Abstract
Abstract. Significant progress has been made in the development of cover data and derived products based on remotely sensed fractional cover information and field data across Australia, and these cover data sets are now used for quantifying and monitoring grazing land condition. The availability of a dense time-series of nearly 30 years of cover data to describe the spatial and temporal patterns in landscape changes over time can help with monitoring the effectiveness of grazing land management practice change. With the advent of higher spatial resolution data, such as that provided by the Copernicus Sentinel 2 series of satellites, we can look beyond reporting purely on cover amount and more closely at the operational monitoring and reporting on spatial arrangement of cover and its links with land condition. We collected high spatial resolution cover transects at 20 cm intervals over the Wambiana grazing trials in the Burdekin catchment in Queensland, Australia. Spatial variance analysis was used to determine the cover autocorrelation at various support intervals. Coincident Sentinel-2 imagery was collected and processed over all the sites providing imagery to link with the field data. We show that the spatial arrangement and temporal dynamics of cover are important indicators of grazing land condition for both productivity and water quality outcomes. The metrics and products derived from this research will assist land managers to prioritize investment and practice change strategies for long term sustainability and improved water quality, particularly in the Great Barrier Reef catchments.
Highlights
High sediment loads and associated nutrients in runoff from grazing lands in the Great Barrier Reef catchments is a major contributor to the degradation of water quality entering the Reef lagoon
The patterns of vegetation clumping that we see in the field data are related to the grazing strategies applied across the paddocks
This clear that these grazing strategies cause clumping to occur at multiple scales from the relationship between the Sentinel-2 based variogram range and the grazing strategy
Summary
High sediment loads and associated nutrients in runoff from grazing lands in the Great Barrier Reef catchments is a major contributor to the degradation of water quality entering the Reef lagoon. Ecosystems self-organise as water infiltrates faster into bare ground (Reitkirk et al, 2002), resulting in rapid decline of the landscape and an increase in ‘leakiness’ (Tongway and Ludwig 1997, in Northup et al, 2005). Higher concentration of nutrients in patches than in surrounding bare areas (Northup et al, 2005), results in more palatable regrowth and preferential grazing (Cid and Brizuela, 1998). Lower stocking rates tend to preserve patch structure, resulting in more stable patches (Cid and Brizuela, 1998, Northup, 2005). Heavier grazing pressures produce less standing crop and more dispersion of tussocks (Northup et al, 2005)
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