Welcome! As a plant and forest community ecologist, I am interested in tracing human impacts across terrestrial landscapes. Global change drivers in forest and grassland communities, including infectious disease, pest outbreaks, invasive plants, and climate change, are at the forefront of my scientific inquiries. I use a variety of methodological approaches to answer important questions about the changes transpiring in natural systems. In particular, I love disentangling the complexity of climate change-induced shifts in abiotic-biotic interactions that shape plant communities across multiple scales.
Climate change shifts infectious tree disease
Combining a long-term study of the epidemic tree disease caused by Cronartium ribicola, with a six-year, field-based assessment of drought-disease interactions, we found evidence that climate change shifted disease prevalence. The shift was asymmetric due to complex host-pathogen interactions and drought occurrences that ultimately contributed to an unexpected decline in mean disease prevalence. Our study underscores that host-pathogen-drought interactions will strongly mediate climate change impacts on infectious disease. Paper in revision (Nature Communications).
Extreme drought effects in the subalpine
Between 2017-18, I designed a study that assessed the impacts of the recent CA drought on subalpine forests in the Sierra Nevada (see map below). Together with collaborators from NPS, USGS, and USFS, we extracted 800 tree cores, 1200 stable carbon isotope samples, and DNA from all whitebark pine trees measured. The remote locations and extreme terrain presented a fun challenge for the crew, but thanks to their insatiable sense of adventure, we recently finished collecting data and are now analyzing our results.
The tree growth patterns and responses were counterintuitive. We found that on average, growth increased during extreme drought, and our stable isotope analysis suggested that photosynthesis also increased throughout most of the Sierra. The genetic data provided evidence that genotypic variation of whitebark pine is relatively low in the Sierra Nevada; the populations are fairly similar across the range. We’re working on two papers that will hopefully be published by 2021!
Forest management impacts on understory species
Fire size and severity are increasing in the western United States. To increase forest resilience to fire, managers are implementing various fuel-reduction treatments. Though treatments can help moderate fire behavior and risk of crown torching, the long-term treatment impacts on introduced, as well as native herbaceous and shrub species, are less well understood. To assess long-term effects of fuel treatments on understory vegetation, we combined a longitudinal experiment (12- to 13-year) comparing mechanical thinning, prescribed fire (that burned twice), mechanical thinning plus fire to untreated control. Paper in review (Forest Ecology and Management).
Mechanisms of bark beetle outbreaks in the Sierra Nevada
I am currently investigating the mechanisms driving mountain pine beetle (MPB, Dendroctonus ponderosae) outbreaks from low to high elevations in the Sierra Nevada. Specifically, we are asking whether post-drought, lagged bark beetle outbreaks are driven primarily by changes in tree density or vulnerability, or rather by beetle population spillover from lower elevation outbreaks. Using a combination of physiological and remote sensing data, we aim to disentangle the complex drivers of MPB outbreaks in the highly vulnerable subalpine forests.
Third chapter of my dissertation on the compounding effects of white pine blister rust, bark beetles, and wildfire was finally published! It’s open access, so anyone can read it here.
“New evidence from over 4,600 studies calls into question the universal application of critical threshold values, or tipping points, along gradients of environmental stress. Identifying never-to-exceed environmental targets may prove elusive for environmental policy and management.”
Class of 2019 Smith Fellows!
I am honored to join the amazing Smith Fellows 2019 cohort. This fall, I am heading to UC Davis and will work with Andrew Latimer, Connie Millar and Phil van Mantgem on whitebark pine research and conservation.
See more about the project here.
We had an out-of-this-time super bloom in Southern California this year. I finally got a glimpse of what John Muir wrote about years ago before the invasive grasses outcompeted our native forbs.
My writing piece on last summer’s research was selected and featured by the UC Berkeley Graduate Division. See the full story here!
Our paper was published in Trends in Ecology and Evolution. We discuss the importance of considering novel elements and ecosystems in resilience-based management.
Novelty is a double-edged sword.
Some novelty is critical for long-term ecosystem resilience, while novelty can also lead to undesirable outcomes, including a reduction of biodiversity and other ecosystem services.
Identifying how we embrace or reject novelty in natural resource management is becoming increasingly important in an era of global change.
CNR press release here.
I am fortunate to conduct my research in various systems, from grasslands, to mixed conifer, to subalpine forests. These systems provide critical ecosystem services and offer endless opportunities for scientific explorations, both outside in the backcountry and inside the lab. Each system offers insight into the next, and I am always amazed that no matter how much time I spend observing in the field, the mysteries grow increasingly more complex—a life-long challenge that will never grow old!