Professor Nielsen's conducts research in pristine and managed ecosystems to address fundamental questions with a focus on hypotheses-driven research. His overarching goal is to use this knowledge to better manage Earth's ecosystems to protect and preserve soil biodiversity, whilst also developing and implementing evidence-based sustainable land use management practices that incorporate the benefits that can be gained from improved soil biodiversity. He places strong on building a collaborative and supportive work environment that promote the development of students and early career scientists, ranging from the involvement of undergraduates in ongoing research projects, capacity building of graduate students to mentoring of junior staff members.

His current research interestes comprise three broad but well-aligned tranches that offer opportunities across fundamental and applied ecology:

Biodiversity, community ecology, and ecosystem function have long been a key research interest for Associate Professor Nielsen. He is increasingly applying this knowledge to ecological restoration and conservation. 

Dryland ecosystem ecology Some 40% of Earth’s terrestrial surface and most of Australia is classified as dryland. He has established a successful program to better understand and manage these sensitive ecosystems in the light of global changes.

Plant pests and pathogens have substantial impacts on Australia’s agriculture and horticulture. Several recently funded projects aim to provide better diagnostics for early detection and enhanced management of economically important pests and pathogens.