EAPSI:Understanding How Seabird Guano Impacts Nutrient Availability and Plant Community Composition in Montane Terrestrial Ecosystems

Rowe Julia A, Keaau HI

Investigators

Abstract

To better understand plant-animal and terrestrial-marine linkages, the project will study the input of nitrogen (N) by seabirds into forested areas in New Zealand. This is an important dynamic to understand as some islands are undergoing predator removal and native habitat and seabird restoration, while others continue to experience seabird declines. This work will be conducted in collaboration with Dr. David Towns of the Auckland University of Technology (AUT). Dr. Towns has over 20 years of experience studying ecosystems in New Zealand as well as many years working with seabird islands and their restoration. Primary research questions include: how do seabird population densities impact nutrient subsidies, how much marine-sourced N do the plants utilize, and do these seabird induced changes in the soil and plants impact the vegetation community structure. It is hypothesized that as seabird burrow density increases, N from seabirds will increase, and vegetation community structure in seabird communities will change, becoming more significantly composed of native plants adapted to utilize the pulsed subsidies provided by the seabirds. This New Zealand research will be compared with previous work in Hawaii to better understand linkages of the marine-seabird-terrestrial ecosystem as seabirds? populations decline across the globe. The N isotope composition of soil and leaves will be measured to understand how N brought from the ocean to the terrestrial system moves through the ecosystem. High d15N values may serve as a signature of marine source of N. A two end member, one isotope mixing model will be used to assess the percentage of N in soil and leaves that is from a marine source, i.e. seabirds. Vegetation community structure will also be measured to determine if there is an appreciable difference between seabird and non-seabird areas in terms of community composition. This award is funded in collaboration with the Royal Society of New Zealand.