Lauren Gersbach:
Resistance vs. Resilience—Alternative Mechanisms to Survive Severe Cyclones in Mabi Type 5b Rainforest Tree Species of North Queensland

Lauren Gersbach on a scooter in Yungaburra, Australia.

During the Fall 2006 semester I was fortunate enough to have the opportunity to attend the School for Field Studies (SFS), Center for Rainforest Studies in Northeastern Queensland, Australia. For three and a half months, 26 other students and I lived, studied, and carried out research in an area of ever decreasing rainforest. Of particular interest at SFS is Mabi type 5b rainforest, an ecosystem declared critically endangered because only 2 percent of the original extent of the forest remains today as a result of pressures from logging, agriculture, and development. For this reason, there is great concern among the local community as to the future of Mabi forest. Conducting my research abroad allowed me the opportunity to contribute to on-going efforts to help conserve and restore a very unique ecosystem only found in that part of the world. I was able to offer my skills and know-how, through my research, to the local community members. Because of where my research took place I felt as though I was contributing to something much greater than myself, in that, I was helping to preserve such a precious piece of this earth. The experience abroad pushed me to put all that I had into my project.

Through the actual hours spent in the field, I gained invaluable hands-on experience conducting research and experiencing all of the organization, time, and effort that goes into seeing field work and data collection to its completion. I was also able to sharpen my analytical skills by carrying out statistical tests and working to understand what my data was telling me. I also know my writing and oral presentation skills were strengthened by the time all was said and done.

A view of the open canopy and a fallen tree.

Finally, and what I feel is the most rewarding thing I took away from my research experience abroad, is that I now have more clarity about where I will take my career. In a part of the world where such vital ecosystems are fading away, the importance of conservation and land management became glaringly obvious to me over the course of the semester. I returned home with a passion to do my part in maintaining and restoring what natural ecosystems remain in my own part of the world.

 

Lauren Gersbach wrote the following project description and abstract based on her full-length research paper, which she submitted to The Forum on Education Abroad.

Click here to read an interview with Lauren (the audio version is coming soon).

Project Description:

Despite ecological theory suggesting a trade-off between safety (resistance) and growth rate (resilience) among plant species, few studies have previously attempted to quantify this relationship in response to a single disturbance event. Using wood density as an indicator trait, this study provided empirical data on the response of six rainforest tree species to a specific disturbance event, namely, tropical cyclone Larry.

Cyclone Larry snapped this rainforest tree, which has since resprouted.

First, trees were categorized as having no damage, severe branch damage, being snapped, or uprooted. Secondly, species’ growth rate, represented by three variables of biomass accumulation (average total biomass accumulated, average biomass accumulated per unit size (diameter at breast height), average rate of biomass accumulation since the cyclone) was measured. Finally, species’ mean wood density was calculated and the relationships between wood density and a species’ ability to resist damage and between wood density and a species’ ability to respond to damage were tested.

Collectively, results of this study supported the existence of a trade-off between the ability to resist cyclone damage and to recover quickly via rapid growth rates post-disturbance. Moreover, results confirmed that a species’ mean wood density can predict a species’ position along this response to disturbance spectrum.

Abstract:

The theoretical trade-off between safety (resistance) and growth rate (resilience) was investigated among Mabi Type 5b tree species in Tropical North Queensland, Australia following the destruction wrought by cyclone Larry. While this trade-off among plant species has been commonly suggested in the past, little empirical data has been provided to support this idea in direct relation to a specific disturbance event. Six species in three Mabi Type 5b rainforest fragments on the Atherton Tablelands were included as part of this study. Where possible, 50 x 50 meter plots were established in areas determined to be of similar, severe cyclone damage, though in one instance a smaller plot was used (30 x 40 meters). This was done to ensure the total area within each plot remained at a consistent level of cyclone damage.

Cyclone damage was assessed within the eight established plots for all trees with a diameter at breast height greater than or equal to 100 mm. Damage categories included no damage, severe branch damage, snapped, or uprooted. Average wood density and growth rate, represented by three variables of biomass accumulation (average total biomass accumulated, average biomass accumulated per unit size (diameter at breast height), average rate of biomass accumulation since the cyclone) were then measured to quantify both resistance and resilience traits of the six study species.

Checking funnel traps for frogs and skinks.

Using a 5.15 mm increment borer, wood cores were taken from all trees given a damage assessment; the green volume was measured using the formula for a cylinder, and after placing the cores in drying ovens, the dry mass was weighed. Average wood densities were then calculated using the formula: wood density = dry mass/green volume. To quantify post-cyclone biomass accumulation variables, all regrowth on selected snapped trees was cut down and placed in drying ovens. The dry mass was then weighed.

Post hoc cell comparisons showed that no two species sustained the same pattern of damage across damage categories, simply meaning species were affected differently by the cyclone. There was a negative correlation between the percentage of damage sustained by each species and wood density, suggesting that a species with a higher average wood density will be more resistant to damage. Moreover, a negative relationship was found between wood density and each of the three biomass accumulation variables indicative of growth rate, suggesting that wood density influences the amount of biomass a tree is able to accumulate post-disturbance. Collectively, these findings support the existence of a trade-off between resistance and resilience and confirm that a species’ mean wood density can predict a species’ position along this response to disturbance spectrum.

Because this study supported the existence of a spectrum of response to disturbance, from resistance to resilience, predictions can be made for the future post-cyclone dynamics of Mabi Type 5b rainforest. The future well-being of this forest type is of particular concern to the local community because it is currently declared critically endangered; only 2 percent of the original extent of the forest remains today as a result of pressures from logging, agriculture, and development. Mabi forest exists in many small fragments and the severity of cyclone Larry seemed to further threaten the forest’s future existence. However, although Mabi forest fragments sustained extensive damage and fragment canopies were significantly opened up, the species composition of the forest should not be greatly altered into the future. Rather, the relative abundances of species will experience shifts over time.

 

Q&A with Lauren Gersbach

A.V.: How did you develop the idea for your research project?

(Lauren, far left) working with her classmates at an SFS information booth set up at the farmer's market in the town of Yungaburra, Australia.

L.G.: During the last month of the School for Field Studies (SFS) semester everyone works on an independent project but contributes to an overall, greater research project, so that as kids are coming in

every semester they are contributing to long-term, broader goals. Cyclone Larry hit the [eastern] coast of Australia during the spring of 2006, so when my semester came up in the fall of that year, all the research in the area shifted focus and was starting to look at the impact of the cyclone on the area and how the rainforest was impacted, and what that [would mean] for the future of the fragments of the rainforest that remain. We got to pick exactly what we wanted to do [but] with that umbrella idea set in front of us.

Since the cyclone had happened eight months prior to when we were doing our research, it provided a very unique opportunity to look at how trees were responding. My particular project was to select actual data in response to a specific disturbance event to either support or not support an ecological theory that plant species employ different mechanisms to survive disturbance [it is thought that there’s a trade-off in plants between traits that enhance survival and traits that enhance growth]. I was able to provide data [for] this theory and test the spectrum of response to disturbance…using six species of trees [in the Mabi Type 5b Rainforest] looking at wood density [which is largely accepted as an indicator of tree strength, and as such, has been shown to have direct influence on a tree’s ability to resist damage during natural disturbances such as cyclones. Many studies have found that trees with higher wood densities (which grow really slowly) are better able to maintain structural integrity, while those with lower wood densities (which grow really fast) are more susceptible to damage].

A.V.: Was your hypothesis correct?

L.G.: Yes, I supported all the hypotheses that I had going into my project. We found that there was this spectrum of the trees that we looked at of response to disturbance. Trees were either really resistant to the damage or they were really resilient to the damage. Trees that had a wood density somewhere in the middle fell in the middle of that spectrum when it came to the mechanisms they employed to survive the disturbance.

A.V.: Were you glad that your project was a part of a larger objective?

Lauren and her classmates take time out from doing research to pose in front of a tree's giant buttresses.

L.G.: I was very happy with my experience. I was excited to be contributing to something that I thought was much larger than myself and larger than my particular project. Especially when it comes to environmental research when [you’re working on an] individual project, it’s often really specific just to make it feasible in terms of collecting data. I really like knowing the fact that, yeah, I was working on an individual project, but I was also contributing to something much greater and there was a larger focus…something more important than the very narrow scope of my project.

No one’s independent research projects would have been finished without the help of the groups that we were working in. We were just under such a time crunch, which I’m sure is true in the real world when people are doing research. Everyone had so much to do for their own independent projects, you definitely heavily relied on the help of other people to get the lab work done and the data collected, and so we were all collectively working on our projects but helping each other get their projects done. I definitely think that’s applicable to people’s professional experiences. I would imagine that more often than not when you are doing research you are involved in a group effort and maybe everyone is doing their own projects but you are contributing to something larger. We had to rely on each other, use teamwork, and be patient with each other after many long days in the field when temperatures were getting short and people were getting irritated with one another, or whatever the case may be. [It was important to] learn how to work with each other and be patient and work hard. If you were not working hard you were not only not finishing your project but you [might have been] letting down someone else who [was] relying on you.

A snapped tree resprouting.

A.V.: What were some of the challenges you faced?

L.G.: The time crunch made it really challenging. We had basically two weeks to get out [in the field] all day every day to [collect data] so that we could spend the next two weeks analyzing the data and writing [our papers]. Other unique challenges had to do with the area we were in. We were in the middle of cyclone-devastated rainforest fragment, and [the conditions were] kind of unbelievable. [You’d be] walking through this beautiful rainforest but enormous trees [would be] snapped, branches down, and trees uprooted. The fact that we were there after the canopy had been opened, meant there were [a lot] of what they call “cyclone sprouts”—all the trees that jump at the availability of light and everything that sprouts up really quickly once the trees are down—[and they are] all things that have thorns and that hurt you: stinging trees, wait-a-while thorns, stinging thistle, and stuff that was really miserable to be pushing your way through. If we could walk on a fallen tree trunk, we did because it was the easiest way to get around.

In Mabi forests there are also mites that get under your skin and make you itch unbelievably. We were just dealing with a lot of things that were making our bodies really uncomfortable, and working in the heat in the wet tropics in the summer, having long days outside pushing your way through cyclone-damage…it all made for short tempers. Everyone really [had] to consciously try to be patient with each other because we knew that everyone was miserable some days, other days were better. That was really just challenging for everyone involved.

The SFS cabin where Lauren stayed.

A.V.: How did you prepare for this type of research?

L.G.: We were living in cabins in the middle of the rainforest, so we were completely immersed in the environment that we were studying. For the first two months we were taking classes like rainforest ecology, forest management, and an environmental policy and socio-economic class. We were really just learning about the area we would be researching and [we were learning] about Queensland’s government. We did a lot of mini-research projects to learn the skills we would need to do our own projects at the end of the semester. Everything was building up to the independent project.

A.V.: What skills helped you succeed with your research?

L.G.: Personally I would say…a hard work ethic and a dedication to the project [at hand]. I had to be very organized with the million things that were going on during the weeks of our project. I had to be patient and work well within a group, but at the same time [I had to be] disciplined and able to work well with [myself] to get my own project done.

I had never done any large scale research before, so the whole semester leading up to the project we were learning the basics of how to go about conducting environmental research—everything from coming up with your hypotheses and how to go about testing them to honing your skills when it comes to the whole scientific process to how then you actually use tools to collect your data. How do you measure the diameters of the trees? How do you take wood cores from a tree to then calculate the tree’s wood density? There were very specific tools and [processes that we needed to learn to later do our research].

SFS student researchers mark trees.

A.V.: How did this experience influence your future?

L.G.: I’m somewhere in between research- and policy-minded. I’ve always had a love of nature and a passion for being outdoors, but [when I went abroad] I was still very uncertain about what I wanted to pursue in graduate school or professionally, because I was also at the time considering the health field. Being [in Australia] and being immersed in the rainforest and just loving every minute of [the experience] completely swayed me to focus on working in the environment in the future, but it made me not want to do research in graduate school solely. I am definitely interested in doing research as part of my master’s but at the same time it made me not want to go to grad school to get my doctorate to do research as my career.

A.V.: As you know, it can be difficult for science students to fit studying abroad into their college curriculum. What advice would you give to other science students who are thinking about studying abroad?

L.G. I would say 100 percent hands down to do it. Especially, if they are like me and questioning whether or not they are interested in doing research, the best way to figure this out is to do it and get experience and to have something to base a decision on. The curriculum does make it hard [for science majors] to go abroad and it was definitely a challenge for me to figure out how to [make it work]. My advice is to look into it. Something’s out there that will fit what you are looking for, and to try to figure out a way to make it work. I really had to do that at Butler before I left. I spent a whole year looking into programs, finding one that works, and then convincing Butler why they should let me go, and how [I was] still going graduate on time, and then prove to them why it would fit into my curriculum, and why it would be great for me to go. I would just say be persistent. Study abroad is so diverse and there are so many opportunities out there that I definitely think you can make it happen.

AV: How did “place,” that is being in Australia, affect your experience?

L.G.: Seeing the importance of conservation and land management in such a beautiful part of the world and a part of the world that has such unique natural resources as opposed to growing up in the Midwest, in the United States, where it’s not as tangible because it’s not in front of your face everyday, I came home with a desire to look into conservation and land management in my own part of the world and have a passion for doing what I can here at home.

The name "Mabi" Forest originates from the local Aboriginal name for the Lumholtz's Tree-kangaroo (mabi or mapi). It is a rare mammal, but one of the most common large mammals in this forest type.

A.V.: What role did the local community play in your experience?

L.G.: [The community’s interests and concerns as they related to the environment] were another focus of our broader research goals. All semester long we [worked] with local community groups, government agencies, and the people in the community who are very invested in the wellbeing of the endangered Mabi rainforest. The local community was very interested in hearing what our research projects found because they are so [committed] to restoration projects and preserving what they have. Only 2 percent of the extent of the original Mabi rainforest remains today because of logging, agriculture, and urban development; and the 2 percent that remains is highly fragmented. The government declared it “critically endangered” a few years ago. The entire ecosystem is critically endangered. That forest type is home to a few of the well know mammals in the area. For those reasons the local community is really invested in doing what they can to help the forest type through restoration projects. They definitely know SFS is right around the corner, where all these American kids come to study and do research, so we worked with them a lot and helped them out throughout the semester doing tree plantings and learning about what they are doing restoration-wise. At the end of our semester we had a community forum where the whole community was invited to come and listen to our research results and hear what we accomplished over the course of the semester.

SFS students listen to a lecture on alternative energy sources while sitting near giant windmills at a wind farm in Queensland.

A.V.: How did the Australian perspective influence your perspective?

L.G.: Environmental issues seem to be way more in the forefront of the Queensland general public as opposed to being at home. On a few different occasions I remember seeing a newspaper article [or a television program] on some local small-town news story that was on a big environmental issue about the rainforest, and thinking every time I saw this, “why [haven’t I seen] a story like this on a local news channel [at home]?” If anything [on the environment is ever on] it’s on one of the big news networks.

It definitely felt like [Australians], because they live in such a unique environment and are seeing things disappear right in front of their eyes, are much more involved and tuned into what’s going on. They try to educate themselves about what’s going on and how they can help. Seeing that made me want to come home and educate more people, because if they don’t know what’s going on they are not going to care to help. It made me return with a [desire] to spread knowledge to our local communities…that’s the way to make things happen.