October 2011 Volume 10 Issue 2 Biomass

How to Request Letters of Recommendation

Since you are asking for a substantial time commitment, you should provide a single document listing the programs you are applying to, the websites for online submissions, the specifics required for the letters, and the date when each letter is due.  You should also provide your letter writer(s) with addressed and postmarked envelopes for any letters that need to be mailed.  Professors may not remember the details of your class work or projects, so it’s not a bad idea to provide them with some description of your work as well as a CV or resume.  Taking time to discuss your work, the programs you are applying to and why is also recommended.  Finally, it is important to remember to send them a thank you card when everything is said and done.

Checklist for requesting letters of recommendation:

• Ask your professors for letters at least two weeks in advance (preferably sooner).
• Bring a list of programs you’re applying to with the due date, websites for online submissions and specific requirements for each letter.
• Provide addressed and postmarked envelopes if your letters of rec need to be mailed.
• If necessary, give your professors a description of your coursework and/or research as well as your CV and/or resume.
• Send a thank you note when everything is complete!

A Q&A with Tamar Resnick, Visiting Assistant Professor in Biology

Where did you go to school?  What did you like most about being an undergraduate in the sciences?

As a freshman at Brown, I was able to take a small seminar class examining how cells work together to make tissues.  The professor was a terrific lecturer and got you to think about things on your own, and taking a class like that was really a privilege.  Usually, students have to wait until the later years of college to get to the in-depth classes, but this early, deep thinking about a single issue in my freshman year was really exciting.

One of the things that’s really great about being an undergrad in the sciences is that you get to think about so many different aspects of the sciences.  There’s a feeling of building as you start with the foundational material, and during the course of four years your classes start to layer on top of each other.  Those synthetic moments when everything comes together are really exciting.

What aspect of biology are you most interested in?  What do you focus on in your own research?

While at Brown, I worked on a yeast (S. cerevisiae), which is a great system for undergraduates because it’s fast and you can ask lots of different questions.  In graduate school at MIT, I was drawn towards multicellular organisms.  I was really interested in the relation of cells to each other and the genetic regulation of systems.  I began working on fruit flies, looking specifically at how the cell divides and in particular how a cell divides its chromosomes, especially as it relates to development.

Then, in my postdoctoral work I moved to the nematode C. elegans and the question of gene regulation during development.  I was curious about how an animal goes from being a single cell to a complex adult, especially how this happens in the right order.  The genes that are involved in development in this worm are conserved all the way up to humans, so understanding the question of developmental timing in C. elegans can help us to understand the biology of humans also.  The disruption of these genes can lead to tumor progression if the timing is off when the cell differentiates.  Essentially, I find the question of developmental timing in this worm very interesting to examine.

Do you have any advice for students that are preparing for graduate school?

Grad school is a great opportunity to explore research and to learn how to do science.  Since you’re so focused on research, you develop tremendous analytical skills.  For the first year, it’s mostly coursework, but after that it’s basically a training job that you will leave one day.  It’s important to remember that it is really a launchpad to your career.  If you have an idea of what you want to do after grad school, your experience will be that much more rewarding.

I saw that you’re teaching the Biology of Women class this interim.  Is there anything you’d like to let us know about the class?

In a lot of science classes, there’s a certain curriculum that you must cover, but this one has a lot more freedom.  There are so many topics we could look at, so I want to be able to explore the areas that the students are interested in.  I’m also excited about bringing in current events that relate to women’s issues and women’s biology.  In the class, we’ll have lots of opportunities for discussion and student-led projects.  It will be a fun, rewarding class.

Research on the St. Olaf Natural Lands

St. Olaf College is located on the border between tall grass prairie and the “Big Woods” forest ecosystems. Original land surveys describe the forest as dominated by elm, maple, oak, and basswood (Grimm 1984). However, due to logging, urbanization and agriculture, the Big Woods ecosystem has been severely fragmented and only 10% of the original forest remains.  Additionally, in the absence of natural predators, densities of herbivores (such as white-tailed deer) have increased and therefore limited regeneration of certain tree species (Rooney and Waller 2002).

The college began planting tree seedlings characteristic of the Big Woods forest in old agricultural fields in 1990. Select trees were tagged and have been measured every 1-4 years.  In the summer of 2010 we resurveyed the 1990 planting in order to 1) track patterns of tree growth and mortality over time, 2) determine if soil characteristics change and become more like older forests with age, and 3) explore possible linkages between soil characteristics and tree success.

Overall mortality was 33.66%, but varied greatly between species from 0 to 60 percent.  Mortality in the restored forest is expected to change very little in the future since few trees died between 2006 and 2010.  Mean diameter at breast height (DBH, a common measurement of tree growth) varied significantly between species, as did tree height. To date, between height, DBH, and mortality, basswood, white ash, and Northern red oak have been most successful.

When planted, some seedlings had white plastic tubing (tubex) placed around them to determine if this was an effective management strategy to protect the trees from herbivory.  We indeed observed differential success between tubex and non-tubex trees: early in their growth, trees with tubex were larger, but after approximately 10 years, non-tubex trees surpassed tubex trees in size.  Greater success early on could be attributed to reduced mechanical stress and herbivory, and discouragement of lateral growth (Sweeney et. al. 2002).  Once the seedling has outgrown the shelter, it loses its advantage and perhaps must invest its resources into increasing in diameter rather than height.

Soil properties have changed over time in the restored forest.  When compared to a nearby mature forest (Norway Valley), the organic matter and PO4-3-P levels are significantly lower in the restored forest, but exhibit increasing trends over time. The same was found for soil moisture. It appears that the restored forest soil characteristics are approaching the Norway Valley levels, and we expect in the future that this pattern will continue.  These patterns could be a result of plant development, plant-soil interactions, or atmospheric deposition (Zhang et. al. 2010).

Although there is no comparable past data, in 2010 NO3-1-N levels and the C:N ratio were significantly lower in the restored forest than in Norway Valley (P ≤ 0.001 and P ≤ 0.001, respectively).  We expect both factors in the restored forest to increase over time, as was found by Zhang et al (2010) and Lee et. al. (2002), approaching Norway Valley levels.

Productivity and soil characteristic patterns in a restored prairie chronosequence
Steve Kannenberg, Rachel Wieme, Andrew Kaul, and Chanda Oviedo

Since European settlement and subsequent conversion to agricultural land, less than 1% of pre-settlement tallgrass prairie remains in Minnesota (Samson and Knopf 1994). Degradation of this ecosystem leads to a reduction in biodiversity and ecosystem services such as erosion control and habitat for native fauna, which underscores the need for restoration. A better understanding of the process of restoration will facilitate successful restoration efforts in the future.

The St. Olaf Natural Lands provide a perfect setting to study the progress of restoration: the college has gradually converted over 150 acres of previously cultivated land into restored prairie, seeding ten different prairie segments since 1989. In the summer of 2011 we sampled seven St. Olaf prairies and one remnant prairie to investigate differences in aboveground biomass, plant diversity, and soil characteristic patterns with regard to the chronosequence of prairie plantings. Additionally, fire is often used as a management tool for prairies, especially for restoring prairies. Since half of our prairies were burned in the fall of 2010, we also investigated the effects that a recent burn might have on the features listed above.

Aboveground net primary productivity (ANPP) was lower in older prairies than in younger prairies, suggesting that restored prairies become less productive with age. Percent grass biomass increased with prairie age and percent forb biomass decreased with prairie age. These data demonstrate a common trend in restored prairies that, over time, the plant composition shifts rapidly to increasing dominance by C4 grasses such as Andropogon gerardii. This happens much quicker in restored prairies and often leads to lower measures of diversity in restored prairies as compared to remnant prairies (Camil et al. 2004). The remnant prairie we sampled had the highest level of diversity, but no other significant trends in species diversity were found across the cronosequence.

We also observed that the fall burn resulted in a significant difference in ANPP (comparing data from summer 2010 to data from summer 2011) in two of the three burned prairies that we sampled. Interestingly, these were two prairies that had never been burned since they were planted (in 2002 and 2004). Fire often promotes increases in ANPP by clearing away detritus which allows more light for emerging plants and increases soil temperature (Knapp and Seastedt 1984).

The soils of the restored prairies also seem to be changing as they age: measures of physical characteristics like bulk density and organic matter show strong trends over time. However, our set of prairies seem to be an anomaly among other studied restorations. It is expected that as prairie plant roots systems develop, organic matter inputs into the soil increase and the bulk density of the soil is reduced. Although the prairie soil has lower bulk density and great levels of organic matter than nearby agricultural land, within our chronosequence the older prairies have higher bulk density than the younger ones, and older prairies have less organic matter than the younger ones – opposite trends than expected. These deviant results have been found in multiple years of studying the St. Olaf natural lands.

The soil nutrient analyses reflected few significant differences; levels of phosphates decrease as prairies age and levels of ammonium tend to decrease as well. The burn did not seem to have an effect on either physical or chemical soil properties, which may be due to a lag in response or a product of the infrequency of prescribed burns. There are still many questions left to be answered regarding the changes that occur as our restored prairies age.

The data collected from the St. Olaf natural lands over the past two summers is just the latest of numerous years of study on these ecosystems. These studies, together with the information from similar studies in previous years, are compiled into larger, long-term data sets. Such information can be used to improve our understanding and management of the ecosystems we are attempting to foster here on our own campus, but also to learn more about the important and challenging process of restoration in general.