Lena Delta habitat disturbance regimes

In the Lena Delta, mainly annual flooding, but also local rapid thaw processes on the land surface of the terraces with ice-rich permafrost, result in disturbance regimes forming distinct habitat types. The floodplains experience seasonal flooding as a regularly occurring disturbance in spring after ice-break up (the spring flood). Very high disturbance regimes due to the most intense scour, erosion and sedimentation result in barren sandbanks or in early-stage plant communities equalling the ‘sparsely vegetated’ habitat class. ‘moist to wet sedge communities’, ‘wet sedge communities’, ‘moist equisetum and shrubs’, ‘dry shrub communities’, ‘dry grass to wet sedge communities’ forms the mid to advanced successional stages on the floodplain (high disturbance regime) with shifting habitat types according to Stanford et al., (2005) and Driscoll and Hauer, (2019). In contrast to the floodplain, habitats on the first, second and third delta terraces are less extensively disturbed (low disturbance) allowing the development of the typical mature-state tundra plant communities: ‘polygonal tundra complex’, ‘tussock tundra’, and ‘dwarsh shrub herb communities’. However, locally, high disturbance occurs by rapid thaw processes of ice-rich permafrost (first and third delta terraces) with habitats characterized by mid to advanced-stage plant succession: ‘moist to wet sedge communities’, ‘wet sedge communities’, ‘dry shrub communities’, and ‘dry grass to wet sedge’ communities. Very high disturbance due to intense rapid thaw processes occurs at eroding cliffs and lake margins, in steep valleys and actively developing gullies resulting in barren surfaces with rims of sparsely vegetated transition zones. Given the link between plant communities and flooding as well as rapid thaw processes, we characterised the disturbance regimes for each habitat class (see legend in table) and provide an upscaling product in the form of a disturbance map for the entire Lena Delta.   References:  Stanford, J. A., Lorang, M. S., and Hauer, F. R.: The shifting habitat mosaic of river ecosystems, SIL Proceedings, 1922-2010, 29, 123-136, 10.1080/03680770.2005.11901979, 2005. Driscoll, K. P. and Hauer, F. R.: Seasonal flooding affects habitat and landscape dynamics of a gravel-bed river floodplain, Freshwater Science, 38, 510-526, 10.1086/704826, 2019.