We studied the association between environmental variables and the terrestrial habitat use by adults of the burrowing toad Rhinella fernandezae in Buenos Aires, Argentina. We assessed the cover type, height of vegetation, soil moisture and hardness. We compared these habitat variables in quadrats where toads were present along a transect (n = 30 quadrats, 19 with toad burrows) with respect to randomly chosen quadrats (n = 17). We found that R. fernandezae does not use the habitat at random, and that habitat variables that mostly infl uenced its habitat use were soil hardness after raining, probably because it facilitates the construction of burrows, and broad-leaved plant cover, which may be affecting toads indirectly through other habitat variables, such as shadowing, air moisture and refuge from predators.
Field observations showed that in many gravel-bed rivers, rice stems and gravel interact with each other and affect the flow structure. This calls to conduct research in more details in laboratory to better understand impacts of interaction between rice stems and gravel bed rivers on the flow structure. The outcome of such investigations can improve the estimation of drag coefficient in hydrodynamic models. Experiments were carried out in a flume with gravel bed and the vegetated vertical flume walls to investigate turbulence characteristics under favorable pressure gradient flows. Results showed that the stress fraction involves both the sweep and ejection dominance near the vegetated flume walls, showing no negative Reynolds shear stress near water surface. The values of exuberance ratio play a significant role on the magnitude of the Reynolds shear stress which varies with the distance from the vegetation. Quadrant analysis reveals that a major part of the momentum flux is transported during a short period of strong turbulence activity near the bed at the central axis. Augmentation of the hole size makes difference between contributions of sweep and ejection with those of the outward and inward interactions near the bed, however, the hole size doesn’t play any role near the water surface.