Right under our feet, the biodiversity of below-ground organisms rivals that of tropical rain forests.
We know precious little about the below-ground organisms responsible for driving critical, life-sustaining ecosystem functions such as decomposition, nutrient cycling and water purification. My research goals:
- to understand the interactions between above- and below-ground biodiversity,
- to investigate the role of below-ground food webs in critical ecosystem processes (e.g., nutrient cycling), and
- to use soil organisms as integrative indicators of ecosystem restoration and human-related impacts
are designed to shed light on this gap in our ecological understanding and promote a more holistic approach to studying terrestrial ecosystems.
Rapid identification of soil invertebrates (Capability Fund)
Developing a knowledge pipeline, from replicated soil samples to DNA extracts and molecular fingerprints, and then linking these fingerprints to expert identifications of soil invertebrates is an essential capability not yet achieved by science. We are integrating biosystematic expert knowledge with ecological sampling of soil invertebrates through an informatics database to permit rapid high-quality species identification of soil invertebrates while providing long-term knowledge capture and greatly increasing consistency of identifications. We will build this capability by developing a database of known invertebrate species linked to their long-read DNA sequences and molecular fingerprints. This combined dataset maximizes utility for biosystematics and ecological applications. We will develop our method using New Zealand nematodes and mites, but it will naturally expand as expertise allows. We envision our work growing to produce a dynamic and accessible database of invertebrate species identities servicing a wide range of needs from general public interest to targeted scientific investigations.
Increasing natural ecosystem resilience to weeds
New Zealand is one of the world's weediest countries. Over half of the flora is composed of naturalised, non-native plants, many of which have become invasive weeds in both managed and natural ecosystems. One of our major research threads is to understand the role of above- and below-ground linkages in mediating the impact of invasive species in ecosystems. Few studies to date have considered the effects of invasive organisms on the abundance, composition and activity of the soil biota. We initiated a series of long-term (10 yr) field experiments at six sites nationally on which we removed existing weeds and prevented weed invasion into indigenous vegetation. This design allows us to quantify the impacts of weeds as they invade new areas, and the effectiveness of weed control to reverse these impacts. We will measure above- and below-ground diversity coincident with productivity, N and P cycling rates and litter decomposition under weeds, in control plots and under uninvaded indigenous vegetation to determine the joint responses of above- and below-ground communities to invasive species.
Reducing threats to forest ecosystem processes
This research focuses on some key processes that drive composition and function in New Zealand's indigenous forests. Invasive herbivores can alter the composition of forest communities, and in doing so may impact emergent ecosystem properties such as above- and below-ground biodiversity and carbon sequestration. New Zealand—having no native mammalian herbivores—provides a rare opportunity to determine if selective feeding by introduced deer translates into changes in forest community composition and ecosystem carbon storage. We are assessing deer-herbivory impacts in New Zealand mixed conifer-hardwood forests using a nation-wide network of 20 by 20 m deer exclosures that had been established 20–30 years prior. In conjunction with plot-level measurements of the plant and soil communities, soils were collected for further lab analysis and experimentation including a glasshouse experiment investigating soil feedback effects on plant growth.
Bi-cultural coastal ecosystem restoration
Seabird-dominated coastal-forest ecosystems support fundamental components of New Zealand's biodiversity, but they continue to degrade nationally because of human-related impacts (e.g., predation by introduced rats and changes in critical land management practices). Our research will inform the enhancement and rehabilitation of once common coastal forest ecosystems by investigating how biological integrity and processes can be improved using marine-terrestrial subsidies and soil disturbance from seabirds. In unison, scientific assessment of seabird-driven above- and below-ground interactions (e.g., flow-through effects of nutrients) and cross-cultural integrated management models will inform on the most productive restoration strategies. We will then determine the relationship between seabird inputs and above- and below-ground biota indicators (e.g., soil and plant %N and %P, invertebrate functional group abundances and litter decomposition rates). We will draw these data streams together to derive predictive models to test theoretical predictions of relaxed management intervention as engineering species effects gain dominance.