Does the burrowing activity of the fossorial rodent Ctenomys haigi (Ctenomyidae) have a great impact on the soil in northwestern Patagonian grasslands?

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Yermén Acebal Ghiorzi, Luciana Ghermandi and Sofia Gonzalez, INIBIOMA (CONICET-National University of Comahue), Bariloche, Argentina

Background/Question/Methods
Fossorial rodents act as ecosystem engineers by changing the physical environment in which they inhabit. The excavation activity for burrows construction involves a large soil displacement forming mounds with different physical, chemical and biological properties. We studied the soil impact by the burrowing activity of Ctenomys haigi (Patagonian tuco-tuco, Ctenomyidae) in northwestern Patagonian grasslands, Argentina. To evaluate the soil impact of C. haigi we recorded all the fresh mounds in three plots of 625 m2 each one and in 30 mounds we measured the two perpendicular diameters and height and in 15 mounds the soil compaction with a penetrometer. The soil compaction was also measured in 15 adjacent gaps between dominant vegetation (undisturbed soil). We calculated the mound density, the area occupied by mounds/ha, and the volume of excavated soil/ha.
Results/Conclusions
We found 1024±241.6 mounds/ha, and an area of 1837.6 m2/ha (18.4%) occupied by mounds. The volume of excavated soil was 120.4 m3/ha. The soil compaction was 10 times higher in gaps than in fresh mounds (3.72 ± 0 kg/cm2 and 38.7± 1.5 kg/cm2, respectively). We concluded that the burrowing activity of C. haigi removes much more soil compared to other congeners. The low soil compaction in fresh mounds could facilitate the root development favoring the plant establishment in this microsite. These findings demonstrated the high impact of C. haigi on the soil, which can affect the vegetation dynamics and productivity in the northwestern Patagonian grasslands.