An interview with Sasha Wright, a graduate student studying plant ecology at the University of Wisconsin-Milwaukee. Mongabay.com’s third in a new series of interviews with ‘Young Scientists’.
Having studied plant communities across three continent and within widely varied ecosystems—lowland tropics, deciduous forests, grasslands, and enclosed ecosystems on hill-tops—graduate student Sasha Wright has gained a unique understanding of shifts in plant communities worldwide as they respond to pressures from land use and global climate change.
“Plant communities are certainly changing,” Wright told Mongabay.com in a March 2009 interview. “These changes are undoubtedly affected by an increased occurrence of extreme weather events, temperature fluctuations, atmospheric CO2 concentrations, human land use, and in some cases urbanization of populations.”
Wright taking measurements of Diameter at Breast Height (DBH) at one of the adult trees at one of her study sites in Panama. Photo by Gemma Rutten.
After growing up in the Pacific Northwest and spending a year as an exchange student in Argentina, Wright first studied plant communities as an undergraduate at Beloit College in Wisconsin. It was there that Wright’s interest in conservation shifted to a new found passion for theoretical studies in ecology. “I like the process of studying large-scale patterns and mechanisms that maintain species diversity but without such an applied focus [of conservation biology],” she says.
In the Midwestern United States, Wright began her career by studying the composition of increasingly threatened grasslands. In “some areas of the United States, fire suppression may be the single most determining factor influencing woody encroachment. In other areas of the United States, woody encroachment into grassland ecosystems is heavily related to competition for soil water,” Wright says,
This pattern is not unique to America, according to Wright: “grasslands around the globe are changing primarily in response to regional human land use (maintenance of livestock and fire suppression) and climate change. This has resulted in the general pattern of woody encroachment into grassland ecosystems.”
She would know. Through a program at Beloit she studied plant ecosystems on inselbergs among the grasslands of far-away Tanzania. Wright describes inselbergs as “an isolated rock outcrop that is surrounded by flat grasslands or plain… If you picture the inselberg habitat in relationship to the surrounding matrix of arid flat grasslands, you can imagine how this habitat introduces an element of spatial environmental heterogeneity.” While studying these unique plant communities rising out of the Serengetti plains, Wright discovered that even light and infrequent contact with humans affected the fragile inselberg plant communities.
Having studied plant diversity changes due to fire, human land use, and even light human contact, Wright next moved on to study interspecies relationships in the world’s most biodiverse ecosystem. Working in the lowland tropics of Panama, Wright is using all her past experiences to help unravel the mysterious and sometimes contentious relationship between lianas and other tropical plants.
Picture of an Aristolochia species of liana, flowering in the forest on Barro Colorado Island in the Panama Canal. Photo by Melody Fears.
There has been a sudden surge in lianas across the Neotropics, yet the cause remains unknown. While Wright offers a number of plausible theories, she says, “whatever the answer to this question, there is abundant evidence that lianas are extremely dynamic and potentially important species in shaping community composition and dynamics.”
In her studies Wright has seen large trends among ecosystems, some playing themselves out on the global scale. One of the most important is a general shift in plant ranges. “It is extremely clear that species ranges are shifting. To be more specific, species ranges appear to be generally moving in a northerly direction and upward in elevation.”
She admits that a lot more research must be done to understand such global changes. “The problem,”she says, “is that we don’t truly understand the implications of these range shifts, we don’t know if range shifts will be proportionate to climate shifts, and we don’t know what our role should be in continuing to manipulate these systems based on our incomplete understanding.”
Wright discussed studying plant communities in flux, climate change’s impact on plants, her teaching methods, what it takes to be a successful research scientist, and why every undergraduate science program should have a research component in a March 2009 interview with Mongabay.com, a leading conservation and environmental science news site.
Wright reading canopy openness using a spherical densiometer at sites in Panama. Photo by Gemma Rutten.
YOUNG SCIENTIST PROFILE
Mongabay: How did you become interested in plant ecology? What is your background?
Sasha Wright:My interests evolved over time. I grew up exposed to a lot of natural beauty on an island in the Pacific Northwest. However, it wasn’t until High School that I started to take a really specific interest in conservation. This interest developed as an undergraduate at Beloit College. I remember having a really influential series of dialogues with other students and several of my professors at Beloit about my passion for conservation biology. At some point around my sophomore year I started to shift towards wanting to study more theoretical ecology as opposed to applied conservation biology. I like the process of studying large-scale patterns and mechanisms that maintain species diversity but without such an applied focus.
Mongabay: At fifteen you moved to Argentina and lived there for 18 months as an exchange student—how do you think this experience affected you?
Sasha Wright: I think about this one a lot. It was so long ago that it’s hard for me to think about the direct effect that it has on my life at this point. It definitely set a course in motion that led to many aspects of where I am today. When I left for Argentina I had an introductory High School Spanish comprehension level. Which basically meant that I was completely lost. I functioned using hand symbols and one-word sentences for almost two months before I started being able to integrate and apply the language in a functional way. And even still, it was nearly 8 months before I could really express myself in a way that truly represented what I was thinking about. In some ways I think that everyone should try being that isolated by language or culture but still surrounded by people. It’s certainly frustrating, but incredibly rewarding as well. So, on one level, learning the Spanish language at a young age opened doors for me throughout my life that I may not have seen as possibilities otherwise. But on another level, the experience made me a much more confident and independent person. And this probably affected my decisions and directions more than anything.
Mongabay: Can you tell us how your experiences as an undergraduate at Beloit College in Wisconsin have helped you as a scientist?
Sasha Wright: Beloit is an excellent teaching institution. The student teacher ratio is something like 12:1 so as a biologist there is a big emphasis on working closely with the scientists who teach there. There is an independently designed research component to nearly all of the upper level science courses and a “publication” component for many of them. There is also a deliberate emphasis on global issues and diversity for the entire campus. This means that as a student at Beloit I had the opportunity to explore research questions locally in Wisconsin as well as internationally in Tanzania. And for several of my research projects I prepared articles for publication in departmental publications such as, “The Beloit Biologist.” Beloit really emphasizes the importance of being a strong writer. I think that Beloit shaped me quite a bit as a scientist, and really gave me the tools I needed to succeed in the field.
Mongabay: Currently, you are conducting research at the Smithsonian Tropical Research Institute, what is it like working at this world-renowned facility?
Sasha Wright: Working at STRI is an incredibly enriching experience as a graduate student. There are exceptional individuals working at every level within this Institution. I work and live with other graduate students from around the world who have a diversity of backgrounds and study topics as different as the evolutionary biology of orchid bees to mutualistic relationships between the fig-fig wasp, to mechanisms that maintain species diversity, to ecological modeling. I hear seminar talks about some of the most exciting research that is going on in the world today. And I get to work in one of the most dynamic and biologically diverse systems on earth. It is fantastic.
Lianas growing on a tree on Barro Colorado Island in the Panama Canal. Photo by Melody Fears.
Mongabay: What is the role of lianas in tropical ecosystems?
Sasha Wright: Lianas are woody vines that occur in much higher abundance and diversity in tropical forests than in temperate forests. The term liana refers to a growth form not a particular species. In fact, the climbing growth form is found in over 130 different plant families. The reason for the largely tropical distribution of the climbing growth form is probably related to freezing tolerance. Lianas tend to have vascular tissue in the xylem that is composed of very large/long vessel elements. The relative size of these vessel elements is what facilitates the transport of extremely large quantities of water to leaves in the forest canopy via relatively small stems (compared to trees). The role that the liana growth form has in tropical ecosystems is clearly shaped by this unique physiology. Understanding the implications that these characteristics have on interactions with other species forms the backbone of my research interests in Panama. A combination of negative interactions (competition) and positive interactions (facilitation) with other species has serious implications for overall species composition in the forest.
Mongabay: Why do you think lianas are increasing across Central and South America?
Sasha Wright: I think that this is a pretty complex question. My PhD advisor, Dr. Stefan Schnitzer, hypothesized a “dry season growth advantage” in tropical dry forests. This means that some physiological or physical property of the liana growth form is more successful at accessing resources during a seasonally (~3 month) dry period. Liana relative growth rates are in fact higher than tree relative growth rates during the dry season in Panama. So, possibly increased seasonality due to extreme weather events (El Nino/La Nina) has something to do with it. My colleague Suzanne Rutsihauser is also exploring the hypothesis that increased liana abundance in tropical rainforests (no dry season) is a reflection of successional changes in young forests. This may be particularly applicable in secondary forests where re-colonization of agricultural lands is relatively recent and we are seeing overall increases in community biomass of all growth forms (lianas as well as trees). Whatever the answer to this question, there is abundant evidence that lianas are extremely dynamic and potentially important species in shaping community composition and dynamics.
Inselberg in Serengetti Park in Tanzania where Wright conducted research. Photo by: John Greenler.
IN THE GRASSLANDS OF TANZANIA
Mongabay: What is an inselberg? Why are these particular geological formations important to biodiversity?
Sasha Wright:Inselberg is a German word for an isolated rock outcrop that is surrounded by flat grasslands or plains. This word is often used to describe these geological formations in southeastern Africa. If you picture the inselberg habitat in relationship to the surrounding matrix of arid flat grasslands, you can imagine how this habitat introduces an element of spatial environmental heterogeneity. Inselbergs are composed of exposed bedrock. They are often relatively cooler than the surrounding exposed plains, tend to have patchy accumulations of soils in crevasses and irregularities on the bedrock surface, are shaded for a longer period of the day, and tend to support a unique composition of forb species that are not common in the surrounding grasslands. So at the landscape scale, this abiotic heterogeneity supports a higher diversity of plant species.
Mongabay: How have humans impacted the biodiversity of inselbergs in Tanzania?
Sasha Wright: Even though human presence is extremely low in the Serengeti National Park (it is limited to park staff and scientists), it appears that human settlements are correlated with lower species diversity on inselbergs.
Inselberg in Serengetti Park in Tanzania where Wright conducted research. Photo by: John Greenler.
Mongabay: What do your findings suggest about current conservation for plant biodiversity in Tanzania?
Sasha Wright: Serengeti National Park (SENAPA) is an extremely well managed park in many ways. It is a UNESCO Biosphere Reserve as well as World Heritage Site. This means that regulations and park decisions are often subject to international standards, but the park also receives significant funding for park maintenance and research. SENAPA is located in an area of Tanzania that was originally inhabited by tribal groups such as the Maasai tribe. However, current park regulations restrict human occupation within the park, to park staff and scientists. Deliberate attention to ecosystem conservation and management is well researched and applied within the park boundaries. Although my results suggest that small populations of humans still have an effect on biodiversity at human settlements, these settlements are necessary for the maintenance of revenue-rich tourism as well as scientific contributions to future park management and internationally relevant research projects. My observations may have implications for the management of human settlements, but the importance of the existence of these settlements is irrefutable.
Base camp in Serengetti National Park in Tanzania where Wright conducted research. Photo by: John Greenler.
STUDYING PLANT LIFE IN THE MIDWEST
Mongabay: How are grasslands around the globe changing?
Sasha Wright: Grasslands around the globe are changing primarily in response to regional human land use (maintenance of livestock and fire suppression) and climate change. This has resulted in the general pattern of woody encroachment into grassland ecosystems that has been observed around the world.
Mongabay: What factors are leading to these ecosystem shifts?
Sasha Wright:In some areas of the United States, fire suppression may be the single most determining factor influencing woody encroachment. In other areas of the United States, woody encroachment into grassland ecosystems is heavily related to competition for soil water. Furthermore, factors related to climate change such as rainfall, atmospheric CO2 enrichment, nitrogen deposition, and temperature have both indirect effect on woody establishment via soil moisture as well as direct effects on woody species success.
Mongabay: Specifically, how are the oak trees you studied affected by these changes?
Sasha Wright:Interestingly, we found that oak establishment in a tightly controlled field experiment in Minnesota was most directly related to grassland species diversity. According to these results, woody seedlings are more likely to survive and establish in more diverse grasslands, at least up to a certain point. This interaction is probably a result of increased shading and protection from desiccation under a more complex cover of grasses and forbs.
Site of oak competition study. Photo by Dave Tilman.
Mongabay: Considering that you have studied plant communities on three continents, how do you think global climate change is affecting plant diversity worldwide?
Sasha Wright: Plant communities are certainly changing. These changes are undoubtedly affected by an increased occurrence of extreme weather events, temperature fluctuations, atmospheric CO2 concentrations, human land use, and in some cases urbanization of populations. These things are certainly related to global climate change, and the rates of these changes are certainly unprecedented in the climate record. Now, that is certainly not as straightforward of an answer as a declaration about plant diversity at the global scale. It is extremely clear that species ranges are shifting. To be more specific, species ranges appear to be generally moving in a northerly direction and upward in elevation. Furthermore, species themselves may be changing via hybridization and strong selection pressures. It is also evident that plant range shifts are sometimes impeded by human land use and obstruction of natural corridors, and other times accelerated by accidental or deliberate transportation of plants along human transportation routes. The problem is that we don’t truly understand the implications of these range shifts, we don’t know if range shifts will be proportionate to climate shifts, and we don’t know what our role should be in continuing to manipulate these systems based on our incomplete understanding.
Wright working on an inselberg in Serengetti National Park, Tanzania. Photo by: John Greenler.
Mongabay: You have a lot of experience teaching underprivileged youth, how do you approach a classroom with diverse socioeconomic and cultural backgrounds?
Sasha Wright: I think that the most important part of teaching any group of students is attempting to teach to every single individual. Clearly that’s a lot easier to do in a classroom of 5 than it is in a classroom of 55. I think that the trick is that every single classroom is full of unique individuals; no matter how diverse or similar their backgrounds look on paper. So for me, teaching any classroom of students is about being personally engaged in the material, encouraging group exploration of the many questions that I don’t know the answers to, and getting to know my students well enough to relate specific questions to particular backgrounds and areas of interest. First of all, all students pick up on the enthusiasm of an engaged scientist as a professor. And students are much more easily engaged in the process of scientific understanding by asking questions, exploring answers through the literature, and forming new questions then they are by an absolute question/absolute answer format.
Mongabay: You have taught GIS (Geographic Information Systems) programs to high school teachers, college students, and sixth graders. How does GIS help bring these various groups closer to understanding scientific ideas and methods?
Sasha Wright:I think that GIS is an extremely powerful conceptualizing tool. At introductory levels of science, whether it be High School or intro level Undergraduate courses, GIS makes seemingly arbitrary data have a spatial identity. I think that the popularity of GoogleEarth, for example, really elucidates the accessibility and enthusiasm that many people have in response to spatially presented data sets. Engaging young students in science can be extremely difficult and this tool really facilitates that. Once students are engaged in the material it is exponentially easier to get students to critically examine problems and explore new research questions.
Mongabay: What role has GIS played in scientific research in general and in your own studies?
Sasha Wright: At the research level, GIS has the capacity to enrich research questions and facilitate analysis in innumerable ways. I think that one of the most significant contributions of GIS to plant ecology is how it has facilitated the spatial analysis of large aerial imagery datasets for landscape scale studies at incredibly reasonable costs. Scale has become increasingly important in our understanding of ecosystem processes. Having the capacity to analyze plant species compositions in relationship to soils, geology, rainfall, mammal surveys, roads, canopy height, history of disturbance, and anything else that has a spatial component is an extremely powerful tool. In my own studies I have used GIS for assessing invasive plant species spread in relationship to wetlands, mapping ground-truthed inselbergs in the Serengeti and comparing local biodiversity numbers to landscape scale vegetation maps, and creating tools for public outreach about coral monitoring and disease in the US Virgin Islands.
Wright taking seedling data in seeding subplots within her site in Panama. Photo by: Gemma Rutten.
Mongabay: What would you most like to see incorporated into science education?
Sasha Wright: I think that in some ways, the most important change in science education would come from renovating the way we teach science to High School students and early undergraduates. I don’t understand why we teach science as a series of arbitrary absolutes that come from text books up to a certain point, and then we reveal the true nature of science as an ever-changing dynamic field that is actually much more interesting and engaging than these textbook absolutes.
Mongabay: You have said that ‘research or an individually designed experiment component’ should be incorporated into undergraduate classes—why?
Sasha Wright: I actually think that this is how science should be taught at all levels. Basically for many of the same reasons that I mentioned before. This is a much more engaging way to approach new material. Students can tailor specific questions to their own interests, but in the process are exposed to much of the same material and background information that they may have originally seen in a textbook, only in this format it actually means something to them.
Mongabay: Given that you have had a very successful career so far, what advice would you have for an undergraduate who is interested in going to graduate school for plant ecology?
Sasha Wright: Get involved in research early! If you are at a small liberal arts style institution you should talk with professors to design small research projects or to work on their research projects. If you are at a larger research institution, start by talking with graduate student TA’s and then get involved with one of the research laboratories on campus. If you are enthusiastic about learning and being involved, and particularly if you are willing to volunteer, these laboratories will be happy to have you. The best way to get on a graduate school track is to start the process of networking with scientists and to get some experience! I would go so far as to say it’s even more important than grades or testing scores combined. One other resource I would recommend in terms of getting research experience is the ECOLOG listserv at https://listserv.umd.edu/archives/ecolog-l.html.
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