The overarching goal of my research is twofold: I aim to test ecological theory about how climate and inter-species interactions combine to create the biodiversity patterns we see on the landscape, and I aim to predict how ongoing human-caused global changes will affect species distributions, natural communities, and ecosystem functioning. In my research program, I build statistical and theoretical models, work with experimental results and observational datasets that span space and time, and develop ecological theory about how biotic and abiotic processes assemble communities at different scales.
Why are there so many species? Why do they live where they do? Why are there more in some places than others? What consequences will ongoing human-caused global change have for patterns of diversity? These are the questions that keep community ecologists up at night. I am working on tackling these questions, and more, through a variety of projects:
Using remote sensing to link biodiversity and geodiversity. In collaboration with researchers from NASA and other academic institutions, I am developing ways to explore the relationship between biodiversity and geodiversity (variation in the physical environment) from small to large spatial scales. We are connecting biodiversity datasets with huge scope in space and time, including the Forest Inventory and Analysis dataset and the Breeding Bird Survey dataset, with remote sensing data from NASA including elevation, climate, geology, and human land use. Combining data with disparate spatial scales requires special techniques of analysis; through this project, we are advancing the cutting edge of spatial statistics.
Land and water biodiversity at nested watershed scales. Biodiversity research in land-based ecosystems and freshwater ecosystems has largely been two separate efforts. With a team of interdisciplinary researchers, we are exploring the mechanisms relating land and freshwater biodiversity. In this project, we are looking at biodiversity at the watershed level. Since watersheds are naturally nested, this lends itself to multiscale comparisons: we hypothesize that the strength of linkages between land and water biodiversity will depend on watershed scale.
Climate and competition effects on northern forests.In collaboration with researchers from the University of Copenhagen and the Norwegian Forest and Landscape Institute, I am analyzing a forest survey dataset that spans the entire country of Norway since the 1980's. I am fitting Bayesian growth models incorporating functional traits, climate, and competition to these data, and building a mathematical model to make country-scale predictions about future forest growth.
How do species coexist?
Following from the observation that species diversity varies across space, especially as you go toward the equator, ecologists think that species' niches may determine how many, and what kind, of species can coexist in a local community. I am working on several projects testing niche theory with big species datasets.
Rodent niches across the continent. We are using a dataset of rodent communities and traits collected at the National Ecological Observatory Network (NEON) sites to develop a novel method to measure niche overlap among co-occurring species and ask whether overlap patterns differ along environmental gradients. Expect a publication in 2017.
Bird niches across the globe. We are also working with a dataset of bird specimens collected around the globe to explore the idea that species closer to the equator have different constraints on their niche breadth than species in the temperate zone. Again, expect a publication in 2017.
How is energy distributed in natural systems?
How is energy distributed in living systems, and how have those patterns changed over time? The answer to that question has consequences for how we understand the relationship between species diversity and the functioning of ecosystems.
Energy equivalence in forests? In a project led by fellow postdoc John Grady, we're asking how growth-mortality tradeoffs and light competition affect how energy is divided among trees of different sizes in temperate and tropical forests. Expect a publication by 2018.
Forest biomass and tree lifespan over time. In collaboration with researchers at the University of Notre Dame, I am using a unique data source of forest surveys from the mid-1800s consisting of gridded measurements of forest composition, combined with tree functional trait information, to map changes in forest carbon cycling since European settlement in the Midwestern USA. This work is part of the PalEON network--read more here.
Can we predict communities of species from their traits?
The functional trait literature in ecology is replete with references to the "Holy Grail"--the elusive goal of predicting what species will be found in a given place, knowing only the traits of species present in the region and the environmental conditions at the location. I have worked to refine these models, but so far their predictive power seems to be lacking in some systems. A paper has recently been accepted--check back soon for the link.
How does global change affect living communities along natural gradients?
My original approach to tackling big ecological questions (as a Ph.D. student at the University of Tennessee) involved making observations and conducting experiments in the field. Through these studies, I observed how natural systems respond to global change and how that response is determined by baseline environmental conditions and by the functional properties of local communities of organisms. We have a good understanding of how physical aspects of the environment affect living things, and how that relationship is changing due to human activities. However, we still don't understand how this relationship varies from place to place and how it is modified by interactions among organisms that differ in their traits. To address these questions, I developed and ran field studies in and around the Rocky Mountain Biological Laboratory in western Colorado. I simulated warming, nitrogen deposition, and loss of dominant species at study sites at different elevations. You can read more about the nitrogen deposition and species loss study here. I also explored trait variation within and among species in nature and in simulated data--read more about this work here and here. Preliminary results from the warming and species loss study conducted across elevations show that loss of dominant plant species has a bigger effect than warming on the remaining plant community, but only at low elevations where plants become dominant due to competitive traits.
This summer (2017), I am working with an REU student to develop methods for dealing with missing data in ecological datasets; we hope to make this work available as an R package in the near future. My goals for my research program are to combine the work I have done with statistical models with process-based models, with the ultimate aim of predicting biodiversity patterns under global change. Finally, I plan to promote open science by developing tools to help researchers share their data--please contact me if you have any ideas we can work together on!