Clark Lab

Renata explains the benefits and challenges of urban tree care, with plenty of examples from Durham NC.

The 2024 New Phytologist Next Generation Scientists Conference took place at Duke University last week. Lauren was on the organizing committee.

Renata’s defense is coming on 15 May, with a public seminar 14 March at 3:30 in Grainger Hall Field Auditorium. It can be joined by zoom. In addition to the link here discusses this work through the Arnold Arboretum that included mentoring of local technicians on urban tree health.

JABES is proud to announce the 2023 best papers published in JABES:

Modeling Community Dynamics Through Environmental Effects, Species Interactions and Movement (this opens in a new tab)
Becky Tang, James S. Clark, Peter P. Marra, Alan E. Gelfand [JABES, 28, 1 (2023) pages 178-195]

Paul is a physics major from Paris, working in the lab and taking courses during spring 2024. Paul is interested in climate impacts and has been working on El Nino cycles in tree mast.

The National Ecological Observation Network (NEON) spotlights the analysis of climate and habitat effects on North American ground beetles:

Are ground beetle populations decreasing? It depends on where you look and what species you look at. A recent paper in Global Ecology and Biology, Habitat–trait interactions that control response to climate change: North American ground beetles, explores the connections between climate change, habitat types, and ground beetle traits. The study could help researchers model which ground beetle species may be at risk and the habitats needing protection to preserve them.

Understanding biodiversity change is complicated by the fact that populations respond to climate and other species both through change in abundance and movement. Thirty years of fisheries data from the Gulf of Maine show that the mechanisms driving biomass trends vary across space, time, and species… [more]

Tang, B., Roberts, S. M., Clark, J. S., & Gelfand, A. E. (2023). Mechanistic modeling of climate effects on redistribution and population growth in a community of fish species. Global Change Biology, 29, 6399–6414. https://doi.org/10.1111/gcb.16963

Apply now: AcademicJobsOnline.  See Job # 25638

Anticipated start: July 1, 2024

The Nicholas School of the Environment invites applications for two tenure-track positions in Terrestrial Ecology, one at the Assistant Professor level and one at either the Assistant or Associate Professor levels. The successful candidates will contribute to an expanding focus on global environmental change as part of the Duke Climate Commitment and participate in the University Program in Ecology. We seek applicants who will establish widely recognized, externally funded research programs. Both positions are encouraged to capitalize  on Duke’s traditional strengths in areas such as biodiversity, biogeochemistry, ecophysiology, forest ecology, tropical ecology, species interactions, watersheds, statistical science, and/or theory.  Research on both plants and animals is encouraged as are technical frontiers in modeling, geo-spatial methods, experimental networks, and/or remote sensing. Combinations of broad-scale studies and site-based research that could use  the Duke Forest and Marine Lab are welcome. The position will be based on Duke University’s main campus in Durham, North Carolina. The successful applicant will contribute to teaching, advising and service activities in the University and the applicant’s professional field. Teaching will be part of the Environment PhD, the professional Master of Environmental Management (MEM) and Master of Forestry (MF) , and undergraduate programs. 

Duke University and The Nicholas School of the Environment are strongly committed to advancing inclusive excellence throughout our research, teaching, and service activities. A diverse faculty – defined broadly as representing a wide range of identities, lived experiences, and perspectives – is a prerequisite for excellence and is essential to driving innovation within our scholarly community. To achieve these goals, it is essential that  all members of the community feel valued and welcome, that the contributions of all individuals are respected, and that all voices are heard. All members of our community are expected to uphold these values, and we seek to hire faculty who are passionate about increasing the participation and success of individuals from all different backgrounds and communities.  

Interested candidates should submit the following by 20 October 2023: a cover letter (with contact information); three publications; a curriculum vitae; a three-page research statement that includes a description of past research accomplishments, plans for future research, and their experience and approach to mentoring and supporting  a diverse and inclusive research environment; a one to two-page statement describing their teaching philosophy, previous experiences, future plans for teaching, and experience and approach to fostering an inclusive learning and mentoring environment for their students; and three reference letters.

Duke University is an Affirmative Action/Equal Opportunity Employer committed to providing employment opportunity without regard to an individual’s age, color, disability, gender, gender expression, gender identity, genetic information, national origin, race, religion, sex, sexual orientation, or veteran status.

Elevated CO2 in Duke’s Free-Air CO2 Experiment (FACE) stimulated growth of woody plants, but none like poison ivy. Not only did it grow fast; it also increased toxicity. The interview includes PhD student Jackie Mohan and collaborator William Schlesinger on our studies of poison ivy growth in response to high CO2. The study showing this effect is here:

Mohan, J. E., L. H. Ziska, R. B. Thomas, R. C. Sicher, K. George, J. S. Clark, W. H. Schlesinger. 2006.  Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO₂.  Proceedings of the National Academy of Sciences.  103 (24): 9086.

Join us in person or virtual:

Time: Aug 18, 2023 12:00 PM Eastern Time (US and Canada)

Place: Grainger Hall 2102, Durham NC

Zoom: https://duke.zoom.us/j/94581301038

Welcome to new PhD student Kira Meyer and technicians Emily Bolander, Gina Givens, and Jon Ley. Kira comes from the University of Bayreuth and is interested in savanna ecology. Emily, Gina, and Jon are with us from Boulder, Tallahassee, and Chapel Hill respectively, all interested in biodiversity and climate change.

The Research Center on Alpine Ecosystems (CREA Mont Blanc) has announced that the citizen science MASTIF study will become part of its phenology monitoring in France. Founded in 1996 and based in Chamonix, CREA Mont-Blanc has specialized in the study of natural mountain environments. For over 20 years, CREA Mont-Blanc has been combining high quality ecological research with communication and education initiatives. CREA Mont-Blanc is a pioneer and leader of citizen science in France and maintains a strong commitment to participatory science, aiming not only to encourage the understanding of ecology, but also to directly involve the public in innovative scientific research.

Georges Kunstler, from INRAE’s Laboratoire Écosystèmes et Sociétés en Montagne, is a PI on the MASTIF project and an administrator of the MASTIF iNaturalist Project. He will host a webinar on MASTIF in CREA on Monday 21 August, join especially if you plan to visit central Europe this year:

https://meet.google.com/orx-ukqz-wzw

Qiu, T., …, and J. S. Clark. Masting is uncommon in trees that depend on mutualist dispersers in the context of global climate and fertility gradients. Nature Plants (2023). https://doi.org/10.1038/s41477-023-01446-5

Erratic seed crops may help trees confound their seed predators, but what does it do to the seed dispersers that trees need to insure successful germination?

Erratic fruit production, or “masting”, may be a strategy trees use to defend their seeds from the many mammals, birds, and insects that consume them. High carbohydrate, fat, and protein content makes seeds, fruits, and nuts among the highest quality plant foods in nature. The provisions needed to give seedlings a head start after germination place them at risk from seed predators. The lean years between large seed crops could keep seed predators at low levels—too low to wipe out a big seed crop that comes along at long intervals. The relatively rare big crop year can be the time to escape.

But there is a problem with this explanation for masting. The same tree species that attract seed predators may also depend on mammals and birds to disperse their seeds. These friends are so valuable that many tree species pack their fruits and nuts with extra resources and advertise them with colorful displays, all to attract their important mutualist dispersers.

Here is the conundrum. Wouldn’t the unreliable seed production that thwarts a tree’s enemies have the same negative impacts on their disperser friends? If masting effectively guards against enemies (it does), then perhaps the species that rely most heavily on disperser species must forego this defensive option.

An analysis of seed production in hundreds of tree species across five continents shows this mixed benefit of masting. Using the Masting Inference and Forecasting (MASTIF) network, our lab showed the relationship between masting behavior and mutualist dispersers. The tree species that depend most on vertebrate dispersers are the ones that avoid masting. In the temperate forests of the North America and Eurasia, oaks and firs are prolific mast species. Pines and spruces also mast, but to a lesser degree. Hickories and walnuts still less. Chestnut and the fleshy fruits of black gum, holly, hack- and sugarberry, persimmon, juniper, yew, and pawpaw, hardly at all—they are “reliable” resources.  

The masting firs, pines, and spruce fall prey to birds and many rodents in the canopy and when they reach the forest floor. In the tree, conifers can defend their seeds in woody, resin coated cones, many of which are armed with spines—they are a mess to handle. Once on the forest floor the exposed seeds are rapidly depleted by rodents. With few mutualist dispersers, they are prime candidates for masting.

At the opposite extreme, rich, colorful fruits avoid wild fluctuations—they depend on their animal dispersers. There is still plenty of year-to-year variation, because a large expensive fruit is sensitive to moisture stress.  A good two-week drought in mid-summer will see many trees abandoning much of their fruit crop—early abortion.  This includes not only fleshy fruits like persimmon, hackberry (including nettle tree in Europe), and black gum. Acorns and hickory nuts also have high moisture content; they too will abort many partially developed seeds to trim the resource demand. Still, a string of years with suitable climate conditions can see reliable crops in many of these species, one after another.

The oaks are exceptional. Nutrient- and moisture-laden acorns are a target for many consumers. Still their size and moisture requirements place them at the mercy of dispersers that could “plant” them quickly. Escaping predators on the forest floor is not enough—unless rains persist through early germination, they risk desiccation. The new five-continent study in Nature Plants does not explain how trees mast. It does show that an effective strategy for enemies can be modified where it may inflict damage on mutualist friends.

Qiu, T., …, and J. S. Clark. Masting is uncommon in trees that depend on mutualist dispersers in the context of global climate and fertility gradients. Nature Plants (2023). https://doi.org/10.1038/s41477-023-01446-5

Phys.org; https://phys.org/news/2023-06-seed-survival-story-trees-friends.html

Earth.com https://www.earth.com/news/when-it-comes-to-seed-survival-trees-have-friends-and-enemies/

Eurekalert! https://www.eurekalert.org/news-releases/994120

Science daily: https://www.sciencedaily.com/releases/2023/06/230629125706

scienceMagazine: https://scienmag.com/a-seed-survival-story-how-trees-keep-friends-close-and-enemies-guessing/

Mirage: https://www.miragenews.com/seed-survival-how-trees-keep-friends-close-and-1037692/

Skynews: https://skynews.icu/science/397449-how-trees-keep-friends-close-and-enemies-guessing/

Life technology: https://www.lifetechnology.com/blogs/life-technology-science-news/a-seed-survival-story-how-trees-keep-friends-close-and-enemies-guessing

Outdoor news: https://www.outdoornews.com/2023/06/30/seed-survival-story-how-trees-keep-friends-close-enemies-guessing/

The working group Unravelling the role of intraspecific variability in tree species coexistence in tropical forests is meeting in Montpelier this week. The project organized by Ghislain Vieilledent and Isabelle Maréchaux answered the joint call for the SYNERGY CESAB-sDIV on “Coexistence and stability in high diversity communities”. Discussions, modeling, writing…

Climate change is shifting weather patterns and landscapes, and forcing animals to adapt in ways that may not be sustainable. Maggie and Lane discuss their research as part of the Climate Commitment at Duke University. Megaherbivores and birds here.

Habitat–trait interactions that control response to climate change: North American ground beetles (Carabidae)

Tong Qiu, Aaron J. Bell, Jennifer J. Swenson, James S. Clark

First published: 23 March 2023

https://doi.org/10.1111/geb.13670

Citations: 1

Trends in Ecology and Evolution has Spotlight articles that highlight important new papers. Greenspoon et al. in PNAS offer an ambitious effort to estimate global mammal abundance. This overview adds context. In terms of biomass, white-tailed deer come out on top…

Clark, J.S., 2023. The most abundant mammals on Earth. Trends in Ecology & Evolution, ISSN 0169-5347, https://doi.org/10.1016/j.tree.2023.05.001. New estimates of global mammal abundance that use relationships between traits, estimates of range size, and International Union for Conservation of Nature’s (IUCN’s) Red List categories to predict the biomass of thousands of species have been developed by Greenspoon et al. This approach and some of the challenges that contribute to these estimates are summarized here.

Collaborators met this week at SERC to finalize data collection plans for the growing season. The study to understand forest regeneration and climate change involves PIs Jim Clark (Duke), Ines Ibanez (U Michigan), Roland Kays (NCSU), Emily Moran (UC Merced), and Miranda Redmond (UC Berkeley). Upcoming field work includes seed production, forest recruitment, and wildlife populations across the continental US. Missing from photos are Roland (holding camera) and Miranda (virtual).

Join us next Tuesday, Lane will present her public PhD seminar entitled:

“The effects of global change on avian biodiversity”

3:30 pm, April 18 

Field Auditorium

Reception follows on Grainger Hall roof. If you can’t join in person, Zoom here.

Avian communities have declined dramatically over the last several decades. I discuss how massive data, much of it crowd-sourced, can be used to understand and anticipate declines. Beginning with a comparison of two widely-used bird monitoring datasets, I identify and quantify biases in reporting rates. Next, I use the data to understand how winter climate and food availability influence bird movements and distributions. Finally, I demonstrate a novel modeling framework that expands the utility of joint species distribution models and apply it to the dynamics of a brood parasite and its host species.  

Jared Lazarus from University Communications came by to interview lab manager Jordan Luongo and Sam Sutton. Jordan coordinates data collections across four continents, including field work, site negotiations, and contractors. Sam works with the team of students, postdocs, and technicians that travels North America for field sampling and processing samples in the lab.