Documenting the fun in Ecology (EES-152) during the 2015 fall semester…
Students in general ecology (EES-152) resurveyed a portion of the Lehigh Experimental Forest, to assess changes in tree growth, mortality, and recruitment since 2013. No new trees greater than 1.4 m high were documented, and both growth and mortality varied considerably among species. Over 500 trees were measured, and the plot above shows data for the dominant trees (those with >15 individuals included in the survey).
We will use these data as a springboard for discussion of processes controlling forest dynamics, and will examine some of these issues in greater depth during our discussions and future lab activities.
For now, students should answer the following questions:
1. The dbh measurements were converted into estimates of area, assuming that each tree was a perfect circle in cross-section. Why do you think basal area was used to compare growth among the different species? Why was this expressed as the average change in basal area per tree, as opposed to the total change in basal area for all individuals of the species? What factors might have caused the observed differences in radial growth among species?
2. What does the pattern of mortality and recruitment suggest about the future of the Lehigh Experimental Forest? What factors might have caused the differences in mortality among species during these two years? What factors might be contributing to the lack of new tree recruitment in the forest?
3. Which species had both very high mortality and very low growth during this time period? Do some research on current threats to this particular species, and summarize your research in a short paragraph.
“A few short weeks of complete immersion in the study of ecology at PLE changed the course of my life.”
– Dr. Alex Ireland
(Alex took general ecology at PLE in summer 2005 and went on to earn his PhD from Lehigh University in 2012)
The Pymatuning Laboratory of Ecology (PLE) is a field station in western Pennsylvania that is operated by the University of Pittsburgh. Each summer the station offers approximately a dozen field-intensive ecology courses, spanning much of the breadth of the ecological sciences, to students from participating schools throughout the region. Lehigh University joined the PLE educational consortium in 2014, and four Lehigh students enrolled in five of the field station’s classes this past summer. I asked these students to share some thoughts on their experience for the benefit of other Lehigh students, and with permission I summarize their comments below.
Bob Mason took the forest ecology course, taught by Dr. Walter Carson of the University of Pittsburgh. Almost all class time was spent in the field for hands-on lectures where the class learned about forest ecosystems and the major threats to forest biodiversity. Field trips to old-growth stands, camping overnight in the Allegheny National Forest, and guest lectures on related ecological topics such as riparian zone restoration and migratory birds were some of the highlights. In Bob’s own words:
The workload appeared heavy from the syllabus (two “full-blown” scientific papers and a final exam), and I did find the course to be challenging. However, it was absolutely worth the effort and I gained real-world insight into data collection, statistics, and scientific writing. This course was truly writing intensive! However, I still found myself with ample down time to enjoy with other students, and it was fun to meet students from a diverse group of universities. I strongly recommend the course to anyone interested in ecological research.
Ecology of Fungi
Charlotte Malmborg took the ecology of fungi course, which was a new offering taught by Dr. Shannon Nix of Clarion University. The students were in the field everyday, identifying fungi and learning about fungal biology, taxonomy, and ecology. Samples were returned to the lab, and the students learned microscopy techniques that enabled them to better identify and examine adaptations of fungi. The class collectively undertook a research project comparing the amount and diversity of mycorrhizae between old-growth and secondary-growth hemlock forests. Charlotte clearly had a fantastic experience (assuming her twitter feed from May is representative! e.g., 1, 2, 3, 4, 5) and learned a tremendous amount about a topic that is not taught at Lehigh University.
Wetland Ecology and Management
Charlotte Malmborg also took the wetland ecology course. I teach this course, so I told her that she didn’t have to share her thoughts on it, but she chose to anyway. Here is an excerpt from her:
If you’re ready to get down and dirty this class is for you. From floating bogs to marshes to swamps, you’ll get to visit and learn about the biota and ecological processes in these unique systems, as well as the ecosystem services that they provide. You’ll learn more about mud than you ever thought possible, and you’ll be happy about it!
Chandler Navara took the disease ecology course, a new course taught by Dr. Thomas Simmons from Indiana University of Pennsylvania. In Chandler’s words:
The disease ecology class explored wildlife and plant diseases and their connection to human populations. Some of the diseases included Lyme disease, malaria, and rabies. From parasites, to vectors, to hosts, the ecological context of these diseases were examined, with a focus on how knowledge of ecology can be used to help control these diseases. We developed expertise in different field techniques used to sample disease vectors. The class was definitely worth every minute, and I made some lifelong friends at PLE!
Kris Abens took the Wildlife Management course, which was taught by Morty Ortega of the University of Connecticut during the last session of the summer. Some of Kris’s comments about the class:
The professor was great and a really nice guy. It was an amazing experience and I learned SO much, and amazingly, virtually none of the learning took place inside a classroom! We worked hard in this class, but it was very much worth it. I would definitely recommend the class to other students.
Interested in taking a PLE field course this summer?
PLE courses are fun, full-immersion experiences. Each course lasts for three weeks, is worth three credits, and covers the material in a semester-long course. All of them are field-based and satisfy the BS field requirement for Lehigh University EES students. The courses are distributed across four sessions, and although you can take multiple courses during the summer, you can only take one course per session (each course meets all day). Courses offered for Lehigh credit in summer 2015 include:
- Conservation Biology (11 May – 29 May)
- Forest Ecology (11 May – 29 May)
- Field Botany (11 May– 29 May)
- Behavioral Ecology (1 Jun – 19 Jun)
- Wetland Ecology (1 Jun – 19 Jun)
- Ecology of Birds (1 Jun – 19 Jun)
- Ecology of Amphibians and Reptiles (1 Jun – 19 Jun)
- Disease Ecology (22 Jun – 10 Jul)
- Limnology (22 Jun – 10 Jul)
- Field Techniques in Ecology and Conservation (13 Jul – 31 Jul)
- Wildlife Management (13 Jul – 31 Jul)
For additional information on these courses see:http://www.biology.pitt.edu/facilities/pymatuning/courses/course-schedule I teach the wetland ecology course and if you are interested in taking this class or one of the courses offered during the same session (1 Jun – 19 Jun), transportation to and from the field station will be provided from Lehigh University. To see more details about the wetland ecology course go here:https://sites.google.com/site/wetlandecologymanagement/syllabus To see more of the kind of FUN we have in this course go here: https://amongthestatelytrees.wordpress.com/category/wetland-ecology-management-ple/
For a Lehigh University student to take one of these classes, you will need to register for EES 395: Field courses at Pymatuning Laboratory of Ecology. The sections of the course will correspond to the list of classes above, so that you can sign up for the particular course of interest to you. Email me (firstname.lastname@example.org) if you have questions.
The Pymatuning wetlanders began the 6th day (“sixth week”) of the wetland ecology course examining adaptations of plants to the wetland environment. Aerenchyma tissue, floating-leaf anatomy, energy-rich rhizomes, heterophylly, pneumatophores, etc..…the students carefully observed and drew anatomical details using the aid of dissecting and compound microscopes. We added a few species to our must-know plant list, including Wolffia sp. (water meal), the smallest known flowering plant! Of course, the students were most interested in the carnivorous plants. We will see a few in the field next week.
We spent the afternoon in Hartstown swamp carefully avoiding poison sumac (Toxicodendron vernix). The students collected plant community data as part of the comparative ecology project they started last week. A number of unknown plant species were encountered along the transects, and I look forward to learning these plants over the next few days. One of great things about this course is that I get to learn a little bit more about wetlands every time I teach it. Just today a student introduced me to dodder (Cuscuta sp.), a parasitic plant. 🙂
Tomorrow we will visit Presque Isle to observe some of the coastal processes that create wetlands at the geologically dynamic land-lake interface. A few more pictures from today are below.
Nice article Michelle. Too bad the paper didn’t publish it. The site has historical significance and is a great outdoor laboratory for students.
Although I submitted this article to Lehigh’s student newspaper a few months ago, The Brown and White, it never got published (in the paper or online) for unbeknownst reasons. It refers to the upcoming plans to renovate Williams Hall, and my concerns for the future fascinating and historical forest directly adjacent to the building.
The recently drafted Campus Master Plan lays out the administrative vision for future improvements to Lehigh’s Campus. (Check out the whole plan at https://www.lehigh.edu/~inspig/lu_cmp_book_10-4-12.pdf). I had the opportunity a few weeks ago to attend a graduate student senate meeting focused on aspects of this plan, and was very troubled by the idea to re-landscape the area behind Williams Hall (the building behind Linderman Library that housed Earth and Environmental Sciences before STEPS was built) to allow more pedestrian access. Although plans have not been implemented yet, I worry that the ecological, historical, and educational significance…
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A 2-minute video advertising a course in wetland ecology offered this June!
Information about the Pymatuning Laboratory of Ecology for Lehigh University students
The wetland ecology course, featured in the video above, and the other courses offered at the Pymatuning Laboratory of Ecology (PLE) represent a fantastic opportunity to gain knowledge in field ecology this summer. These courses are fun, full-immersion experiences that cover a diverse array of ecological topics. Each course lasts for three weeks, is worth three credits, and covers the material in a semester-long course. All of them are field-based and satisfy the BS field requirement for Lehigh University EES students. The courses are distributed across four, 3-week sessions, and although you can take multiple courses during the summer, you can only take one course per session (each course meets all day). Courses offered this summer include:
Conservation Biology (12 May – 30 May)
Forest Ecology (12 May – 30 May)
Ecology of Fungi (12 May – 30 May)
Field Botany (2 Jun – 20 Jun)
Wetland Ecology (2 Jun – 20Jun)
Ecology of Birds (2 Jun – 20 Jun)
Ecology of Amphibians and Reptiles (2 Jun – 20 Jun)
Disease Ecology (23 Jun – 11 Jul)
Ecology of Fish (23 Jun – 11 Jul)
Field Techniques in Ecology and Conservation (14 Jul – 1 Aug)
Wildlife Management (14 Jul – 1 Aug)
For additional information on these courses see: http://www.biology.pitt.edu/facilities/pymatuning/courses/course-schedule
I teach the wetland ecology course and if you are interested in taking this class or one of the courses offered during the same session (2 Jun – 20 Jun), transportation to and from the field station will be provided from Lehigh University. To see more details about the wetland ecology course go here: https://sites.google.com/site/wetlandecologymanagement/syllabus To see more of the kind of FUN we have in this course go here: https://amongthestatelytrees.wordpress.com/category/wetland-ecology-management-ple/
For a Lehigh University student to take one of these classes, you will need to register for EES 395: Field courses at Pymatuning Laboratory of Ecology. The sections of the course will correspond to the list of classes above, so that you can sign up for the particular course of interest to you. Go here to sign up: https://cf.lehigh.edu/summer/?page=summer&year=2014. Email me (email@example.com) if you have questions.
An opportunity for experiential learning
In 1967 Lehigh University Professor Francis Trembley convinced the university to stop mowing a small area of the campus. Professor Trembley named the area the “Tangled Bank,” and it became a place where students could observe nature right outside the classroom. At one point in time there was even a “Tangled Bank” sign on the slope. One year after the mowing stopped, Professor Trembley had the foresight to encourage an undergraduate student to collect and identify all plant species growing on the Tangled Bank, and these collections were archived in the Lehigh Herbarium. Read the full story of the Tangled Bank here (including some great recollections of Lehigh alumni in the comments).
In the fall of 2013, the Lehigh University ecology class (EES-152) completed a botanical survey of the “Tangled Bank” to document what species occupy the site today. The primary objective of this project was for the students to use their data in conjunction with the 1968 plant collections to assess how plant characteristics, such as functional and life history traits, change from early to mid succession. In addition to learning about plant traits and succession, the project allowed students to learn how to apply some commonly used statistical tests to assess differences between groups. They also compared their tree data to a similar dataset collected earlier in the semester from the Lehigh University Experimental forest, a forest that has undergone secondary succession for approximately twice as long as the Tangled Bank. The goal of this comparison was to assess how tree density and biomass change with succession.
Functional traits and succession
What are functional traits? Functional traits are characteristics of species that strongly influence performance, and are therefore fundamental to survival and reproduction. They can be physiological, morphological, or represent reproductive strategies (the latter are oftentimes referred to as life history traits). Plant functional traits include things like photosynthetic pathway (C3, C4, CAM), growth rate, shade tolerance, number of seeds, size of seeds, growth form, life span, seed-dispersal method, and seed viability. Functional diversity (i.e., the total diversity of these traits represented by an ecological community) is increasingly used as an important measure of biodiversity.
What functional traits might be expected to change with ecological succession? Shade tolerance, growth form (herb versus tree), and lifespan might be a few of the more obvious traits that would be expected to change, as plants of later succession include many long-lived trees that compete for light. However, changes in other traits with succession may be less obvious. For example, how might you expect seed viability (i.e., the length of time a seed can survive in the soil before germination) to change with succession?
The Tangled Bank was divided into nine plots, with 3 or 4 students responsible for a complete botanical inventory of each plot. The students identified and estimated the abundance of all plant species, and collected voucher specimens for archival in the Lehigh Herbarium. For trees, diameter at breast height (dbh) was measured and used to calculate total basal area of the forest and the average basal area per tree. The total density of trees (per 1000 m2) was also calculated. Each group submitted an excel spreadsheet with their inventory results and dbh measurements as the first deliverable for the project.
Data compilation and research on plant traits
The data from each group were combined into a class dataset. Students developed lists of the dominant species that grew on the bank in 1968 and 2013 (Table 1, above). Each student was then assigned two plant species (one from 1968 and one from 2013), and required to gather information about the attributes of these species, particularly with respect to life history and functional traits. The objective was to compile as much quantitative and semi-quantiative information on the traits of these species as possible.
The students could use any source of information for this research, as long as they documented their sources; but, we anticipated that they would rely heavily on some of the publicly available databases that have been developed to describe plant characteristics. Unfortunately the shutdown of the US government prevented access to several of these resources, and limited the number of traits that we could examine. However, the students made the best of the situation and found as much information as possible using a variety of sources. They submitted their research in the form of an excel spreadsheet (a template was provided to help standardize the data collection), and this was the second deliverable for the project. Information on sixteen characteristics were found for most species, so we focused our analyses on these (Table 2).
Data analysis and results
Students then performed chi-squared and t-tests using excel, for categorical and continuous data respectively, to assess differences in functional traits of the plant communities in 1968 and 2013 (Table 2). The results of these statistical tests were submitted by each student as the third deliverable of the project.
The students found that plants of early succession generally had smaller seeds, longer seed viability in seedbanks, lower age of first flowering, shorter lifespans, smaller maximum height, and smaller average leaf area (Table 2, Figures 1 & 2). The mid-successional plant community had a greater percentage of species with seed dispersal via mammals and birds (Table 2, Figure 1). Early successional species also tended to be less tolerant of shade and were likely more readily eaten by vertebrate herbivores than those of mid succession (Table 2, Figure 1). Plants of early succession also tended to produce more seeds per plant and have faster growth rates, although differences in these two traits did not meet our threshold for statistical significance (p<0.05). Also, no significant differences were found between N-fixation capacity, frost tolerance, fire tolerance, and drought tolerance of plants in the two communities.
Connecting functional traits to Grime’s life history classification
Various life-history classification methods have been developed by ecologists to facilitate thinking about how species are adapted to environmental conditions. J.P. Grime proposed one such classification scheme for plants, which focused on adaptations to the amount of disturbance (i.e., processes that destroy biomass) and stress (i.e., external constraints that limit the rate of production) in the environment. Under conditions of frequent disturbance, ruderal (i.e., “weedy”) species tend to be favored. Under conditions of high stress, plants tolerant of environmental extremes (e.g., cacti, carnivorous plants) tend be favored. Under conditions of low stress and infrequent disturbance, competitive species tend to be favored.
As an example of how species during succession may fit into Grime’s classification scheme, the functional trait data from the Tangled Bank was used to develop indices related to competition, stress, and disturbance. Traits that would likely be selected for in these different environments were grouped and each species was given a composite score for each of the axes shown in Figure 3 based on the total standardized score of the grouped traits. The figure highlights the shift from ruderal species to better competitor species that has taken place between 1968 and 2013 on the Tangled Bank (Figure 3).
Changes in tree density and biomass with succession
Tree data from the Tangled Bank was compared with data that the students collected earlier in the semester from the Lehigh Experimental Forest. Tree density (trees/1000m2) was higher on the Tangled Bank than the Lehigh Experimental Forest, and the average size (basal area) of trees was larger in the Lehigh Experimental Forest (Figure 4A, 4B). Total basal area of trees, which takes into account both density and size, was greater on the Tangled Bank (Figure 4C).
For the students, deliverable #4. Due 8 November. Complete the following tasks/questions:
1) In less than one page (single-spaced), summarize the differences in functional traits of plant communities in early and mid succession on the Tangled Bank. Your summary should include descriptions of why the observed differences likely occur (i.e., processes).
2) What other functional traits, not included in our analyses, might be expected to differ between 1968 and 2013?
3) For many of the traits we were only able to obtain categorical values, and the number of categories we defined varied among traits. For example, dispersal mode had six defined categories whereas nitrogen fixation capacity only had two. Do you think that the number of categories and how we defined them affected our statistical results and interpretation? Using the original excel spreadsheet, create new, broader categories for a trait of your choice by merging data into a smaller number of categories. Does reducing the number of categories impact the chi-squared test result? Does it change the interpretation?
4) What are the assumptions of a t-test? Did our data violate any of these assumptions?
5) Describe the position of the 1968 and 2013 species in the Grime’s life history diagram (Figure 3). What traits do you think were used to develop the species scores along each axis? In other words, which particular traits would likely be most related to each axis? Some traits could be favored under more than one environmental condition (i.e., high stress, high competition, high disturbance). Justify your answers.
6) Where would the species of the Lehigh Experimental Forest likely be place on Figure 3?
7) Assuming that the differences in successional age are solely responsible for the differences in the density, size of trees, and total tree basal area of the Tangled Bank and the Lehigh Experimental Forest, what specific processes likely resulted in these differences?
8) Your answer to #7 assumed that the only difference between the two sites was age, a common approach often referred to as space-for-time substitution. However, what other factors might contribute to the differences between the two sites?
9) Using the data in Table 3 (below), calculate the rate of change of tree density and average tree basal area in a) early succession (first 45 years) and in b) mid-succession (45 to 98 years). Explain what processes likely contribute to these different rates of change.