Dr David Johnson

BEd (CCAE), GCEMD, MENVR, PhD (ANU)
ANU College of Science

Areas of expertise

  • Conservation And Biodiversity 050202
  • Environmental Management 050205
  • Environmental Rehabilitation (Excl. Bioremediation) 050207
  • Environmental Monitoring 050206
  • Terrestrial Ecology 060208
  • Landscape Ecology 050104
  • Natural Resource Management 050209
  • Wildlife And Habitat Management 050211
  • Soil Sciences 0503

Research interests

Grassland ecology

Forb diversity

Grassland management

Environmental conservation

 

Biography

I grew up on a sheep farm in rural NSW and for the past 25+ years have lived on a bush property in the southern tablelands of NSW. I have been interested in our natural environment all my life, although professionally I worked in several vocations prior to starting formal environmental studies at ANU. I taught maths and computing at highschool and college level and later worked in a variety of roles within the IT industry. 

I completed my Master of Environment (Research) in 2012 and I was awarded a PhD in grassland ecology in December 2018. University studies have given me a deep understanding of grasslands and general ecology and research methods, data analysis and writing.  My general goal is to continue contributing to scientific research to increase our understanding of natural ecosystems and how we should manage earth’s resources and biodiversity.

My main research area is grassland ecology with a focus on forb diversity.  My aim is to understand the drivers of grassland diversity and the threats, and the barriers to restoration, so that I can provide science-based practical advice for grassland managers and restoration practitioners.

Researcher's projects

I continue to collect annual data from the field experiment commenced during my PhD, and intend to write up the long-term results (after 4 years) for comparison with the results already published from the first year's results. Each year I record native and exotic forb counts and cover estimations following a fully-crossed combination of four treatments that reduced the level of competition from dominant grasses and exotic species, removed ground litter, and added seed of 14 native forb species. 

Past student projects

My PhD Research included 4 major projects.

1.  A detailed survey of the ground-layer vegetation and soils in 192 random locations within the study area, stratified by nine different vegetation types. I compared native and exotic forb responses and occupancy likelihood over a broad range of environmental conditions. I analysed soil chemistry and physical properties, and I obtained topographic information from a digital model based on GPS coordinates. I used Bayesian fourth corner analysis in R to predict responses of native and exotic, annual and perennial forbs to eight environmental variables representing landscape, soil, and vegetation biomass.

2. A case-control study of the differences between the vegetation and soil surface conditions in the immediate vicinity of a native forb (the case), and two equivalent areas randomly located within five meters where no native forbs exist (the controls). I analysed data from 145 cases and 290 controls, using conditional logistic regression in R to identify the most significant variables and calculate their influence on the odds ratios of native forb presence/absence.

3. A field experiment designed to test responses of native and exotic forb seedlings to a fully-crossed design of four treatments that reduced the level of competition from dominant grasses and exotic species, removed biomass, and added seed of 14 native forb species. In addition to trialing plant responses to the treatments, as is commonly done to test the effectiveness of treatments, the I also measured a range of structural and resource variables influenced by the treatments to help us understand the mechanisms behind forb responses to the treatments. I used GLMM statistical analyses in R to measure seedling emergence responses to the treatments, and to identify the structural and resource variables significantly associated with native and exotic forb responses.

4. As a synthesis of my research results, I presented a conceptual model representing native forb habitat suitability in relation to gradients of available soil phosphorus and total biomass (grass and litter combined). I suggest some thresholds for these variables and discuss appropriate actions for restoration and management.

My masters research project was a greenhouse experiment to compare the growth and survival response of three different native forb groups to increasing levels of competition from a dominant native grass.

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Updated:  19 October 2019 / Responsible Officer:  Director (Research Services Division) / Page Contact:  Researchers