This post is part of the LTER’s Short Stories About Long-Term Research (SSALTER) Blog, a graduate student driven blog about research, life in the field, and more. For more information, including submission guidelines, see lternet.edu/SSALTER
From Manhattan to the Arctic Tundra: 3 student’s summer adventure in Alaska
Hi LTER! Our names are Frances Cohen, Amelia Harris, and Jessie Motes, and we’re undergraduate and graduate students with the Arctic LTER from Barnard College and Columbia University. We spent this summer coming up with creative ways to bear call, climbing up thermokarst slumps, fording rivers, walking on frozen lakes, and, of course, watching Love Island! But perhaps more notably, we spent nearly three months at Toolik Field Station studying processes in the Arctic tundra that range from individual fluorescence in leaves to tree growth north of the treeline!
Credit: Jessie Motes, CC BY-SA 4.0.
Fertilization effects on thermal tolerance in plants
by Frances Cohen
As part of my REU project, I collected leaf samples from dominant vegetation in the LTER’s long-term fertilization gradient experiment and measured how increased nutrient addition affects plants’ thermal tolerance. As the arctic warms, increased temperatures are projected to increase nutrient availability and cycling rates which has been shown to increase shrub dominance while decreasing the prevalence of tussocks, yet smaller-scale effects on plant physiology, and in particular photosynthetic thermal tolerances (Tcrit) for the common tundra species, Betula nana and Eriophorum vaginatum, aren’t well understood. Initial results showed no increase in Tcrit with higher nutrient levels for either species. Betula nana and Eriophorum vaginatum average Tcrit values were 37.8±0.4°C and 42.4±0.4°C, respectively, which exceeds current summer temperatures. However, my study suggests that increasing nutrients doesn’t alter photosynthetic heat tolerance, suggesting that future thermal stresses from increased temperatures may not be alleviated by increasing nutrient availability.
Credit: Jessie Motes, CC BY-SA 4.0.
Tree growth and photosynthesis north of the tree line
by Amelia Harris
For my REU project, I chose to study how the effects of climate change may impact tree physiology and treeline advancement in the arctic tundra. Toolik Field Station is situated north of the Brooks Mountain Range, and north of the treeline, so the occasional stands of poplar trees around Toolik are of great interest to me and others on my team. Every week, I would travel to the three known poplar stands within a driving or boating distance from Toolik to collect growth data and measure photosynthesis in Populus balsamifera. I found that fluorescence, a proxy for photosynthesis, varied across the season, with Fv/Fm values as low as 0.67 in mid-June and ranging from 0.79 to 0.82 in mid-July. Additionally, I found that fluorescence rose sharply after leaf-out, leveled off in mid-summer, and declined with senescence. I also collected data from dendrometers that showed rapid tree growth starting in May, peaking after senescence in September, and slowing as temperatures dropped. This suggests that the timing of tree growth, leaf production, and leaf function are asynchronous, with poplars storing carbon during warmer months to support future growth.
Credit: Jessie Motes, CC BY-SA 4.0.
The timeless value of long term research
by Jessie Motes
In 2018, I began an REU at the Coweeta Hydrologic Lab (then Coweeta LTER), studying nitrogen fixation by Black Locust through succession. I spent the summer scrambling around southern Appalachian hillslopes and picking through roots from trees ranging from one to a hundreds of years old. This experience sparked my interest in the relationship between forest succession and soil processes—which carried on into a masters studying the role of historical disturbance on current nitrogen cycling dynamics. Now, my research has shifted to a much longer timescale in the Arctic tundra with the LTER. Here, climate warming is thawing permafrost, the soil frozen for tens to hundreds of thousands of years. This thawing is expected to fertilize the typically nutrient-poor tundra ecosystem. My current focus is on the spatial and temporal coupling of this fertilization effect with plant nutrient demand. My fieldwork involves, once again, digging around in the soil, and, now, getting a birds-eye-view of the vast, open landscape using drones to measure vegetation greenness.Thanks to these two LTER sites, my perspective on long-term research has evolved significantly. I started my research career studying centuries of forest recovery at one of the original LTER sites. Now, I’m investigating how climate change affects ecosystem properties that have remained stable for millennia and developing models to project future climate scenarios. My journey through LTER research has been a lesson in perspective, bridging the gap between my own brief six-year experience, the decades-long commitment of LTER sites, and the millennia-spanning processes of ecosystem change—highlighting the critical importance of long-term ecological studies in understanding and predicting Earth’s complex dynamics.
