Allen Larocque

Allen Larocque

Thesis research:

Central to ‘the ecological thought’ is a deep message of interconnection. This concept is engagingly symbolized by the existence of Common Mycorrhizal Networks (MNs) – networks of fungal hyphae that connect plants together and establish pathways for nutrient, water, and communication molecules. My project will examine these processes in the ‘salmon forests’ of BC, where the coming of spawning salmon and their subsequent deaths represent a large nutrient pulse that subsidizes the terrestrial ecosystem with marine-derived nutrients. These salmon-derived nutrients are taken up and incorporated by the mycorrhizal fungi of trees and plants, and then may be transferred a considerable distance from the stream through MNs, providing a nutrient subsidy at a distance into the surrounding forest away from salmon-bearing streams and rivers. These nutrients change the dynamics of the forest – forests along a gradient of streams showing different salmon abundance, for example, have different vegetation, insect, and bird communities. The fate of 15N in different tree, plant, and soil components can be examined to elucidate seasonal, annual and decadal nutrient fluxes from marine to terrestrial systems. In addition to their effects on nutrient cycling and aboveground biotic communities, the effects of salmon subsidies on soil communities in general has never before been investigated. I propose to examine salmon forests using dendrochronology, heavy isotopes and molecular genetics to elucidate the roles of MNs in mediating nutrient uptake, transfer and cycling by trees, plants, fungi and soils; test and parameterize competing models of network patterns and system dynamics; and investigate the ecological and evolutionary pros and cons of being a MN participant.