Soil health in savannas

Leader: Dr Tracy  Dawes-Gromadzki, CSIRO Sustainable Ecosystems, Darwin

Full title: Soil health in tropical savannas: soil biological drivers of landscape function

Long-term landscape health can only be achieved if the basic ecosystem function of capturing and cycling water and nutrients is maintained.

Soil macrofauna are vital contributors to these processes through their feeding and foraging activities, and through creation of soil macroporosity.

However, their activity and functional diversity varies considerably between different types of vegetation-soil patches within savanna landscapes. Fire and grazing can significantly alter the ability of a landscape to capture and retain vital water and nutrient resources through changes in patch structure and dynamics.

Understanding these biological drivers of key landscape processes that underpin soil health, and the influence of disturbance on these key processes at scales ranging from small patches to whole landscapes, is critical. It is this fundamental knowledge that provides a basis upon which to develop and adapt land management practices to promote soil health and the productivity of savanna landscapes.

This project will synthesise previous biophysical data on soil health collected during the first three years of TS-CRC Project 1.1.3 and address the identified knowledge gaps regarding the impacts of grazing on soil health. It will incorporate this knowledge into the Savanna.au simulation model so that the effects of different grazing management scenarios on soil health can be predicted. Based on this knowledge and these model predictions, this project will produce resource material on the effects of savanna management on soil health, and will incorporate this material into Meat and Livestock Australia’s (MLA) Grazing Lands Management (GLM) package. 

Objectives

The three main objectives of this project are:

1. Based on a synthesis of findings from the first three years of TS-CRC Project 1.1.3 and an identified knowledge gap regarding the influence of grazing on soil health, this project will address this gap by:
2. 1. quantifying soil macrofaunal diversity, activity and water and nutrient dynamics (patch functionality) in different patch types;
   2. quantifying the relationships between patch functionality and landscape health and productivity;
   3. measuring the effects of grazing intensity on the above relationships, and
   4. determining the potential of soil macrofauna as indicators of soil health (subject to previous findings).
3. Based on previously collected data (TS-CRC Project 1.1.3) and new knowledge gained under objective 1, this project will incorporate this knowledge into the Savanna.au model so that the effects of soil health on eco-hydrological processes can be predicted, through:
4. 1. initial parameterisation of Savanna.au for a selected sub-set of common soils in the Burdekin catchment;
   2. Savanna.au grazing simulations at a one-hectare scale on these soil types (TS-CRC Project 1.1.3 results)
   3. Savanna.au spatial simulations of the effects of soil health on hydrological processes and productivity for Wambiana hillslope catchments, including model validation and further improvements (incorporating new research results), and
   4. validation of the eco-hydrological sub-model of Savanna.au to account for eco-hydrology through simulation of the effects of soil health in patches on infiltration, run-off and hillslope erosion processes.
5. Based on this new knowledge on soil health and productivity, this project will take steps to improve the ability of land managers and regional National Action Plan (NAP) management bodies to take account of soil health, through:
6. 1. the production of resource materials that synthesise results on the effects of management on soil health. This will include resource material for the MLA GLM package; other resource materials (e.g. field-day handouts and posters, case studies) to illustrate the effects of changes in land management on soil health and productivity.

TS-CRC Objectives and key result areas (KRA’s)

This project aims to increase our understanding of the effects of patch functionality on soil health and landscape productivity, and the influence of grazing on these relationships. In doing so it will improve the ability of land managers and regional National Action Plan (NAP) Boards to account for soil health in management, through mechanisms of adoption of these findings. It will address these aims through the following approach:

1. addressing identified knowledge gaps regarding how grazing affects soil health;
2. incorporating the above knowledge and previously collected data on soil health from the first three years of TS-CRC Project 1.1.3 into the Savanna.au computer simulation model so that the effects of grazing on soil health can be predicted, and
3. producing resource material on the effects of management on soil health for the benefit of land managers and regional bodies.

This project will contribute to Healthy Savanna Landscapes (Key Result Area 1) by providing signals of soil health, and by improving the predictive capacity of the Savanna.au model.

This project indirectly contributes to Sustainable Management Systems (Key Result Area 2) by increasing our understanding of grazing effects on patch functionality and landscape eco-hydrology, and, in turn, the consequences these effects on productivity. This knowledge provides a critical basis for the development of improved grazing management strategies.

The project also contributes to Viable and Socially Desirable Regions (Key Result Area 3), as the information on rangeland condition and productivity will contribute to the development, implementation and assessment of the NAP for salinity and water quality in the Burdekin Dry Tropics and other NAP catchments.

This project will also contribute to Productive and Capable People (Key Result Area 4) through the production of communication products (resource material for MLA’s GLM Package and Savanna.au) and the development of cross-sectoral networks through the development of a new and diverse project team.

Project team

T. Dawes-Gromadzki, CSIRO SE

A. Liedloff, CSIRO SE

Garry Cook, CSIRO SE

Gus Wanganeen, CSIRO SE

Peter O’Reagain, QDPIF

Peter Allen, QDPIF

Sue Berthelsen, CSIRO LW

Leah Ballaam, CSIRO LW

Brigid Nelson, QDPIF

Bob Shepherd, QDPIF

Jill Aisthorpe, QDPIF