults. In addition, we hypothesized that irrigated and shaded resprouts would display reduced cavitation resistance and biomechanical strength in comparison to controls and adults. We tested these hypotheses by using a centrifuge method to compare the vulnerability of xylem to water stress induced cavitation. We used 50% loss in hydraulic conductivity due to water stress (PLC₅₀) as our estimate of vulnerability to cavitation. A Universal Materials …

Foraging Preference By Wild Deer On Toyon Populations From Santa Catalina Island Versus The Santa Monica Mountains, Amelia I. Clark, Rodney Honeycutt, Anjel Helms, Stephen Davis

Biology

Post-fire regeneration of Toyon (Heteromeles arbutifolia), a chaparral shrub on Santa Catalina Island is impeded by mule deer (Odocoileus hemionus), a non-native species introduced during the 1930’s. Mainland and island populations of Toyon were examined for potential differences in defense mechanisms that act as natural deterrents to over-browsing by ungulate herbivores, with the hypothesis that island populations, void of natural ungulate herbivores, may lack such defense mechanisms. Several characteristics of leaf morphology, including number and length of spines, leaf area and depth, and tensile strength of leaves, were compared between island and mainland populations. Leaves of Toyon from Santa Catalina …