Patch Configuration Non-linearly Affects Sediment Loss across Scales in a Grazed Catchment in North-east Australia John A. Ludwig, 1, * Rebecca Bartley, 2 Aaron A. Hawdon, 3 Brett N. Abbott, 4 and David McJannet 2 1 Tropical Savannas Cooperative Research Centre and CSIRO Sustainable Ecosystems, P.O. Box 780, Atherton 4883, Australia; 2 CSIRO Land and Water, 120 Meiers Rd, Indooroopilly, Brisbane 4068, Australia; 3 CSIRO Land and Water, Davies Lab, Aitkenvale, Townsville 4814, Australia; 4 CSIRO Sustainable Ecosystems, Davies Lab, Aitkenvale, Townsville 4814, Australia ABSTRACT A principle of the cross-scale interaction (CSI) framework is that disturbance-induced landscape changes resulting in coarser-grained spatial struc- ture may non-linearly amplify transfer processes across scales. We studied suspended sediment losses at two spatial scales (0.24 m 2 plots and ca. 0.25 ha hillslopes of about 140 m in length) in a semiarid savanna landscape to determine whether the spa- tial structure of grassy and bare soil areas intro- duced a non-linear amplification of sediment loss. Sediment loss rates from 0.24 m 2 bare plots aver- aged 1.527 t ha )1 y )1 , which was 23 times the loss rate from nearby grassy plots (0.066 t ha )1 y )1 ). These rates were then extrapolated linearly to two hillslopes separated by only 200 m and having similar total grass cover, slope and soil type but differing in the spatial structure of bare soil patches. The coarse-grained hillslope had a large bare patch on its lower slope, whereas the fine-grained hills- lope had no bare soil patches when quantified at a 4 m grid-cell resolution. Measured sediment loss from the fine-grained hillslope averaged 0.050 t ha )1 y )1 , whereas the average sediment loss from the coarse-grained hillslope was 2.133 t ha )1 y )1 . By linearly extrapolating from the plot scale, the expected sediment loss for the fine-grained hillslope was 0.066 t ha )1 y )1 , which is similar to that observed. The expected sediment loss for the coarse-grained hillslope was 0.855 t ha )1 y )1 , where linear extrapolation as- sumed a 46:54 ratio of bare to grassy plots and that the spatial arrangement of plots does not affect sediment loss processes. For the coarse-grained hillslope observed sediment loss is 2.5 times greater than that expected by linear extrapolation from the plot scale. This result indicates a cross-scale inter- action related to spatial configuration of patches. We suggest that there were non-linearities in hillslope ecohydrological transfer processes (runoff, erosion) across scales due to a specific patch con- figuration that greatly amplified sediment loss be- cause the pattern failed to slow runoff and retain sediment before it entered a creek. This example supports the CSI framework and indicates the importance of considering the effect of spatial structure when predicting system dynamics at dif- ferent scales. Key words: ecohydrology; erosion; rangeland; savanna; semiarid; soil. Received 24 May 2007; accepted 29 May 2007; published online 26 June 2007. *Corresponding author; e-mail: john.ludwig@csiro.au Ecosystems (2007) 10: 839–845 DOI: 10.1007/s10021-007-9061-8 839