A new study just out in Nature Communications provides new insights into the causes of past drying in central North America. These long periods of aridity are best thought of as persistent and long-lasting shifts in the background state of the climate system, rather than brief disruptions such as droughts. These long-lasting changes can have devasting impacts on forests, water availability and the water table, and agricultural societies. Fossil pollen records, such as those collected at UW-Madison and compiled globally into the Neotoma Paleoecology Database, clearly show a period of sustained aridity in the Great Plains and Great Lakes regions, between approximately 8,000 and 5,500 years ago.
Now, a new generation of paleoclimatic simulations from Earth system models, combined with networks of fossil pollen and other paleoclimatic indicators, strongly indicate that this midcontinental aridity were caused by the retreat of the Laurentide Ice Sheet and changes in insolation. As the ice sheet melted, its effect on atmospheric circulation waned, causing a reduction of storm tracks though the north-central US. In combination, intensified summer insolation during the early Holocene led to enhanced evaporative water loss and soil drying. The patterns of drying produced by Earth system models when driven by these factors agree well with paleoclimatic data networks, suggesting that we are gaining an increasingly good understanding of why central North America dried out during the early to middle Holocene.
This work was led by Dr. Sakari Salonen at the University of Helsinki (press release) with collaborators here at UW-Madison, Stockholm University, the University of Wyoming, and other institutions.
Congratulations to Dr. Nora Schlenker for the successful defense of her PhD dissertation Vegetation dynamics in a novel and rapidly changing world - using a biogeographical and palaeoecological lens. Nora passed her defense with flying colors, using data and concepts from the past to better understand how species will respond to current and future climate changes.
Nora is off to Aarhus University in Denmark for a postdoc, leaving in July, so it’s exciting to see her move to the next stage of her career and scholarship. Congratulations Nora!
Dear Ecological community,
We are happy to announce a workshop at the Ecological Society of America, in which we will present and provide hands-on training in a new R package that uses a state-space modelling approach to test hypotheses about the environmental and abiotic factors governing species and community dynamics. The workshop will be of interest to community ecologists and paleoecologists working with community time series data and interested in drawing inferences about biotic and environment-species interactions within their multinomially distributed datasets. See workshop details below.
We are offering support to workshop participants on the order of $1000 to help cover travel and accommodation costs. This support is provided by the National Science Foundation. To apply, please fill in this short application form by April 30, 2024. We will review applications and respond by May 10, 2024. Graduate students and early career researchers will be prioritized for travel support, as will scholars from communities that are traditionally underrepresented in ecology. We encourage applicants from all backgrounds to apply.
Please direct any enquiries to Quinn Asena: qasena@wisc.edu. Please note that this participant fund is only available to those intending to attend the workshop at ESA and travel awards will be made after the meeting closes.
Kind regards, Quinn Asena, Tony Ives, and Jack Williams
Workshop details:
Title:
State-space methods for testing hypotheses about environmental drivers and biotic interactions in community and paleoecological time series.
Session description:
We will introduce a newly developed state-space modeling approach for testing hypotheses about environmental drivers and species interactions. We focus on data consisting of time-series of multinomial count data (e.g., pollen or diatom counts) when only relative, rather than absolute, information is available. Multinomial data are not appropriate for classical time-series analyses, and the resulting statistical gap has challenged efforts to formally test causal hypotheses in palaeoecological records. State-space modeling provides a rigorous framework to test hypotheses about the environmental and abiotic factors governing past species and community dynamics. The workshop aims to:
Attendees will learn how to apply the models using paleoecological data such as pollen counts. However, the modeling approach is applicable to any time-series data with a multinomial distribution. We will conduct the analyses in R, so experience using R will be useful; however, we have designed the workshop to focus on the ecological relevance and application of the model, and prior knowledge of R is not required.
Welcome to Eric and Andria! Eric Giese is an incoming MSc student who is working on understanding the post-glacial geomorphic and ecological history in eastern Wisconsin. Eric joins us from UW-Oshkosh and is currently working up new sediment cores collected from Long Lake, WI. Dr. Andria Dawson is a faculty member on sabbatical leave from Mount Royal University, and is a quantitative ecologist interested in reconstructions of past land cover and biophysical parameters, as a way of better understanding past vegetation-atmosphere feedbacks. Andria is here to advance a couple of papers, reconnect with colleagues (she’s a former postdoc), and enjoy Wisconsin in the fall.
We’ve recently received funding from the UW Research Forward funding initiative to build a new team and research capacity to retrieve ancient DNA from lake sediments, as a way of studying changes in plant communities and diversity caused by climate change and human land use. This project is in collaboration with colleagues in Botany (Ken Cameron), the Center for Limnology (Jake Vander Zanden), and the Biotechnology Center (Josh Hyman and colleagues). Ismael Espinoza is the lead PhD student working on this project. We’ve collected short cores from a first set of lakes this summer, and will be conducting first analyses designed to test methods and assess the ability of aeDNA to detect changes in plant communities associated with EuroAmerican Settlement and land clearance.
We’re excited to announce the release of Range Mapper, a new set of online interactive and animated maps of tree, shrub, and grass distributions and their changes in North America, Europe, and Oceania since the peak of the last Ice Age. The accompanying paper by Adrian George et al, Range Mapper: An adaptable process for making and using interactive, animated web maps of Late-Quaternary open paleoecological data, is published in Open Quaternary. These animated maps illustrate the dynamic changes in species’ ranges in response to past climate and other environmental changes. They can be readily used by educators and students interested in learning about the effects of climate change and ecosystems. Experts may also find these maps useful for quick-look insights into past patterns and processes at broad scales. Each map is based upon networks of fossil pollen data drawn from the Neotoma Paleoecology Database. All underlying code is posted to Github and Zenodo and can be readily adapted by other interested users to show other species or taxonomic groups of interest. Range Mapper was developed by Adrian George and Sydney Widell, with advice from Rob Roth and Jack Williams and support from the National Science Foundation (NSF). Check out Range Mapper!
We always knew that Dr. Jacquelyn Gill (lab alumna, PhD 2012) was an outstanding science communicator, but now it’s official: she’s one of the best in the country! The National Academy of Sciences has just awarded Jacquelyn an Eric and Wendy Schmidt Award for Excellence in Science Communication. This honor is so well-deserved: from the start, Jacquelyn has always been passionate about science communications and always ready to try creative new ways of reaching audiences - whether it be live-streaming her dissertation (way back before this was a thing), social media, podcasts Warm Regards, or heartfelt essays. Jacquelyn brings her full self to her science and her science communications, and her fierce authenticity has made her a role model to so many. Thank you, Jacquelyn, for your tireless efforts to fight misinformation and share knowledge.
Angie Perrotti’s paper Diverse responses of vegetation and fire after pleistocene megaherbivore extinction across the eastern US is now published in Quaternary Science Reviews. Alongside collaborators, Angie tested the hypothesis that end-Pleistocene megaherbivore extinction caused a cascade of changes including an incursion of woody vegetation, no-analog vegetation assemblages, and fire activity increase in eastern North America. Using the largest-to-date network of dung fungal spores, pollen, and macrocharcoal proxy records, this research found that ecosystems in the northern US are more sensitive to megaherbivory than those in the southeastern US.
Welcome to Ismael Garcia Espinoza! Ismael is a Fulbright Scholar, who has just arrived from Colombia to pursue his PhD studies in the US. Ismael has a Masters in Geography and an undergraduate degree in Geology, and he is interested in studying climate-driven ecological dynamics. He’s already started ice skating lessons, so he’ll be ready for the Wisconsin winters soon!
Congratulations to Sam Wiles for defending their Masters Thesis! Sam’s thesis presented a new pollen record from beautiful Sunrise Lake, Michigan. They then combined this new record with 20 additional records from the Neotoma Paleoecology Database to reconstruct the past shifts of the Michigan Tension Zone (MTZ) over the last 10,000 years. Their work also tested the hypothesis that communities close to the MTZ were more sensitive to environmental change than communities far from the MTZ.