Mackenzie is a member of Jen Lau's lab studying how elevated soil nitrogen affects ecological and evolutionary interactions between plants and nitrogen-fixing rhizobium bacteria. She has used a combination of fieldwork and greenhouse studies to disentangle direct and indirect effects of soil nitrogen on both plants and rhizobia in a variety of contexts, including native species, widespread introduced species, and crops.

Sierra is a PhD candidate in the Lau lab and EEB graduate program. Her research explores the factors influencing the resilience of plant populations and communities to anthropogenic global changes.