Tree tip pit-and-mound topography
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Tree tip pit and mound topography,also know as pit and mound topography, is a small scale rolling topography consisting of depressions and adjacent mounds that are irregularly spread across the landscape. The depressions and mounds are the result of exposure of a trees’ root ball after tipping over. The root ball uplifts a large amount of soil, forming a depression, and as the roots decay the sediment is deposited back to the forest floor forming the adjacent mound[1]. This topography is commonly found in
forested areas where tree roots are shallow. In the Pacific Northwest of the United States it is not uncommon to encounter fallen over Douglas Fir[2]. Their shallow root system makes them more likely to tip over.
This pit and mound topography is also characteristic of old-growth forests. The older, larger trees are more likely to be thrown over by strong winds (wind-thrown) rather than younger skinny trees. Besides root systems, weather is the largest contributor to fallen trees and pit and mound topography. A regular abundance of rain will promote shallow root systems and loose soil.
As these trees fall over and deposit soil, they are changing the strata surrounding them by erasing the soil horizon and creating dissimilarities. Yet pit and mound topography plays an important role in maintaining species richness on a microtopographic level[3]. The mixing of the soil is extremely beneficial for forest flora and fauna. This topography is especially important in successful tree regeneration.