Carbon dynamics at the hillslope and catchment scale Greg Hancock1, Jetse Kalma1, Jeff McDonnell2, Cristina Martinez1, Barry Jacobs1, Tony Wells1
1. The University of Newcastle2. Oregon State University
BackgroundTerrestrial carbon fluxes account for more than half of the carbon transferred between the atmosphere and the earths surface
Terrestrial ecosystems represent a critical element of the carbon interchange system
A lack of understanding of the carbon dynamics at the hillslope, catchment and regional scales represents a large source of uncertainty
Agricultural scientists understand carbon dynamics at the point to paddock scale
Speculative about what happens on the hillslope to catchment scale
We know little about how soils and land management affect carbon sequestration at the hillslope and catchment scale
Whats driving catchment soil carbon dynamics?
Textural properties?Soil moisture, soil temperature?Vegetation?Hillslope/catchment hydrology/geomorphology?
Problem of scaleDEM grid size of 5m, 10m, .250m???
Vegetation, soil moisture, soil temperature quantification at 5m DEM. ???????
At what scale do we need to examine the hillslope and catchment to quantify and model soil carbon?
Whats been done?Studies concentrated on forested tropical and subtropical regions or in cool temperate landscapes with anthropogenic influence
Australia has received much less attention
No reported attempt to examine the spatial and temporal scaling properties or to scale up data to larger catchments
Location- Arnhem Land, NT- monsoonal tropics- no European disturbance geologically similar to the ERA Ranger uranium mineExtensive catchment analysis-rainfall/runoff plots-hydrology and erosion model calibration-DEM scale analysis-soil erosion assessment by 137Cs-soil carbon assessmentCase study Tin Camp CreekTransect 2Transect 1
Results- position on hillslope and soil carbonTransect 1Transect 2No relationship with soil carbon and hillslope position!
Results- soil carbon and soil erosionTransect 1Transect 2No relationship between soil carbon and soil erosion!
Results - hillslope profile and soil textureTransect 1Transect 2No relationship with hillslope position and soil texture!
Results - soil carbon with soil textural propertiesWeak relationship with soil carbon and texture!Transect 1Transect 2
Whats driving catchment soil carbon dynamics?
Textural properties?Soil moisture, soil temperature?Vegetation?Hillslope/catchment hydrology/geomorphology?What scale?
Project: Carbon dynamics on the hillslope and catchment scale
The Goulburn catchment Use existing equipment (Scaling and Assimilation of Soil Moisture and Streamflow-SASMAS) within the 7000 km2 Goulburn catchment
Mixed grazing and cropping region located 200 km west of Newcastle
26 monitoring sites (soil moisture, temp) stream gauges 4 climate stations
Location of Instrumentation
Project aimThe identification of spatial and temporal patterns within carbon dynamics at the hillslope, subcatchment and catchment scales
Model and predict the distribution (temporal and spatial) of catchment soil carbon
Project requirementsExisting network (SASMAS) of ground based weather, soil moisture and temperature and stream gauges
Complemented with additional stream gauges to quantify Dissolved Organic Carbon, as well as ground based vegetation and soil carbon quantification at each of the field sites
To be done at three scalesHillslopeSmall catchment (Stanley), second sandstone catchmentGoulburn catchment
Remote sensingNever enough ground based data
Can we use remote sensing to extrapolate ground based data (veg., soil moisture and temp.) over the wider region?
Catchment scaleDigital elevation models provide a framework for catchment examination
What grid scale do we use?-25m (commercial)-250m (free)-3-arc second (90m) NASA (free)
Digital elevation model creationDo we need to create our own DEM using differential GPS (time consuming) or LIDAR?
LIDAR offers great potential
Eco-Dimona-Scanning lidar altimeter-0.1m vertical, 1m horizontal
We believe that a 10m DEM the minimum
Remote sensing of vegetation, soil temperature and moisture
NDVI (biomass) data from LANDSAT 5 or 7, Soil moisture (interpreted) from GMS and NOAA-AVHRR
Eco-Dimona aircraft-Thermal infrared imager (1m resolution at 500ft) - Tri-spectral scanner (NDVI) (1m resolution at 500ft) - PLMR soil moisture
Large scaleRemote sensing used to extrapolate both soil moisture and biomass levels observed at the subcatchment and catchment scales to the larger region
Calibration and validationCalibration of NVDI data by comparing the remotely sensed data with on-the-ground sampling of the surface vegetation cover
Validation of soil moisture and soil temperature obtained with microwave and infrared sensors mounted on aircraft and satellite platforms over a range of scales
What we can provide to the NAFE and what we need from the NAFE
What we can provide from ground based measurementSoil carbon, biomass, temperature, moisture, textural data - 26 SASMAS sites (7000 km2 Goulburn)- 2 small catchments (750 ha Stanley + one other)- hillslope (Stanley + one other)
Soil erosion/sediment transport data for 2 small catchments (hillslope and stream)
Water quality data for 2 small catchments
NAFE requirementsHigh resolution data (Eco-Dimona aircraft)-Thermal infrared imager -Tri-spectral scanner (NDVI) -PLMR (soil moisture)
for the Stanley (basalt) catchment and for a second (yet to determined) sandstone catchment within the study region
ConclusionThe calibration of remotely sensed data on the smaller subcatchment together with the sparse data collected at SASMAS monitoring site allows us to make predictions about the impact of biomass changes on carbon dynamics
Remotely sensed vegetation data can be coupled with SASMAS soil moisture, soil temperature, rainfall, climate and streamflow data in combination with NDVI/biomass data and the DEM to model hillslope/catchment carbon dynamics