Using fractals to describe ecologically-relevant patterns in distributions of large rocks in streams
AuthorDwyer, GK; Cummings, C; Rice, SP; Lancaster, J; Downes, BJ; Slater, L; Lester, RE
Source TitleWater Resources Research
University of Melbourne Author/sDownes, Barbara
Document TypeJournal Article
CitationsDwyer, G. K., Cummings, C., Rice, S. P., Lancaster, J., Downes, B. J., Slater, L. & Lester, R. E. (2021). Using fractals to describe ecologically-relevant patterns in distributions of large rocks in streams. Water Resources Research, https://doi.org/10.1029/2021WR029796.
Access StatusThis item is currently not available from this repository
ARC Grant codeARC/DP160102262
Measuring the physical complexity of habitats or ecological resources is often achieved using 27 system-specific methods that make comparisons across ecosystems difficult. One measure 28 that is applicable across multiple ecosystems and scales is the fractal dimension, which has 29 the benefit of generality as well as potential scale independence. This study evaluated the use 30 of box-counting and entropy fractal dimensions for characterising the complexity of emergent 31 rock distributions in six streams across Scotland and Australia. Emergent rocks (ER) are 32 important hydraulic features and ecological resources, including as oviposition sites for 33 aquatic insects and cover for fish. We complete fractal analysis on counts of ER in 5-m 34 segments along longitudinal stretches of the six streams. All six streams exhibited fractal 35 behaviour (self-similarity), suggesting that fractals can be used to measure the complexity of 36 longitudinal ER distributions in a way that is scale independent. Entropy was a superior 37 measure due to its ability to differentiate among the six streams whereas box-counting could 38 not. Together, field results and numerical simulations showed that fractal dimensions of 39 emergent rock distributions were related to stream geomorphology. Well-developed 40 bedforms, like alternating pools and riffles had better organised emergent rocks because large 41 bed materials were more likely to be emergent in topographic highs. Streams with coarser 42 bed materials had more chaotic arrangements of emergent rocks because this increased the 43 general abundance of emergent rocks, making differentiation between topographic highs and 44 lows less distinctive. Fractal dimensions, therefore, can measure the complexity of river 45 systems in a way that is relevant to geomorphological and ecological processes.
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