USA NPN National Phenology Network

Taking the Pulse of Our Planet

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The USA-NPN's National Coordinating Office (NCO) guides the development of the Network, facilitates communication between scientists, land managers, policy-makers, and the public who are interested in assessing the effects of global change on natural ecological systems. Staff members work for the US Geological Survey and The University of Arizona.

Jake WeltzinJake Weltzin
Executive Director
USA National Phenology Network
National Coordinating Office
1311 E 4th St., Tucson, AZ 85721
(520) 626-3821
Fax: (520) 621-7834
Full CV - Résumé

Jake Weltzin assumed his position as Executive Director of the USA-NPN in August 2007. Jake’s interest in natural history developed as he grew up in Alaska and served as an exchange student in the Australian outback. He obtained his B.S. from Colorado State University, M.S. from Texas A&M University, and Ph.D. from the University of Arizona. Following a post-doctoral fellowship at the University of Notre Dame, Jake went to the University of Tennessee, where he served as Assistant and then Associate Professor.

Jake is interested in how the structure and function of plant communities and ecosystems might respond to global environmental change, including atmospheric chemistry, climate change, and biological invasions. His research spans temperate and tropical grasslands and savannas, temperate woodlands, deciduous forest, and sub-boreal peatlands. His recent experience as a science administrator at the National Science Foundation underscored the need to foster large-scale science initiatives such as the USA-NPN. As its first Executive Director, Jake’s vision for USA-NPN is “to develop a continental-scale instrument for integrative assessment of global change that simultaneously serves as an outreach and educational platform for citizens and educators.”

Theresa CrimminsTheresa Crimmins 
Assistant Director
(520) 621-8523
Short CV 
Follow me on Twitter @TheresaCrimmins

Theresa Crimmins assumed the role of Assistant Director in August, 2015. For nearly seven years prior to this, she served as the USA-NPN’s Partnerships & Outreach Coordinator. Theresa works enthusiastically to support involvement in Nature’s Notebook, the growth and use of phenology data and resources curated by the USA-NPN, and a broader appreciation of phenology among scientists and non-scientists alike.

Theresa obtained a B.S. in biology and an M.A. in geography from Western Michigan University and a Ph.D. in natural resources from the University of Arizona. She currently serves on the editorial board for Ecosphere. Theresa was selected as a Distinguished Alumnus of Western Michigan University in 2018. Her research interests encompass plant response to global change, spatial analysis, and engaging citizen scientists of all ages in scientific discovery. 

LoriAnne Barnett
Education Coordinator
(520) 621-1803
Find me on LinkedIn

LoriAnne's Resume
Follow me on Twitter @loriannebarnett

LoriAnne Barnett coordinates the USA-NPN's education activities, focused on engaging a variety of formal and non-formal audiences in experiential education and phenology via the Nature's Notebook program.  She has worked in a number of educational settings over the last two decades, teaching both youth and adults the importance of place and connections to the natural world, and serves as an advocate for citizen science, education and stewardship of the land.

LoriAnne holds a B.A. in Environmental Studies from Shippensburg University in Pennsylvania and a M.A. in Environmental Science and Environmental Education from Prescott College in Arizona.  She has led workshops on leadership development, Wilderness First Aid, outdoor adventure safety, and risk management.  Her areas of expertise include youth development, program and curriculum development, and environmental education. Current Board service includes President of the Arizona Association for Environmental Education and founding board member and Statewide Coordinator of the Arizona Master Naturalist Association

Ellen DennyEllen Denny
Monitoring Design & Data Coordinator
Full CV

Ellen Denny coordinates the development of the USA-NPN protocols for the collection of standardized ground-based plant and animal phenology observations across the nation.  She also serves as a scientific data manager for the National Phenology Database, and as a global liason, helping to advise developing national phenology networks around the world, and working towards global integration of phenology data.
Ellen has a B.S. in Aquatic Biology from Brown University, and an M.F.S. (Forest Science) from the Yale School of Forestry & Environmental Studies. Her professional interests began in marine invertebrate ecology, shifted to ecological restoration, and eventually landed in terrestrial ecosystem ecology. She spent a decade working as a field ecologist and data manager in the forests of New England before coming to the USA-NPN in 2008. Ellen still lives in Kittery, Maine, and participates remotely in the Tucson-based National Coordinating Office.

Kathy Gerst
Associate Research Scientist
Data Product Coordinator
(520) 621-1740
Full CV

Kathy Gerst is an ecologist conducting research and development for phenology data products derived from the National Phenology Database. Previously, she was a liaison with the California Phenology Project facilitating the implementation of plant phenology monitoring in California National Parks. In this role, she collaborated with agency and academic partners to develop project documentation, protocols, data summary and analysis products, and outreach materials.

Kathy received a B.S. in Ecology, Behavior and Evolution from UCLA in 2001. She completed her PhD in Ecology and Evolutionary Biology in 2011 at the University of Arizona where she carried out research on the evolutionary ecology, reproductive biology, and physiology of desert annual plants. Broadly, she is interested in understanding how species, communities, and populations respond to a variable and changing environment.

Lee MarshLee Marsh
IT Coordinator
Applications Programmer
(520) 621-1636


Lee Marsh manages the development of IT tools and infrastructure, including the database, web site, mobile apps and physical hardware that all make the NPN run. He also helps develop, enhance and maintain the USA-NPN's PHP, Java and AngularJS web applications. He also plays a key role in data integration efforts.

Lee graduated from the University of Illinois, Springfield, with a B.S. in computer science, and spent several years working in the private industry before coming to the NPN. His interests include computer gaming, creative writing and weight lifting.

Sharon Oliver

Administrative Associate
(520) 621-8571

Sharon Oliver, Administrative Associate, manages the administrative details of the National Coordinating Office, including budget and travel processes, supports the planning of conferences and meetings, and works on special projects.

Sharon received a B.A. in psychology from the University of Arizona and brings a wide range of experience to her position. She worked for a number of years in the federal sector in administrative, professional and management positions. Most recently, she worked at the U.S. Embassy in Athens, Greece where she was part of the administrative team supporting the Ambassador and Deputy Chief of Mission.

Erin Posthumus

Erin Posthumus
Outreach Coordinator and US Fish & Wildlife Service Liaison
(520) 621-1670
Full CV

Erin Posthumus leads USA-NPN's outreach and engagement efforts through communication with observers and resource development. She is also the USA-NPN's liaison to the US Fish & Wildlife Service, and is working with National Wildlife Refuges across the country to implement phenology monitoring to meet their resource management and outreach goals.

A Seattle native, Erin received her B.A. in Environmental Biology from the University of Colorado at Boulder, then worked on a variety of field biology projects around the US and abroad. She first came to the USA-NPN as a Peace Corps Fellow in 2010, during her graduate program in the University of Arizona's School of Natural Resources and the Environment. In 2013 she was awarded a Master of Science for her research on wildlife species diversity at endangered red squirrel middens. 

Alyssa RosemartinAlyssa Rosemartin 
Partner & Application Specialist
Full CV

Alyssa Rosemartin supports partnerships with resource management agencies and researchers to advance the USA National Phenology Network's mission to improve scientific understand and decision-making. She also contributes to in-house data product development, including quality control.

Alyssa has fourteen years of experience working in the field of natural resources, in IT, research, education and project management.  Alyssa received a B.A. in Spanish and environmental science in 2000 from Smith College and an M.S. in wildlife conservation and management from the University of Arizona's School of Natural Resources and the Environment in 2008. Her thesis explores the relationship between food availability and reproductive investment in terns, as well as breeding bird use of wetlands in the northern Gulf of California. 

Sara Schaffer
Web Designer & Developer
(520) 621-1631

Sara Schaffer works for the USA-NPN as a Website designer and developer, working on website modifications using drupal.  She has experience with graphic design, photography and publishing. She creates, formats and edits several of the documents produced by the NPN. Sara also provides support by completing various tasks related to daily operations and procedures. Her work varies depending on the tasks and events occurring in the NCO.

Sara is a born and raised Tucsonan, and received her B.S. in Microbiology from the University of Arizona in May 2010. In her free time, she enjoys the company of her dog, traveling, hiking, canyoneering, yoga and cycling.  Sara teaches indoor cycling, weightlifting and yoga for a few local gyms, and rides the annual Tour de Tucson.

Jeff Switzer
Systems Analyst
(520) 621-1636

Jeff Switzer will be using his programming skills to enhance and debug all aspects of the USA-NPN's IT infrastructure. His duties will range from solving problems with the mobile apps, to creating features for the website to optimizing the database. He will assist the USA-NPN team in making processes and functionalities more efficient and more adept to handling observer’s needs.  

Jeff graduated from the University of Wyoming with B.S. degrees in computer science and mathematics. As a graduate student he researched resource bounded dimension and joined a startup where he developed an electronic medical records system. He then spent two years teaching in Africa before joining the NPN team. When he's not coding you can find him camping, mountain biking, making music, and drinking tea.


Sierra Frydenlund
Undergraduate Research Assistant

Sierra Frydenlund

Sierra Frydenlund volunteered for USA-NPN for a year before being hired as a research assistant for the Flowers for Bats Project in Fall of 2017. In this project, Sierra is helping construct a monitoring plan for the flowering phenology of agaves and saguaro. The data will be used by the U.S. Fish and Wildlife Service in conserving and protecting the lesser-long nosed bat.

Sierra is a Junior at the University of Arizona working on a B.S. in Natural Resources with an emphasis in Conservation Biology. She is also working on a minor in Sustainable Plant Systems.

Dionna Hatch Hatch Photo
Community Outreach Associate

Dionna Hatch is originally from Michigan, but left in 2002 and has since lived in Guatemala, Ohio, Pennsylvania, India, Sri Lanka, Kenya, and Nigeria before settling with her family of 6 in Tucson, Arizona in 2014. She served as an Agroforestry and Income Generation Peace Corps Volunteer in Guatemala from 2002 to 2004. In Guatemala, she worked with 2 women's groups on projects like aloe shampoo, flower nurseries, cooking and baking classes, and wood-burning stoves. Dionna is also pursuing her Masters in Landscape Architecture as the logical combination of a Bachelors of Science in Environmental Science and Management (Michigan State University; 2000) and a Masters in Public Health (Wright State University; 2008). Her academic interests include utilizing green spaces to fight climate change, improve human health, and provide a soothing aesthetic in a busy world. Dionna will be helping to develop some curriculum materials for local schools, assisting with the development of a new school garden project, and checking in with our partners at Manzo Elementary School's Ecology Lab as they use Nature's Notebook.

Jenny Moscato Jenny Moscato Photo
Community Outreach Associate
(520) 621-1803

Jenny began her second year of work at the USA National Phenology Network this fall as a Paul D. Coverdell Peace Corps Fellow. She is a 2nd year, Masters of Landscape Architecture student at the University of Arizona. She grew up nearby in southern New Mexico and so is naturally a lover of the Sonoran desert and Tucson. She works with and trains volunteers at the Friends of Tucson’s Birthplace Mission Gardens Project. She enjoys our community and the passion of all the citizen scientists that she has met using Nature’s Notebook. She hopes to incorporate phenology into her landscape architecture capstone project next year.

Jenny received a B.A. in Environmental Studies from Emory University in 2009. During a Peace Corps service assignment as a Natural Resource Conservation volunteer in Ecuador from 2011-2013, she lived in a rural, fishing village where her work in elementary and middle schools focused on environmental education activities. In addition, she formed a women’s artisan group that sold products made from recycled materials. She is pursuing a Masters in Landscape Architecture which will give her the opportunity to work on projects she is passionate about in the Southwest such as restoration of retired mining sites, access to public spaces, watershed management, and native ecosystems.

Taylor HubbardTaylor Hubbard
Field Technician for Flowers for Bats Campaign

Taylor is an undergraduate student at the University of Arizona studying Natural Resources with a Restoration and Rangeland Management emphasis. She plans to study fire ecology in graduate school. She is thrilled to be working for the USA-NPN this summer since she grew up here in Tucson and is very passionate about the environment and our beautiful Sonoran Desert. Her previous environmental work includes conducting a masked bobwhite quail study at Buenos Aires National Wildlife Refuge for the U.S. Fish & Wildlife Service, assisting with wildlife camera studies at national parks, and working on trails and gardens and developing visitor content at the National Park Service’s Desert Research Learning Center.