Stacey Robbins - May 2018

My name is Stacey Robbins and I will begin my junior year at MSU this fall in the Land Resources and Environmental Sciences department with a focus in land rehabilitation.  This summer, I am studying how patterns of plant and soil mycorrhiza effect tree establishment along a tree line, with Dr. Lisa Rew.  The questions we are focusing on are 1) ‘how does vegetation cover and composition change across the tree line?’  2) ‘how does the density and size distribution of trees change across the tree line?’ and 3) ‘do soil biota limit tree expansion over tree line?’.  These questions are important to understand the biological shifts that are occurring around the globe in response to Earth’s rapidly changing climate.  Because trees play a dominant role in an ecosystem, how they respond to a changing climate can in turn affect many species and shift an entire ecosystem.  Current research expects tree lines to move upward in elevation, but many thresholds must be overcome for this to occur.

The first few weeks of research have been focused on locating three to four potential sites to collect data within the Beartooth Mountain range, refining what data to collect at each site by furthering my literature review of previous relevant research. At each experimental site we expect to collect data on plant species composition, the size distribution of trees and soil pH and texture. Current studies surrounding the topic have mainly focused on how factors, such as temperature and precipitation, are related to historical tree line shifts.  Although these two variables play a major role, there are many other thresholds that must also be overcome for trees to successfully establish and migrate upward.  We will assess vegetation composition changes across the treeline gradient and correlate this with tree density and size as well as soil factors. We will also evaluate historic temperature and precipitation differences across these gradients to determine their role. These could include microclimates that arise from disturbances or establishment of another plant to create a positive feedback loop for colonization.  Additionally, relationships between the trees and mycorrhiza fungi, or other soil biota, could potentially play a governing role in successful tree establishment. Therefore, we will be taking soil samples at each site, along the treeline gradient, and bringing them back to the greenhouse where we will assess tree seedling establishment. Establishment and growth of the tree seedlings will be assessed beyond the period of this study.

By doing this summer internship, I am excited about the opportunity to select a topic that is interesting to me, and to gain experience in designing and carrying out a research plan from start to finish.  I expect to learn a lot along the way not only from research as I come up to speed on the current studies surrounding tree line shifts, but also about adjusting methods, better developing experimental design where necessary and especially in communicating within the science community.  One of the current challenges I am facing for the internship is the ability to access the selected sites and collect data as we wait for the snow to melt from the upper mountains.  Another challenge I continue to face is that few related studies have been conducted in Beartooth Mountains, so a background picture about the tree lines in the area has been difficult to accurately build. 

Potential site #1 in the Beartooths, off Highway 212 and near Christmas Lake

Potential site #2 in the Beartooths, East side of the top of the pass

Potential site #3, outside of Red Lodge, MT area​


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