98 Works

Bark characteristics affect epiphytic bryophyte cover across tree species

Devan Becker, Alistair Dobson & Kristen Klitgaard
Forest tree communities are shifting as a result of changes in regional climate and human management, which has cascading effects on other members of the community such as epiphytic bryophytes. Epiphytic bryophytes play important roles in ecosystem function, and their distribution is highly dependent on the characteristics of their substrate. To see how epiphytic substrate characteristics affect bryophyte abundance, we measured bark thickness, pH, and water holding capacity as it varied with bryophyte coverage on...

Impacts of fire suppression and drought stress on patterns of conifer mortality in eastern Sierra Nevada montane forest

Josh Brandt, John Laux, & Benjamin Weaver
In the age of fire suppression, a major killer of coniferous forests has shifted from wildfires to beetle infestations and drought stress. We examined a conifer forest in the Eastern Sierra Nevada to obtain demographic data on the area and to determine the factors affecting conifer mortality. We found a positive relationship between the number of boreholes and mortality across tree species. Bark beetle tree mortality in lodgepole pine (Pinus contorta) was related to density,...

Population and community-level impacts of increased fire frequency in serpentine chaparral

Miranda Martin, Casey Pfahler, Francesca Shackleford & Emily Wapman
Wildfires are natural processes that revitalize the native biodiversity of many habitats by clearing landscapes and creating sunlight rich areas with low competition. This process occurs in the serpentine chaparral of California, which is home to a variety of fire obligate seeders, including whiteleaf manzanita (Arctostaphylos viscida) and MacNab cypress (Cupressus macnabiana), as well as fire facultative seeders such as chamise (Adenostoma fasciculatum). In our study, we surveyed serpentine chaparral habitats in sites with different...

Formica ant and Cinara aphid mutualisms on limber pines (Pinus flexilis)

Charles Chen, Lori Liu &
Ant-aphid mutualisms play important ecological roles in many ecosystems. While Formica ants are well studied model organisms, pine-specialist Cinara aphids remain understudied. Moreover, there is little research on ant-aphid mutualism in subalpine ecosystems. We investigated multiple species of Formica ants and their mutualistic interactions with Cinara aphids on the limber pine Pinus flexilis in a subalpine ecosystem. Cinara apini colonies were found tended to by silver, black, and red Formica ants, and they occupy older...

Effects of volatile compounds in California bay trees (Umbellularia californica) on vegetation growth and insect herbivory

Ashley Adornato, Hannah Gerber, Sarah Haas & Jennifer Perez
Secondary metabolites are volatile compounds produced by plants that can be used as defense mechanisms for reducing stressors such as herbivory and competition. Leaves, roots, and stems of California bay trees (Umbellularia californica) get their notable aroma from secondary metabolites called monoterpenes, which are allelopathic constituents in many other plants, such as eucalyptus. In this study, we investigated the potential allelopathic and anti-herbivory effects of California bay trees by examining their understory composition, germination rates...

Acorn woodpeckers (Melanerpes formicivorus) exhibit more predator avoidance behavior post-fire

Emily Drake, , Youssef Hanna & Johnson Ku
Climate change has increased the frequency of wildfires globally. This increase in wildfires causes many animals to adjust their behaviors in order to cope with the more regular disturbances occurring in their habitats. It is often thought that birds are less affected by disturbances such as fire because of their ability to easily relocate by flying, but species with high levels of territoriality, such as acorn woodpeckers (Melanerpes formicivorus), may be more greatly affected by...

Bird community interactions at water sources at Hastings Natural History Reservation

Christina Cen, Killian Fay, Joselyne Jaramillo & Jason Ku
In seasonally dry areas, artificial water sources become a gathering place for a variety of avian species, leading to interactions between birds whose niches otherwise do not overlap. To maximize water use while reducing negative costs associated with conflict and predation, birds adopt anti-predation behaviors and engage in differing levels of tolerant and conflict interactions. In order to better understand how birds interact and behave at artificial water resources, we examined whether species and flock...

Plant morphology and behavior of Simmondsia chinensis in the Colorado Desert

Sarah Eskander, Kayla M. Kettmann, Jeramy Ott & Sarah Payne
At the edges of its range in the Colorado Desert, jojoba (Simmondsia chinensis) has been known to exhibit local morphological adaptations not found elsewhere in its distribution. In this study, we expand upon jojoba’s known sexually dimorphic adaptations and examine its behavioral adaptations to a xeric environment. Specifically, we investigate how jojoba avoids intense solar radiation through leaf orientation. We found that jojoba does not exhibit paraheliotropic leaf tracking but instead orients its leaves to...

An ancient forest on the move: Range shifts in bristlecone pines

Angela Delos Santos, Katherine Pratt, Grace Rosburg-Francot, Linnea Schaefer & George Sidarous
Recent changes in global climate are causing many species to shift their ranges towards higher elevations. The rate at which species can shift their ranges may determine whether or not they will be able to persist in light of such rapid environmental change. In this study, we examined the effect of elevation on recruitment, mortality, and intraspecific competition in Great Basin bristlecone pines (Pinus longaeva, BC), a long-lived subalpine species whose upper limit is often...

Alpine wet meadows: soil properties’ effect on plant diversity

Madeline Castro, Fidel Machado-Perez & Rebecca Raven
Alpine ecosystems are a harsh environment with little nutrients and the abiotic effect that the soil has on the plant community is relatively unknown. The focus of this study is to illuminate the role that soils play in the plant diversity of alpine wet meadows. In doing so we investigated the function of clay and root content, organic matter, pH and soil moisture in determining plant diversity in three meadows in the White Mountains, California....

Seed preference in a desert harvester ant, Messor pergandei

Tonia Brito-Bersi, Emily Dawes, Richard Martinez & Alexander McDonald
Optimal foraging theory states that foragers maximize their energy intake by minimizing the energy expended to collect their food. The harvester ant, Messor pergandei, provides a model system to study foraging energy expenditure due to their dependable group foraging behavior. Exploring seed preference could give us further insight into how their harvesting affects the surrounding vegetation and ecosystem as a whole. Choice trials were conducted on M. pergandei using three native seeds and one non-native...

The impact of shallow landslides on primary productivity

Addison Eftekhari, Carly Lam, Francesca Penny & Ian Silberstein
Shallow landslides provide us with a closer look at succession in response to disturbances and their long-term impact on a landscape. Shallow landslides are commonly found in low hills of coastal California, and while research has been conducted on the impacts to human infrastructure and habitation, effects on plant communities and subsequent succession has not been well researched. This study looked at the effect of shallow landslides on vegetation in the grasslands of UC Santa...

Long-term changes in composition of old-growth mixed evergreen forests in Mendocino County

, Charlie Schiebl, Gabriel Perez & John Salib
Abiotic factors have caused changes in old-growth California forests. These changes may be indicators of environmental stressors such as decreases in precipitation, increases in temperature, and changes in historic fire regimes. We aim to examine these changes by doing a 40-year follow-up study on Ashley Boren’s 1981 undergraduate thesis, conducted at Angelo Coast Reserve in Mendocino County, California. The purpose of this study is to examine whether or not the predictions made in 1981 would...

Herbivory defense and growth tradeoffs along a moisture gradient in Lupinus latifolius var. columbianus

Lilly Boiton, James Powers & Jordan Waits
Hypotheses such as the plant stress hypothesis, apparency theory, and the resource availability hypothesis provide contrasting predictions to how plants respond to abiotic stress and their interactions with herbivores. In this paper we examined the effects of a water availability gradient on the morphological characteristics and herbivory of Lupinus latifolius var. columbianus. We measured the abundance of the leaf beetle, Galeruca rudis, and Aphididae as well as the amount of leaf herbivory damage on lupine...

Factors affecting woodrat abundance over 70 years

Wolfgang Abad, Jose Morales-Doo, Carly Pomeroy & Adrienne Ung
Woodrats are ecosystem engineers that can increase biodiversity by physically changing the environment. In doing so, they alter landscapes and increase the number of microhabitats for other organisms. In order to better understand woodrats’ role in their ecosystem, we surveyed big-eared woodrat (Neotoma macrotis) houses in Hastings Natural History Reservation located in Monterey County, California. For each house, we determined its usability and measured its size. We found a 26 percent increase in population density...

Competition between exotic honey bees (Apis mellifera) and native pollinators on late-blooming desert scrub

Janelle M. Osteen, Alexis M. Necarsulmer, Jessica J. Fan Brown & Nhung H. Nguyen
Pollinators are essential to worldwide biodiversity. This study focuses on pollinator communities on Isocoma acradenia, a late blooming shrub in the Colorado desert. We hypothesize that late in the flowering season, exotic honey bees and native pollinators experience increased competition for floral resources. We surveyed pollinator species richness, abundance, and competitive interactions. Our results reveal that honey bee presence does not have effects, competitive or otherwise, on native pollinators. Continuing to research exotic and native...

The effects of sunlight and slope on the lichen community of the Sweeney Granite Mountains reserve

Kha Cung, , & Samantha Spiegel
Lichen communities are essential to their ecosystems as they provide a means of nitrogen fixation, suitable growing conditions, and resources to other organisms across diverse environments. Their community structure can be impacted by changes in abiotic factors such as temperature, pollution, precipitation, and sunlight. It is widely assumed that lichen prefer to grow on the northern faces of their substrates because it is believed they experience less desiccation and UV radiation from sunlight exposure. This...

Habitat preference and species interactions of the desert woodrat (Neotoma lepida) in the Mojave Desert

Becca Cosmero, Emily Fieberling, Katherine Marlin, Ricardo Ruiz, & Lara Volski
Ecosystem engineers often have cascading impacts on the ecosystems in which they occur. Understanding the factors that contribute to their habitat selection can provide valuable information on how ecosystems function. Our study investigates the habitat distribution of desert woodrats (Neotoma lepida) in the Eastern Mojave Desert. We show that there is a difference in desert woodrat abundance among habitats, and found that specific aspects of these environments are associated with woodrats. These aspects include grass...

The fungus among us: Ecological succession within decomposer communities

Marta Alvarez, Ashlyn Bahrychuk, Kellie Cutsinger, Alexander Gallandt & Thomas Lenihan
The process of succession can be a major driving force in sculpting ecological communities over time. Decomposers play a crucial role in forest succession, recycling nutrients from fallen logs back into the ecosystem. In this study, we examined the community of plants, fungi, and invertebrates living in fallen log microhabitats across decomposition stages in a mixed conifer forest. We predicted there would be a shift in species composition among decomposer communities in Douglas fir logs...

Succession and soil development of Pleistocene glacial remnants in a sagebrush steppe

Sophie Borison, Charlotte Bruggeman & Sam Steuart
Following glacial retreat, soils and plant communities often undergo drastic changes as succession occurs. As bare soil is colonized, the plant community shifts and drives future succession patterns. The aim of this study was to assess the modern stage of succession on different-aged glaciated areas by sampling a Tahoe-era glaciation (130 to 70 ka) lateral moraine, a Tioga-era glaciation (28 to 13 ka) lateral moraine, a flat which the Tahoe-era glacier covered, and a flat...

Spatial and behavioral ecology of riparian lizards in rock bar microhabitats

Mark Barsoum, Emma Campbell, Zoe Marsh & Kyra Sullivan
Ecosystems are comprised of many different microhabitats which are distinguished from each other by abiotic and biotic properties. In these microhabitats, large scale ecosystem dynamics such as community utilization of resources can be observed on an individual scale. Within rock bar microhabitats along the South Fork Eel River in the Angelo Coast Range Reserve, we observed the behavior of western fence lizards (Sceloporus occidentalis) and sagebrush lizards (Sceloporus graciosus) with respect to abiotic factors. We...

Patterns of vegetative reproduction and distribution of Cylindropuntia

Ryan Fong, Lucy Johnson & Joseph Saucedo
Cylindropuntia can reproduce sexually, asexually, or both ways, highlighting the spectrum of reproductive strategies within a single genus. This diversity in reproduction provided an excellent framework for better understanding the distributive differences between sexually and asexually reproducing species within the same habitat. The sole use of asexual reproduction in C. bigelovii is not well studied, despite being such an iconic desert species. We investigated factors that might affect vegetative reproduction, such as water content and...

Life on the edge: Abiotic stress and competitive exclusion affect plant communities across a subalpine edaphic gradient

, Willem Schep, Hanan Abels-Sullivan & Casey Kwok
Abiotic stress and heavy competition each limit the assemblages of plant communities, defining their composition as well as their boundaries. One plant community governed by stress and another by competition may abut one another, forming a biotic gradient called an ecotone. In California’s White Mountains, this gradient occurs across the meeting point between a calcareous (dolomite) and non-calcareous (quartzite) soil types. In this study, we tested the effects of this gradient on plant community compositions...

Shade informs the size and distribution of incense cedar (Calocedrus decurrens) in a fire-managed montane forest

Sandy Navarro, Cristina Villalobos-Heredia, Sierra Teemsma & Patrick Lee
The biological diversity observed in forest ecosystems can be influenced by environmental factors. This diversity may be threatened by long term fire suppression which can result in dramatic shifts in forest composition. In an observational study following cedar recruitment, we found that cedar sapling abundance was the greatest under the shaded conditions of adult cedars in comparison to their oak and pine counterparts. Investigating landscape-scale impacts of environmental conditions resulting from continuous fire suppression allow...

Species interactions and abiotic effects on stand structure of bristlecone pine (Pinus longaeva) and limber pine (Pinus flexilis)

Selene Arellano, Anna Douglas, & Janette Jin
Plants experience a wide range of biotic and abiotic stresses based on their environmental conditions. Demographic stages—recruits, saplings, and adults—may react differently under stress. In this study, we examine how the factors of aspect, substrate, and competition affect the stand structure of Great Basin bristlecone pine (Pinus longaeva) and limber pine (Pinus flexilis), which are among the few trees that can withstand the stressful subalpine environment. We surveyed an even distribution of north and south-facing...

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