Putting Down Roots
Marquette’s Klingler College cultivates faculty strength in ecology and research while establishing its new environmental science program
By John Blum
From tropical rain forests to temperate forests to prairie grasslands, Klingler College ecology and evolutionary biology faculty travel near and far to understand the complex interrelationships between living organisms and their physical environments.
Over the last decade at Marquette, there’s been a steady drumbeat of interest in all types of academic investigations into the environment. A critical mass of student interest, for instance, led to the creation of an interdisciplinary environmental studies major, one that examines political, social, economic and ethical dimensions of environmental issues.
That student interest, together with several relatively recent faculty hires in the Department of Biological Sciences, led the university to approve an environmental sciences major for fall 2021, a STEM-intensive program that includes course work in biology, chemistry, physics, math, statistics and data sciences, with elective crossovers to environmental engineering.
These developments, alongside an expanding portfolio of faculty research, signal the Klingler College is making its mark in a field grappling with the health and survival of our environment.
One of the college’s noteworthy hires, Dr. Stefan Schnitzer, Mellon Distinguished Professor of Biological Sciences, studies lianas — woody vines that weave serpent-like through tropical rain forests. Long intrigued by these plants, he has received National Science Foundation and other external support to study them since 2006 and was recently awarded another NSF grant to continue his studies to 2025.
Lianas climb the trunks of their host trees to deploy their leaves above the canopy to gather light. Until recently, lianas were relatively ignored by the scientific community, always playing the backup singers to the rock star rain forest trees. Schnitzer has changed all that.
His previous work, which garnered national attention, has shown how lianas actually diminish the tropical rain forest’s ability to store carbon. The thinner-stemmed lianas store much less carbon than trees — most of the lianas’ biomass resides in its leaves, not wood, and wood stores more carbon for a much longer time. If not as much carbon is being sequestered, climate change may accelerate because these tropical forests currently store 25 to 30 percent of the Earth’s carbon.
An infestation of lianas would compound this problem, and that’s what has been occurring in tropical forests around the world. Schnitzer’s field sites in Panama have jumped from 32 percent infested in 1968 to 75 percent infested in 2007. Scientists aren’t yet sure exactly what is causing the infestation — drought, disturbance, elevated CO2 and nitrogen deposition are possible culprits — but Schnitzer has been studying this for a while and anticipates results in the near future.
The liana story, however, is not all doom and gloom. “When people read the results of my work, some cry out ‘Kill all the lianas,’ but that’s not my message,” says Schnitzer. “Compared to previous opinions about the insignificance of the lianas, we’re finding that they have a huge effect.” Although they may be detrimental when it comes to storing carbon, they are beneficial in many ways, including providing passage for arboreal animals, supporting large pollinator populations and promoting tree diversity.
In fact, Schnitzer’s recent NSF grant will allow him to test the notion that the lianas maintain this tree diversity by suppressing the growth of dominant tree species, which better tolerate shade, to allow for the survival and coexistence of diverse, more light-oriented subordinate trees.
At his Panamanian experiment site, Schnitzer has set up equally sized plots where he has removed all the lianas, which he can then compare with an equivalent number of control plots that still retain their lianas. The site comprises about 30,000 trees and 300 different species, giving him ample opportunities to compare changes in tree density richness, diversity and composition with and without lianas. At a nearby 124-acre observation site, the Schnitzer Lab has been tracking the fates of 67,500 lianas since 2007. Having spent the last two years updating the census, Schnitzer feels that the data are now finally refined enough that his team can soon publish findings about those changes to the lianas over the last 10-plus years.
Schnitzer’s lianas ecological work looks to answer questions in two broad areas. First, what explains species coexistence, and what mechanisms allow for diversity to be maintained? “Are there specific mechanisms that produce these diverse communities, or is it just random drift — species come, species go?” Second, what explains the distribution of organisms? Is it biotic interactions — the interplay among the living creatures in an ecosystem such as animals, plants and bacteria? Or is there an alignment with abiotic factors, such as different combinations of water, soil nutrients and sunlight?
This summer Schnitzer received a prestigious Fulbright Scholar Award. The award will allow him to spend time at Wageningen University in the Netherlands, where he and his colleagues will combine efforts to understand how the tropical forests might be reaching a tipping point in transitioning from being tree-dominated to liana-dominated — especially in terms of species diversity and carbon loss — and its potentially harmful impact on climate change.
Fire’s effects on plant-pollinator interactions
Dr. Joseph LaManna, assistant professor of biological sciences, tackles problems complementary to Schnitzer’s work. But whereas Schnitzer has been navigating the tropical rain forests, LaManna has been hiking among the temperate forests.
LaManna sees “two fronts” to his ecological research: biodiversity and carbon sequestration. He looks at how species interact and form communities across food-chain levels: from microbes in the soil to plants and trees, insects, birds and mammals. And in his research into forest ecosystem dynamics, he’s interested in how species’ interactions influence the amount of carbon stored in a forest and how quickly that forest carbon is turning over.
His research methodologies range from experiments and observational studies in the field to powerful quantitative analyses that allow him to crunch the numbers of extremely large data sets. His analytics on the Monitoring Avian Productivity and Survival data set — which provided data for nearly 300,000 individual birds over 16 years from more than 500 bird-banding stations — were instrumental in understanding how West Nile virus affected different bird species. And his work with the data supplied by the Smithsonian Center for Tropical Science Forest Global Earth Observatory helped to understand how predators, pathogens and parasites maintain biodiversity by limiting abundances of dominant species.
He recently teamed up with other scientists to research the effect that western wildfires have had on plant-pollinator interactions. Those results showed that the right kind of fires — those of mixed intensity, not the “scorched earth,” high-intensity fires — can result in greater abundances of both plants and pollinators. Findings like these are being used to establish best land-management practices, such as controlled burns.
Current NSF funding will allow LaManna to convene panels of experts to come to a consensus on one process for maintaining plant diversity. If too many plants of the same species grow too closely together, many will die off because of shared diseases and intense competition — and these deaths allow other types of plants to move in, thereby increasing diversity. But it’s not yet known how significant this is for overall plant diversity. These workshops, to be held at Marquette, hope to establish “a common currency” to evaluate these ecological processes. With some standards established, the groups look to set pathways to understand if these operate across the globe. “It’s a way for us to forge ahead, to plot a way forward for the entire field,” says LaManna. “And it’s very exciting for us — to bring these world experts to Milwaukee and to showcase Marquette’s Environmental Science program.”
Drought’s impact on insect ecosystem contributions
It’s hard to imagine squeezing water from a blade of grass, but for Dr. Nathan Lemoine, assistant professor of biological sciences, it’s part of his job — and part of his NSF-funded project to study the role of insect herbivores in grasslands and how extreme drought can strengthen or weaken those insects’ contributions to an ecosystem.
At field sites near Dousman and Spring Green, Wisconsin, Lemoine has set up rainout shelters that let him impose different drought conditions on prairie grasses such as little bluestem and sideoats grama. He can then track key physiological data about the grasses: their ability to absorb nutrients from the soil, disturbances to their photosynthesis capabilities, chlorophyll levels and more.
He then looks at how herbivore insects — in this case, grasshoppers — respond to drought and affect the ecosystem. “The role of insects in U.S. grasslands and their responses to extreme drought are poorly understood,” says Lemoine. Although we might be most familiar with photographs of swarms, or “outbreak densities,” of grasshoppers destroying crops during the Dust Bowl, under the right conditions, “They actually stimulate grass activity,” he says. For instance, in that great cycle of life, decaying grasshopper carcasses contribute to soil nutrients. “We don’t really have a good sense about where, when and why grasshoppers are deleterious or beneficial to grasslands.”
As it turns out, southern Wisconsin has proved to be an excellent location to study prairie grasses. It’s home to many prairie types, which makes it easier to undertake comparative analyses. The Spring Green site, for instance, has sandy soil, so it can be considered almost a semi-arid desert even though it’s still in the same moderately wet climate as all of southern Wisconsin. In the future, Lemoine will be running similar experiments in the Black Hills of South Dakota.
In a related project, Lemoine’s graduate students will survey 16 grasslands sites from the Mississippi River to Lake Michigan, so that they can get a pretty good sense of “what’s out there.” They will also bring back seeds and test them under drought conditions in Marquette’s growth chambers. They hope to answer the question: “Is there a specific trait that dictates how grasslands respond to drought?”
With an overarching interest in how climate change affects species’ interactions, Lemoine focused his interests as a postdoctoral fellow in a grasslands lab in the vast, desert-like plains of eastern Colorado, where there was a lot of research into drought and water loss — but not so much on “the trophic levels above the grass, the insects.” From there, he chose to pursue two big gaps in knowledge that inform his current work: Whether grasshoppers are beneficial or harmful to the grasslands, and how drought might modify the role of grasshoppers.
Signaling Marquette’s growing commitment to the study of the environment, additional members of Marquette’s environmental program include assistant professors of biological sciences Drs. Chelsea Cook, Tony Gamble and Chris Marshall, and associate professor of biological sciences Dr. Krassi Hristova, and also can be found in nearly every department in the Klingler College.
For Schnitzer, the Klingler College’s robust assemblage of ecology researchers coupled with the new environmental science major really boosts Marquette’s bona fides. “Marquette is building its research profile, and it’s letting undergraduates get research experience from leading scientists. Teaching and scholarship go hand in hand. It’s this teacher-scholar model of higher education that Marquette understands really well.”
And LaManna points out, “The addition of the environmental science major will certainly make us much more attractive to students who might have gone elsewhere.”
Taking care of the environment “is really important for the Jesuit mission,” Schnitzer reminds us. “Marquette is changing with the times, responding to student and societal needs — all that you would expect from a forward-thinking university.”
Related: Read how Marquette strengthens interdisciplinary environmental studies with a theologic perspective at “Called to Stewardship.”
