Cascading effects of animal disturbances to moss and lichen communities on soil characteristics in northeastern Siberia

Background/Question/Methods

Arctic ecosystems, including boreal forests and tundra, occur at high latitudes where cold and moist conditions favor ground layer dominance by mosses and lichens. These functional types play critical roles in insulating soils which protects underlying permafrost from warming, and support nitrogen fixing microorganisms necessary for the growth of vascular plants. Mosses and lichens also provide food and shelter for arctic animals, especially during harsh winter months. Animal disturbances affecting mosses and lichens can have indirect effects on soil properties that feedback to influence both stability of underlying permafrost and establishment and growth of other vegetation types. Here, we assess the cascading effects of animal disturbances of moss in a boreal treeline ecosystem and lichen in a tundra ecosystem in far northeastern Siberia. In both ecosystems, soil measurements (thaw depth, soil temperature, and soil moisture) were measured at the center of disturbed patches and in adjacent undisturbed locations at 0.2 m and 1 m from the edge of the disturbed patch. Disturbance age and size were measured to determine if correlations existed with soil measurements. Plants growing within disturbed patches were recorded to examine plant recolonization post disturbance.

Results/Conclusions

Preliminary results show that soils at disturbed moss patches had deeper thaw depths (patch: 0.68 ± 0.06 m vs. 1 m: 0.44 ± 0.09 m), warmer soil temperatures (patch: 6.69 ± 0.69^oC vs 1 m: 2.9 ± 0.79^oC) and higher moisture (patch: 0.41 ± 0.05 m³/m³ vs 1 m: 0.07 ± 0.08 m³/m³) than soils under undisturbed areas of the moss mat. There was no difference in size between old (0.95 ±0.08 m²) and freshly disturbed (0.94 ±0.14 m²) moss patches. Thaw depth increased as patch size of old disturbance increased (R² = 0.54), however, there was no clear relationship between thaw depths and patch size of freshly disturbed patches. This is likely due to older disturbed patches being exposed to sunlight and air temperatures longer resulting in a more unified response.  These results suggest that animal disturbances can alter soil characteristics in ways that increase plant access to nutrients and water that would otherwise be locked in permafrost and have the potential to shift dominance relationships within the plant community. As climate continues to change, understanding influence of animal disturbances on soil characteristics is important for predicting future changes in plant community composition.