Category Archives: Lab Happenings

South African Field Trip

In March, the lab group made a trip to Kruger National Park in South Africa to survey the tree resprouting experiment.  Savanna trees suffer frequent damage from large herbivores. Often the whole crown of the tree is knocked over and crushed.  How fast and vigorously a damaged tree can resprout determines survival, growth, and reproduction–things that plant ecologists, like us, find fascinating.  Resprouting is also important for maintaining forage for animals, firewood for humans, and for carbon storage in these ecosystems.  In 2011, we set up an experiment across the Kruger Climate Gradient to examine what factors control tree resprouting.  Is it soil moisture?  Soil nutrients?  Tree species? Tree age or size?  We are exploring these questions while enjoying the southern hemisphere sun!

Tree carnage

Becky Hewitt (left), Samantha Miller (center), and Ben Ketter (right) chortle over trees decapitated for developing allometric relationships.

Xan tree height

Xanthe Walker discovers that savanna trees are much taller than those in the taiga ecosystems of the high northern latitudes.

Small measurements

Thoughtful measurement of stem diameters by Ben Ketter (left), Becky Hewitt (middle) and Corey Nielson (right).

Rico cage

Ricardo Holdo (center) protects himself from herbivores while Ben Ketter (left) takes notes.

Xanthe Walker joins lab as new postdoc!

The Mack lab is very excited to welcome Dr. Xanthe Walker to the lab in her new role as a postdoctoral researcher.  Xanthe brings her expertise in fire ecology and dendrochronology. She will work on the new NASA Arctic Boreal Research project, studying the impacts of severe fires on the loss of old carbon from boreal forest and arctic tundra soils.  Xanthe also brings her expertise in Brett Michaels-style Buff wearing, braving mosquitos without a bug shirt (see Samantha’s attire for contrast), and multivariate statistics.

Xanthe 2015

New Postdoc Joins the Mack Lab

Rebecca Hewitt recently finished her PhD with Drs. Terry Chapin and Teresa Hollingsworth at University of Alaska Fairbanks. Her dissertation investigated whether plant-fungal interactions after wildfire influenced seedling establishment at and beyond current treeline. She explored the effects of post-fire mycorrhizal community structure on the physiological performance of treeline seedlings and collaborated with the Scenarios Network for Alaska and Arctic Planning to investigate the landscape implications of her plot-level studies by implementing a mycorrhizal-submodel in simulations of tree migration using the fire-vegetation-climate model ALFRESCO. As a postdoctoral researcher in the Mack Lab at Northern Arizona University she will investigate the belowground plant traits and plant-fungal interactions that confer access to nitrogen released from thawed permafrost.

Mack Lab Welcomes a Visitor

Mélanie Jean is currently visiting the Mack Lab to process moss samples for isotope analysis that she collected near Fairbanks, Alaska. Mélanie is a Ph.D. student in Jill Johnstone’s Northern Plant Ecology Lab at the University of Saskatchewan. She is studying the functional role of mosses in driving successional dynamics of boreal forests.


Mélanie Jean sampling mosses at her study site in  Murphy Dome, Alaska.
Mélanie Jean sampling mosses at her study site in Murphy Dome, Alaska.

Relocated in the Southwest

Michelle and family, pictured below amidst the sunflowers, have moved to Northern Arizona University in Flagstaff, AZ, to join the Center for Ecosystem Science and Society and the Department of Biological Sciences.  Samantha Miller, lab manager extraordinaire pictured in stylish field gear, made the move from Florida, too, to set up the new lab.  The truck full of lab gear arrived last week, bringing hundreds of boxes of archived samples and all of our equipment to a new home.

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Congratulations, Camila!

Camila Pizano, a postdoctoral associate in the Mack Lab, recently accepted a position as adjunct researcher in charge of the scientific component of a national project on tropical dry forest at the Instituto de Investigación de Recursos Biológicos Alexander von Humboldt in Bogota, Colombia. Congratulations, Camila!