Scaling spatial pattern in river networks: the effects of spatial extent, grain size and thematic resolution

2021 ◽  
Author(s):  
Darin Kopp ◽  
Daniel Allen
2016 ◽  
Vol 40 (4) ◽  
pp. 598-615 ◽  
Author(s):  
Ellen Wohl

One component of geomorphic complexity results from spatial heterogeneity in river corridors. The characteristics of this form of complexity have important implications for habitat and biodiversity, attenuation of downstream fluxes, resistance and resilience of river ecosystems, river processes, ability to characterize patterns and changes through time, and river management and restoration. Numerous measures of complexity have been applied to heterogeneity from spatial scales of bed grain size distribution to entire river networks. Studies explicitly incorporating geomorphic complexity have increased substantially since 2000, but there is no single, widely used metric of complexity. Despite increasingly explicit scientific appreciation of the importance of complexity in river corridors, public attitudes toward rivers continue to emphasize an attractive appearance, which commonly equates to a physically simple and homogeneous river corridor.


2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Ophélie Planckaert ◽  
André Desrochers

We investigated landscape resistance to movements of American marten (Martes americana) based on snow-tracking data. We generated movement cost maps of the study area with different grain size, thematic resolution, and habitat-specific resistance to movements. We compared simulated tracks obtained from resistance maps to real tracks plotted along transects that we surveyed in winters 2004 to 2008 at the Montmorency Forest, Quebec, Canada. Simulated tracks were located at the intersection between least-cost paths simulated across the study area and transects. We used nearest-neighbour distances between simulated and real tracks to assess the performance of resistance maps and estimate landscape resistance parameters. Simulations with specified costs to movement for open areas, young forest, and mature forest performed better than simpler resistance scenarios, suggesting that resistance to marten movements differed among those landscape attributes that were considered. Simulations with a map grain size of 100 m performed significantly better than 5, 25, and 300 m, possibly because of gap crossing avoidance. Model performance (compared to null model) was maximal when resistance to movement in open habitat was set to 20 times higher than in mature forest, but uncertainty around this estimate was large. This research demonstrates that presence-only (point) data can be used to parameterize movements using spatially explicit modelling.


2012 ◽  
Vol 37 (2) ◽  
pp. 161-177 ◽  
Author(s):  
Athanasios S. Kallimanis ◽  
Nikos Koutsias

Land cover diversity is often used as a surrogate of habitat heterogeneity. Nevertheless, its spatial pattern has received limited attention. Here, we examine Corine land cover diversity patterns across Europe, and test (1) if geographical (longitudinal, latitudinal) gradients exist, (2) if the scale of analysis (and specifically the grain of analysis) influences the patterns, and (3) if the thematic resolution affects the results. We estimated diversity landscape metrics for 2818 locations throughout Europe. We analysed the spatial pattern at five grains (0.25, 1, 25, 100 and 625 km2), and for three hierarchical levels of the Corine Land Cover 2000 classification scheme. To account for spatial autocorrelation, we used Clifford’s test. Latitude was significantly correlated with land cover diversity (once spatial autocorrelation was taken into account) only at large grain sizes. Longitude, with a few exceptions at fine grain, was not correlated to land cover diversity. The spatial pattern of land cover diversity is scale-dependent, with spatial pattern at fine grain (<1 km2) being statistically independent of the pattern at large grain (625 km2). Also the grain of the analysis affected the spatial autocorrelation of land cover diversity. Fine grain analysis displayed autocorrelation, but over short (hundreds of kilometres) distances, while large grain analysis displayed autocorrelation over longer distances (thousands of kilometres). Increasing the detail of the thematic resolution seems to have effects similar to increasing the grain size. The thematic resolution in certain cases influenced the results qualitatively and thus inference from low-resolution landscape analysis should be done with caution.


2004 ◽  
Vol 61 (11) ◽  
pp. 2085-2096 ◽  
Author(s):  
John M Buffington ◽  
David R Montgomery ◽  
Harvey M Greenberg

A general framework is presented for examining the effects of channel type and associated hydraulic roughness on salmonid spawning-gravel availability in mountain catchments. Digital elevation models are coupled with grain-size predictions to provide basin-scale assessments of the potential extent and spatial pattern of spawning gravels. To demonstrate both the model and the significance of hydraulic roughness, we present a scenario for optimizing the spatial extent of spawning gravels as a function of channel type in Pacific Northwest catchments. Predictions indicate that hydraulic roughness could control more than 65% of the potential available spawning habitat at our study sites. Results further indicate that bar roughness can be important for maintaining spawning gravels in lower mainstem reaches, while wood roughness may be required for spawning-gravel maintenance in steeper, upper mainstem channels. Our analysis indicates that wood loss and consequent textural coarsening could deplete up to one third of the potentially usable spawning area at our study sites.


2014 ◽  
Vol 42 (2) ◽  
pp. 229-240 ◽  
Author(s):  
Sabela Lois ◽  
David E. Cowley ◽  
Adolfo Outeiro ◽  
Eduardo San Miguel ◽  
Rafaela Amaro ◽  
...  

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