1. Soil Carbon Dynamics: A Catchment Based Approach C. Martinez, G. Hancock, J.D. Kalma & T. Wells NAFE’06 Workshop February 13-14, 2006

2. Introduction Significance of terrestrial C fluxes within global C budget Lack of understanding of C dynamics at hillslope, catchment & regional scales – particularly lack of studies within Australia – Northern Hemisphere (US, Canada) studies dominate (different environments/conditions) What’s driving catchment soil C dynamics? – textural properties? – soil moisture/temperature? – vegetation? – hillslope/catchment hydrology/ geomorphology?

3. Introduction cont… Traditional methods of soil sampling for estimation of SOC –attempts to reduce/remove the need for soil sampling –using remotely sensed data

4. Project Aims Investigate the spatial & temporal patterns of soil C dynamics at hillslope & catchment scales Model & predict distribution (temporal & spatial) of soil C within Goulburn River catchment using ground based & remotely sensed data

5. Data Requirements Existing SASMAS network of ground based weather, soil moisture/temperature & stream gauges Complement with ground based soil & vegetation sampling & additional water quality instrumentation for quantification of DOC at Stanley Data collected at 4 scales: –Hillslope (Stanley transects) –Small catchment (Stanley) –Large catchment (Krui) –Regional (SASMAS & NAFE’05)

6. Data Requirements cont… Remotely sensed data (NDVI) –Use to extrapolate ground based hillslope & sub- catchment scale data to larger catchment & regional scales –Satellite vs aircraft vs ground based Digital elevation models (DEMs) –25m LPI DEM –High resolution 5m DEM (DGPS) for Stanley –LIDAR (1m)???

7. Current Study Soil C dynamics at hillslope (Stanley) & catchment scales (Stanley = small; Krui = large) –Stanley micro-catchment (C, N & 137 Cs) 7 SASMAS stations (1 = weather station) 1 flume 5m DEM (DGPS) water quality instrumentation (DOC) –Krui River catchment (C & N) 13 SASMAS stations (including Stanley) NAFE’05 (soil moisture, vegetation, soil C & N) Regional SOC dynamics –SASMAS network & NAFE’05

8. Current Study cont… Land use management effects on SOC (C & N) Remotely sensed data –Landsat (NDVI) > ground (above-ground biomass [AGB]), aircraft & satellite SOC dynamics modelling (RothC, CENTURY)

9. NAFE’05 Regional Data AMSR regional scale sampling (Mondays) – Week 3 (14/11) & Week 4 (21/11) – teams collected additional soil samples for C & N determination – total of 88 soil samples (5cm core depth) collected over Krui & Merriwa River catchments by the 4 teams over 2 days

10. Catchment Scale Stanley catchment 1ha grid sampling strategy (Week 4 of NAFE’05) – 175ha Stanley catchment sampled on a 1ha grid (i.e. sample pt every 100m) – 133 points sampled (see Figure) – at each sample point, data collected: soil core (max. depth 22cm) AGB sample (0.5m x 0.5m quadrat) soil moisture via thetaprobe (mV)

11. Stanley Catchment

12. Sample Processing Regional scale samples –wet & dry weights recorded for all samples (determination of volumetric moisture content) –oven dried at 40 0 C (Uni of Newcastle) –samples disaggregated using mortar & pestle and passed through 2mm sieve –50g acidified samples for C & N analysis (LECO – UWA) –particle size analysis (Malvern); pH; EC; CEC Stanley catchment samples (same as above) –*** IN ADDITION remaining <2mm fraction analysed for 137 Cs (Uni of Newcastle) Relationships between SOC & soil redistribution processes (i.e. erosion & deposition)

13. Initial Results Above-ground Biomass (t/ha)Volumetric Soil Moisture (%) Soil Depth Sampled (cm)Vegetation Water Content (kg/m 2 )

14. Initial Results cont… DATA TO COME: –Process soil samples & analyse for C & N (LECO) –NAFE’05 aircraft data (NDVI & LIDAR?) –Landsat OR SPOT NDVI data for sampling period (Nov’05) – 137 Cs analysis –PSA (Malvern) –pH –EC –CEC NDVI (Landsat, May’05)

15. Conclusions SOC = key element in global C cycle Lack of understanding of SOC dynamics at hillslope and catchment scales What’s driving catchment SOC dynamics? Need for better & faster (BUT still reliable) methods for quantifying SOC dynamics

16. Conclusions NAFE’05 –Regional scale data Soil moisture/temperature Vegetation (NDVI) Soil C & N LIDAR??? Stanley catchment scale data –SOC – 137 Cs –Soil moisture –Above-ground biomass Ground-based & remotely sensed (aircraft platform)