Management of wild canids and trophic cascades: How is vegetation influenced by top-order predators?

Abstract

Abstract: data was collected to develop new field-based techniques: 1) estimate macropod grazing density using camera trapping, and 2) estimate herbaceous biomass using digital photography in order to 3) use both methods with a species composition cover and biomass assessment in a 3-year, 5-survey, field-based grazing exclusion experiment, which also measured a range of environmental variables at each site. Methodology Macropod grazing density was estimated using camera trapping. Details of method, data handling and analysis are the subject of Chapter 4 in the thesis. In the kangaroo enclosure at the University of New England, kangaroo habitat areas were stratified, camera traps were deployed on 13 measured plots at 1-minute time-lapse for 5 days in 2014 and 10-minute time-lapse for 13 days in 2017, on me assured plots. Numbers of kangaroos in each image were counted and data analysed to gain density and activity patterns. Dung pellet counts were also collected from each plot in each sampling period as verification and pellet deposition rates obtained using kangaroo counts and pellet counts. Camera images were tagged in EXIF Pro Image Viewer 2.1, image metadata was then extracted and exported using exif3.exe version 1, to Microsoft Excel 2010 for analysis. Dung pellet counts were stored and analysed in Microsoft Excel 2010. 2) Herbaceous biomass was estimated using digital photography at Booroolong NR and Naree Station. Details of the method, data handling and analysis are the subject of Chapter 5 in the thesis. In the field photographs were taken of the biomass to be estimated with a set of biomass photographs for calibration. The calibration quadrats were then clipped, dried and weighed. The set of images for biomass estimation were ranked by estimated weight against calibration images of known biomass in the laboratory. Images were ranked and stored in Windows Explorer, weight data was stored and analysed in Microsoft Excel 2010. 3) Species composition, cover and biomass data was recorded in the field at 20 experimental plots, entered, stored and analysed in Microsoft Excel 2010. Details of data collection in the field, data handling and analysis are in the thesis Chapter 6. Data was stored in rows and columns of individual % cover score for all species recorded at each survey, and estimated biomass of the biomass-dominant species. Data was analysed in Microsoft Excel 2010, PAST (Hammer et al. 2001), and Canoco 5 (ter Braak and Šmilauer 2012) 4) Environmental variables were recorded at Booroolong NR to be used in data analysis. Details of data collection in the field, data handling and analysis are in the thesis Chapter 6. Data was analysed with the Species composition, cover and biomass data in Microsoft Excel 2010, PAST (Hammer et al. 2001), and Canoco 5 (ter Braak and Šmilauer 2012)

Sources: Species composition, cover and biomass, environmental site characteristics and macropod data was collected in the field experiments. Rainfall and temperature data was accessed from Australian Government. Bureau of Meteorology. (n.d.). Climate Data Online Retrieved 30/11/15, 06/6/16, 30/06/17,06/01/18, from http://www.bom.gov.au/ Naree Station biomass photographs were sourced from Dr John Hunter, supervisor and co-author, Invergowrie, NSW. Soil sample analysis was provided by Agronomy and Soil Science laboratory at the University of New England (UNE).