Research

Within a single representative watershed in a semi-arid landscape, south-facing slopes (SFS) receive greater amounts of solar radiation compared to north-facing slopes (NFS)11. These solar radiation differences may provide us a glimpse into how ecosystems will respond in hotter and drier future climate projections. An observable contrast in vegetation dynamics, particularly trees, occurs between NFS and SFS in many ecosystems. Previous hydrologic research has demonstrated that landscape ET dynamics vary by tree species and density. However, more research must address how tree water use patterns influence subsurface water flow paths. I will address this fundamental knowledge gap by investigating two hypotheses: H1: Recharge rates into the weathered bedrock are controlled by aspect-dependent percolation mechanisms. Vertical water percolation will be dominated by preferential flowpaths (e.g. macropores) created by abundant tree roots on NFS compared to matrix-dominated flow paths on SFS with minimal trees. H2: Mature oak species on NFS use a seasonally variable combination of water stored within different depths of the subsurface including soil moisture, weathered bedrock moisture, and groundwater, while oak species on SFS are more reliant on deeper water sources (weathered bedrock moisture and groundwater).

CHI-Freshwater will develop a system of ground-based microclimate and remotely sensed data products to both quantify and monitor the pulse of freshwater through California’s protected lands to enable development of statewide forecasts of hydrologic and environmental health. Five to 15-year forecasts will offer a ‘look ahead’ for scientists, resource managers, political leaders, farmers, business leaders and the public. CHI-Freshwater will serve as a public informational and solutions hub, with an online data portal for historical and current hydrologic, environmental and climate data. The initiative will sponsor solution-focused research throughout California institutions specifically aimed at improving environmental water forecasting and management for the state, and projecting economic, health, and wild-lands impacts due to climate change. Working with our educational partners, CHI-Freshwater will also provide information and support for people’s lifelong learning in and about water in the natural world.

Prior studies have shown that lower latitude birds are exposed to more predators and have adjusted their anti-predator behaviors to these higher predator-pressure environments. I will use flight-initiation distance (FID), the distance between a bird and experimenter when the bird begins to flee, to quantify avian risk-assessment. I will work at seven University of California Natural Reserve System field sites that were chosen because they have a set of similar species both at lower and higher elevations and at lower and higher latitudes. To further maximize latitudinal variation, I will also work at one or two sites (TBD) in Washington State. If altitude is a substitute for latitude (there are fewer predators at both locations), I expect that each species studied at higher elevations will have similar FIDs as the same species studied at higher latitudes. If elevation substitutes for latitude, these findings will have direct implications on how California birds are managed; those designing set-back zones to reduce human impact on birds may have to modify them based on both latitude and elevation.

I am a graduate student in the Digital Art and New Media Department at UC Santa Cruz. For my thesis project, I am making an augmented reality phone application that visualizes climate change effects in the local California ecosystem. I am interested in visiting the UC Natural Reserves in order to document the reserve, to take photographs that will be utilized in my research, and to explore the nature/resources that the reserves have to offer pertaining to my thesis project.

Coast live oak (Quercus agrifolia Née) woodlands in Santa Clara County California are complex and critical habitats. By the end of this century, California coast live oaks in Santa Clara County will experience rising temperatures of ‘3.6 to 10.8’ . This temperature and climatic shift will affect the ecological performance of coast live oak woodland.

This study aims to assess 250 oak specimens’ climate-associated herbivory rates from generalist Lepidoptera foliar feeders in elevational study plots from 250m to 950m. The study also evaluates the predictions of the Resource Availability Hypothesis to coast live oak communities in Mt. Hamilton. Methods include 1) standing tree herbivory surveys 2) estimation of annual mean temperature and precipitation and 3) land manager interviews from Fall 2018 to Fall 2019. Field sites are located in the Diablo Range, especially near Mt. Hamilton. This range includes coast live oak woodlands within Grant Ranch County Park, Blue Oak Ranch Reserve and Cañada de los Osos Ecological Reserve.

One of the more problematic and under-examined groups within Mygalomorphae is the family Halonoproctidae. Two of its species, Hebestatis theveneti (Simon 1891) and Bothriocyrtum californicum (O. Pickard-Cambridge 1874) are represented in the California Floristic Province (CFP) and surrounding regions. Dispersal-limited groups of organisms, such as mygalomorph spiders, are excellent subjects for phylogeographic studies that focus on questions related to species delimitation and speciation pattern and process. The CFP contains a rich mygalomorph fauna (Starret & Hedin 2007; Bond 2012). Biogeographic studies of the family Antrodiaetidae in California have recovered deep evolutionary divergence among species coincident with Californias complex geological history (Starrett & Hedin 2007). Further study in this group uncovered a previously unknown biogeographical link between northern Sierran and south Coast Ranges which seems to reflect the remarkably low dispersal ability of mygalomorphs (Hedin et al. 2013). The fact that both H. theveneti and B. californicum occur in California, specifically in the CFP, and are generally understudied makes them ideal candidates for systematic and phylogeographic study. The objective of this study will be to combine molecular techniques, morphology, and ecological data to explore the species delimitation, phylogeny, and biogeographical history of Bothriocyrtum californicum and Hebastatis theveneti.

This study aims to address the following questions: (1) What can I infer from sequence data about the population genetic structure within B. californicum and H. theveneti, and are these observed patterns consistent with what is known about their limited dispersal abilities? (2) Do multilocus sequence data yield genealogical patterns congruent with morphological findings, and if so what are the implications for the geographical limit and number of species of each of these groups? I predict that B. californicum and H. theveneti will contain multiple lineages reflecting population structuring and likely some amount of undocumented diversity in the form of cryptic species. I also expect that the phylogeographic history of these two species will align with patterns found in other CFP taxa and the known geological and climatic history of California.

Calochortus venustus, a California endemic bulbous lily, displays striking variation in floral pigmentation and patterning with a spatial geographic distribution experiencing sequential change in phenotypic variation from the founding population, ie. populations in the south appear to be polymorphic with petals of individuals ranging from deep red to pink to white, while populations in the north are mainly monomorphic with petals of individuals being white. I will take a population genetic approach through RAD-Sequencing to elucidate the history of dispersal (range expansion) and population dynamics.

Host-parasite interactions are embedded within dynamic, often highly disturbed environments, which can sharply alter patterns of infection and disease risk among hosts. Changes in land use and the resulting shifts in biological communities have been linked to the emergence of pathogens with medical and veterinary importance. However, the ecological mechanisms responsible for increases in infection often remain conjectural. This proposal examines how the ongoing transformation of landscapes surrounding wetlands influences an emerging issue of conservation importance: amphibian limb deformities. The flatworm parasite Ribeiroia ondatrae, which sequentially infects freshwater snails, larval amphibians, and birds, has been linked to widespread limb deformities in amphibians. Infection and the resulting malformations also increase amphibian mortality, potentially causing declines in amphibian populations. Building upon previously funded NSF research and ecological theory, the current proposal combines broad-scale field surveys and mechanistic experiments to understand how land use change, by altering host density and host diversity, will promote or limit R. ondatrae abundance and amphibian malformations. This effort will specifically seek to identify how biodiversity losses in freshwater ecosystems affect the transmission of pathogenic parasites, such as R. ondatrae. Considering the growing number of emerging infections that threaten human health and wildlife conservation, results of the proposed efforts have broad application potential. Ribeiroia ondatrae is not only growing in conservation importance itself, but is an excellent analog for other parasite infections of economic and human-health significance (e.g., human blood flukes). This proposal would further support cooperative efforts among amphibian biologists and ecologists to address ongoing declines in amphibian populations worldwide.

The chytrid fungus, Batrachochytrium dendrobatidis (Bd), impacts amphibian populations in California, and worldwide. Recent evidence suggests that the fungus may also have a number of non-amphibian reservoirs, including soil nematodes. In this project, we will collect soil samples at ponds with and without amphibians, extract the nematodes, and assay them for the presence of Bd.

The number of emerging pathogens threatening animal, plant, and ecosystem health is rapidly escalating, jeopardizing food security and the economy. One of the most lethal of these emergent pathogens is Batrachochytrium dendrobatidis (Bd), which causes chytridiomycosis and is responsible for the decline and/or extinction of many amphibian species worldwide. A great deal of research has focused exclusively on Bds effect on and relationship with its amphibian hosts, however it is unlikely that amphibians are the only host or reservoir for the pathogen. Our objective is to test if Bd can persist and be vectored by soil, nematodes, and insects, which may be contributing to Bds long-term persistence in some systems. Our results would provide new management and decontamination strategies for Bd and will enhance our understanding of this emerging infectious fungal pathogen. In this project, we will examine whether live Bd spore can be found in soil and on insects or detritus, and if Bd persistence in non-amphibian reservoirs is related to Bd infection of nearby amphibians. To answer these questions, we will collect water, soil, decaying organic material, and insects from study sites across central and northern California, and we will swab amphibians to determine Bd prevalence in the amphibian community.

Many studies of native and invasive plant species have either detected plastic responses of phenological traits (e.g., flowering time) to experimentally induced or inter-annual climatic variation or have reported changes in the strength or direction of phenotypic selection in populations exposed to different environments. Few studies, however, have documented the process of adaptive evolutionary change, in real time, in phenological, morphological, or physiological traits. The ability to forecast a species capacity to adapt to drought or heat stress is as important for forecasting its persistence as predicting its phenological response or the strength of selection on phenotypic traits. The proposed research will integrate the study of geographic variation in fitness-related traits among populations of a widespread annual herb (Nemophila menziesii, Boraginaceae) with measures of: phenotypic selection on traits that contribute to drought-tolerance or drought-avoidance; inter-generational change in additive genetic variance in fitness; and the response to selection in order to test predictions regarding adaptation to environmental conditions across an aridity gradient. We will use the quantitative genetic aster models to estimate additive genetic variance in individual lifetime fitness in pedigreed populations under field conditions as well as to estimate the strength and direction of selection on phenological, morphological, and physiological traits. This will allow us to test Fishers Fundamental Theorem of Natural Selection, which predicts the rate of change in population mean fitness as the ratio of additive genetic variance in fitness to mean absolute fitness. This ratio represents a populations capacity to adapt to current conditions, or its adaptive capacity. We will take advantage of N. menziesiis broad geographic range and latitudinal gradient in mean total annual precipitation and temperature to test several predictions regarding its capacity to adapt to local environmental conditions. This study will contribute to our understanding of how natural selection operates across a species range, potentially identifying mechanisms such as the existence of multiple combinations of traits associated with fitness optima that promote the maintenance of genetic variation in wild populations.

By conducting this experiment at four different UC reserves (which differ in temperature and rainfall), we hope to be able to predict how natural selection will operate in annual plants under future (hotter/drier) conditions.

My goal is to determine 1) whether topographic variation in soil water potential in the field is predictive of the composition of arbuscular and ectomycorrhizae in soils, 2) how differences in soil moisture in a greenhouse setting influence seedling establishment with arbuscular versus ectomycorrhizae, and 3) whether the topographic origin of the soil microbial community significantly influences the type of mycorrhizal association that becomes established.

These questions are important because the distribution of soil moisture across a hillslope is related to physical position as well as precipitation patterns. With climate change, increased intensity and/or duration of dry seasons will accentuate water stress experienced by vegetation in dry topographic positions. Mycorrhizae are critical for plant nutrient acquisition, changes in soil moisture availability may impact both plant moisture and photosynthetic capacity. By elucidating the links between moisture, topography, and mycorrhizal associations, we can start to understand how trees in California may be both nutrient and water limited due to the ecology of their fungal symbionts.

Measuring variance in flowering time and plant-pollinator mismatch Functional trait variation among California grasses

California’s grasslands are heavily impacted by exotic species. Restoration efforts seek to shift the balance towards native species, often by attempting to leverage differences in ecological strategies of native and exotic species. Examples include soil nutrient reductions to favor less nitrogen-demanding species (Alpert and Maron 2000) or mowing in early spring to reduce annual cover (Sandel et al. 2011). However, native and exotic species may often occupy very similar functional roles in the ecosystem, making it challenging to implement an intervention that promotes one over the other (Corbin and DAnotnio 2010). Within California, exotic grasses on average do differ from natives in some key functional traits, but the distributions are nevertheless largely overlapping (Sandel and Dangremond 2012, Sandel and Tsirogiannis 2016). This study will aim to better understand the differences and overlaps of native and exotic grass strategies along a precipitation gradient using plant functional traits as an indicator of plant strategy (Westoby 1998).

Along environmental gradients, the trait composition of plant communities changes. This occurs in part because species with disfavored traits in a particular environmental condition are likely to be absent or rare, and in part because species can shift their traits as environmental demands change. This latter aspect intraspecific trait variation is not well understood in many cases (Albert et al. 2010, Bolnick et al. 2011). In particular, it is not clear how native and exotic species may differ in their strategic plasticity, though one metaanalysis has found higher plasticity in invasive species (Davidson et al. 2011).

Batrachochytrium dendrobatidis (Bd) is the fungal infection that causes the disease, chytridiomycosis in frogs, and is one of the leading causes of frog population declines worldwide. Frog susceptibility to Bd has been shown to differ between populations, even within the same species, which leads to some populations being driven to extirpation while others remain seemingly unaffected. Bd virulence has also been shown to differ by strain within the same lineage. To date, several candidate genes have been identified that may contribute to host susceptibility and pathogen virulence in this system, but so far the results have been inconclusive – in some populations, alleles confer resistance and in other cases, the same ones do not. The goal of this project is to determine the genetic basis for this difference in susceptibility and resulting disease dynamics in both the host and pathogen across California. We can do this by extending the current knowledge of this system and sampling across a broad range of species and populations to find a pattern between genotype, disease, and location.

Although recent studies suggest that land plants close stomata prior to embolism formation within stems, tests of this claim in a field setting remain scarce. In addition, there is some debate about whether transpiration can be sustained in the event of declining hydraulic conductance. Quercus douglasii Hook. and Arn., is a long-lived, winter-deciduous obligate phreatophyte tree species that transpires throughout the summer dry season. As such this species provides an excellent opportunity to test the hypothesis that all species close stomata prior to embolism formation. The objective of this work is to fully characterize the seasonal trends of transpiration and stomatal behavior in blue oaks to test the hypothesis that they close stomata prior to embolism formation.

To do so we will quantify sapflow in situ using miniature external gauges and perform periodic measurements of leaf water potential and leaf-level gas exchange (using a Li-Cor 6800). Miniature external sapflow gauges are a useful tool for investigating water use of leaves and small shoots, yet have been utilized sparingly in academic research, agriculture and related fields possibly as a result of prohibitively high cost of commercially available products and/or significant time requirements to independently manufacture the instruments. We make use of an inexpensive, easy-to-manufacture external sapflow gauge with integrated Arduino-based logger that we believe has the potential to be widely and rapidly applied. All measurements will be conducted on sunlit, upper canopy, south facing branches from adult trees.